Marine Microbial Community Response to Inorganic and Organic Sediment Amendments in Laboratory Mesocosms
UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES CENTER FOR EARTH SCIENCES
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Sediment amendments provide promising strategies of enhancing sequestration of heavy metals and degradation of organic contaminants. The impacts of sediment amendments for metal and organic remediation including apatite, organoclay and apatite and organoclay in geotextile mats, acetate, and chitin on environmental microbial communities in overlying water and sediment profiles are reported here. These experiments were performed concurrent with an ecotoxicity evaluation data submitted in companion paper and X-ray absorption spectroscopy of zinc speciation post apatite amendments. X-ray absorption spectra showed that a modest modification of zinc speciation occurred in amended treatments. Significant changes in both bacterial cell densities and populations were observed in response to amendments of apatiteorganoclay, chitin, and acetate. The enriched bacteria and breakdown of these amendments were likely attributed to water quality degradation e.g. ammonia and dissolved oxygen. Molecular fingerprints of bacterial communities by denaturant gradient gel electrophoresis DGGE showed that distinct bacterial populations occurred in overlying waters from different amendments aapatiterganoclay led to the dominance of Gammaproteobacteria, acetate enriched Alphaproteobacteria, and chitin treatment led to a dominance of Bacteroidetes and Alphaproteobacteria. In amended sediments, Firmicutes, Bacteroidetes, and Deltaproteobacteria Desulfovibrio were commonly found with chitin and apapatiteitin treatments. Finally, sulfate-reducing bacteria e.g. Desulfovibrio and metal-reducing bacteria were also recovered with most probable number MPN analyses in treatments with acetate, chitin, and apaapatitetin. These geochemically important bacteria were stimulated by amendments and may play critical functional roles in the metal and organic contaminant remediation process for future investigations of contaminated sediments.
- Inorganic Chemistry
- Organic Chemistry