Effect of bioremediation on the microbial community in oiled mangrove sediments

Bioremediation was conducted in the field on a mature Rhizophora stylosa ma ngrove stand on land to be reclaimed near Fisherman's Landing Wharf, Gladst one Australia. Gippsland crude oil was added to six large plots (>40 m(2)) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled o nly plots. The bioremediation strategy consisted of actively aerating the s ediment and adding a slow-release fertilizer in order to promote oil biodeg radation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 10(4)-10(5)/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-deg rading population, increasing the population size by three orders of magnit ude from 10(5) to 10(8) cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-deg raders increasing from 10(4) to 10(6) cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-de graders in oiled mangrove sediment in the field. (C) 2000 Elsevier Science Ltd. All rights reserved.