PARENT SESSION
Posters P2D Marine photosynthesis and production. Abstracts (711-719)

Group-specific primary production in the Scheldt Estuary. Nicole Dijkman^*,1, Jacco Kromkamp¹, ¹ Netherlands Institute of Ecology-Centre for Estuarine and Marine Ecology, Yerseke, the Netherlands

ABSTRACT- Natural phytoplankton communities consist of species from various taxonomic groups. Measurements of primary production usually provide a number for the complete phytoplankton community, without differentiating between the algal groups present in the sample. The aim of our work is to calculate group-specific primary production, i.e. the contribution of the different taxonomic groups to primary production. This is done using 13C labeling of phospholipid-derived fatty acids (PLFA′s). Similar to pigments, some PLFA′s are specific for certain phytoplankton groups and can be used as chemotaxonomic markers. Field measurements during which this method was tested were done in the Scheldt Estuary, which is a well mixed tidal system situated in the border region of the Netherlands and Belgium. At five stations along the salinity gradient phytoplankton composition and group-specific primary production were determined using PLFA′s as chemotaxonomic markers. At all salinities both diatoms and green algae were found to be present, with diatoms dominating at most stations. A bloom of Phaeocystis sp. was detected during spring. Primary production by both green algae and diatoms, and of Phaeocystis sp. when present, was also measured at all stations. Remarkable was the high production rate of green algae compared to diatoms at stations where green algae were far less abundant than diatoms. This technique will be helpful in answering ecological questions, especially since other taxonomic groups, like bacteria, also posses characteristic PLFA′s. This allows for example to study the transfer of photosynthetically fixed carbon to other trophic levels.

KEY WORDS: primary production, fatty acids, phytoplankton, biomarkers