Woods Hole Oceanographic Institution

Matthew First

»Environmental factors shaping microbial community structure in salt marsh sediments
»The model high molecular weight DOC compound, dextran, is ingested by the benthic ciliate, Uronema marinum, but does not supplement ciliate growth
»Microzooplankton growth and trophic interactions and their effects on herbivory in coastal and offshore environments
»Protistan bacterivory and benthic microbial biomass in an intertidal creek mudflat
»Microzooplankton growth patterns across natural and experimental trophic gradients: Implications for herbivory studies
»Growth and grazing rates of bacteria groups with different apparent DNA content in the Gulf of Mexico

First, M.R. and J.T. Hollibaugh , Protistan bacterivory and benthic microbial biomass in an intertidal creek mudflat , Marine Ecology Progress Series, 2008

We examined 8 sediment samples collected at 3 h intervals at Dean Creek (Sapelo Island, Georgia) to assess the impact of protist bacterivory on the standing crops of benthic bacterial biomass. The combined biomass of the benthic microalgae (BMA), bacteria, heterotrophic protists, and meiofauna ranged from 0.41 to 0.57 mg C g-1 wet sediment (gws) in the samples examined. BMA represented >80% of total biomass and remained relatively stable throughout the study period. Bacterial biomass ranged from 28 to 91 µg C gws-1 (5 to 16% of total biomass) in the samples. Heterotrophic protists (mainly ciliates, flagellates, and testate amoeba) and meiofauna (mainly nematodes) each contributed small (<1% each) amounts to the total biomass. Protist grazing accounted for the loss of <1.1 and <4.7% h-1 of the total and enzymatically active bacterial standing stock, respectively. Grazing rates were highest in the morning samples, concurrent with the highest portion of potentially active bacteria. However, there was no statistically significant change in grazing impact throughout the day and in most cases bacterivory would not reduce the standing bacterial biomass. Food web simulations demonstrate that the confluence of protist loss factors (such as meiofaunal predation) and reduced grazing at low bacterial concentrations can limit the production of bacterivorous protists and, in turn, their use of the large store of benthic bacterial biomass.

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