Y. Nakamura et F. Kerciku, Effects of filter-feeding bivalves on the distribution of water quality and nutrient cycling in a eutrophic coastal lagoon, J MAR SYST, 26(2), 2000, pp. 209-221
The horizontal variation of water quality was investigated through field su
rveys in a cross-section of Lake Shinji, the littoral region of which is de
nsely populated by the filter-feeding bivalve, Corbicula japonica. The dist
ributions of chlorophyll a (chl. a) and nutrients (NH4-N and PO4-P) in the
lake are greatly affected by the filtration and excretion rates of C. japon
ica. Minimum values for chi. a and maximum values for nutrients were both f
ound to occur in the littoral region during summer. Chi. a concentration pe
aked about 1 km from the shoreline, indicating that the presence of the biv
alve not only reduces the biomass of phytoplankton in the near shore region
through filtration, but also stimulates primary production further offshor
e by supplying nutrients through excretion. Calculated results of a mathema
tical model reproduced well the observed horizontal distributions of chi. a
and nutrients, indicating that the interaction between the filter-feeding
bivalve and phytoplankton populations dominates material cycling and water
quality distribution in the lake. Water mass exchange between littoral and
pelagic water enables the nutrient exchange between the bivalves in the ben
thic zone and the phytoplankton in the pelagic zone, thereby forming a bent
hic-pelagic zone coupling. Other related findings were that seasonal patter
ns of water quality variations in the north-south cross-section were affect
ed by metabolic rates of C. japonica, and that differences in concentration
s between pelagic and littoral regions are largest when water temperature i
s optimal for bivalve activity. (C) 2000 Elsevier Science B.V. All rights r
eserved.