The impact of the
freshwater bivalve Corbicula leana on
plankton community dynamics was examined during a cyanobacterial bloom period.
Nutrient and
chlorophyll concentrations, primary
productivity, and
phytoplankton and
zooplankton communities in the experimental enclosures were measured at 2-3 day intervals. The introduction of
mussels reduced net primary
productivity and
phytoplankton and
chlorophyll.
Chlorophyll decreased immediately following addition of 100
mussels and then increased over
time. After 600
mussels were added,
chlorophyll decreased continuously from 87 to 25 μg l-1, approaching that in the
mussel-free enclosure. Simultaneously,
water transparency increased and concentrations of
suspended solids and total
phosphorus decreased.
Mussel addition caused short-term increases in
nutrient concentrations, especially following high-density
treatment phytoplankton density decreased, while
cell density in the
mussel-free enclosure increased.
Zooplankton densities in the two enclosures were
similar; however,
carbon biomass in the
mussel enclosure increased, associated with an increase in large
zooplankton. The trophic relationship between
phytoplankton and
zooplankton was positive in the
mussel-free enclosure and negative in the
mussel-
treatment enclosure, possibly reflecting effects of
mussels on both consumer and
resource control in the
plankton community. Thus, filter
feeding by
Corbicula affects nutrient recycling and
plankton community structure in a
freshwater ecosystem through direct
feeding and competition for
food resources.