SS3.06 Large Scale Change in Prominent Ecosystems
Date: Wednesday, June 12, 2002
Time: 12:00:00 PM
Location: Lecture Theatre
 
BarnardC, Universite du Quebec a Trois-Rivieres, Departement de chimie-biologie, Trois-Rivieres, Canada, christine_barnard@uqtr.ca
Frenette, J, J, Universite du Quebec a Trois-Rivieres, Departement de chimie-biologie, Trois-Rivieres, Canada, jean-jacques_frenette@uqtr.ca
Vincent, W, F, Universite Laval, Departement de biologie, GIROQ, Ste-Foy, Canada, Warwick.Vincent@bio.ulaval.ca
 
ST. LAWRENCE MIDDLE ESTUARY INVADERS : ZEBRA MUSSEL VELIGERS AND THE ENVIRONMENTAL VARIABLES PREDICTING THEIR DISTRIBUTION AND IMPACTS
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Zebra mussel veligers have recently become a dominant species in the plankton of the estuarine transition zone (ETZ) of the St. Lawrence River. Since their arrival, the zooplankton community (>63um) has altered dramatically. This study describes the previously undocumented distribution of these veligers in the dynamic ETZ as well as critical aspects of their chemical, physical and biological environment. Their longitudinal distribution across the ETZ is mainly controlled by salinity with a sharp decrease at > 4 psu, but other factors such as mortality due to stress associated with advective transport (turbulence) and predation may also be responsible. Their vertical distribution is homogeneous throughout the water column and this was observed even in a stratified environment. Stations with high veliger densities were associated with high concentrations of chlorophyll a and photosynthetic picoplankton (0.2-2um). These findings suggest that their dominance has not affected the total biomass of phytoplankton. However, their impacts on the biomass size spectrum of the plankton community (<63um) is currently being investigated and will be discussed.