Document: DAV-3-71-1

Dynamics of bivalve species replacement during the zebra mussel invasion of the Hudson River.

STRAYER, D.L.* and H.M.MALCOM

Institute of Ecosystem Studies, Millbrook, NY 12545 ¹

Abstract:
The 3 families of bivalves that live together in the freshwater tidal Hudson River have different life cycles and showed different dynamics during the first decade of the zebra mussel invasion of the river. Zebra mussels, which have planktotrophic larvae and a life span of 3-5 years, appeared in the Hudson in 1991 and have dominated the ecosystem since fall 1992. They reduced phytoplankton biomass in the river by 80%. Because of strong adult-larval interactions, the zebra mussel population underwent large cycles with a 3-4 year period, the size and coherence of which appear to be diminishing. The native unionid mussels have parasitic larvae and live for more than 10 years. Formerly constituting more than half of zoobenthic biomass in the river, their populations have fallen by 80% and have not yet stabilized 7 years after the invasion. The 2 unionid species that breed in late summer have disappeared, while the single species that breeds in spring still persists. The sphaeriids have direct development and an annual life cycle. Although we have the least information about this family, it appears that sphaeriid populations in the Hudson fell by 72% in the first 2 years after the zebra mussel invasion and have remained low. Because bivalve populations have slow demographic response times, it may take years to decades for the effect of a perturbation to be fully expressed.

Keywords: invasions, zebra mussel, Bivalvia

This abstract is being presented at: 12:00 PM in session:
Oral Session #7: Aquatic Ecology: Shellfish to Snails.