Bioassay responses of micro-organisms to sediment elutriates from the St. Lawrence River (Lake St. Louis)

A sediment study, involving both chemical and biological analyses, was carried out in the St. Lawrence River near Montreal (Lake St. Louis). About 60 stations were sampled during 1984–85, and the sediments were analyzed for support variables, heavy metals, and organochlorinated compounds. Subsamples were elutriated using a 1 to 4 sediment/water ratio. The resulting elutriates were analyzed for several chemical variables, while toxicity was measured using the Microtox test, algal ¹⁴C assimilation, and lethality/developmental inhibition in cladocerans, rotifers, and nematodes. The results showed a great variety of responses and sensitivity, and correlations between the tests were non-significant. In terms of toxic responses, the algal and Microtox tests were the most sensitive. Toxic responses could not be explained in simple terms of contaminant concentrations. Therefore, the chemistry of elutriates is not predictive of the toxic potential of contaminated sediments. Biotests can give an insight into the hazard assessment of sediments, but no single test will be sufficient; the use of a battery of standardized biotests, representing different levels of organization/food chain, including representative natural species, is highly recommended.     

Lake sturgeon management in the Menominee River, a Wisconsin-Michigan boundary water

The Menominee River, a boundary water between northeastern Wisconsin and the upper peninsula of Michigan, contains a sport fishery for lake sturgeon, Acipenser fulvescens, which is jointly managed by both states. Previous studies indicated that overfishing of this sturgeon population was occurring, and this investigation examined the impact of new angling regulations. The sturgeon population is fragmented into sections by hydroelectric dams. Stocks from the three main sections of the river were compared before and after implementation of the new angling regulations. Records of the legal harvest of lake sturgeon from each river section were obtained through a registration system, which has been in effect since 1983, and estimates of exploitation were derived from these data. Overfishing of lake sturgeon stocks in two of the three sections of the Menominee River is still occurring. Management recommendations are made which would allow for a continued fishery by providing further protection to the stocks.     

Bioremediation and Biorestoration of a Crube Oil-Contaminated Freshwater Wetland on the St.Lawrence River

Biostimulation by nutrient enrichment and phytoremediation were studied for the restoration of an acutely stressed freshwater wetland experimentally exposed to crude oil. The research was carried out along the shores of the St. Lawarence River at Ste. Croix, Quebec, Canada. The research determined the effectiveness of fertilizer addition in enhancing the biodegradation rates of residual oil. It further examined the rate at which the stressed ecosystem recovered with and without the addition of inorganic fertilizers and the role of nutrients in enhancing wetland restoration in the absence of healthy wetland plants. Chemical analysis of integrated sediment core samples to the depth of oil penetration within the experimental plots indicated that addition of inorganic nutrients did not enhance the disappearance of alkanes or PAHs. In surface samples, however, hydrocarbon disappearance rates were higher when the metabolic activity of wetland plants was suppressed by the removal of emergent plant growth. These results suggest that oxygen limitation plays a major role in preventing rapid biodegradation of hydrocarbons in anoxic wetland sediment.     

Evidence of spawning by green sturgeon, Acipenser medirostris, in the upper Sacramento River, California

This study reports the only direct evidence of spawning of green sturgeon, Acipenser medirostris, in the upper Sacramento River, CA. Two green sturgeon eggs were collected with substrate mats immediately below Red Bluff Diversion Dam. One green sturgeon larva was collected with a larval net at Bend Bridge. We concluded that green sturgeon spawn in the upper Sacramento River, both above and below RBDD. Temperature ranges in the study area (10–15°C) are similar to conditions used in successful artificial rearing of green sturgeon and do not appear to be a limiting factor to successful spawning of green sturgeon; however, suitable habitat upstream of RBDD is inaccessible when dam gates are lowered.     

Historical changes in herbaceous wetland distribution induced by hydrological conditions in Lake Saint-Pierre (St. Lawrence River,Quebec, Canada)

Historical changes (1961–2002) in the distribution of herbaceous wetland plant associations were inferred from the hydrological regime of Lake Saint-Pierre, a 312 km² broadening of the St. Lawrence River (Quebec, Canada), to assess the cumulative effects of human interventions and climatic variability. Relative abundance index (height × percent cover) of wetland plants in 630 field quadrats sampled at 13 sites (1999–2002) were used to derive a model predicting the occurrence of nine herbaceous plant classes with a 71% (24–84%) accuracy. Wetland types included seasonally dry (meadows), mudflats and wet (low marshes and submerged) assemblages. Over the 1961–2002 period, the total surface area of Lake Saint-Pierre herbaceous wetlands ranged between 11 (in 1972) and 128 (in 2001) km² and was negatively correlated (Spearman r = –0.86, p < 0.0001) to average water level during the current growing season. Within-season variability and level conditions over the previous season defined 5 marsh assemblages characterized by different species composition, relative abundance and diversity. Significant hydrological variables included quadrat elevation, water depth, number of days flooded and depth variability experienced over the current and/or previous growth seasons. The hydrological model suggests that for a given level, wetland plant assemblages differed markedly whether the multi-year sequence of water levels was rising or falling. Lake Saint-Pierre alternated between three broad-scale wetland configurations, dominated by meadows and open marsh with floating-leaved vegetation (in the 1960s), scattered tall Scirpus marshes (in the 1970s and early 1980s) and closed marsh with aggressive emergents (since 1996). The strong response of Lake Saint-Pierre wetlands to hydrological conditions in the current and previous growth seasons underlines their vulnerability to future water level variations resulting from regulation and climate variability.     

Gulf sturgeon summer habitat use and fall migration in the Pascagoula River, Mississippi, USA

The locations and habitat features of freshwater holding areas and the timing of fall migration are undocumented for Gulf sturgeon in the Pascagoula River drainage, Mississippi. Our objectives were to identify and characterize holding areas for Gulf sturgeon (Acipenser oxyrinchus desotoi), document their summer and fall movement patterns, and determine migration cues. To do this we captured, radio‐tagged, and monitored movement of Gulf sturgeon in the Pascagoula River drainage and analyzed these data using geographic information systems. From May to November Gulf sturgeon congregate in a holding area in the lower portion of the Pascagoula River and Big Black Creek [river kilometers (rkm) 57–68] and near Cumbest Bluff (rkm 40), before they return to the Gulf of Mexico. While in the holding area, Gulf sturgeon were typically found in deep locations, either in or downstream from river bends. As found in other rivers, Gulf sturgeon in the Pascagoula River showed little movement within the holding area and often stayed within a single river bend; although we observed local movements by some individuals (under 10 rkm). In the Pascagoula River, Gulf sturgeon initiated their migration out of fresh water from late‐September to mid‐October, coincident with shorter day length, falling water temperature (mean = 23.7°C, range 21–26°C), and elevated river flow. Our work demonstrates that the lower Pascagoula River serves as a vital area for Gulf sturgeon.     

Biota of Lake St. Clair: habitat evaluation and environmental assessment

As a shallow, productive lake in the drainage system between Lake Huron and Lake Erie, Lake St. Clair provides habitat for a diverse biota including significant populations of fish and wildlife that are of use to man. Of the more than 70 species of native and migrant fishes, 43 use the lake for spawning. Peak numbers of waterfowl utilizing the lake and adjoining wetlands have been estimated at 60 000 in spring and 150 000 in autumn. In addition to recreational fishing and hunting, the lake is also used for swimming, boating and as a source of municipal water. It is located downstream from an industrial centre and adjacent to a population estimated at about four million. Mercury contamination closed the fisheries in 1970 and concentrations of the metal persist above consumption guidelines in some species. Almost all of the Michigan shoreline is urbanized and much of it altered through dyking and bulkheading. Coastal wetlands of the lake have declined 41 percent in the past century and only about one-half of the remaining area is open to the lake.Despite impacts from the large urban population and users, ecosystem quality remains reasonably good. The flushing action of relatively clean water from Lake Huron has slowed the eutrophication process. Major habitat problems are toxic substances from industries located on the St. Clair River and the continued loss of shoreline and wetlands to urbanization and agriculture. Further research and monitoring of sources, fates and impacts of toxic substances in sediments and biota are required. In addition, there is a need for environmental and economic evaluations of shorelines and wetlands to prevent further losses of these important habitats.Contribution No. 90-16 of the Ontario Ministry of Natural Resources, Research Section, Fisheries Branch, Box 5000, Maple, Ontario.     

Detection of viral hemorrhagic septicemia in round gobies in New York State (USA) waters of Lake Ontario and the St. Lawrence River

In May 2006 a large mortality of several thousand round gobies Neogobius melanostomus (Pallas, 1814) occurred in New York waters of the St. Lawrence River and Lake Ontario. Necropsies of sampled fish from these areas showed pallor of the liver and gills, and hemorrhagic areas in many organs. Histopathologic examination of affected tissues revealed areas of necrosis and hemorrhage. Inoculations of fathead minnow Pimephales promelas (Rafinesque, 1820) cell cultures with dilutions of tissue samples from the necropsied gobies produced a cytopathic effect within 5 d post-inoculation. Samples of cell culture supernatant were tested using RT-PCR and confirmed the presence of viral hemorrhagic septicemia virus (VHSV). Sequence analysis of the VHSV isolate resulted in its assignment to the type-IVb subgroup. The detection of VHSV in a relatively recent invasive fish species in the Great Lakes and the potential impact of VHSV on the ecology and economy of the area will require further investigation and careful management considerations.     

Cryptic invaders: nonindigenous and cryptogenic freshwater Bryozoa and Entoprocta in the St. Lawrence River

The distributions of most cosmopolitan invertebrate species are assumed to result from natural processes. Cryptic invertebrates with obscure biogeographic origins are often considered native by default, resulting in potentially severe underestimation of the extent of human-assisted invasions. This problem is exemplified by freshwater Bryozoa (Ectoprocta) and Entoprocta—small and widely distributed invertebrates commonly found in lakes and rivers. A benthic survey of a thermally modified section of the St. Lawrence River revealed the presence of two nonindigenous bryozoans: Carter’s moss animal Lophopodella carteri (Hyatt) and the crystal moss animal Lophopus crystallinus Pallas. Also discovered was a cryptogenic entoproct, the goblet worm Urnatella gracilis Leidy. These species were collected as statoblasts and (in the case of U. gracilis) colonial fragments downstream of the Gentilly-2 nuclear power plant at Bécancoeur, Quebec. Local densities of both U. gracilis and L. carteri increased by an order of magnitude at sites closer to the power plant. The occurrence of Lophopus crystallinus statoblasts in St. Lawrence River sediments is the first documented physical evidence of the species in North America. Contrary to the presumed natural Holarctic distribution of L. crystallinus, our literature review found that published historical records of L. crystallinus in the United States are erroneous or unsubstantiated. We propose that L. crystallinus is a western Palearctic species recently introduced to the St. Lawrence River, most likely as statoblasts discharged with ballast water from transoceanic ships.     

Biota of the St. Marys River: habitat evaluation and environmental assessment

The St. Marys River provides vital habitat for many species of plants, invertebrates, fish, and birds. It is also subject to many at times conflicting uses, including recreational boating, sport and subsistence fishing, municipal and industrial withdrawals and inputs, as well as commercial ship traffic and hydroelectric power generation.In 1984, the United States and Canada jointly initiated the Upper Great Lakes Connecting Channels Study to identify and quantify the impacts of contaminants on these channels and their biota and to develop recommendations for more effective pollution control and surveillance programs. Results of the study in the St. Marys River showed that water entering the river from Lake Superior is of excellent quality. Industrial and municipal discharges in the Sault Ste. Marie, Ontario area have resulted in heavily contaminated sediments and a severely impaired benthic invertebrate community in this area and downstream; however, no major impacts on fish have been demonstrated. Nevertheless, major impacts of man on fish spawning and rearing habitats and on benthic and fish productivity have resulted from the alteration of channels, construction of navigation locks, and regulation of flow in the St. Marys Rapids. Increases in the productivity of such raptors as osprey during the 1980s suggest a reduction in organochlorine contaminants levels in their diet; however, the increasing numbers of gulls with low concentrations of PCBs, p,p-DDE and other organochlorines in their eggs may adversely affect gull young or their predators.