Production of transparent exopolymer particles (TEP) by benthic suspension feeders in coastal systems

In the marine environment, transparent exopolymer particles (TEP) are ubiquitous and abundant, playing a significant role in carbon cycling and the structuring of food webs. Previous studies have shown that phytoplankton, bacteria, and oysters contribute to the production of TEP through the release of exopolymers. However, little is known about other potential sources of TEP and TEP precursors, especially in coastal systems. It was hypothesized that suspension feeders contribute to the TEP pool in near-shore environments through the release of exopolymers in both the dissolved and particulate form, and tested these hypotheses in both laboratory and field experiments. In the laboratory, the production of TEP by several species of benthic suspension feeders (the blue mussel, Mytilus edulis, the bay scallop, Argopecten irradians; the slipper snail, Crepidula fornicata; and the solitary ascidians, Ciona intestinalis and Styela clava) was investigated from October to November 2002 and June 2003. Concentrations of TEP and DOC were determined by spectrophotometry after alcian blue staining and high-temperature, catalytic oxidation, respectively. Similar analyses were conducted on water samples from the field in July 2003, collected in close proximity to dense beds of mussels in the Poquonnock River, Connecticut, USA (41 degrees 19' N, -72 degrees 02' W). Laboratory results indicated that activelypumping blue mussels, bay scallops, slipper snails, and both species of solitary ascidians significantly enhanced TEP concentrations above background levels over a five-hour period. However, only the solitary tunicate S. clava significantly enhanced DOC concentrations above background levels over the same period of time. Field samples indicated that TEP and DOC concentrations were high in close proximity to dense beds of mussels. These results imply that a variety of benthic suspension feeders produce TEP during feeding activities which could lead to enhanced flocculation of organic matter and carbon deposition in near-shore waters. (c) 2006 Elsevier B.V. All rights reserved.