The effect of an exotic serpulid on the planktonic community in estuarine environments

MA MARCOVAL; J PAN

Providence, Rhode Island, USA

Congreso; 19th Biennial Conference of the Estuarine Research Federation; 2007

Estuarine Research Federation

The reef-building polychaete Ficopomatus enigmaticus has become an exotic species to most temperate brackish waters. Like other serpulids, this suspension-feeder has the potential to graze on a broad range of particle sizes. In order to analyze preferences for different planktonic food sources from natural communities, we performed short grazing mesocosm experiments. Clumps of worms (~3.51 gDW) were placed into 9L cylindric tanks and filled in situ with ambient water from Mar Chiquita (MC) coastal lagoon and La Tigra (LT) coastal mixohaline stream (37-38ºS, Argentina). Relative clearance rates of phytoplankton were assessed partitioning the samples into total, <20µm and <5µm size-fractions using chlorophyll a concentration. Clearance rates for different groups of micro- and nanoplanktonic protists were calculated from microscopy counts. 40% of the chlorophyll in the coastal lagoon is >20µm, while in the mixohaline stream, 80% is <20µm (nanophytoplankton). No major differences were observed in clearance rates for the different chlorophyll fractions. Preliminary results indicate that in MC, where 57% of the protistan biomass was represented by centric diatoms and 40% by pennates, clearance rates were higher for the later. The same is true for LT, where the protistan biomass was 70 % pennate and 30 % centric diatoms.