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DIONNE, S., J.A. GAGNÉ, D. GILBERT, C. ROULEAU, 2011. Processus consultatif scientifique régional sur lexamen du plan de suivi écologique de la zone de protection marine Estuaire du Saint-Laurent, 3-5 Mai 2011, Institut Maurice-Lamontagne, Mont-Joli, Qc ; Regional Science Advisory Process on the Review of the St. Lawrence Estuary Marine Protected Area Ecological Monitoring Plan, Mai 3-5, 2011, Maurice Lamontagne Institute, Mont-Joli, Qc. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2011/037, 18 p .
JURANEK, L.W., R.A. FEELY, D. GILBERT, H. FREELAND, L.A. MILLER, 2011. Real-time estimation of pH and aragonite saturation state from Argo profiling floats : prospects for an autonomous carbon observing strategy. Geophys. Res. Lett., 38(17): art. no. L17603 .
We demonstrate the ability to obtain accurate estimates of pH and carbonate mineral saturation state (O) from an Argo profiling float in the NE subarctic Pacific. Using hydrographic surveys of the NE Pacific region, we develop empirical algorithms to predict pH and O using observations of temperature (T) and dissolved O2. We attain R2 values greater than 0.98 and RMS errors of 0.018 (pH), 0.052 (Oarag), and 0.087 (Ocalc) for data between 30—500 m, σθ < 27.1. After calibrating optode-based O2 data, we apply the algorithms to T and O2 data from an Argo profiling float to produce a 14 month time-series of estimated pH and Oarag in the upper water column of the NE subarctic Pacific. Comparison to independent data collected nearby in 2010 indicates pH and Oarag estimates are robust. Although the method will not allow detection of anthropogenic trends in pH or Oarag, this approach will provide insight into natural variability and the key biogeochemical controls on these parameters. Most importantly, this work demonstrates that an assemblage of well-calibrated regional algorithms and Argo float data can be used as a low-cost, readily-deployable component of a global ocean carbon observing strategy.©2011 American Geophysical Union
GENOVESI, L., A. DE VERNAL, B. THIBODEAU, C. HILLAIRE-MARCEL, A. MUCCI, D. GILBERT, 2011. Recent changes in bottom water oxygenation and temperature in the gulf of St. Lawrence : micropaleontological and geochemical evidence. Limnol. Oceanogr., 56(4): 1319-1329 .
Micropaleontological and geochemical analyses of a sediment core collected in the Laurentian Trough of the Gulf of St. Lawrence were carried out to reconstruct temporal variations in pelagic productivity and benthic environmental conditions. Dinoflagellate cyst assemblages reveal relatively stable pelagic productivity over the last two centuries. Similarly, geochemical (organic C, Corg :N) and isotopic (δ13Corg, δ15N) data reveal that organic matter fluxes to the seafloor have been relatively constant over the same period. In contrast, significant changes are recorded in the benthic foraminifer assemblages. A sediment surface peak in the abundance of Cassidulina laevigata and Brizalina subaenariensis is consistent with the recent record of oxygen depletion in the bottom water. A decrease in the relative abundance of Nonionellina labradorica, concomitant with a relatively higher occurrence of Oridorsalis umbonatus in the upper part of the core, reflects a significant warming of the bottom water. Changes in bottom-water properties are further constrained by a negative trend of the δ18O in Bulimina exilis carbonate shells over the last century, corresponding to a warming of about 2 °C. These results strongly suggest that the recent oxygen depletion in the bottom waters of the Gulf of St. Lawrence is due to changes in water masses that have led to increased bottom-water temperatures and, to some extent, a resultant increase in organic matter respiration rates.©2011 American Society of Limnology and Oceanography, Inc.
PETTIGREW, B., P. LAROUCHE, D. GILBERT, 2011. Validation des images composites des températures de surface produites au laboratoire de télédétection de lInstitut Maurice- Lamontagne. Rapp. tech. can. hydrogr. sci. océan., 270, 39 p .
An entirely automated operational system having the task to produce composite images of sea surface temperature (SST) of Canadian waters has been set up at the remote sensing laboratory of Maurice Lamontagne Institute (MLI) using data from Advanced Very High Resolution Radiometer (AVHRR) sensors. In situ sea surface temperatures from six stations located in the Estuary and the Gulf of St. Lawrence have been used to validate composite images from August 1995 to August 2004. Differences over all stations between mean SST and mean in situ temperature for averaging periods of 1, 7 and 15 days were respectively -0,26 °C (1,06 °C), -0,21 °C (0,90 °C) and -0,13 °C (0,84 °C) where the values in parentheses are the standard deviations. Results showed that the accuracy of the daily mean is highly correlated to the number of measurements used to compute it. However for most validation stations, that correlation decreased rapidly for the 7 and 15 days averages. Finally, we estimated the maximum daily and weekly absolute error at the 95 % confidence level for most stations.
GALBRAITH, P.S., J. CHASSÉ, D. GILBERT, P. LAROUCHE, D. BRICKMAN, B. PETTIGREW, L. DEVINE, A. GOSSELIN, R.G. PETTIPAS, C. LAFLEUR, 2011. Physical oceanographic conditions in the Gulf of St. Lawrence in 2010 ; Conditions océanographiques physique dans le golfe du Saint-Laurent en 2010. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2011/045, 86 p .
An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2010 is presented. Air temperatures reached record highs when averaged from January to March and from October through December as well as annually. The monthly averaged freshwater runoff measured at Québec City was normal overall in 2010 but was unusually high during winter and fall, and the spring freshet was almost absent. Near-surface water temperatures in the Gulf were normal or above normal all year and in all regions except for the Mécatina Trough and Esquiman Channel in June. Maximum sea-ice volume within the Gulf and on the Scotian Shelf was 11 km³, a record low since 1969. The duration of the 2009–2010 ice season was shorter than normal and associated with the early ice melt. Winter inflow of cold and saline water from the Labrador Shelf occupied the Mécatina Trough over the entire column in winter 2010. The spread of the intrusion was confined close to the Strait of Belle Isle, leading to an overall small volume of 809 km³. However, this intrusion volume represented 29 % of the unusually small volume of mixed layer waters that were colder than -1 °C. The winter cold mixed layer volume in the Gulf, excluding the Estuary, was 13 900 km³, a value higher than the 1996–2009 average by 0.7 SD. This cold-water volume corresponded to 42 % of the total water volume of the Gulf. However, it was very warm, on average about 1 °C above the freezing point. This is the first time in 15 years of winter surveys that such high temperatures were recorded. The cold intermediate layer (CIL) index for summer 2010 was - 0.04 °C, which is similar to observations in 2000. This is an increase of 0.38 °C since 2009. On the Magdalen Shallows, none of the bottom area was covered by water with temperatures < 0 °C in September 2010, similar to conditions in 2005, 2006, 2007, and 2009. In other regions of the Gulf, very few areas had bottom temperatures below 0 °C. Regional patterns of the August and September CIL show that the layers for T < 1 °C and < 0 °C were much thinner in most parts of the Gulf in 2010 than in 2009 and had a generally higher core temperature everywhere. Conditions in March 2010 were characterized by a very thick winter mixed layer, although very warm, including a thick intrusion of Gulf waters into the Estuary. By June 2010, the CIL thickness returned to nearnormal but still had above-normal minimum temperatures. The CIL warming rate appeared to be slower than usual because core temperatures were closer to normal in certain regions by August and more so by November. The warm deep waters in the Estuary in 2009 were replaced by colderthan- normal waters by June 2010. Colder-than-normal deep waters also occupied the northwest Gulf at that time. Very warm waters occupied Cabot Strait in June at 250 m—the depth of the temperature maximum—and there is a hint that the top portion of this water mass was sampled during the March survey. The warm deep waters were still present in Cabot Strait in August as well as in November. Gulf-wide average temperatures were below normal at 200 to 300 m and salinities were below normal from 150 to 300 m. Temperatures at 300 m increased marginally overall but significantly (by 1 SD) at Cabot Strait, where the anomaly is now +1 SD. Salinity at 200 m and 300 m decreased overall by 0.6 SD but increased at Cabot Strait to reach +0.6 SD at 200 m. The 300 m waters of the Estuary are expected to cool further during the next two years, but it will be interesting to follow the warm anomaly present in 2010 at Cabot Strait as it progresses up the channel toward the Estuary. The surface mixed layer in November was anomalously thick but more importantly very warm, warmer in fact than in November 2009 which were the preconditions for the record conditions of March 2010.
DE VERNAL, A., G. ST-ONGE, D. GILBERT, 2011. Oceanography and quaternary geology of the St. Lawrence Estuary and the Saguenay Fjord. IOP Conf. Series: Earthand and Environmental Science, 14(1): Art. no 012004 .
The St. Lawrence Estuary is an environment marked by important freshwater discharge and well stratified water masses, recording large seasonal contrast in surface waters from freezing conditions in winter to temperate conditions in summer due to a very strong seasonal cycle in overlying air temperature. High productivity takes place in the pelagic and benthic environments, where a recent trend toward bottom water hypoxia is observed. The area was profoundly marked by the Quaternary glaciations. Thick glaciomarine sequences dating from the last deglaciation are observed in the Estuary and along the shores, whereas a relatively thin layer (a few meters at most) of hemipelagic mud was deposited during the Holocene.©2011 IOP Publishing Ltd
Accumulation of metabolic CO2 can acidify marine waters above and beyond the ongoing acidification of the ocean by anthropogenic CO2. The impact of respiration on carbonate chemistry and pH is most acute in hypoxic and anoxic basins, where metabolic CO<sub}2 accumulates to high concentrations. The bottom waters of the Lower St. Lawrence Estuary (LSLE), where persistently severe hypoxia has developed over the last 80 years, is one such case. We have reconstructed the evolution of pH in the bottom waters from historical and recent data, and from first principles relating the stoichiometry of CO2 produced to oxygen consumed during microbial degradation of organic matter. Based on the value of the atmospheric partial pressure of CO2 that best reproduces the preformed dissolved inorganic carbon concentration in the bottom waters, we estimate the average ventilation age of the bottom waters to be 16 ± 3 years. The pH of the bottom waters has decreased by 0.2 to 0.3 over the last 75 years, which is four to six times greater than can be attributed to the uptake of anthropogenic CO2. The pH decrease is accompanied by a decline in the saturation state with respect to both calcite and aragonite. As of 2007, bottom waters in the LSLE are slightly supersaturated with respect to calcite (Oc ≈ 1.06 ± 0.04) but are strongly undersaturated with respect to aragonite (Oa ≈ 0.67 ± 0.03).©2011 Taylor & Francis
OUELLET, M., B. PETRIE, J. CHASSÉ, D. GILBERT, 2011. Temporal and spatial scales of temperature, salinity and current velocity on the Newfoundland Grand Banks and in the Gulf of St. Lawrence. Can. Tech. Rep. Hydrogr. Ocean Sci., 272, 85 p .
In order to assess the representativity of the Atlantic Zonal Monitoring Program (AZMP) stations, an analysis of the spatial and temporal variability of temperature, salinity and current velocity in Canadian Atlantic waters is presented here using historic mooring series. Spatial correlation functions are estimated in the horizontal and vertical directions between simultaneous sensors. Temporal auto-correlation is used to investigate the temporal scales. The analysis focuses on two regions: Newfoundland Grand Banks and Gulf of St. Lawrence. In the Grand Banks, Avalon Peninsula, Flemish pass, SouthEast Shoal and the CASP2 zone. In the Gulf, Strait of Belle Isle, Jacques Cartier Passage, St. Lawrence Estuary, Gaspé Current, Central Gulf and Cabot Strait.
GILBERT, D., 2011. Aller en ligne droite sur une planète qui tourne : la force de Coriolis. Accromath, 6(2): 24-29 .
PENA, M.A., S. KATSEV, T. OGUZ, D. GILBERT, 2010. Modeling dissolved oxygen dynamics and hypoxia. Biogeosciences, 7(3): 933-957 .
Hypoxia conditions are increasing throughout the world, influencing biogeochemical cycles of elements and marine life. Hypoxia results from complex interactions between physical and biogeochemical processes, which can not be understood by observations alone. Models are invaluable tools at studying system dynamics, generalizing discrete observations and predicting future states. They are also useful as management tools for evaluating site-specific responses to management scenarios. Here we review oxygen dynamics models that have significantly contributed to a better understanding of the effects of natural processes and human perturbations on the development of hypoxia, factors controlling the extent and temporal variability of coastal hypoxia, and the effects of oxygen depletion on biogeochemical cycles. Because hypoxia occurs in a variety of environments and can be persistent, periodic or episodic, models differ significantly in their complexity and temporal and spatial resolution. We discuss the progress in developing hypoxia models for benthic and pelagic systems that range from simple box models to three dimensional circulation models. Applications of these models in five major hypoxia regions are presented. In the last decades, substantial progress has been made towards the parameterization of biogeochemical processes in both hypoxic water columns and sediments. In coastal regions, semi-empirical models have been used more frequently than mechanistic models to study nutrient enrichment and hypoxia relationships. Recent advances in three-dimensional coupled physical-ecological-biogeochemical models have allowed a better representation of physical-biological interactions in these systems. We discuss the remaining gaps in process descriptions and suggest directions for improvement. Better process representations in models will help us answer several important questions, such as those about the causes of the observed worldwide increase in hypoxic conditions, and future changes in the intensity and spread of coastal hypoxia. At the same time, quantitative model intercomparison studies suggest that the predictive ability of our models may be adversely affected by their increasing complexity, unless the models are properly constrained by observations.©2010 European Geosciences Union
RABALAIS, N.N., R.J. DIAZ, L.A. LEVIN, R.E. TURNER, D. GILBERT, J. ZHANG, 2010. Dynamics and distribution of natural and human-caused hyposia. Biogeosciences, 7(2): 585-619 .
Water masses can become undersaturated with oxygen when natural processes alone or in combination with anthropogenic processes produce enough organic carbon that is aerobically decomposed faster than the rate of oxygen re-aeration. The dominant natural processes usually involved are photosynthetic carbon production and microbial respiration. The re-supply rate is indirectly related to its isolation from the surface layer. Hypoxic water masses (<2 mg L-1, or approximately 30 % saturation) can form, therefore, under "natural" conditions, and are more likely to occur in marine systems when the water residence time is extended, water exchange and ventilation are minimal, stratification occurs, and where carbon production and export to the bottom layer are relatively high. Hypoxia has occurred through geological time and naturally occurs in oxygen minimum zones, deep basins, eastern boundary upwelling systems, and fjords. Hypoxia development and continuation in many areas of the world's coastal ocean is accelerated by human activities, especially where nutrient loading increased in the Anthropocene. This higher loading set in motion a cascading set of events related to eutrophication. The formation of hypoxic areas has been exacerbated by any combination of interactions that increase primary production and accumulation of organic carbon leading to increased respiratory demand for oxygen below a seasonal or permanent pycnocline. Nutrient loading is likely to increase further as population growth and resource intensification rises, especially with increased dependency on crops using fertilizers, burning of fossil fuels, urbanization, and waste water generation. It is likely that the occurrence and persistence of hypoxia will be even more widespread and have more impacts than presently observed. Global climate change will further complicate the causative factors in both natural and human-caused hypoxia. The likelihood of strengthened stratification alone, from increased surface water temperature as the global climate warms, is sufficient to worsen hypoxia where it currently exists and facilitate its formation in additional waters. Increased precipitation that increases freshwater discharge and flux of nutrients will result in increased primary production in the receiving waters up to a point. The interplay of increased nutrients and stratification where they occur will aggravate and accelerate hypoxia. Changes in wind fields may expand oxygen minimum zones onto more continental shelf areas. On the other hand, not all regions will experience increased precipitation, some oceanic water temperatures may decrease as currents shift, and frequency and severity of tropical storms may increase and temporarily disrupt hypoxia more often. The consequences of global warming and climate change are effectively uncontrollable at least in the near term. On the other hand, the consequences of eutrophication-induced hypoxia can be reversed if long-term, broad-scale, and persistent efforts to reduce substantial nutrient loads are developed and implemented. In the face of globally expanding hypoxia, there is a need for water and resource managers to act now to reduce nutrient loads to maintain, at least, the current status.©2010 European Geosciences Union
ZHANG, J., D. GILBERT, A.J. GOODAY, L. LEVIN, S.W.A. NAQVI, J.J. MIDDELBURG, M. SCRANTON, W. EKAU, A. PENA, B. DEWITTE, T. OGUZ, P.M.S. MONTEIRO, E. URBAN, N.N. RABALAIS, V. ITTEKKOT, W.M. KEMP, O. ULLOA, R. ELMGREN, E. ESCOBAR-BRIONES, A.K. VAN DER PLAS, 2010. Natural and human-induced hypoxia and consequences for coastal areas : synthesis and future development. Biogeosciences, 7(5): 1443-1467 .
Hypoxia has become a world-wide phenomenon in the global coastal ocean and causes a deterioration of the structure and function of ecosystems. Based on the collective contributions of members of SCOR Working Group #128, the present study provides an overview of the major aspects of coastal hypoxia in different biogeochemical provinces, including estuaries, coastal waters, upwelling areas, fjords and semi-enclosed basins, with various external forcings, ecosystem responses, feedbacks and potential impact on the sustainability of the fishery and economics. The obvious external forcings include freshwater runoff and other factors contributing to stratification, organic matter and nutrient loadings, as well as exchange between coastal and open ocean water masses. Their different interactions set up mechanisms that drive the system towards hypoxia. Coastal systems also vary in their relative susceptibility to hypoxia depending on their physical and geographic settings. It is understood that coastal hypoxia has a profound impact on the sustainability of ecosystems, which can be seen, for example, by the change in the food-web structure and system function; other influences include compression and loss of habitat, as well as changes in organism life cycles and reproduction. In most cases, the ecosystem responds to the low dissolved oxygen in non-linear ways with pronounced feedbacks to other compartments of the Earth System, including those that affect human society. Our knowledge and previous experiences illustrate that there is a need to develop new observational tools and models to support integrated research of biogeochemical dynamics and ecosystem behavior that will improve confidence in remediation management strategies for coastal hypoxia.©2010 European Geosciences Union
GILBERT, D., N.N. RABALAIS, R.J. DIAZ, J. ZHANG, 2010. Evidence for greater oxygen decline rates in the coastal ocean than in the open ocean. Biogeosciences, 7(7): 2283-2296 .
In the global ocean, the number of reported hypoxic sites (oxygen <30 % saturation) is on the rise both near the coast and in the open ocean. But unfortunately, most of the papers on hypoxia only present oxygen data from one or two years, so that we often lack a long-term perspective on whether oxygen levels at these locations are decreasing, steady or increasing. Consequently, we cannot rule out the possibility that many of the newly reported hypoxic areas were hypoxic in the past, and that the increasing number of hypoxic areas partly reflects increased research and monitoring efforts. Here we address this shortcoming by computing oxygen concentration trends in the global ocean from published time series and from time series that we calculated using a global oxygen database. Our calculations reveal that median oxygen decline rates are more severe in a 30 km band near the coast than in the open ocean (>100 km from the coast). Percentages of oxygen time series with negative oxygen trends are also greater in the coastal ocean than in the open ocean. Finally, a significant difference between median published oxygen trends and median trends calculated from raw oxygen data suggests the existence of a publication bias in favor of negative trends in the open ocean.©2010 European Geosciences Union
GILBERT, D., J. CHRISTIAN, 2010. Fertilisation des océans : atténuation des impacts environnementaux de la recherche scientifique. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2010/012, 15 p .
EKAU, W., H. AUEL, H.-O. PORTNER, D. GILBERT, 2010. Impacts of hypoxia on the structure and processes in pelagic communities (zooplankton, macro-invertebrates and fish). Biogeosciences, 7(5): 1669-1699 .
Dissolved oxygen (DO) concentration in the water column is an environmental parameter that is crucial for the successful development of many pelagic organisms. Hypoxia tolerance and threshold values are species- and stagespecific and can vary enormously. While some fish species may suffer from oxygen values of less than 3 mL O2 L-1 through impacted growth, development and behaviour, other organisms such as euphausiids may survive DO levels as low as 0.1 mL O2 L-1. A change in the average or the range of DO may have significant impacts on the survival of certain species and hence on the species composition in the ecosystem with consequent changes in trophic pathways and productivity. Evidence for the deleterious effects of oxygen depletion on pelagic species is scarce, particularly in terms of the effect of low oxygen on development, recruitment and patterns of migration and distribution. While planktonic organisms have to cope with variable Dos and exploit adaptive mechanisms, nektonic species may avoid areas of unfavourable DO and develop adapted migration strategies. Planktonic organisms may only be able to escape vertically, above or beneath the Oxygen Minimum Zone (OMZ). In shallow areas only the surface layer can serve as a refuge, but in deep waters many organisms have developed vertical migration strategies to use, pass through and cope with the OMZ. This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity. We describe processes in two contrasting systems, the semi-enclosed Baltic Sea and the coastal upwelling system of the Benguela Current to demonstrate the consequences of increasing hypoxia on ecosystem functioning and services.©2010 Copernicus Publications on behalf of the European Geosciences Union
GILBERT, D., J. CHRISTIAN, 2010. Ocean fertilization : mitigating environmental impacts of future scientific research. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2010/012, 14 p .
GRUBER, N., S.C. DONEY, S.R.EMERSON, D. GILBERT, T. KOBAYASHI, A. KÖRTZINGER, G.C. JOHNSON, K.S. JOHNSON, S.C. RISER AND O. ULLOA, 2010. Adding oxygen to Argo : developing a global in-situ observatory for ocean deoxygenation and biogeochemistry. 10 pages in J. Hall, D.E. Harrison & D. Stammer (eds.). Proceedings of OceanObs'09 : Sustained Ocean Observations and Information for Society (Vol.2), Venice, Italy, 21-25 September 2009 (ESA Publication, WPP-306) .
We propose to add dissolved oxygen sensors to the Argo float program in order to determine, on a global-scale, seasonal to decadal time-scale variations in dissolved oxygen concentrations throughout the upper ocean. Such observations are especially important to document the oceans expected loss of oxygen as a result of ocean warming, but there are many other benefits including the opportunity to estimate net community and export production, the assessment of changes in low oxygen regions, and improved estimates of the oceanic uptake of anthropogenic CO2. The proposed joint Argo-Oxygen program is made possible by the recent development of dissolved oxygen sensors that are both precise and stable over extended periods and can be easily integrated with the currently used Argo floats. Results from the more than 200 oxygen equipped Argo float have not only demonstrated the feasibility of the program, but also produced already many insights and discoveries. Achieving the main goal of the Argo-Oxygen program does not require any appreciable changes in the deployment and operating strategies of the current Argo program and can therefore be implemented without a significant impact on Argos core mission. A two-phase implementation is proposed, consisting of a small set of regional pilot-studies, followed by a build-up toward a global implementation. The cost of adding oxygen sensors to all floats of the Argo program is estimated to be about USD 4.2 million per year. The proposed Argo-Oxygen program will add substantial value to Argo by expanding the number of Argo data users, as well as by creating new synergies between the physical and the biogeochemical ocean research communities. The new observations will also contribute to the activities of various international networks and partnerships for Earth Observing Systems.©2010 OceanObs'09
DALE, V.H., C. KLING, J.L. MEYER, J. SANDERS, H. STALLWORTH, T. ARMITAGE, D. WANGSNESS, T.S. BIANCHI, A. BLUMBERG, W. BOYNTON, D.J. CONLEY, W. CRUMPTON, M.B. DAVID, D. GILBERT, R.W. HOWARTH, R. LOWRANCE, K. MANKIN, J. OPALUCH, H. PAERL, K. RECKHOW, A.N. SHARPLEY, T.W. SIMPSON, C. SNYDER, D. WRIGHT, 2010. Hypoxia in the Northern Gulf of Mexico. Springer, New York, 284 p. .
Hypoxia in the Northern Gulf of Mexico is based on an extensive review conducted by the Hypoxia Advisory Panel of the Science Advisory Board for the Environmental Protection Agency, which was chaired by the editor. The book examines scientific advances that, since 2000, have increased understanding of hypoxia in the Gulf. It discusses characterization of its cause, characterization of its nutrient fate, transport, and sources, and the scientific basis for goals and management options. Using available data, including models, model results, and uncertainty, the advisory team addresses the strengths and limitations of managing the Gulf hypoxia problem. This book will be of interest to specialists in the fields of environmental sciences, social sciences, economics, landscape architecture, planning, and communication of risks.©2011 Springer
GILBERT, D., 2010. National Advisory Meeting on Ocean Fertilization Consequences and Impacts, September 29 and 30, 2009, Boulton Room, 615 Booth Street, Ottawa, Ontario ; Réunion davis scientifique nationale sur les conséquences et impacts de la fertilisation, les 29 et 30 septembre 2009, Salle Boulton, 615, rue Booth, Ottawa (Ontario). DFO, Canadian Science Advisory Secretariat, Proceedings series, ; MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus, 2010/025, 28 p .
The Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter was adopted in 1972 (updated to London Protocol in 1996) to prevent marine pollution and prohibit deliberate dumping of wastes or other matter at sea, except by permit. In 2008, a nonbinding resolution was adopted limiting ocean fertilization activities to "legitimate scientific research". As a result, a Draft Assessment Framework for Scientific Research was developed for assessing scientific research proposals on a case-by-case basis. On September 29 and 30, 2009, Canadian academic and federal government scientists met in Ottawa, Ontario to discuss ocean fertilization and provide science advice to Canadas delegation at the London Convention and to provide feedback to the Scientific Working Group on their Draft Assessment Framework. A discussion document, distributed prior to the meeting, examined the intended and unintended consequences of ocean fertilization and postulated the scale where a project would not cause irreversible and unacceptable harm to an open-ocean ecosystem. The document also examined the Draft Assessment Framework and considered priority areas for future research. There was consensus that fertilization experiments to date increase our understanding of ocean ecosystems and biogeochemical cycles, but provide little insight into the consequences of widespread ocean fertilization on the ocean system and global climate. Future scientific research on ocean fertilization should have both temporal and spatial restrictions and should focus on improving our understanding of ocean processes, not the viability of geoengineering. The Draft Assessment Framework was viewed as an acceptable mechanism for regulating scientific research in the open oceans. The Science Advisory Report 2010/012, "OCEAN FERTILIZATION: Mitigating Environmental Impacts of Future Scientific Research" was a product of this meeting.
GALBRAITH, P.S., R.G. PETTIPAS, J. CHASSÉ, D. GILBERT, P. LAROUCHE, B. PETTIGREW, A. GOSSELIN, L. DEVINE, C. LAFLEUR, 2010. Physical Oceanographic Conditions in the Gulf of St. Lawrence in 2009 Conditions docéanographie physique dans le golfe du Saint-Laurent en 2009. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2010/035, 77 p .
An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2009 is presented. Air temperatures were close to normal when averaged from January to March. Air temperatures were in general either normal or above normal for the remainder of the year. The monthly averaged freshwater runoff measured at Québec City was normal overall in 2009 but consisted of aboveaverage runoff in July compensated later by lower runoff in the fall. Near-surface water temperatures in the Gulf were above normal in all regions except the Northwest Gulf and the Estuary in June and in every region in August. Maximum sea-ice volume within the Gulf and on the Scotian Shelf was 65 km³, a value that is below normal using updated ice volume estimates for 1971-2000. The duration of the 2008-09 ice season was longer than normal in the Estuary, normal in the central Gulf and Cabot Strait, and shorter elsewhere. This was mostly associated with the variability of the first occurrence of ice. Winter inflow of cold and saline water from the Labrador Shelf occupied the Mécatina Trough over the entire column in winter 2009. The spread of the intrusion was confined a bit closer to the coast compared to 2008 conditions, leading to an overall smaller volume of 1270 km³, which is similar to the 2002 observations. The winter cold mixed layer volume in the Gulf, excluding the Estuary, was 14 000 km³, a value higher than the 19962009 average by 0.7 SD. This cold-water volume corresponded to 42% of the total water volume of the Gulf. The cold intermediate layer (CIL) index for summer 2009 was -0.42°C, which is similar to observations in 2002, 2004, 2005 and 2007. This is an increase of 0.32°C since 2008. On the Magdalen Shallows, almost none of the bottom area was covered by water with temperatures < 0°C in September 2009, similar to conditions in 2005, 2006 and 2007. Regional patterns of the August and September CIL show that the layers for T < 1°C and < 0°C were much thinner in most parts of the Gulf in 2009 than in 2008 and had a generally higher core temperature everywhere. In the northern Gulf, the area covered by low temperature water (< 1°C) decreased in 2009 relative to 2008 conditions. Temperatures in March 2009 were characterized by a very thick cold layer, including a thick intrusion of Gulf CIL waters into the Estuary. By June 2009, CIL temperatures returned to normal with a warming trend that continued into August, especially on the Magdalen Shallows. By OctoberNovember, CIL conditions were normal in most regions except the estuary and Northwest Gulf, where the CIL and the surface mixed layer were anomalously deep. Overall, temperature and salinity were generally normal from 150 m to 200 m, and slightly lower than normal at 250 and 300 m. Temperature and salinity at 300 m decreased for a third consecutive year, from 2008 to 2009. The lower-than-normal Gulf-wide water temperatures at 300 m were composed of normal waters in the Estuary and northwest and colder waters in the centre and coming into the Gulf at Cabot Strait. This cold anomaly has propagated inward in the last few years and is expected to continue toward the Estuary during the next few years.
CHRISTIAN, J., A. PENA, K. DENMAN, D. GILBERT, P. LYON, 2010. Information in support of Science Advisory Report (SAR) 2010/012 : «Ocean Fertilization : Mitigating Environmental Impacts of Future Scientific Research» ; Information à l'appui de lavis scientifique (AS) 2010/012 : «Fertilisation des océans : atténuation des impacts environnementaux de la recherche scientifique». DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2010/106, 23 p .
Various geoengineering schemes are being proposed to decrease the rate of global warming associated with the buildup of greenhouse gases from human activities. Ocean fertilization attempts to sequester more carbon dioxide from the atmosphere in the ocean interior by adding nutrients to the ocean to stimulate growth of phytoplankton. Phytoplankton convert carbon dioxide to organic matter, which can settle into the subsurface ocean to remain sequestered for decades or centuries. The London Convention/London Protocol (LC/LP) is the global body with authority to regulate ocean fertilization. In 2008, the Scientific and Legal Working Groups of the LC/LP recommended proceeding toward regulation of the activity, and proposed that Parties agree to the concept of regulation such that commercially driven activities are prohibited. This document reviews the state of the science of ocean fertilization and its impacts in support of Canadian Science Advisory Secretariat Science Advisory Report 2010/012. The Report addresses four questions: (1) What are the most significant deleterious intended and unintended consequences of ocean fertilization and what is the level of scientific confidence regarding their impacts? (2) Is there sufficient knowledge to determine at what scale a project would likely not cause irreversible and unacceptable harm to an ecosystem? If so, what are the criteria that would define the upper limit of such a project? (3) Is the Conventions Draft Assessment Framework adequate for assessing scientific research proposals involving ocean fertilization? (4) What are the most pressing or most important research areas on ocean fertilization? The report considers both the scientific basis for regulation of ocean fertilization and the impact of regulation on scientific research. This supporting Research Document presents a more extensive and technical review of the supporting scientific literature.
THIBODEAU, B., M.F. LEHMANN, J. KOWARSYK, A. MUCCI, Y. GÉLINAS, D. GILBERT, R. MARANGER, M. ALKHATIB, 2010. Benthic nutrient fluxes along the Laurentian Channel : impacts on the N budget of the St. Lawrence marine system. Estuar. Coast. Shelf Sci., 90: 195-205 .
Water column concentrations and benthic fluxes of dissolved inorganic nitrogen (DIN) and oxygen (DO) were measured in the Gulf of St. Lawrence and the Upper and Lower St. Lawrence Estuary (USLE and LSLE, respectively) to assess the nitrogen (N) budget in the St. Lawrence (SL) system, as well as to elucidate the impact of bottom water hypoxia on fixed-N removal in the LSLE. A severe nitrate deficit, with respect to ambient phosphate concentrations (N*˜ -10 μmol L-1), was observed within and in the vicinity of the hypoxic bottom water of the LSLE. Given that DO concentrations in the water column have remained above 50 μmlol L-1, nitrate reduction in suboxic sediments, rather than in the water column, is most likely responsible for the removal of fixed N from the SL system. Net nitrate fluxes into the sediments, derived from pore water nitrate concentration gradients, ranged from 190 μmol m-2 d-1 in the hypoxic western LSLE to 100 mmol m-2 d-1 in the Gulf. The average total benthic nitrate reduction rate for the Laurentian Channel (LC) is on the order of 690 μmol m -2 d -1, with coupled nitrification-nitrate reduction accounting for more than 70%. Using average nitrate reduction rates derived from the observed water column nitrate deficit, the annual fixed-N elimination within the three main channels of the Gulf of St. Lawrence and LSLE was estimated at 411 × 106 t N, yielding an almost balanced N budget for the SLmarine system. ©2010 Elsevier Ltd.
GILBERT, D., P. CUMMINS, 2009. Preface : The interacting scales of ocean dynamics : a tribute to Chris Garrett ; Préface : Les échelles d'intéraction de la dynamique océanique : un hommage à Chris Garrett. Atmos.-Ocean, 47(4): 1-4 .
MacCRACKEN, M., E. ESCOBAR-BRIONES, D. GILBERT, G. KOROTAEV, W. NAQVI, G.M.E. PERILLO, T. RIXEN, E. STANEV, B. SUNDBY, H. THOMAS, D. UNGER, E.R.Jr. URBAN, 2009. Vulnerability of semi-enclosed marine systems to environmental disturbances. Pages 9-29 in E.R. Jr. Urban, B. Sundby, P. Malanotte-Rizzoli, & J. Mellilo (eds.). Watersheds, bays, and bounded seas : the science and management of semi-enclosed marine systems. Island Press (Scientific Committee on Problems of the Environment (SCOPE) series,70) .
FENNEL, W., D. GILBERT, J. SU, 2009. Physical processes in semi-enclosed marine systems. Pages 97-114 in E.R. Jr. Urban, B. Sundby, P. Malanotte-Rizzoli, & J. Mellilo (eds.). Watersheds, bays, and bounded seas : the science and management of semi-enclosed marine systems. Island Press (Scientific Committee on Problems of the Environment (SCOPE) series,70) .
RABALAIS, N.N., D. GILBERT, 2009. Distribution and consequences of hypoxia. Pages 209-225 in E.R. Jr. Urban, B. Sundby, P. Malanotte-Rizzoli, & J. Mellilo (eds.). Watersheds, bays, and bounded seas : the science and management of semi-enclosed marine systems. Island Press (Scientific Committee on Problems of the Environment (SCOPE) series,70) .
KEMP, W.M., J.M. TESTA, D.J. CONLEY, D. GILBERT, J.D. HAGY, 2009. Temporal responses of coastal hypoxia to nutrient loading and physical controls. Biogeosciences, 6(12): 2985-3008 .
The incidence and intensity of hypoxic waters in coastal aquatic ecosystems has been expanding in recent decades coincident with eutrophication of the coastal zone. Worldwide, there is strong interest in reducing the size and duration of hypoxia in coastal waters, because hypoxia causes negative effects for many organisms and ecosystem processes. Although strategies to reduce hypoxia by decreasing nutrient loading are predicated on the assumption that this action would reverse eutrophication, recent analyses of historical data from European and North American coastal systems suggest little evidence for simple linear response trajectories. We review published parallel time-series data on hypoxia and loading rates for inorganic nutrients and labile organic matter to analyze trajectories of oxygen (O2) response to nutrient loading. We also assess existing knowledge of physical and ecological factors regulating O2 in coastal marine waters to facilitate analysis of hypoxia responses to reductions in nutrient (and/or organic matter) inputs. Of the 24 systems identified where concurrent time series of loading and O2 were available, half displayed relatively clear and direct recoveries following remediation. We explored in detail 5 well-studied systems that have exhibited complex, non-linear responses to variations in loading, including apparent "regime shifts". A summary of these analyses suggests that O2 conditions improved rapidly and linearly in systems where remediation focused on organic inputs from sewage treatment plants, which were the primary drivers of hypoxia. In larger more open systems where diffuse nutrient loads are more important in fueling O2 depletion and where climatic influences are pronounced, responses to remediation tended to follow non-linear trends that may include hysteresis and time-lags. Improved understanding of hypoxia remediation requires that future studies use comparative approaches and consider multiple regulating factors. These analyses should consider: (1) the dominant temporal scales of the hypoxia, (2) the relative contributions of inorganic and organic nutrients, (3) the influence of shifts in climatic and oceanographic processes, and (4) the roles of feedback interactions whereby O2-sensitive biogeochemistry, trophic interactions, and habitat conditions influence the nutrient and algal dynamics that regulate O2 levels. ©2009 European Geosciences Union
FREELAND, H., D. GILBERT, 2009. Estimate of the steric contribution to global sea level rise from a comparison of the WOCE one-time survey with 2006-2008 argo observations. Atmos.-Ocean, 47(4): 292-298 .
It is well known from observations by altimetric satellites (predominantly TOPEX/Poseidon and Jason-1) that global sea level is rising. What is less well known is exactly how the observed sea level rise is partitioned between a steric contribution (sea level rising because of changes in ambient temperature and salinity) and a contribution arising from the addition of new water mass to the oceans. Strictly speaking, such a separation is not possible because of the non-linearity in the equation of state for sea water, but in practice the non-linearities are sufficiently small to allow this separation as a very good first approximation. A careful comparison of the World Ocean Circulation Experiment (WOCE) one-time survey with recent observations by the Argo array indicate a steric component to sea level rise of 2.2 mm y-1 between the early 1990s and 2006 to 2008. This is a significantly larger rise rate than previously estimated and, along with recent estimates of melt rate from ice sheets, is in much closer agreement with the total rise rate as reported by altimetric satellites, 3.2 ± 0.4 mm y-1 over this period.©2009 Canadian Meteorological and Oceanographic Society
LEHMANN, M.F., B. BARNETT, Y. GÉLINAS, D. GILBERT, R.J. MARANGER, A. MUCCI, B. SUNDBY, B. THIBODEAU, 2009. Aerobic respiration and hypoxia in the Lower St. Lawrence Estuary : stable isotope ratios of dissolved oxygen constrain oxygen sink partitioning. Limnol. Oceanogr., 54(6): 2157-2169 .
We measured the concentration and the stable isotope ratios of dissolved oxygen in the water column in the Estuary and Gulf of St. Lawrence to determine the relative importance of pelagic and benthic dissolved oxygen respiration to the development of hypoxic deep waters. The progressive landward decrease of dissolved oxygen in the bottom waters along the axis of the Laurentian Channel (LC) is accompanied by an increase in the 18O:16O ratio, as would be expected from O-isotope fractionation associated with bacterial oxygen respiration. The apparent O-isotope effect, εO-app, of 10.8 ‰ reveals that community O-isotope fractionation is significantly smaller than if bacterial respiration occurred solely in the water column. Our observation can best be explained by a contribution of benthic O2 consumption occurring with a strongly reduced O-isotope effect at the scale of sediment–water exchange (εO-sed ˜ 7 ‰). The value for εO-sed was estimated from benthic O2 exchange simulations using a one-dimensional diffusion-reaction O-isotope model. Adopting this εO-sed value, and given the observed community O-isotope fractionation, we calculate that approximately two thirds of the ecosystem respiration occurs within the sediment, in reasonable agreement with direct respiration measurements. Based on the difference between dissolved oxygen concentrations in the deep waters of the Lower St. Lawrence Estuary and in the water that enters the LC at Cabot Strait, we estimate an average respiration rate of 5500 mmol O2 m-2 yr-1 for the 100-m–thick layer of bottom water along the LC, 3540 mmol O2 m-2 yr-1 of which is attributed to bacterial benthic respiration.©2009 American Society of Limnology and Oceanography inc.
GALBRAITH, P., R.G. PETTIPAS, J. CHASSÉ, D. GILBERT, P. LAROUCHE, B. PETTIGREW, A. GOSSELIN, L. DEVINE, C. LAFLEUR, 2009. Physical oceanographic conditions in the Gulf of St. Lawrence in 2008 ; Conditions docéanographie physique dans le golfe du Saint-Laurent en 2008. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2009/014, 73 p .
An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2008 is presented. Air temperatures were close to normal when averaged from January to March, contributing to an ice cover volume that was also close to the climatological mean. Air temperatures were in general either normal or above normal for the remainder of the year. The monthly averaged freshwater runoff measured at Québec City was normal overall in 2008, but consisted of above-average runoff in summer compensated later by lower runoff in the fall. The high summer runoff contributed to higher-than-normal stratification. Near-surface water temperatures were generally above normal throughout the Gulf for the months of May, July and November and were also above-normal on the Magdalen Shallows in June and in the northern Gulf from August to October. In August the northern parts of the Gulf saw positive anomalies while the southern parts experienced negative anomalies. This lead to the unusual occurrence that the waters around Prince Edward Island and in Northumberland Strait had higher temperature in July than in August 2008. On the Magdalen Shallows, a large area of the bottom was covered by water with temperatures < 0 °C in September 2008, similar to the cold period observed in the 1990s and in contrast to conditions in September 2005, 2006 and 2007 when such cold waters were not observed. Maximum sea-ice volume within the Gulf and on the Scotian Shelf was 81 km3, a value now considered about normal using updated ice volume estimates for 1971-2000. Ice first appeared early in the season and stayed later than normal (later by about 8 days later on the Magdalen Shallows). Winter inflow of cold and saline water from the Labrador Shelf occupied the Mécatina Trough from top to bottom in winter 2008. The spread of the intrusion was confined a bit closer to the coast compared to 2007 conditions, leading to an overall smaller volume of 1850 km3, which is similar to 2001 and 2006 observations. The winter cold mixed layer volume was 13 700 km3, a value higher than the 1996–2008 average by 0.8 SD, and corresponded to 41 % of the total water volume of the Gulf. The summer CIL (cold intermediate layer) index for 2008 was -0.70 °C, comparable to the very cold conditions observed in 2003 and a large decrease (by 0.47 °C) from the previous summer. Regional patterns of the August and September CIL show that the layers for T < 1 °C and < 0 °C were much thicker in most parts of the Gulf in 2008 than in 2007 and had a generally lower core temperature throughout the Gulf. In the Northern Gulf, the area covered by water of low temperature (from < -1 °C through < 1 °C) increased in August 2008 relative to August 2007. Temperatures in the water column in June 2008 were characterized by a very thick and cold CIL in most regions except the Estuary and by warm deep waters in the Estuary and the northwest Gulf. This overall pattern persisted in the August– September mean conditions. By October and into November, CIL conditions were still thick and cold, while waters above the CIL were anomalously warm. Overall, temperature and salinity were generally normal from 150 m to 300 m, with the exception of slightly lower than normal (by 0.6 SD) temperature at 150 m. Temperature and salinity in this depth range decreased for a second consecutive year. The near-normal Gulf-wide water temperatures at 300 m were composed of warmer waters in the Estuary, near-normal temperatures in the northwest and central, and colder waters flowing into the Gulf at Cabot Strait.
GILBERT, D., É. NAULT, 2008. Temperature, Salinity and Oxygen Measurements from Argo Profiling Floats in the Slope Water Region. AZMP Bull. PMZA, 7: 47-52 .
[Abstract only available in French]
Le programme Argo de suivi du climat océanique mondial permet lacquisition en temps réel de profils verticaux de température et de salinité entre 2000 m de profondeur et la surface. Parmi les quelques 3000 flotteurs-profileurs Argo déployés dans locéan mondial, près dune centaine sont équipés de senseurs doxygène et cinq de ceux-ci ont été déployés dans les eaux de la pente continentale au sud de Terre-Neuve et de la Nouvelle-Écosse. Dans cet article, nous présentons des statistiques de température, salinité et oxygène, dans la région comprise entre les latitudes 35°N et 48°N et entre les longitudes 45°O et 75°O, calculées à partir de l'ensemble des données recueillies par les flotteurs-profileurs Argo de 1998 à 2007.
GALBRAITH, P.S., D. GILBERT, R.G. PETTIPAS, J. CHASSÉ, C. LAFLEUR, B. PETTIGREW, P. LAROUCHE, L. DEVINE, 2008. Physical oceanographic conditions in the Gulf of St. Lawrence in 2007 ; Conditions d'océanographie physique dans le golfe Saint-Laurent en 2007. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2008/001, 59 p .
An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2007 is presented. Air temperatures ranged from normal to cooler than normal for most of the year in the western parts of the Gulf; however, the eastern regions were only significantly cooler than normal in April and May. Averaged over the whole Gulf for the entire year, air temperature was normal. The monthly averaged runoff at Québec City was below normal during all months of 2007. Near-surface water temperatures were much cooler in 2007 overall than in 2006 in all regions of the Gulf. Near-surface waters were warm in the St. Lawrence Estuary in January and February. Summer maximum surface temperatures occurred earlier than usual, followed by earlier-than-usual cooling. Surface temperatures were generally below normal for the rest of the year except for October in the Estuary. On the Magdalen Shallows, there was (almost) no bottom area covered by water with temperatures <0 °C in September 2007. Maximum sea-i ce volume within the Gulf and on the Scotian Shelf was below normal but still much higher than the volume recorded in 2006. Winter inflow of cold and saline water from the Labrador Shelf occupied the Mecatina Trough from top to bottom. The spread of the intrusion had an area similar to that of 2006, but its volume was much larger and similar to that observed in 2004. The winter cold mixed layer volume was 13100 km3, slightly above the 1996-2007 average, and corresponded to 39 % of the total water volume of the Gulf. The higher winter volume of cold water compared with 2006 conditions led to a decrease of 0.44 °C in the Cold Intermediate Layer (CIL) index, reaching -0.23 °C in summer 2007, which is comparable to conditions observed in 2004. The index saw a large decrease after three consecutive years of warming. Regional patterns of the CIL show that the layer for T < 1 °C and < 0 °C was much thicker in the northern half of the Gulf in 2007 than in 2006 and had a generally lower core temperature almost everywhere as well. Seasonal and regional patterns of water column temperatures in June were generally close to the 1971-2000 climatology at all depths, except for the very thick and cold CIL in the Anticosti Channel and warm deep waters in the northwest. This overall pattern persisted from August to September, but by late fall conditions were about normal everywhere except for the anomalously warm nearsurface mixed layers in the northwest and warm near-surface waters on the Magdalen Shallows and in Cabot Strait. Averaged annually for the entire Gulf, the temperature and salinity from 150 m to 300 m were normal in 2007. Spatially, at 300 m, this was composed of warmer than normal waters near the Estuary, near-normal temperatures in the centre and colder than normal waters coming into the Gulf at Cabot Strait. The outlook for 2008 from the March 2008 survey is for a slight cooling of the CIL index to -0.47 °C resulting from a thicker cold winter surface layer.
CRAIG, J., D. GILBERT, 2008. Estimation of Mixed Layer Depth at the AZMP Fixed Stations. AZMP Bull. PMZA, 7: 37-42 .
[Abstract only available in French]
Nous examinons des données récoltées aux sept stations fixes du Programme de Monitorage de la Zone Atlantique afin de comparer des méthodes destimation de la profondeur de la couche mélangée (Mixed layer depth, MLD). Ces sites sont diversifiés du point de vue océanographique, géographique et des facteurs climatiques qui les affectent et fournissent donc dexcellents contrastes pour évaluer la méthode du seuil, du gradient et une méthode mixte destimation du MLD. Nous avons trouvé que les estimations du MLD basées sur le maximum du gradient de densité étaient toujours plus élevées que celles obtenues par la méthode du seuil ou la méthode mixte du seuil du gradient. Malgré que ce résultat soit dû en partie au fait que la zone de mélange immédiatement au-dessus du milieu de la pycnocline soit incluse dans lestimation par la méthode du maximum du gradient, le cycle annuel plus marqué révélé par cette méthode en fait un indice plus robuste dans la perspective de relier les processus biologiques et physiques.
CHABOT, D., D. GILBERT, 2008. The impact of hypoxia on cod from the Baltic and the Gulf of St. Lawrence. ICES CM 2008/J:15, 23 p .
Both the Baltic Sea and the Gulf of St. Lawrence are characterised by low levels of dissolved oxygen (DO) below a halocline. When hydrographical conditions are favourable, salty oxygenated water from the North Sea flows into the deep basins of the Baltic. Between such events, oxygen levels are progressively depleted. During the last few decades, the frequency of inflows has decreased and eutrophication has increased oxygen consumption. As a result, young cod have been displaced to shallower waters whereas adult cod live in mid-water, on top of the most hypoxic or even anoxic water. Diet has changed and cod rely less on benthic prey, although it is not clear if this has resulted in a reduced energy intake. Worse, reproduction failure has become common as low salinity typical of the Baltic Sea surface water causes negative buoyancy in cod eggs, which sink into the severely hypoxic or anoxic deep waters and die. In the deep channels of the Gulf of St. Lawrence, water originating at the mouth of the Laurentian channel flows landward. DO averages 50-65 % sat. In the Cabot Strait and declines progressively towards the heads of the deep channels. Natural variability in the DO level at the mouth of the Laurentian Channel and possibly also eutrophication have resulted in a drop from about 40 % down to about 20 % sat. in the estuary. Cod have suffered habitat loss as a result, but the main impact appears to be a slowing of growth caused by a reduction of the metabolic scope.
OGUZ, T., D. GILBERT, 2007. Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960-2000: evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate-induced variations. Deep-Sea Res., Part I, Oceanogr. Res. Pap., 54: 220-242 .
Functioning of the Black Sea ecosystem has profoundly changed since the early 1970s under cumulative effects of excessive nutrient enrichment, strong cooling/warming, over-exploitation of pelagic fish stocks, and population outbreak of gelatinous carnivores. Applying a set of criteria to the long-term (1960-2000) ecological time-series data, the present study demonstrates that the Black Sea ecosystem was reorganised during this transition phase in different forms of topdown controlled food web structure through successive regime-shifts of distinct ecological properties. The Secchi disc depth, oxic-anoxic interface zone, dissolved oxygen and hydrogen sulphide concentrations also exhibit abrupt transition between their alternate regimes, and indicate tight coupling between the lower trophic food web structure and the biogeochemical pump in terms of regime-shift events. The first shift, in 1973-1974, marks a switch from large predatory fish to small planktivore fish-controlled system, which persisted until 1989 in the form of increasing small pelagic and phytoplankton biomass and decreasing zooplankton biomass. The increase in phytoplankton biomass is further supported by a bottom-up contribution due to the cumulative response to high anthropogenic nutrient load and the concurrent shift of the physical system to the cold climate regime following its _20-year persistence in the warm climate regime. The end of the 1980s signifies the depletion of small planktivores and the transition to a gelatinous carnivore-controlled system. By the end of the 1990s, small planktivore populations take over control of the system again. Concomitantly, their top-down pressure when combined with diminishing anthropogenic nutrient load and more limited nutrient supply into the surface waters due to stabilizing effects of relatively warm winter conditions switched the high production regime of phytoplankton to its background low production regime. The Black Sea regime-shifts appear to be sporadic events forced by strong transient decadal perturbations, and therefore differ from the multi-decadal scale cyclical events observed in pelagic ocean ecosystems under low-frequency climatic forcing. The Black Sea observations illustrate that eutrophication and extreme fishery exploitation can indeed induce hysteresis in large marine ecosystems, when they can exert sufficiently strong forcing onto the system. They further illustrate the link between the disruption of the top predators, proliferation of new predator stocks, and regime-shift events. Examples of these features have been reported for some aquatic ecosystems, but are extremely limited for large marine ecosystems. ©2006 Elsevier Ltd.
GILBERT, D., D. CHABOT, P. ARCHAMBAULT, B. RONDEAU, S. HÉBERT, 2007. Appauvrissement en oxygène dans les eaux profondes du Saint-Laurent marin : causes possibles et impacts écologiques. Naturaliste can., 131(1): 67-75 .
[Abstract only available in French]
Depuis les années 1930, les concentrations d'oxygène ont baissé de moitié dans l'estuaire maritime du Saint-Laurent, à 300 m de profondeur. Un accroissement de la proportion d'eau chaude et pauvre en oxygène du GulfStream, au détriment de la proportion d'eau froide et bien oxygénée du courant du Labrador, expliquerait entre la moitié et les deux tiers de la baisse. Parmi les autres facteurs naturels et anthropiques susceptibles d'expliquer le reste de la baisse d'oxygène, les plus probables impliquent un flux accru de matières organiques des eaux de surface vers les fonds marins, où leur décomposition augmente la consommation d'oxygène. Nous montrons notamment une faible tendance à la hausse des nitrates à Lauzon, depuis 1990. Certaines espèces d'animaux marins comme le turbot, la crevette nordique et les polychètes Myriochele et Ampharete sont très abondantes dans les zones les plus pauvres en oxygène de l'estuaire et du golfe du Saint-Laurent, tandis que d'autres espèces comme la morue en sont absentes. Le seuil de tolérance aux faibles teneurs d'oxygène varie donc d'une espèce à l'autre. Nous devrons améliorer nos connaissances à cet égard afin de mieux comprendre les conséquences de l'appauvrissement en oxygène sur la biodiversité et le fonctionnement de l'écosystème.©2007 La Société Provancher d'histoire naturelle du Canada
GALBRAITH, P.S., D. GILBERT, C. LAFLEUR, P. LAROUCHE, B. PETTIGREW, J. CHASSÉ, R.G. PETTIPAS, W.M. PETRIE, 2007. Physical oceanographic conditions in the Gulf of St. Lawrence in 2006 ; Conditions d'océanographie physique dans le golfe Saint-Laurent en 2006. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2007/024, 51 p .
An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2006 is presented. Air and surface water temperatures were above normal except for late summer in most parts of the Gulf. Bottom water temperatures on the Magdalen Shallows were unusually warm; no observations below 0 °C were recorded in September. The yearly total freshwater runoff at Québec City was normal but included an anomalous strong fall peak. Sea ice coverage and volume within the Gulf during the winter was the lowest recorded since 1969. The winter cold mixed layer volume was the smallest recorded in the 11 year history of the winter helicopter survey and corresponded to 29 % of the total water volume of the Gulf. This shallow winter mixed layer led to the CIL index for summer 2006 increasing to +0.21 °C. This is the warmest value since 1983, but only 0.1 °C warmer than in 2000 which was the second warmest. Regional patterns of the CIL minimum temperatures show that increases between 2005 and 2006 were more pronounced in the Laurentian Channel than elsewhere. The minimum temperature actually decreased in Mecatina Trough, presumably due to the increased inflow of a thick layer of cold and highly saline water, which was observed from the annual March survey, through the Strait of Belle Isle. Regional patterns similar to those found for the CIL minimum temperatures were seen in the regional CIL thickness distribution. The CIL volume (T <1 °C) for the Magdalen Shallows during the September groundfish survey was the lowest since 1982. Water temperatures were generally one standard deviation above the mean, based on the 1971-2000 climatology at all depths for most of the year. Exceptions to this included the CIL in Esquiman Channel and Mecatina Trough and the deeper waters (>300 m) of the southern half of the Laurentian Channel which were colder. The most noteworthy thermal features in November were the anomalously deep CIL in the Estuary and northwestern Gulf regions and the anomalously warm waters above the CIL everywhere in the Gulf. The outlook for 2007 based on the March 2007 survey is for a 0.6 °C cooling of the summer CIL index forecast from a thicker winter cold surface layer and increased inflow of Labrador Shelf water through the Strait of Belle Isle.
SAINTE-MARIE, B., R. DUFOUR, L. BOURASSA, D. CHABOT, M. DIONNE, D. GILBERT, A. RONDEAU, J.-M. SÉVIGNY, 2005. Critères et proposition pour une définition des unités de production du crabe des neiges (Chionoecetes opilio) dans l'estuaire et le nord du golfe du Saint-Laurent ; Criteria and proposition for the definition of snow crab (Chionoecetes opilio) production units in the estuary and northern Gulf of St. Lawrence. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2005/059, 20 p .
The current borders of snow crab management areas in the Department of Fisheries and Oceans (DFO) Québec region are not based on biological or oceanographical criteria and some times enclose territories with very different characteristics. As noted by the FRCC (2005), there is a need to define biological production units to better monitor the status and ensure conservation of populations. Toward that goal, we conducted a literature review and used trawl data from the Gulf of Saint Lawrence to identify the biological and physical factors that constrain the distribution and dispersal of snow crab. This information allows us to characterize snow crab habitat, which can be defined as a territory with bottoms of soft sediments, bathed by waters with a salinity > 26 ‰, part of which is at a temperature of 0-2 °C and the remainder at a temperature varying from about -1.5 to 4 °C. The surface waters above this territory must generally have a salinity > 26 ‰ and warm up to 5-15 °C for several weeks for larvae to survive and grow. Snow crab larvae can disperse themselves over long distances and this may explain the weak genetic differentiation of populations within the Gulf. However, the various benthic stages generally have a much smaller dispersal capability. We describe the criteria used to define biological production units and on that basis we propose to divide the territory under the responsibility of DFO-Québec into seven units.
PEPIN, P., B. PETRIE, J.-C. THERRIAULT, S. NARAYANAN, G. HARRISON, J. CHASSÉ, E. COLBOURNE, D. GILBERT, D. GREGORY, M. HARVEY, G. MAILLET, M. MITCHEL, M. STARR, 2005. The Atlantic Zone Monitoring Program (AZMP) : review of 1998-2003. Can. Tech. Rep. Hydrogr. Ocean Sci., 242, 87 p .
We outline the results of the self-assessment by the Atlantic Zone Monitoring Program (AZMP) based on the milestrones set out in the original proposal and on a series of key issues identified during the Fifth Annual General Meeting of the Atlantic Zone Monitoring Program and supported by the Atlantic Science Directors. The report is divided into 12 sections which aim at providing an overview of the program's accomplishments, progress to date as well as identifying key concerns about maintaining current program activities and future developments. The report is capped with four sections that outline some of the benefits in the understanding and predictability of marine systems that have been derived from continued long-term monitoring activities.
GILBERT, D., B. SUNDBY, C. GOBEIL, A. MUCCI, G.-H. TREMBLAY, 2005. A seventy-two-year record of diminishing deep-water oxygen in the St. Lawrence estuary: the northwest Atlantic connection. Limnol. Oceanogr., 50(5): 1654-1666 .
Oxygen concentrations in the bottom waters of the Lower St. Lawrence estuary (LSLE) decreased from 125 αmol L-1 (37.7 % saturation) in the 1930s to an average of 65 αmol L-1 (20.7 % saturation) for the 1984-2003 period. A concurrent 1.65 °C warming of the bottom water from the 1930s to the 1980s suggests that changes in the relative proportions of cold, fresh, oxygen-rich Labrador Current Water (LCW) and warm, salty, oxygen-poor North Atlantic Central Water (NACW) in the water mass entering the Laurentian Channel probably played a role in the oxygen depletion. We estimate that about one half to two thirds of the oxygen loss in the bottom waters of the LSLE can be attributed to a decreased proportion of LCW. This leaves between one third and one half of the oxygen decrease to be explained by causes other than changes in water mass composition. An increase in the along-channel oxygen gradient from Cabot Strait to the LSLE over the past decades, combined with data from sediment cores, suggests that increased sediment oxygen demand may be partly responsible for the remainder of the oxygen decline. In July 2003, approximately 1,300 km2 of seafloor in the LSLE was bathed in hypoxic water (<62.5 αmol L-1).©2005 The American Society of Limnollogy and Oceanography
GILBERT, D., 2004. State of the ocean 2003: physical oceanographic conditions in the Gulf of St. Lawrence. Science, Ecosystem Status Report, 2004/002, 8 p .
GILBERT, D., 2004. Temperature and salinity data from the 2003 summer shrimp and groundfish survey in the Gulf of St. Lawrence. In Fisheries and Oceans Canada. St. Lawrence Observatory. Publication Directory [Online]. http://www.osl.gc.ca/en/info/publications/missions-needler/needler2003ctd_en.html (Pages accessed on February 25, 2008) .
GILBERT, D., 2004. Température et salinité pendant la mission estivale d'évaluation des stocks de crevette et poissons de fond dans le golfe du Saint-Laurent en 2003. In Ministère des pêches et des océans. Observatoire du Saint-Laurent. Répertoire de publications [En ligne]. http://www.osl.gc.ca/fr/info/publications/missions-needler/needler2003ctd_fr.html (Pages consultées le 25 février 2008) .
HARRISON, G., E. COLBOURNE, D. GILBERT, B. PETRIE, 2004. Oceanographic observations and data products derived from large-scale fisheries resource assessment and environmental surveys in the Atlantic zone. AZMP Bull. PMZA, 4: 17-23 .
[Abstract only available in French]
Les grands relevés standard dévaluation de poissons pélagiques,démersaux et dinvertébrés commerciaux,ainsi que de plancton (krill) et des variables environnementales comme la température et la salinité, plusieurs en cours depuis le début des années 1970, sont les principales sources de données qui sont utilisées par le PMZA pour caractériser la variabilité spatiale des propriétés océanographiques (physique, biologique et chimique) dans la zone Atlantique. Approximativement 2,500 stations et sites de pêche sont échantillonnés annuellement.Dans le passé, les propriétés hydrographiques (température, salinité et densité) étaient les plus communément mesurées mais des mesures biologiques (abondance du plancton et chlorophylle) et chimiques (oxygène et sels nutritifs) ont été ajoutées à plusieurs missions depuis que le PMZA a débuté en 1999. En plus de fournir des estimations de la variabilité spatiale des conditions océanographiques des régions surveillées,plusieurs produits de données à valeur ajoutée sont générés de façon routinière pour caractériser lhabitat océanographique.Parmi les produits basés sur la surface couverte, on note la température du fond (i.e., lindex thermal de lhabitat ou «Thermal Habitat Index») et la saturation des eaux du fond en oxygène. Parmi les produits de données basés sur le volume,on note la CIF (couche intermédiaire froide) pour le golfe du Saint-Laurent,les indices de masse deau basés sur les propriétés de température et de salinité, les indices de stratification de la colonne deau et les patrons spatiaux de la structure verticale du phytoplancton (la fluorescence). Les nouvelles applications en cours incluent les efforts pour lier le forçage à grande échelle de la météorologie (e.g., indice ONA ou «NAO») aux habitats et à la distribution des poissons.
GILBERT, D., P.S. GALBRAITH, C. LAFLEUR, B. PETTIGREW, 2004. Physical Oceanographic Conditions in the Gulf of St. Lawrence in 2003 ; Conditions docéanographie physique dans le golfe Saint-Laurent en 2003. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2004/061, 63 p .
An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2003 is presented. Air temperatures and surface water temperatures were below normal in winter and above normal in the fall. During winter 2003, sea ice coverage within the Gulf was about 10 % above the long-term mean, the first year above normal since 1995. But of more significance, a record amount of ice was advected out of the Gulf through Cabot Strait during winter 2003, and the total volume of ice formation in the Gulf was much higher than normal. Moreover, the inflow of water through the Strait of Belle Isle in the northeast Gulf was by far the largest one observed over the 9-year period of helicopter CTD surveys conducted in March. This inflow of cold and salty water from Belle Isle Strait together with the large amount of ice produced in the Gulf in the winter of 2003 caused a huge increase in the summertime thickness and volume of T < 0 °C waters (+300 %) and T < 1 °C waters (+40 %) relative to 2002. This was accompanied by a 0.65 °C drop in the cold intermediate layer minimum temperature index which is now 0.54 °C below the 1971-2000 normal conditions and the fifth coldest in 57 years. The annual mean runoff of the St. Lawrence River at Québec City was 13.4 % below normal. This led to above normal surface salinities and below normal surface layer stratification during most of 2003. In the 30-100 m layer, the 2003 temperature was colder than normal while salinity was higher than normal. In the 100-200 m layer, the 2003 temperature was colder than normal but salinity was close to normal. Finally, in the 200-300 m layer, both temperature and salinity were close to normal. The 2003 annual mean oxygen concentration in the bottom waters (≥ 300 m) of the Lower St. Lawrence Estuary (18.3% saturation) was the second lowest ever observed.
DRINKWATER, K.F., D. GILBERT, 2004. Hydrographic Variability in the Waters of the Gulf of St. Lawrence, the Scotian Shelf and the Eastern Gulf of Maine (NAFO Subarea 4) During 1991-2000. J. Northwest Atl. Fish. Sci., 34: 85-101 .
This paper examines the hydrographic variability within the Gulf of St. Lawrence, the Scotian Shelf and the eastern Gulf of Maine, including the Bay of Fundy, during the decade 1991-2000. Comparisons are made with previous decadal means to place the 1990s into a longer-term perspective. The 1990s decadal means of the near-surface salinity were the lowest ever recorded for the northern Gulf of St. Lawrence, the Scotian Shelf and the Bay of Fundy. These low salinities were advected into these regions from the Labrador and Newfoundland Shelves and led to record or near record high vertical stratification in the upper layers of the water column. Also during the 1990s, the decadal means of the temperature of the intermediate layer waters (approximately 30-150 m) were well below normal throughout the Gulf of St. Lawrence and over much of the Scotian Shelf. Similar low temperatures were first observed in the late 1980s and were mainly caused by advection from the Labrador and Newfoundland Shelves, although local atmospheric cooling also contributed. In the deep channels and basins of NAFO Subarea 4, near-bottom decadal mean temperatures were high and linked to the persistence of Warm Slope Water along the shelf break. A notable exception occurred in 1998 when Labrador Slope Water moved southward along the continental slope as far as the Middle Atlantic Bight, pushing the Warm Slope Water offshore. This much colder water subsequently penetrated onto the Scotian Shelf and into the Gulf of Maine resulting in the coldest conditions in the deep basins since the 1960s.
GILBERT, D., 2004. État de locéan en 2003 : océanographie physique dans le golfe du Saint Laurent. Rapport sur l'état des écosystèmes, 2004/002, 9 p .
GILBERT, D., 2003. Temperature and salinity data from the 2001 summer shrimp and groundfish survey in the Gulf of St. Lawrence. In Fisheries and Oceans Canada. St. Lawrence Observatory. Publication Directory [Online]. http://www.osl.gc.ca/en/info/publications/missions-needler/needler2001ctd_en.html (Pages accessed on February 25, 2008) .
DIONNE, M., B. SAINTE-MARIE, E. BOURGET, D. GILBERT, 2003. Distribution and habitat selection of early benthic stages of snow crab Chionoecetes opilio. Mar. Ecol. Prog. Ser., 259: 117-128 .
GILBERT, D., 2003. Température et salinité pendant la mission estivale d'évaluation des stocks de crevette et poissons de fond dans le golfe du Saint-Laurent en 2000. In Ministère des pêches et des océans. Observatoire du Saint-Laurent. Répertoire de publications [En ligne]. http://www.osl.gc.ca/fr/info/publications/missions-needler/needler2000ctd_fr.html (Pages consultées le 25 février 2008) .
GILBERT, D., 2003. Temperature and salinity data from the 1999 summer shrimp and groundfish survey in the Gulf of St. Lawrence. In Fisheries and Oceans Canada. St. Lawrence Observatory. Publication Directory [Online]. http://www.osl.gc.ca/en/info/publications/missions-needler/needler1999ctd_en.html (Pages accessed on February 25, 2008) .
GILBERT, D., 2003. 2002 state of the ocean : physical oceanographic conditions in the Gulf of St. Lawrence. Ecosystem Status Report, 2003/006, 8 p .
GILBERT, D., 2003. État de l'océan en 2002 : océanographie physique dans le golfe du Saint-Laurent. Rapport sur l'état des écosystèmes, 2003/006, 9 p .
GILBERT, D., 2003. Temperature and salinity data from the 2000 summer shrimp and groundfish survey in the Gulf of St. Lawrence. In Fisheries and Oceans Canada. St. Lawrence Observatory. Publication Directory [Online]. http://www.osl.gc.ca/en/info/publications/missions-needler/needler2000ctd_en.html (Pages accessed on February 25, 2008) .
GILBERT, D., 2003. Temperature and salinity data from the 2002 summer shrimp and groundfish survey in the Gulf of St. Lawrence. In Fisheries and Oceans Canada. St. Lawrence Observatory. Publication Directory [Online]. http://www.osl.gc.ca/en/info/publications/missions-needler/needler2002ctd_en.html (Pages accessed on February 25, 2008) .
SUNDBY, B., A. MUCCI, C. GOBEIL, D. GILBERT, Y. GRATTON, P. ARCHAMBAULT, 2002. Hypoxia in the Deep Waters of the Laurentian Trough, Lower St. Lawrence Estuary. Pages 29-31 in J.J. Martin (ed.). Developments for a Canadian GEOHAB (Global Ecology and Oceanography of Harmful Algal Blooms) program: 2001 Workshop report. Rapp. tech. can. sci. halieut. aquat., 2400 .
DUTIL, J.-D., M. CASTONGUAY, D. GILBERT, D. GASCON, 2002. Production analyses for cold-water and warm-water stocks and their use to predict surplus production. Pages 50-54 in N. Anderson, G. Ottersen & D. Swain (ed.). Report of the ICES/GLOBEC Workshop on the Dynamics of Growth in Cod. International Council for the Exploration of the Sea (ICES Coop. Res. Rep., 252 .
Surplus and net production per capita became nil or negative in the mid-1980s in the northern Gulf of St. Lawrence (Dutil et al., 1999). This situation was partly explained by a marked decline in growth production and is consistent with smaller sizes-at-age (Chouinard and Fréchet 1994) but also lower condition factor values during the same period (Lambert and Dutil 1997). The nutritional condition of cod in the Gulf of St. Lawrence varies markedly both seasonnally and annually (Lambert and Dutil 1997, Schwalme and Chouinard 1999) and this has been found to be associated with changes in swimming capacity (unpublished data), reproductive investment (Lambertet al., 2000, Lambert and Dutil 2000) and risks of natural mortality (Dutil and Lambert 2000; and unpublished data). Positive slopes between size-at-age and temperature suggested faster growth rates at higher temperatures for northern Gulf cod, but correlations between size-at-age and temperature were not significant (Dutil et al., 1999). Production analyses conducted for the northern Gulf of St. Lawrence were extended to other stocks. Growth production was assessed in order to determine its variability among and within stocks as a first step to measure its impact on the stock biomass.©2008 ICES
STARR, M., M. HARVEY, P.S. GALBRAITH, D. GILBERT, D. CHABOT, J.-C. THERRIAULT, 2002. Recent intrusion of Labrador Shelf waters into the Gulf of St. Lawrence and its influence on the plankton community and higher trophic levels. ICES C.M., 2002/N:16, 10 p .
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 2001. Overview of environmental conditions in the Northwest Atlantic in 2000. NAFO SCR Doc., 01/36, 84 p .
PLOURDE, J., D. GILBERT, 2001. La plus longue période froide de l'histoire climatique récente du golfe du Saint-Laurent. AZMP Bull. PMZA, 1: 18-19 .
A prominent feature of the water of the Gulf of St. Lawrence is the presence of a cold intermediate layer (CIL) that persists throughout the year. In summer, the cold intermediate layer (temperature below 2 degree C) is isolated from the atmosphere by the surface layer. In winter, the surface layer disapears and the cold layer extends to the surface. The fluctuations of the minimum temperature of the CIL largely reflect climate variability. During the year 2000, the minimum temperature of the CIL was above the long term average for the first time since 1983, ending the longest period observed in the Gulf of St. Lawrence since 1948.
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 2000. Overview of environmental conditions in the Northwest Atlantic in 1999. NAFO SCR Doc., 00/21, 87 p .
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 2000. Overview of environmental conditions in the Northwest Atlantic in 1998. NAFO Sci. Counc. Stud., 33: 39-87 .
DUTIL, J.-D., M. CASTONGUAY, D. GILBERT, D. GASCON, 2000. Production analyses for cold-water and warm-water stocks and their use to predict surplus production. Pages 61-65 in N.G. Andersen, G. Ottersen & D.P. Swain (ed.). Report of the ICES/GLOBEC workshop on the dynamics of growth in cod, Dartmouth, Canada, 8-10 May 2000 (ICES C.M., 2000/C:12) .
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 1999. Overwiew of environment conditions in the Northwest Atlantic in 1997. NAFO Sci. Counc. Stud., 32: 75-121 .
DUTIL, J.-D., M. CASTONGUAY, D. GILBERT, D. GASCON, 1999. Growth, condition, and environmental relationships in Atlantic cod (Gadus morhua) in the northern Gulf of St. Lawrence and implications for management strategies in the Northwest Atlantic. Can. J. Fish. Aquat. Sci., 56(10): 1818-1831 .
Northern Gulf of St. Lawrence Atlantic cod (Gadus morhua) is one of several stocks that collapsed in eastern Canada following a long period of intensive exploitation. Surplus and net production per capita became nil or negative in the mid-1980s so that any level of exploitation would have caused a decline of the stock. This was partly explained by a marked decline in growth production and is consistent with smaller sizes-at-age but also lower condition factor values during the same period. Correlations between size-at-age and temperature were not significant when corrected for autocorrelation, but slopes were always positive, suggesting higher growth rates at higher temperatures. Smaller sizes-at-age in the 1980s were not associated with changes in the fishery or increased fishing mortality, nor were they consistent with the density-dependence hypothesis. Lengths at age 8 decreased by more than 10 cm as the stock decreased 10-fold in abundance. While size-at-age and temperature covary in cod when all stocks are examined, size-temperature relationships are not as clear if the analysis is restricted to cold-water stocks, possibly because of differences in food availability. Biological production varies from year to year and among stocks and should be taken into consideration when managing fisheries in variable or extreme environments.
GILBERT, D., 1999. Oceanographic conditions in the Gulf of St. Lawrence in 1998 : physical oceanography. Science, Stock Status Report, G4-01, 7 p .
CASTONGUAY, M., C. ROLLET, A. FRÉCHET, P. GAGNON, D. GILBERT, J.-C. BRÊTHES, 1999. Distribution changes of Atlantic cod (Gadus morhua L.) in the northern Gulf of St. Lawrence in relation to an oceanic cooling. ICES J. Mar. Sci., 56: 333-344 .
GILBERT, D., 1999. Conditions océanographiques dans le golfe du Saint-Laurent en 1998 : océanographie physique. Rapport sur l'état des stocks, G4-01, 7 p .
GILBERT, D., 1998. Conditions océanographiques dans le golfe du Saint-Laurent en 1997. Rapport sur l'état des stocks, G4-01, 8 p .
GRÉGOIRE, F., D. GILBERT, 1998. La pêche au maquereau bleu (Scomber scombrus L.) dans les sous-régions 2 à 6 de l'OPANO pour 1997 ; The 1997 Atlantic mackerel (Scomber scombrus L.) fishery in NAFO subareas 2 to 6. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Stock Assessment Secretariat, Research Document, 98/98, 49 p .
Landings of Atlantic mackerel (Scomber scombrus L.) in the northwest Atlantic totalled 35,050 t in 1997. Of this volume, 16,475 t were taken in NAFO subareas 5 and 6 and 18,575 t in subareas 3 and 4. In the latter subarea, the highest catches were made in divisions 4T, 4X and 4R, with landings of 13,909 t, 1,985 t and 1,140 t respectively. The biggest landings were made on Prince Edward Island and in Quebec, with values of 6,111 and 5,442 t. The most important unit areas were 4Tf, 4Tl and 4Tg in division 4T and unit areas 4Rc and 4Xm in divisions 4R and 4X. Over 8,500 t were caught using handlines and jigs, close to 6,000 t by gillnets and approximately 3,000 t using traps. The three largest year-classes, or cohorts, were, in descending order, those of 1995, 1994 and 1996. They alone accounted for 62 % of all catches. The dominant cohort of 1988 was still present in 1997 and represented 8.51 % of the catches. As in recent years, the main comments made by the industry concerned the large regional year-to-year variations in mackerel landings. In the case of the seine fishing off the west coast of Newfoundland, water temperature seems to play a significant role in these variations.
SAINTE-MARIE, B., D. GILBERT, 1998. Possible effects of changes in CIL temperature and thickness on population dynamics of snow crab, Chionoecetes opilio, in the Gulf of Saint Lawrence. DFO, Canadian Stock Assessment Secretariat, Research Document, 98/38, 19 p .
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 1998. Overview of environmental conditions in the Northwest Atlantic in 1996. NAFO Sci. Counc. Stud., 31: 111-146 .
DUTIL, J.-D., M. CASTONGUAY, M.O. HAMMILL, P. OUELLET, Y. LAMBERT, D. CHABOT, H. BROWMAN, D. GILBERT, A. FRÉCHET, J.-A. GAGNÉ, D. GASCON, L. SAVARD, 1998. Environmental influences on the productivity of cod stocks : some evidence for the northern Gulf of St. Lawrence, and required changes in management practices. DFO, Canadian Stock Assessment Secretariat, Research Document, 98/18, 42 p .
GILBERT, D., 1997. Conditions océanographiques dans le golfe du Saint-Laurent en 1996. Rapport sur l'état des stocks, G4-01, 7 p .
GILBERT, D., 1997. Oceanographic conditions in the Gulf of St. Lawrence in 1996. Science, Stock Status Report, G4-01, 7 p .
GILBERT, D., B. PETTIGREW, 1997. Interannual variability (1948-1994) of the CIL core temperature in the Gulf of St. Lawrence. Can. J. Fish. Aquat. Sci., 54 (Suppl. 1): 57-67 .
The interannual variability (1948-1994) of the cold intermediate layer(CIL), defined here as the layer with T < 3 °C, was investigated for 6 subregions of the Gulf of St. Lawrence. First a mean annual cycle of CIL properties was calculated for the 6 subregions(the Estuary, the Northwest, Northeast, Central, and Southern Gulf, and Cabot Strait). The midsummer warming rates thus obtained were then used to construct time series of the CIL core temperature extrapolated to July 15, using all available data from May 1 to September 30 of each year. The important result is that the mid-summer CIL core temperature was below normal from 1986 to 1994, this cold period being most intense from 1990 to 1994. The time series of CIL core temperature was correlated with average winter air temperatures from several weather stations inside and outside the Gulf to try to distinguish between local and remote atmospheric forcing and obtained the highest correlations with weather stations from the west coast of Newfoundland.
GILBERT, D., A.F. VÉZINA, B. PETTIGREW, D.P. SWAIN, P.S. GALBRAITH, L. DEVINE, N. ROY, 1997. État du golfe du Saint-Laurent : conditions océanographiques en 1995. Rapp. tech. can. hydrogr. sci. océan., 191, 113 p .
We present an overview of the oceanographic conditions in the Gulf of St. Lawrence for 1995. The highlights are that 1) winter air temperatures were near normal in the western Gulf, but were close to 2 °C below normal in the eastern Gulf; 2) the summer was warm and dry in the western Gulf; 3) the ice cover was slightly above normal, with more severe ice conditions in the northeastern Gulf than in the western Gulf; 4) the core temperature of the cold intermediate layer was colder than normal; 5) the bottom area with a temperature below 0 °C reached a record high in the southern Gulf; 6) the deep layers cooled relative to 1994, and the cooling was more intense in he 100-200 m layer (O.9 °C) than in the 200-300m layer (0.3 °C); 7) the dissolved oxygen content of the 200-300 m layer was slightly below the 1981-1995 average in the Cabot Strait and Honguedo Strait sections; 8) the distribution of chlorophyll and nitrate in the surface layer corresponded roughly with the patterns inferred from historical data, i.e. a gradient of decreasing biomass from the West and south towards the east and north that is strongly inversely correlated with salinity; 9) in Northumberland Strait, the concentrations of chlorophyll near the bottom were much higher than elsewhere.
[Abstract only available in French]
La mer nest pas inépuisable. La chute des stocks de morue dans lest du Canada et les manchettes faisant état depuis quelques années des difficultés des pêcheurs aux deux extrémités du pays ont puissamment contribué à sensibiliser le grand public à la nécessité de mieux connaître le milieu marin, si lon veut en gérer les ressources durablement.©1997 Saint-Laurent Vision 2000
The authors present an overview of the physical oceanographic conditions in the Gulf of St. Lawrence for 1994, with special emphasis on the temperature and salinity profiles collected furing the August-September 1994 shrimp and groundfish survey. The main highlights for 1994 are that 1) winter air temperatures were below the 1961-1990 normal for the sixth consecutive year, 2) the ice cover was above the 1962-1987 median areal extent, 3) the cold intermediate layer was colder than normal for the ninth consecutive year, 4) intense upwelling occurred along Quebec's north shore during the month of August, as evidenced by the very cold surface temperatures, and 5) the deep layers (100-200 m and 200-300 m) warmed in the Gulf, except in Cabot Strait where the temperatures dropped by about 0.5 °C.
PETRIE, B., K. DRINKWATER, A. SANDSTRÖM, R. PETTIPAS, D. GREGORY, D. GILBERT, P. SEKHON, 1996. Temperature, salinity and sigma-t atlas for the Gulf of St. Lawrence. Can. Tech. Rep. Hydrogr. Ocean Sci., 178, 256 p .
We divide the Gulf of St. Lawrence into 21 subareas based primarily on the topography. For each area, we calculated the monthly means, standard deviations and extrema of temperature, salinity and sigma-t. We present the results as tables, time series plots at selected depths and contoured plots with time (depth) as the horizontal (vertical) axis. We used optimal estimation to calculate the temperature, salinity and sigma-t, distributions at 0, 30, 100, 150 m, and near bottom for the 15th of February, May, August and November corresponding to the winter, spring, summer and fall. In addition, we present the seasonal volumetric temperature and salinity distributions.
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 1996. Overview of environmental conditions in the Northwest Atlantic in 1995. NAFO Sci. Counc. Stud., 27: 1-37 .
DRINKWATER, K.F., E. COLBOURNE, D. GILBERT, 1996. Overview of environmental conditions in the Northwest Atlantic in 1994. NAFO Sci. Counc. Stud., 25: 25-58 .
GILBERT, D., B. PETTIGREW, 1996. Variations de la couche froide intermédiaire du golfe du Saint-Laurent de 1948 à 1995. Naturaliste can., 120(2): 69-70 .
GILBERT, D., 1996. Conditions océanographiques dans le golfe du Saint-Laurent en 1995. MPO, Pêches de l'Atlantique, Rapport sur l'état des stocks, 96/51, 7 p .
GILBERT, D., 1996. Oceanographic conditions in the Gulf of St. Lawrence in 1995. DFO, Atlantic Fisheries, Stock Status Report, 95/51, 7 p .
CASTONGUAY, M., D. GILBERT, 1995. Effects of tidal streams on migrating Atlantic mackerel, Scomber scombrus L. ICES J. Mar. Sci., 52: 941-954 .
GRATTON, Y., B. PETTIGREW, B. PELCHAT, D. GILBERT, M. COUTURE, J. LANDRY, 1994. Overview of the environmental conditions in the Gulf of St. Lawrence in 1993. DFO, Atlantic Fisheries, Research Document, 94/55, 45 p .
GILBERT, D., B. PETTIGREW, 1993. Current-meter data from Bonne Bay, Newfoundland, during the summer of 1991. Can. Data Rep. Hydrogr. Ocean Sci., 122, 63 p .
During the summer of 1991, eleven current-meters were deployed at four mooring sites near the mouth of Bonne Bay, a fjord on the west coast of Newfoundland. The means and standard deviations of the time series of temperature, salinity, density, and velocity components are given here, together with the main tidal constants obtained from harmonic analysis of the currents. Each time series and its corresponding low-passed time series are plotted. Wind data from Daniel's Harbour, located 80 km northeast of Bonne Bay, are also shown for comparison with the current-meter data.
GILBERT, D., 1993. A search for evidence of critical internal wave reflection on the continental rise and slope off Nova Scotia. Atmos.-Ocean, 31: 99-122 .
GILBERT, D., 1991. Vers des modèles couplés Océan-Atmosphère. Géosci. Can., 18(3): 109-110 .
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