|
Pace, M.L., S.E.G. Findlay, and D. Fischer, 1998. Effects of an Invasive
Bivalve on the Zooplankton Community of the Hudson River, Institute of
Ecosystem Studies.
Reprinted with Permission from Freshwater
Biology (1998) 39(1): 103-116
Effects of an Invasive Bivalve on the Zooplankton Community of the Hudson
River
Abstract
- Previous studies documented that zebra mussels became abundant in the
Hudson River during 1992 causing an N-90% reduction in phytoplankton
biomass. This study used intervention time series analysis of abundance,
biomass and reproduction over the period 1987-95 to assess changes in
zooplankton in response to the invasion.
- Zebra mussels caused a size-dependent decline in zooplankton.
Microzooplankton, including tintinnid ciliates, rotifers and copepod nauplii
all declined in 1992 and were scarce thereafter. Mean abundances of post-naupliar
copepods and of cladocerans were also lower following the invasion but these
changes were not statistically significant (P > 0.05). Egg ratios and
clutch sizes for the dominant cladoceran, Bosmina freyi, were not
significantly related to zebra mussels, even though relatively low egg
ratios were observed after the invasion.
- The strong declines in microzooplankton were probably caused by direct
zebra mussel predation. Estimated consumption rates by mussels were roughly
equivalent to maximum microzooplankton growth rates.
- The total biomass of zooplankton in the Hudson River declined by more than
70% following the invasion. Annual average zooplankton biomass was
correlated with chlorophyll, but biomass per unit chlorophyll in the Hudson
River was much lower than in lakes. The present study hypothesizes that this
lower biomass reflects limitations by riverine flow and by predation during
summer.
Contact: Michael Pace, Institute of Ecosystem Studies, Box AB,
Millbrook, NY 12545-0129
Key Words: Zebra_mussel, Environmental_impacts,
Population_dynamics
Product Type: Research,
Impact
User Type: General
|