The zebra mussel Dreissena polymorpha and the Asian clam Corbicula fluminea
are invasive, bio-fouling species that were introduced into North America during the last
century. Invasive bivalve introductions may result in a loss of biodiversity, particularly
among vulnerable native freshwater mussel populations. The goal of this project was to
investigate the temporal and spatial distribution of native and invasive freshwater
bivalves in Bayou Lafourche, a controlled distributary of the Mississippi River. This
study also addressed the temperature tolerance of zebra mussels collected from a warm
water (31ºC), high sediment environment.
Native and invasive bivalves were sampled during ten sampling trips from 2007
to 2010, using a ponar sampler and bridge scrapings. Zebra mussel thermal tolerance was
assessed in a laboratory study. High densities (6,070 clams/m2
) of Asian clams were
found in the upper part of Bayou Lafourche (Donaldsonville to Thibodaux) accounting
for 94% of the bivalves collected. Mean benthic zebra mussel densities were low (< 60
mussel/m2
) in Bayou Lafourche, with 1.8% of ponar samples (19 of 1,050 ponar grabs)
containing live zebra mussels. During the summers, cooler water temperatures that may
have served as thermal refugia for zebra mussels (< 31ºC) occurred closest to the
Donaldsonville pumping station, and temperature increased by 0.1ºC for each kilometer
downstream. Few (N=46) native freshwater mussels were collected during this study,
although five previously undocumented species were identified from Bayou Lafourche.
Native freshwater mussels of southeastern Louisiana are poorly studied and the impacts
and distribution of invasive species in the Lower Mississippi River Basin should be
determined if native species are to be managed and conserved.