Vertical distribution of micro- and nanoplankton in the San Francisco Estuary in relation to hydrography and predators

摘要: Temperate estuaries are characterized by significant seasonal variability in the vertical salinity gradient, which, along with biological factors, may play a role determining plankton ver- tical distribution. We examined distribution of microplankton (20 to 200 µm) and nanoplankton (~5 20 San Francisco Estuary (SFE) over diel, interannual time scales, assessed degree which abiotic (hydrography) biotic (predation) factors influenced these patterns. sampled 2 hydrographically-distinct locations within SFE: Pablo Bay, partially-mixed estuary, South lagoonal estuary. conducted replicate Niskin bottle casts during day night at each location on 6 occasions between 1998 1999. also pump sampling for mesozooplankton (>153 4 dates. The micro- was often homogeneous depth, even under substantially different hydrographic conditions. ANOVA testing weighted mean depths (WMD) chlorophyll, major taxa nanoplankton, cope- pods (factors: location, year, season, day) revealed that only (specifi- cally ciliates) showed differences period. most WMD were observed seasonally. Ciliates copepods (Acartia spp.) diel several occasions, but rarely among other nanoplankton. stratification never correlated any or group, however distributions heterotrophic loricate aloricate ciliates dinoflagellates significantly chlorophyll autotrophic nanoflagellates (presumed food), as well Acartia spp predators). conclude relatively homogeneously distributed respect depth SFE. However, when more heterogeneous, had greater influence than (stratification)