Phytoplankton distributions observed during a % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaG4mamaali% aabaGaaGymaaqaaiaaikdaaaaaaa!3833!\[3{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\] days fixed-station in the lower St. Lawrence Estuary

Abstract

Phytoplankton biomass and species composition distributions, and the associated variability in the physiological vigor of the mixed populations, were described during a % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaG4mamaali% aabaGaaGymaaqaaiaaikdaaaaaaa!3833!\[3{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\] days fixed-station study in the Lower St. Lawrence Estuary. The relative constancy in the temperature-salinity curves, and the current meter data, suggest that a single water mass of complex surface structure on a spatial scale of tens of kilometers was being observed during the % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaG4mamaali% aabaGaaGymaaqaaiaaikdaaaaaaa!3833!\[3{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\] days fixed-station observations. The species composition was relatively constant but in the peak biomass samples the dominance of net plankton, two species of Thalassisira, was evident. At a surface discontinuity in S‰, pennate diatoms and flagellates dominated. Power and coherency spectra of the temperature, S% and chlorophyll a time series suggest that the biomass distributions are a function of physical rather than biological processes over the scale observer (10⁻² to 10² cycle per h). There was strong variability in the esturary at intermediate scales (hours, kilometers) in biomass, primary production and the derived parameters. The major features of the latter distributions (production/biomass ratios and carbon/chlorophyll ratio) were associated with species composition differences. The relative constancy in species composition over tens of kilometers is discussed in relation to other pelagic environments. The highly turbulent nature of estuaries and the frequency at which energy enters the environment in relation to the time necessary for differentiation of species composition suggests that niche diversity in this environment may be low.