St Lawrence River Research Articles

Were abrupt Lateglacial and early-Holocene climatic changes in northwest Europe linked to freshwater outbursts to the North Atlantic and Arctic Oceans?

During the Lateglacial and early Holocene, abrupt, millennial-scale climatic variations are recorded in a wide range of high-resolution proxy records from marine and terrestrial archives in NW Europe. Our review of the evidence for these rapid climate events do not show an apparent link to possible forcing factors such as long-term, orbitally induced variations in solar radiation, short-term variations in solar activity as inferred from 14C, atmospheric carbon dioxide concentration, or volcanic sulphate as recorded in the GISP2 ice-core record. There is, however, a remarkable degree of similarity with the number, duration and timing of episodes of increased flux of fresh water to the north Atlantic and Arctic Oceans from the Laurentide ice sheet and from the Baltic ice lake in SW Sweden. These freshwater outburst events occurred when continental runoff from the Laurentide ice sheet was rerouted from the Mississippi River to the Hudson River, St Lawrence River, Hudson Strait and along the Mackenzie River to the Atlantic and Arctic Oceans, and when the Baltic ice lake in SW Sweden drained to Skagerrak. Periods of increased freshwater flow to the North Atlantic and Arctic Oceans may thus provide a mechanism to explain the abrupt and significant Lateglacial and early Holocene climate events in NW Europe. The idea that freshwater outbursts might drive abrupt climate events is not new, but previous work may have underestimated the extent of support from proxy data and overestimated the influence of the Laurentide ice sheet.

Spring hunting changes the regional movements of migrating greater snow geese

Summary Human‐induced disturbance such as hunting may influence the migratory behaviour of long‐distance migrants. In 1999 and 2000 a spring hunt of greater snow geese Anser caerulescens atlanticus occurred for the first time in North America since 1916, aimed at stopping population growth to protect natural habitats. We evaluated the impact of this hunt on the staging movements of geese along a 600‐km stretch of the St Lawrence River in southern Quebec, Canada. We tracked radio‐tagged female geese in three contiguous regions of the staging area from the south‐west to the north‐east: Lake St Pierre, Upper Estuary and Lower Estuary, in spring 1997 (n = 37) and 1998 (n = 70) before the establishment of hunting, and in 1999 (n = 60) and 2000 (n = 59) during hunting. We used multi‐state capture–recapture models to estimate the movement probabilities of radio‐tagged females among these regions. To assess disturbance level, we tracked geese during their feeding trips and estimated the probability of completing a foraging bout without being disturbed. In the 2 years without hunting, migration was strongly unidirectional from the south‐west to the north‐east, with very low westward movement probabilities. Geese gradually moved from Lake St Pierre to Upper Estuary and then from Upper Estuary to Lower Estuary. In contrast, during the 2 years with hunting westward movement was more than four times more likely than in preceding years. Most of these backward movements occurred shortly after the beginning of the hunt, indicating that geese moved back to regions where they had not previously experienced hunting. Overall disturbance level increased in all regions in years with hunting relative to years without hunting. Synthesis and applications. We conclude that spring hunting changed the stopover scheduling of this long‐distance migrant and might further impact population dynamics by reducing prenuptial fattening. The spring hunt may also have increased crop damage. We propose that staggered hunt opening dates could attenuate secondary effects of such management actions.

Dissolve gaseous mercury distribution in a wetland: Influence of macrophyte beds

In wetlands, the presence of macrophytes and associated organisms may alter the redox chemistry of Hg, affecting the cycling of atmospheric Hg species at the air/water interface. As part of a contribution to the Collaborative Mercury Research Network (COMERN), we investigated the spatial distribution of dissolved gaseous mercury (DGM) in subsurface waters from the Baie St. Francois wetland, in the St Lawrence River DGM concentrations varied in different macrophyte beds and in macrophyte-free areas, ranging from 48.6 to 75.3 pg/L (1388-2151% saturation relative to atmospheric equilibrium). The highest DGM concentration was observed in the bed of Elodea canadensis, a submerged plant, and the lowest, in open areas. The results indicated that macrophyte beds may constitute a significant site for Hg reduction. Macrophytes may also interfere with the evasion of Hg to the atmosphere, by providing a shelter against wind and waves.

Exotic plant species of the St Lawrence River wetlands: a spatial and historical analysis

AbstractAim To evaluate the importance (number of species, plant cover) of the exotic flora in seven well‐defined sectors of one of the most important transportation waterways in North America. To determine the impact of exotic species on wetland plant diversity and reconstruct the spread of some invasive species.Location St Lawrence River, southern Québec.Methods The exotic flora (vascular plants) of wetlands bordering the St Lawrence River was studied using 713 sampling stations (25 m2) along a 560‐km long corridor.Results Exotic species represent 13.7% of the vascular flora of the St Lawrence wetlands. The relative plant cover occupied by exotic species is high in some of the fluvial sectors (42–44%), but low (6–10%) in the estuarine sectors. Wetlands (marshes) surrounding islands were particularly susceptible to invasion by exotic plants. Historical, abiotic and landscape factors may explain the differences observed between sites. Purple loosestrife (Lythrum salicaria L.) is the most common exotic species of the St Lawrence wetlands, but other species, namely flowering‐rush (Butomus umbellatus L.) and reed canary grass (Phalaris arundinacea L.) are much more invasive. There is no linear relationship between the exotic species cover and the diversity of wetland plants; low diversity sites can be dominated by either exotic or native plant species. In the other sites, exotic species generally have little impact on plant communities and can contribute to increase diversity. Common reed (Phragmites australis (Cav.) Trin. ex Steudel) and reed canary grass, both considered as exotic species in this study, clearly have a stronger impact on plant diversity than flowering‐rush and purple loosestrife.Main conclusions This study shows that the global impact of an invader cannot be adequately evaluated with only a few highly invaded sites. While nationwide strategies have been developed to control exotic species, large surveys are essential to adapt them to regional particularities.

Trend analysis reveals a recent reduction in mirex concentrations in coho (Oncorhynchus kisutch) and chinook (O. tshawytscha) salmon from Lake Ontario.

Lake Ontario, bordering both Canada and the United States, is the only Great Lake with persistent, significant levels of mirex in its biota. Some models suggested that it would take hundreds of years before mirex disappeared from the ecosystem. From 1977 to 1996 the mirex concentrations in coho and chinook salmon greater than 2 kg in weight exceeded the 0.1 mg/kg Food and Drug Administration (FDA) action level for mirex. To determine temporal trends in salmonine mirex levels, slopes and elevations of the regression lines of mirex concentration versus fish weight were compared for each of the six sampling years (1977, 1982, 1986, 1992, 1996, and 1999) by ANCOVA with weight as a covariate. Within 24 years of mirex being banned, mirex least-squares mean concentrations in salmon fillets had decreased significantly. ANCOVA revealed that the slope of the 1999 regression line was significantly flatter (P < or = 0.014) than the slopes of all other regression lines except 1996 (P = 0.966). A Tukey test revealed that the elevation of the 1999 regression line was also significantly lower than all other years (P < 0.001). Based on our results, mirex concentrations in the fillets of most salmon under the size of 12 kg are now below the 0.1 mg/kg United States FDA action level for human consumption. Models suggest that mirex reductions in biota are most likely due to the settling of mirex-contaminated organisms to the sediments and the loss of mirex from the lake through the St Lawrence River. A third mechanism is suggested as the cause of the higher rate of reduction observed in the mid to late 1990s--the control and removal of contaminated groundwater at the former Hooker Chemical site on the Niagara River, the major source of mirex in the watershed of Lake Ontario.

Spectral gradients of downwelling light in a fluvial lake (Lake Saint-Pierre, St-Lawrence River)

Large fluvial lakes are understudied with respect to their underwaterlight climates. Fluvial lakes pose unique challenges for photobiologistsinterested in the interactions amongst light climate, nutrients and microbialcommunity structure and biodiversity. This is because fluvial lakes are typifiedby highly dynamic flow regimes often incorporating different inflows anddischarges each characterized by their own unique physico-chemical composition.These compositional characteristics include the concentrations of chromophoricdissolved organic matter (CDOM), suspended solids, and pigments such aschlorophyll. Together these factors contribute to the distribution andcomposition of the water masses that make up fluvial lakes. These water masses,in turn, flow over lakebeds that are typically complex in their morphometry andfeature extensive macrophyte beds, further enhancing the habitat heterogeneityof these ecosystems. We here report on the spectral attenuation of ultravioletradiation (UVR = 280–400 nm) and photosyntheticallyactive radiation (PAR = 400–700 nm) in the three mainwater masses of Lake Saint-Pierre and evaluate the relative contribution ofCDOM, and particulate organic material to UVR attenuation. We demonstrate thatUVR penetrates 18 to 30% of the water column (1% penetration depth) in the LakeSaint-Pierre ecosystem, and show how the underwater spectral UVR varies withinthe three water masses.

Movements and aggregation areas of adult Atlantic sturgeon (Acipenser oxyrinchus) in the St Lawrence River estuary, Quebec, Canada

Journal of Applied IchthyologyVolume 18, Issue 4-6 p. 586-594 Movements and aggregation areas of adult Atlantic sturgeon (Acipenser oxyrinchus) in the St Lawrence River estuary, Québec, Canada D. Hatin, D. Hatin Société de la faune et des parcs du Québec, Direction de la recherche sur la faune, Québec, QC, Canada; Université du Québec à Montréal, Département des Sciences biologiques, Succursale Centre-ville, Montréal, QC, Canada Réjean Fortin died prematurely in September 2001. He was an excellent scientist having a keen eye for natural facts and events and an excellent pedagogue who turned out several graduate students in fisheries science. His contribution to the knowledge of Lake sturgeon (Acipenser fulvescens) biology and management will remain pertinent for future decades. Réjean was also a great colleague and a great friendSearch for more papers by this authorR. Fortin, R. Fortin Société de la faune et des parcs du Québec, Direction de la recherche sur la faune, Québec, QC, Canada; Université du Québec à Montréal, Département des Sciences biologiques, Succursale Centre-ville, Montréal, QC, Canada Réjean Fortin died prematurely in September 2001. He was an excellent scientist having a keen eye for natural facts and events and an excellent pedagogue who turned out several graduate students in fisheries science. His contribution to the knowledge of Lake sturgeon (Acipenser fulvescens) biology and management will remain pertinent for future decades. Réjean was also a great colleague and a great friendSearch for more papers by this authorF. Caron, F. Caron Société de la faune et des parcs du Québec, Direction de la recherche sur la faune, Québec, QC, Canada; Université du Québec à Montréal, Département des Sciences biologiques, Succursale Centre-ville, Montréal, QC, Canada Réjean Fortin died prematurely in September 2001. He was an excellent scientist having a keen eye for natural facts and events and an excellent pedagogue who turned out several graduate students in fisheries science. His contribution to the knowledge of Lake sturgeon (Acipenser fulvescens) biology and management will remain pertinent for future decades. Réjean was also a great colleague and a great friendSearch for more papers by this author D. Hatin, D. Hatin Société de la faune et des parcs du Québec, Direction de la recherche sur la faune, Québec, QC, Canada; Université du Québec à Montréal, Département des Sciences biologiques, Succursale Centre-ville, Montréal, QC, Canada Réjean Fortin died prematurely in September 2001. He was an excellent scientist having a keen eye for natural facts and events and an excellent pedagogue who turned out several graduate students in fisheries science. His contribution to the knowledge of Lake sturgeon (Acipenser fulvescens) biology and management will remain pertinent for future decades. Réjean was also a great colleague and a great friendSearch for more papers by this authorR. Fortin, R. Fortin Société de la faune et des parcs du Québec, Direction de la recherche sur la faune, Québec, QC, Canada; Université du Québec à Montréal, Département des Sciences biologiques, Succursale Centre-ville, Montréal, QC, Canada Réjean Fortin died prematurely in September 2001. He was an excellent scientist having a keen eye for natural facts and events and an excellent pedagogue who turned out several graduate students in fisheries science. His contribution to the knowledge of Lake sturgeon (Acipenser fulvescens) biology and management will remain pertinent for future decades. Réjean was also a great colleague and a great friendSearch for more papers by this authorF. Caron, F. Caron Société de la faune et des parcs du Québec, Direction de la recherche sur la faune, Québec, QC, Canada; Université du Québec à Montréal, Département des Sciences biologiques, Succursale Centre-ville, Montréal, QC, Canada Réjean Fortin died prematurely in September 2001. He was an excellent scientist having a keen eye for natural facts and events and an excellent pedagogue who turned out several graduate students in fisheries science. His contribution to the knowledge of Lake sturgeon (Acipenser fulvescens) biology and management will remain pertinent for future decades. Réjean was also a great colleague and a great friendSearch for more papers by this author First published: 17 December 2002 https://doi.org/10.1046/j.1439-0426.2002.00395.xCitations: 32AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume18, Issue4-6December 2002Pages 586-594 RelatedInformation

Biological characteristics of adult Atlantic sturgeon (Acipenser oxyrinchus) in the St Lawrence River estuary and the effectiveness of management rules

Biological characteristics of adult Atlantic sturgeon (Acipenser oxyrinchus) in the St Lawrence River estuary and the effectiveness of management rules

Montreal's golden age

Between the mid-nineteenth century and the Great Depression of the twentieth, Montreal was transformed from a small colonial town into Canada's leading metropolis. Waterworks, telephone, gas and electrical systems were laid, the Lachine canal was widened and deepened, and the port installations completely rebuilt and greatly expanded. The Victoria Bridge crossing the mighty St Lawrence River was completed in 1860 and the transcontinental railways spanned the nation by the late 1880s, which opened up the west and created new markets. People flocked into the city from the countryside to work in the burgeoning industries, to be joined by ever increasing numbers of immigrants.

Status of the belugas of the St Lawrence estuary, Canada

A population of belugas (Delphinapterus leucas) inhabiting the estuary of the St Lawrence river in Quebec, Canada, was depleted by unregulated hunting, not closed until 1979. Surveys in 1977 showed only a few hundred in the population. Surveys since then have produced increasing estimates of population indices. An estimate of the population, fully corrected for diving animals, was 1,238 (SE 119) in September 1997. The population was estimated to have increased from 1988 through 1997 by 31.4 belugas/yr (SE 13.1). Observations of population age structure, as well as data on age at death obtained from beach-cast carcasses, do not indicate serious problems at the population level, although there are indications that mortality of the oldest animals may be elevated. Few animals appear to live much over 30 years. From examination of beach-cast carcasses, it appears that most deaths are due to old age and disease; hunting is illegal, ship strikes and entrapments in fishing gear are rare, ice entrapments and predation are unknown. Among beach-cast carcasses recovered and necropsied, about 23% of the adults have malignant cancers, while most of the juveniles have pneumonia; other pathological conditions are diverse. No factors are known to be limiting numbers of this population. Habitat quality factors, including persistent contaminants, boat traffic and harassment, may affect the population’s rate of increase, but these effects have not been quantitatively evaluated. Comprehensive legislation exists with powers to protect the population and the environment of which it is a component, but application and enforcement of the laws is not without problems.

Regional streamflow trend detection with consideration of both temporal and spatial correlation

AbstractIt is known that serial correlation within time series at sites and cross‐correlation among sites in a specific region will influence the ability of statistical tests to assess the field significance of trends over the region. However, serial and/or cross‐correlation has been ignored in field trend‐analyses. This study attempts to develop a methodology that takes into account both serial and cross‐correlation in the assessment of the field significance of trends. The regional average Mann–Kendall (RAMK) statistic is used to represent the regional properties of trends at a regional scale. The null distribution of the RAMK statistic is derived on the basis that the joint probability distribution of m independent normal variables is also normally distributed. The variance of the RAMK statistic is then modified by serial and cross‐correlation. The applicability of the method was demonstrated by applying it to assess the field significance of trends in annual mean, annual maximum, and annual minimum daily streamflow from 1967 to 1996 in ten major homogeneous climate regions of Canada. The results indicate that the method developed provides more accurate assessment of the field significance of trends than that without consideration of serial and cross‐correlation.At the significance level of 0.10, annual mean daily flow increased significantly in the region of Yukon and northern BC mountains whereas it decreased significantly in the Pacific and the Prairie regions. Annual maximum daily flow decreased significantly across southern Canada, except in the Pacific region. Annual minimum daily flow decreased significantly in the Pacific region and in southeastern Canada, with the exception of the region of Great Lakes and St Lawrence river basin, whereas it increased significantly in the region of Yukon and northern BC mountains. Copyright © 2002 Royal Meteorological Society

Potential effects on zooplankton from species shifts in planktivorous mussels: a field experiment in the St Lawrence River

1. Suspension feeding by bivalves exceeds that by other planktivores in many North American rivers, and food webs may be altered substantially by differences in feeding patterns between native unionid mussels and invading dreissenid mussels.2. We conducted an experiment comparing zooplanktivory by one unionid and two dreissenid species that addressed several primary questions. Is benthic planktivory important in this river? Has this linkage been altered substantially by dreissenids? Do the two dreissenid species differ in planktivory, and is this ecologically important if quagga mussels extend their geographical range?3. Our 12‐day experiment consisted of controls (no mussels) and treatments with unionid (Elliptio complanata), quagga (Dreissena bugensis) or zebra (D. polymorpha) mussels in 3500‐L, 80‐μm mesh enclosures placed in a slackwater area of the St Lawrence River.4. The density of the most abundant calanoid copepod Eurytemora affinis increased in the presence of dreissenids, probably as an indirect food web response. By day 12, a cumulative effect was shown by the most overwhelmingly abundant rotifer, Polyarthra, whose density declined dramatically in dreissenid enclosures compared with control and unionid enclosures. Rotifer densities in unionid enclosures were not different from controls, nor were dreissenid treatments different from each other. The effects on rotifers were probably from predation, as Chl‐a did not vary among treatments.5. We conclude that benthic‐pelagic coupling via planktivory is important in slackwater areas. Dreissenids have strengthened this linkage, but range extension of quaggas should not appreciably alter effects produced by a similar biomass of zebra mussels.

Testing a New Anti-Zebra Mussel Coating with a Multi-plate Sampler: Confounding Factors and other Fuzzy Features

In situ experiments were conducted to assess the use of multi-plate samplers for antifouling experiments and to test the antifouling effectiveness of a chitin-based coating against zebra mussels (Dreissena polymorpha). A series of multi-plate samplers consisting of three parallel plates coated with chitin, and untreated control samplers, were submerged horizontally or vertically in a marina of the St Lawrence River for 3 1/2 months (July-October) in 1998 and 1999. Mussels attached to the chitin-treated substrates were on average 2.75 times more abundant than on the control samplers, indicating that chitin is not effective as an antifouling agent against zebra mussels. The abundance, size distribution and spatial dispersion of mussels on the plates varied both between plates and between top vs bottom sides of plates in horizontal collectors, but not in vertical samplers. The three plates composing each multi-plate horizontal sampler do not represent true replicates for statistical analysis. The bottom side of plates exhibited the least variability and might therefore serve as the experimental unit. Substrate heterogeneity and plate orientation were identified as confounding factors to be controlled for in future experiments. Sunlight exposure and colonization by sponges strongly influenced zebra mussel abundance and should be considered when performing in situ experiments. Because of the influence of uncontrolled factors, it is recommended that in situ pilot studies be conducted to statistically test the effectiveness of antifouling products once the threshold level of the desired effectiveness is defined.

Ultra-trace analysis of pesticides by solid-phase extraction of surface water with carbopack B cartridges, combined with large-volume injection in gas chromatography

A method has been developed for determination of twenty-four polar pesticides—nine organophosphorus pesticides, thirteen organonitrogen compounds, and two triazine degradation products—in surface water. It entails extraction of the target pesticides from 1-L water samples by solid-phase extraction (SPE), then gas chromatography (GC) with large-volume (40 μL) injection. Filtered surface water, from the St Lawrence River in Canada and the River Loire and its tributaries in France, was extracted on cartridges filled with 500 mg Carbopack B (120–400 mesh). Analysis was performed by gas chromatography with a thermionic specific detector (GC-TSD) and a mass spectrometric (MS) detector. Overall percentage recoveries were satisfactory (>70%) for all target pesticides, with precision below 10%. Detection limits were between 0.5 and 4 ng L−1.

Plasma non-esterified fatty acid profiles and 17β-oestradiol levels of juvenile immature and maturing adult American eels in the St Lawrence River

Plasma non-esterified fatty acid profiles and 17β-oestradiol levels of juvenile immature and maturing adult American eels in the St Lawrence River

Plasma non‐esterified fatty acid profiles and 17β‐oestradiol levels of juvenile immature and maturing adult American eels in the St Lawrence River

American eels Anguilla rostrata, collected from three distinct locations along the St Lawrence River (Lake St Lawrence, Quebec City and Kamouraska), were thought to consist entirely of out‐migrating adults at Quebec City and Kamouraska and of both resident and migrants at Lake St Lawrence. The mean plasma levels of 17β‐oestradiol closely paralleled the trend observed with gonadosomatic index (IG) and oocyte development. The highest levels of 17βoestradiol and IG were observed in Quebec City and Kamouraska, while the levels observed in the resident eels from Lake St Lawrence were very low. Generally, the concentration of total plasma non‐esterified fatty acids (NEFA) appeared to follow the trend of 17β‐oestradiol and IG and increased with sexual maturity. However, the most sexually mature group, eels from Kamouraska, had the lowest total plasma NEFA levels. The reason for the drop is not clear at present. In addition, a number of shifts in the plasma NEFA profiles of American eels did occur during their migration in a downstream direction, with several fatty acids either increasing or decreasing in relative abundance. The ratio of n3: n6 fatty acids declined with increasing sexual maturity as most n3 fatty acids became less abundant. Although the correlation between gonadal development and the relative concentration of individual fatty acids was not always clear, both arachidonic acid (20: 4n6) and docosahexaenoic acid (22: 6n3) were significantly higher in the plasma of out‐migrating adults than in resident yellow phase eels.

Global predictive real-time control of Quebec Urban Community's westerly sewer network

Quebec Urban Community (QUC) has selected Global Predictive Real-Time Control (GP-RTC) as the most efficient approach to achieve environmental objectives defined by the Ministry of Environment. QUC wants to reduce combined sewer overflows (CSOs) frequency to the St Lawrence river to two events per summer period in order to reclaim the use of Jacques-Cartier Beach for recreational activities and sports of primary contact. QUC's control scheme is based on the Certainty Equivalent Control Open Loop Feedback (CEOLF) strategy which permits one to introduce, at each control period, updated measurements and meteorological predictions. A non-linear programming package is used to find the flow set points that minimise a multi-objective (cost) function, subjected to linear equality and inequality constraints representing the physical and operational constraints on the sewer network. Implementation of GP-RTC on QUC's westerly network was performed in the summer of 1999 and was operational by mid-August. Reductions in overflow volumes with GP-RTC compared to static control are attributed to the optimal use of two existing tunnels as retention facilities as well as the maximal use of the wastewater treatment plant (WWTP) capacity.

Assessment of rates of deformity in wild frog populations using in situ cages: a case study of Leopard Frogs (Rana pipiens) in Ontario, Canada

High rates of deformity in wild amphibian populations from north-eastern North America have been increasingly reported since 1995. In the St Lawrence River basin (Canada) elevated frequencies of limb and eye deformities in mudpuppies (Necturus maculosus) and leopard frogs (Rana pipiens) were recorded in the early 1990s. A caging study was conducted during 1998 to verify the rates recorded in leopard frogs and pursue the potential causes of deformities seen in juveniles and adults. Week-old leopard frog tadpoles were collected from a reference wetland and maintained through to metamorphosis in cages in previously identified high risk wetlands. Deformity frequencies were measured and compared with frequencies measured in wild populations of leopard frogs inhabiting the same wetlands. The results of caging studies and sampling of wild populations were also compared with corresponding data collected from a reference wetland. No deformities were observed in caged or wild reference animals. Very low deformity frequencies (up to 2.2%) were observed in frogs caged in high risk wetlands, but greater frequencies (3.4-10%) were observed in wild young-of-the-year frogs captured at the same sites. The types of deformities were similar among groups; they included fused, missing or extra digits and disproportionate hindlimb length or eye pupil size. In addition, mortality rates were elevated in two cages in high risk wetlands. In general, the caging procedure was effective in establishing the potential for production of deformities in the waters of a given wetland, but tended to underestimate the rates calculated for samples of wild populations. The ramifications of the first-year findings for similar assessments of amphibian deformity rates and establishment of cause-effect linkages are discussed.

Concentrations and patterns of organochlorine contaminants in white whales ( Delphinapterus leucas) from Svalbard, Norway

Blubber was collected from live-captured, adult male white whales ( Delphinapterus leucas) from Svalbard, Norway, and analysed for levels and patterns of organochlorine (OC) contaminants. The OC compounds analysed were HCB, dieldrin, ΣHCH (α-HCH, β-HCH and γ-HCH), ΣChl (heptachlor epoxide, oxychlordane, cis-chlordane, trans-nonachlor, and cis-nonachlor), ΣDDT ( pp′-DDT, pp′-DDE and pp′-DDD) and ΣPCB (27 PCB congeners). The major OC compounds detected in the blubber were ΣPCB (5103±1874 ng/g l.w.) and ΣDDT (5108±1089 ng/g l.w.), which made up 70% of the ΣOC. These compounds were followed in prevalence by ΣChl (2872±1177 ng/g l.w.), which contributed 20% of the ΣOC burden. ΣHCH, HCB and dieldrin were present, but at low concentrations. This OC pattern is typical of top predators in Arctic marine food chains. OC levels in white whales from Svalbard are lower than white whales from the St Lawrence River in Canada and are generally similar to values reported previously for other Arctic white whale stocks. Some geographic patterns in relative prevalence of various OC compounds appear to be quite consistent among various marine mammal species in the Arctic. PCB and DDT concentrations in Svalbard's white whales are below the levels that are thought to have negative effects on reproduction or the immune system.

The influence of macrophyte beds on plankton communities and their export from fluvial lakes in the St Lawrence River

1. To determine the influence of macrophyte beds on plankton abundance within fluvial lakes of the St Lawrence River, planktonic components (macrozooplankton, heterotrophic bacteria, and phytoplankton as chlorophyll‐a [Chl‐a]) were sampled in Lake St Francis and Lake St Pierre during summer 1998. We tested the hypothesis that the abundance of planktonic components was higher within macrophyte beds in comparison to the more rapidly flushed open water areas of the fluvial lakes. 2. The large cross channel variation in zooplankton biomass was indeed correlated with the presence of dense beds of submerged macrophytes. Total macrozooplankton biomass was nine‐fold greater within the beds (mean=180 μg L−1 dry mass) than in either the open water or areas with only sparse vegetation (mean=20 μg L−1 dry mass). 3. Chl‐a and heterotrophic bacterial abundance were also higher in the beds, but only slightly so. There was no difference in total phosphorus or dissolved organic carbon concentrations between areas of dense vegetation, sparse vegetation or open water. 4. Macrophyte beds on the margins of the fluvial lakes allow the development of high planktonic abundance relative to the fast flowing central channel. Macrozooplankton biomass was much higher at the outflows of the lakes (∼50 μg L−1 dry mass) in comparison to the inflows (&lt;20 μg L−1 dry mass). The increase is due to the transfer of organisms from submerged macrophyte beds into the central channel in the downstream quarter of the two lakes where the marginal littoral waters enter central channel waters. 5. Along rivers, shallow fluvial lakes appear to act as sources of plankton which is exported downstream during years of extensive littoral macrophyte development.