ABSTRACT: To test the response of a natural benthic microbial assemblage to differences in the composition of organic matter supply, surface sediments from the Arctic continental slope (1000 m water depth) were enriched with a variety of organic compounds. Glycine and glucose represent substrates which can be directly utilized by bacteria; protein, chitin, cellulose, starch and the lipid Tween require extracellular hydrolysis by peptidase, chitobiase, beta-glucosidase, alpha-glucosidase and lipase, respectively. The effect of these enrichments on hydrolytic activity potentials and on several parameters of microbial biomass was observed over a period of 63 d. Within 10 d, specific activities of beta-glucosidase and chitobiase were enhanced by their respective substrates by a factor of 10 to 20. alpha-Glucosidase and peptidase were greatly inhibited in the presence of glucose and glycine, respectively. Peptidase, alpha-glucosidase and lipase activities were not induced by their respective substrates. The supply of starch, lipid and cellulose did not cause detectable growth of the bacterial assemblage for the whole period of the experiment. Enrichment with glycine, albumin, chitin and glucose resulted in significant biomass production of the bacterial populations with similar growth rates of 0.1 d^-1 after a lag phase of up to 10 d. However, the supply of amino acid sources resulted in a 60% higher bacterial biomass yield after 63 d compared to chitin and glucose.

KEY WORDS: Extracellular enzymes · Bacterial growth · Benthic bacteria · Organic matter supply · Deep-sea sediments

Published in MEPS Vol. 140 (1996) on September 12
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996