Effect of the invasive filter-feeder Ficopomatus enigmaticus (Polychaeta: Serpulidae) on the zooplankton assemblage in a coastal lagoon.

MARTIN BRUSCHETTI; TOMAS LUPPI; OSCAR IRIBARNE

MAR DEL PLATA

Conferencia; The Changing Coastal & Estuarine Environment: A Comparative Approach; 2012

Coastal and Estuarine Research Federation (CERF)

Invasive species may exert strong effects on structure and function of marine ecosystem. One of the main direct effects of the invasive benthic filter-feeders in several ecosystems is the decrease of biomass of primary producers. Also, certain filter-feeders can affect the pelagic food web and reduce the zooplankton abundance and species composition. Depletion of phytoplankton biomass by the invasive reef forming polychaete Ficopomatus enigmaticus has previously been observed in the Mar Chiquita coastal lagoon (37º 40´ S, 57º 23´ W; Argentina), but the effect of polychaete filtration on the higher trophic levels has not been studied. To evaluate the direct and indirect effect of these reefs on the zooplankton assemblage, in situ replicated mesocosms (1 m diameter, 1.2 m depth) enclosing reefs and without reefs were installed in spring, summer and winter. The results shows that in winter and spring the zooplankton assemblage was dominated for the crustacean nauplii larvae. Contrary, in summer was dominated for polychaete larvae and cladocerans. The number of individuals in the cold season was lower, but the evenness and diversity of the zooplankton assemblage was higher than in the warm season. However, the reefs generated minor changes on abundance and composition of zooplankton assemblage. Nevertheless, in summer during the peak abundance of cladocerans and during the major effects of the reefs on Chlorophyll a concentration, the number of cladocerans strongly decreased in mesocosms with added reefs. Consequently, this outcome generated an increase of evenness and diversity of the zooplankton. Although Ficopomatus would not control the overall abundance and diversity of zooplankton assemblage, our work shows an important impact on other filter-feeder zooplankters and possibly on higher trophic levels in estuarine food web.