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Aquatic Microbial Ecology

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AME 39:135-144 (2005)  -  doi:10.3354/ame039135

Grazing on diatoms by harpacticoid copepods: species-specific density-dependent uptake and microbial gardening

Marleen De Troch1,*, María Björk Steinarsdóttir3, Victor Chepurnov2,Emil Ólafsson4

1Marine Biology Section, and 2Protistology and Aquatic Ecology, Biology Department, Ghent University, Campus Sterre, Krijgslaan 281 – S8, 9000 Gent, Belgium
3Institute of Biology, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland
4Department of Zoology, Stockholm University, 10691 Stockholm, Sweden

ABSTRACT: Four common intertidal harpacticoid species (Paramphiascella fulvofasciata, Tigriopus brevicornis, Nitocra spinipes and Harpacticus obscurus) were offered pelagic diatoms (Phaeodactylum tricornutum) as food in laboratory experiments. To ensure generality we used copepod species originating from diverse habitats with different ecological characteristics. The diatoms were enriched in the stable carbon 13C isotope to facilitate tracing in the harpacticoids. Uptake of diatoms was clearly species-specific and in general P. fulvofasciata was more efficient than the other species. We found significant uptake by 24 h of incubation for T. brevicornis. From 24 h onwards we found an increase for all 3 species. Species had similar δ13C values before and after starvation, indicating that labeled material was efficiently assimilated in their tissues. We tested whether diatom assimilation is density-dependent and this was true for 2 species (N. spinipes and P. fulvofasciata) but not for the semi-pelagic T. brevicornis. Finally, a positive effect of faecal pellets on food uptake for the less mobile species was shown, indicating that microbial gardening occurs within benthic harpacticoids as it does for several other crustacean species.

KEY WORDS: Copepoda · Diatoms · Grazing · Assimilation · Stable isotopes

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