Laboratory study of disturbance in marine sediments: response of a microbial community

Abstract

ABSTRACT. Disturbance has been shown to be an important component of the ecology of soft-bottom macrobenthic and meiobenthic marine communities. Its importance in the ecology of microbial com- munities was investigated by using sieving of marine sediments as a controlled disturbance. Following the disturbance, sediments were maintained in microcosms. Using a suite of biochemical measures, sieving was found to influence microbial biomass, community structure, and metabolic activity. Sieving caused an immedate decrease in microbial growth rates and a shift in metabolic status towards the synthesis of phospholipid. Microbial biomass was initially unaffected. Several hours later, growth rates increased and biomass had decreased by 75 %. Microbial biomass returned to pre-disturbance levels 8 h after sieving. Groups of phospholipid, ester-linked fatty acids, each associated with different functional groups of microorganisms, varied in their response to sieving. This result suggested that components of the microbial community differed in their reaction to this disturbance. Ambient sediments collected at the time of the construction of the microcosms were contrasted with sediments maintained in the laboratory microcosms for 5 d. Laboratory conditions significantly altered the microbial community structure and growth rates were significantly lower. Measures of metabolic status indicated that some of the microorganisms were stressed. This study demonstrates the potential significance of disturbance in the ecology of the benthic microbial community and that uncoupling sediment from the biotic and abiotic influences of the environment significantly affects the composition and activity of the microbial community. rates