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Aquatic Microbial Ecology

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AME 18:187-196 (1999)  -  doi:10.3354/ame018187

Hydrolysis and mineralization of chitin in the Delaware Estuary

David L. Kirchman*, Jacques White**

College of Marine Studies, University of Delaware, Lewes, Delaware 19958, USA
**Present address: People for Puget Sound, Seattle, Washington 98101, USA

ABSTRACT: We examined various aspects of chitin degradation in order to estimate degradation rates and the contribution of chitin to supporting bacterial growth in the Delaware estuary. Hydrolysis of the chitin analog, methylumbelliferyl-N,N'-diacetyl-chi tobioside (MUF-diNAG), and mineralization of 14C-chitin varied in a complex pattern in the estuary and correlated only weakly at best with various indices of chitin production. Rates of MUF-diNAG hydrolysis and 14C-chitin degradation were within an order of magnitude of each other, with hydrolysis rates usually exceeding chitin mineralization. Consistent with hydrolysis being greater than mineralization, we found substantial release of 14C-labeled dissolved organic matter (DOM) during degradation of the 14C-chitin; DOM release was roughly equal to respiration of 14C-chitin. This DOM release could support growth of bacteria not attached or otherwise associated with the chitin, but rates of DOM release and direct chitin degradation seem low relative to bacterial production. During 2 cruises in July and October, chitin appeared to support 5% or less of bacterial production, whereas during one cruise in September the percentage was about 30%. Estimates of chitin inputs into marine systems indicate that on the order of 10% of bacterial production could be supported by chitin. Although it appears low, few individual biochemicals are likely to support much more bacterial growth than chitin, with the possible exception of protein and amino acids.

KEY WORDS: Chitin · DOC · DOM · Heterotrophic bacteria · Detritus

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