MEPS prepress abstract  -  DOI:

Impact of Eastern oyster, Crassostrea virginica, biodeposit resuspension on the seston, nutrient, phytoplankton and zooplankton dynamics: A mesocosm experiment

Elka T. Porter*, Heather Franz, Richard Lacouture


ABSTRACT: To test the effect of Crassostrea virginica biodeposit resuspension on nutrient and plankton dynamics, a 4 wk experiment was performed in six 1000 l shear-turbulence-resuspension-mesocosms (STURM) without a sediment bottom (R). Three tanks received 5.77 ± 3.33 mg total suspended solids daily additions of oyster biodeposits (R_BD). Tidal resuspension of biodeposits in the R_BD tanks resulted in 90 mg l-1 total suspended solids concentrations when mixing was on, decreasing to ca 20 mg l-1 when mixing was off. However, bulk settling speeds of particles in the R_BD tanks increased 3-fold over the experiment. Particulate nitrogen, phosphorus and carbon concentrations, as well as dissolved inorganic nitrogen, nitrate + nitrite, dissolved organic phosphorus and total dissolved phosphorus levels were significantly higher in the R_BD tanks. While 72% of the nitrogen was partitioned in the total dissolved nitrogen in the R_BD tanks, 51.5% were partitioned in microphytobenthos in the R tanks. While chlorophyll a concentrations were higher in the R_BD tanks than in the R tanks (despite tunicates being found in the R_BD tanks) phytoplankton biomass (Carbon) as estimated using direct cell counts, was not significantly different and there was little difference in phytoplankton composition. However, the ratio of Chl a:C was higher in the R_BD tanks suggesting phytoplankton adjusted to low light in the R_BD tanks by increasing chl a in their cells. Acartia sp. abundance was also increased in the R_BD tanks. Addition and regular tidal resuspension of oyster biodeposits profoundly affected nutrient dynamics, nitrogen partitioning, and zooplankton community dynamics.