Do transparent exopolymer particles (TEP) inhibit grazing by the euphausiid Euphausia pacifica?
The hypothesis that ubiquitous, sticky transparent exopolymer particles (TEP) formed from phytoplankton exudates will adhere to and coat the feeding structures of marine zooplankton grazers, and thus depress feeding on phytoplankton, was tested using the euphausiid, Euphausia pacifica, as a model organism. During two feeding experiments, E.pacifica were offered cells of the diatom Thalassiosira weissflogii, TEP, or both TEP and T.weissflogii cells. Ingestion rates on cells were lower in the presence of TEP. However, contrary to the hypothesis, grazing on cells was not inhibited by TEP. Rather, TEP-clusters, aggregates which formed from TEP and nano-sized particles normally too small for the filtering apparatus of E.pacifica to retain, served as an alternative food source for E.pacifica, reducing their ingestion of cells. These clusters were very similar in form to the TEP actually available to marine grazers in nature. TEP-clusters were similar to cells in size and food quality, and we
