Keywords: bacteria, benthic microbial loop, microphytobenthos, meiofauna, oil spills
Benthic microbial loop and meiofaunal response to oil-induced disturbance in coastal sediments: a review
This review of benthic microbial loop and meiofaunal response to oil-induced disturbance describes examples from field investigations on some of the major oil spills of the past 20 years. It focuses on the microbial and meiofaunal compartments that, being characterized by short generation time, life cycle, sensitivity to environmental disturbance, are expected to respond rapidly to environmental changes and to provide accurate indications on the oil spill impact. The results of these researches demonstrate that increased sedimentary oil contents have generally limited effects on microphytobenthic assemblages, but stimulates benthic bacterial response (in terms of biomass and activity). Benthic protozoa appear to be initially sensitive to oil contamination but are afterwards stimulated. Such increased organic levels (i.e. oil input) might change the structure and functioning of the benthic microbial loop, with important consequences on the higher trophic levels. Generally, oil toxicity induces only initially strong meiofaunal mortality (particularly on copepods, turbellarians and ostracods, but in certain cases also on nematodes) with consequences in terms of diversity, richness and k-dominance curves. Oil disturbance has generally only temporary effects, but changes in trophic structure of meiofaunal assemblages suggest an adaptation of these communities to changes in the benthic microbial loop structure. The use of different microbial and meiofaunal indicators of oil disturbance are discussed and proposed for future monitoring studies.