PAN Jeronimo
congresos y reuniones científicas
A mesocosm study of shellfish suspension-feeding effects on the plankton community of a coastal lagoonal estuary.
Mar del Plata
Congreso; The Changing Coastal and Estuarine Environment: A Comparative Approach; 2012
Mesoscale (0.4 m3) field incubations incorporated commercial (hard clam, Mercenaria mercenaria) and non-commercial (ribbed mussel, Geukensia demissa) bivalves, at varying densities, and in single- and multispecies assemblages, to assess the potential ecological effects of increased benthic suspension-feeding on the planktonic structure of Great South Bay, USA. The rationale behind incorporating shellfish at different densities was to create increased water turnover due to bivalve filtration, simulating the conditions of the system when benthic suspension-feeders were dominant. M. mercenaria and G. demissa differ in habitat requirements; the former burrowing subtidally in soft-bottoms, and the latter inhabiting intertidal Spartina alterniflora saltmarshes, albeit sharing a common trophic resource (i.e., plankton). The effects on the biomass of several planktonic components (picocyanobacteria, picoeukaryotes, auto- and heterotrophic nano- and microplankton, and micrometazoa) and concentration of other environmental parameters (total and < 5-µm chlorophyll a, nutrients) was quantified through different methods, and analyzed with multivariate techniques (redundancy analysis, RDA). Both bivalve species invariably exerted top-down control on phytoplankton biomass, and drove changes in plankton community composition (e.g., G. demissa had positive effects on centric diatom biomass, while effects on pennate diatoms were mostly negative). The bivalves controlled densities of rotifers, while they had positive effects on eggs and larvae of copepods, pointing to complex relationships among planktonic components. Interactive effects arose in two-species bivalve tanks, exerting diverging effects on planktonic groups than either shellfish alone. Results from this study contribute to ecological restoration plans for Great South Bay and indicate that a mult-shellfish re-stocking strategy might yield diverging results from a single-population stocking strategy.