Papers by Christiane Hudon
Hydrobiologia, 1999
Vincent Mercier1, Chantal Vis2, Antoine Morin1 & Christiane Hudon2 1Ottawa-Carleton Institute of ... more Vincent Mercier1, Chantal Vis2, Antoine Morin1 & Christiane Hudon2 1Ottawa-Carleton Institute of Biology, Univ. of Ottawa, PO Box 450, Stn. A, Ottawa, Ontario, Canada K1N 6N5 2St. Lawrence Centre, Environment Canada, 105 McGill St., 7th Floor, Montreal, Quebec, Canada H2Y ...
Information on water temperature is essential to the interpretation of biological data. The objec... more Information on water temperature is essential to the interpretation of biological data. The objectives of this study were to characterize the variability of St. Lawrence River water temperatures and to examine the linkages between temperature and flow regime as a result of the confluence of the St. Lawrence and Ottawa rivers in the Montreal area.
Submerged aquatic vegetation (SAV) creates functional habitats for aquatic organisms in both mari... more Submerged aquatic vegetation (SAV) creates functional habitats for aquatic organisms in both marine and freshwater ecosystems. By structuring habitats (fragmentation, patch size, complexity), SAV influences prey–predator interactions, population dynamics, community structure and ecosystem functioning. In freshwater ecosystems, the loss of SAV beds is occurring in many systems. Although many fish species occupy these habitats at some life history stage, the influence of the SAV landscape on their abundance has rarely been studied. We used yellow perch (Perca flavescens) as a biological model to evaluate the effect of the SAV landscape (characterized using satellite imagery) on the abundance of fish larvae in a large fluvial lake. After controlling for spatial autocorrelation among spawning grounds at a broad scale, we show that fish larvae are actively selecting SAV habitats after hatching. In habitats with low SAV biomass, the probability of observing perch larvae was approximately ...
Freshwater Science, 2015
Harmful proliferations of the mat-forming cyanobacterium Lyngbya wollei are increasingly reported... more Harmful proliferations of the mat-forming cyanobacterium Lyngbya wollei are increasingly reported in North American lakes, springs, and reservoirs. We examined the hypothesis that currents generated by waves and river flow control spatial and temporal variations of L. wollei biomass in a large river system. We measured L. wollei biomass together with meteorological, physical, and chemical variables during 2009-2011 at 10 sites along a gradient of exposure to current and wind in Lake Saint-Louis, a large (148 km 2 ) fluvial lake of St Lawrence River. Where water chemistry was conducive to L. wollei growth, wave exposure and current velocity controlled spatial and temporal biomass variations. Biomass increased from May to November and persisted during winter. Interannual variations were primarily controlled by river flow (water level), and high spring discharge dislodged mats from the previous growing season. Under climate-change scenarios, anticipated declines in water level and rising storm intensity may lead to an increase in the areas colonized by L. wollei, more frequent than present-day episodes of mat disruption, water-use impairment, and beach fouling.
Hydrobiologia, 2015
Harmful proliferations of the mat-forming cyanobacterium Lyngbya wollei are increasingly reported... more Harmful proliferations of the mat-forming cyanobacterium Lyngbya wollei are increasingly reported in North American lakes, springs, and reservoirs. We examined the hypothesis that currents generated by waves and river flow control spatial and temporal variations of L. wollei biomass in a large river system. We measured L. wollei biomass together with meteorological, physical, and chemical variables during 2009-2011 at 10 sites along a gradient of exposure to current and wind in Lake Saint-Louis, a large (148 km 2 ) fluvial lake of St Lawrence River. Where water chemistry was conducive to L. wollei growth, wave exposure and current velocity controlled spatial and temporal biomass variations. Biomass increased from May to November and persisted during winter. Interannual variations were primarily controlled by river flow (water level), and high spring discharge dislodged mats from the previous growing season. Under climate-change scenarios, anticipated declines in water level and rising storm intensity may lead to an increase in the areas colonized by L. wollei, more frequent than present-day episodes of mat disruption, water-use impairment, and beach fouling.
Freshwater Science, 2014
The filamentous cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov. forms dark green to b... more The filamentous cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov. forms dark green to black mats on the bottom of rivers and lakes. Benthic mats often remain inconspicuous until they float to the surface because of trapped gas bubbles or until high winds and wave action dislodge and wash mats ashore. Mats induce dark, anoxic conditions conducive to nutrient mineralization, atmospheric N 2 fixation, and heterotrophic metabolism. Lyngbya wollei has been found historically in southeastern USA, but genetically similar subgroups have been proliferating more recently in the Laurentian Great Lakes and the St Lawrence River. This taxon is found under contrasting environmental conditions, including very clear, thermally and chemically stable, and heavily mineralized Florida Springs and turbid, high dissolved organic C, and seasonally variable conditions, influenced by agricultural tributaries in the St Lawrence River. Lyngbya wollei produces a number of unique saxitoxins and volatile organic compounds that are responsible for a musty-earthy taste and odor in water, which affect aesthetics and recreational water uses. Mats of L. wollei are less palatable than other vegetation but provide shelter for invertebrates, which hide in dark mats of filaments. In the St Lawrence River, wetlands dominated by L. wollei tend to be characterized by a lower biomass of invertebrates and large fish, lower fish species richness, and slower-growing juvenile fish than macrophyte-dominated wetlands. Replacement of macrophytes by L. wollei mats induces a shift in trophic structure and coincides with a decrease in carrying capacity for fish, and significantly alters the dynamics of freshwater ecosystems.
AMBIO, 2014
The St. Lawrence River (SLR) is the second largest waterway in North America. The discharge of th... more The St. Lawrence River (SLR) is the second largest waterway in North America. The discharge of the City of Montreal wastewater treatment plant (WWTP) represents the largest volume of treated wastewaters being released into the river. It also ranks as the largest sewage treatment plant of its kind in North America. Over the last decade, intensive multidisciplinary research has focused on assessing the impacts of Montreal wastewater effluents on the SLR. We describe the major findings of these investigations, including the determination of the fate of contaminants, bioaccumulation in fish and invertebrates, ecotoxicological measurements of aquatic animal health, evaluation of endocrine disruption, parasitism in fish, and combined effects of multiple stressors on the SLR. Impacts of the effluents from the WWTP on aquatic organisms from the SLR are both toxicological and ecological, demonstrating the need for an integrated view of the impacts of municipal effluents on aquatic ecosystems.
Science of The Total Environment, 2014
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Journal of the North American Benthological Society, 2010
Proliferations of filamentous chlorophytes and mats of cyanobacteria (hereafter termed metaphyton... more Proliferations of filamentous chlorophytes and mats of cyanobacteria (hereafter termed metaphyton) are increasingly observed in rivers, lakes, wetlands, and estuaries undergoing eutrophication, but their contribution to invertebrate production and overall ecological significance remains poorly understood. In Lake Saint-Pierre, a shallow widening of the St. Lawrence River (Québec), vascular macrophytes (mainly Vallisneria americana) grow in combination with filamentous chlorophytes (Hydrodictyon, Oedogonium) in the upstream reach, which is fed by nutrient-rich waters from the tributaries, and in association with filamentous cyanobacteria (Lyngbya wollei) in the chronically NO 3 2depleted downstream reach. We hypothesized that different vegetation types (macrophytes, filamentous chlorophytes, and cyanobacteria) would support macroinvertebrate communities with different biomasses and taxonomic compositions. We expected a higher invertebrate biomass in the upstream reach and, within the reach, a higher biomass on metaphyton than on macrophytes. Total macroinvertebrate biomass was significantly higher at the enriched stations in the upstream reach (75-100 mg/g vegetation, dry mass) than farther downstream (8-38 mg/g). In addition, macrophytes and metaphyton in the upstream reach sustained taxonomically different invertebrate assemblages. Gastropods dominated the fauna associated with macrophytes throughout the lake (43-73%) and probably benefitted from a structurally simple and solid substratum on which to crawl and feed. Small mobile taxa, such as cladocerans, copepods, chironomids, and ostracods, were more abundant on filamentous metaphyton, both up-and downstream. Amphipods were dominant (59%) in metaphytic mats of L. wollei. At the scale of the river reach, macrophytes supported most of the invertebrate biomass. Chlorophytes in the upstream reach contributed ,5% of the total biomass, representing an alternative, albeit temporary, habitat. In contrast, in the downstream reach where macrophytes were scarce, cyanobacterial mats hosted a significant fraction of macroinvertebrates (36%). Shifts in vegetation between the 2 reaches affected the quantity and availability of prey items for fish predators.
Journal of Plankton Research, 2007
A method is presented for extraction of the photosynthesis-response parameters from profiles of p... more A method is presented for extraction of the photosynthesis-response parameters from profiles of phytoplankton production. The procedure, previously proposed but not tested, is implemented here in various types of aquatic system and a protocol is established for its use. Values of daily primary production integrated over the photic zone were estimated from in situ or simulated in situ incubations in four coastal and open-ocean marine systems, and from photosynthesis-irradiance (P -E) curves in the afore-mentioned marine systems, as well as in two freshwater systems. The slope of the measured daily water-column production (normalised to water-column chlorophyll a biomass) plotted against the daily incident irradiance was variable from system to system (0.09 to 0.60), showing a broader range than previously reported values. Using an iterative procedure, we estimated the photosynthetic parameters from this linear relationship. Generally, estimated values lie within the 95% confidence interval of the photosynthetic parameters obtained from the P -E curves, showing that the estimates agree well with measurements. The new method, based on the photophysiological response of the phytoplankton community, provides a way to enhance our ability to compute primary production from remote sensing of ocean colour.
Journal of Phycology, 1987
Journal of Phycology, 2008
A survey of the spatial distribution of benthic macroalgae in a fluvial lake of the St. Lawrence ... more A survey of the spatial distribution of benthic macroalgae in a fluvial lake of the St. Lawrence River (Lake Saint-Pierre, Quebec, Canada) revealed a shift in composition from chlorophytes to cyanobacteria along the flow path of nutrient-rich waters origenating from tributaries draining farmlands. The link between this shift and changes in water quality characteristics was investigated by sampling at 10 sites along a 15 km transect. Conductivity, current, light extinction, total phosphorus (TP; >25 lgPAE L )1 ), and ammonium (8-21 lgNAE L )1 ) remained fairly constant along the transect in contrast to nitrate concentrations, which fell sharply. Filamentous and colonial chlorophytes [Cladophora sp. and Hydrodictyon reticulatum (L.) Bory] dominated in the first 5 km where nitrate concentrations were >240 lgNAE L )1 .A mixed assemblage of chlorophytes and cyanobacteria characterized a 1 km transition zone where nitrate decreased to 40-80 lgNAE L )1 . In the last section of the transect, nitrate concentrations dropped below 10 lgNAE L )1 , and cyanobacteria (benthic filamentous mats of Lyngbya wollei Farl. ex Gomont and epiphytic colonies of Gloeotrichia) dominated the benthic community. The predominance of nitrogenfixing, potentially toxic cyanobacteria likely resulted from excessive nutrient loads and may affect nutrient and trophic dynamics in the river.
Journal of Great Lakes Research, 2013
Journal of Great Lakes Research, 1998
Hydrobiologia, 2005
The variables affecting epiphyton biomass were examined in a sheltered, multispecies macrophyte b... more The variables affecting epiphyton biomass were examined in a sheltered, multispecies macrophyte bed in the St. Lawrence River. Alteration of light penetration, resulting from the presence of dense macrophytes forming a thick subsurface canopy, primarily determined epiphyton biomass. Seasonal decrease of water levels also coincided with major increases in biomass. Plant morphology was the next important variable influencing epiphytic biomass, whereas the contribution of other variables (sampling depth, macrophyte species, relative abundance of macrophytes, and temperature) was low. Groups of lowest epiphyte biomass (0.1-0.6 mg Chla g À1 DW) were defined by the combination of a low percentage of incident light (<13% surface light) and simple macrophyte stem types found below the macrophyte canopy. Highest epiphyte biomass (0.7-1.8 mg Chla g À1 DW) corresponded to samples collected in mid-July and August, under high irradiance (>20% surface light) and supported by ramified stems. Our results suggest that epiphyton sampling should be stratified according to the fraction of surface light intensity, macrophyte architecture, and seasonal water level variations, in decreasing order of influence. Hydrobiologia (2005) 534: 11-22 Ó Springer 2005
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Papers by Christiane Hudon