MEPS 361:59-68 (2008)  -  DOI: https://doi.org/10.3354/meps07422

ABSTRACT: 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.

KEY WORDS: Tidal creeks · Sapelo Island · Salt marsh · Microzoobenthos · Microphytobenthos ·Ciliates · Meiofauna · Benthic food web