ROA: Associated and Abiotically Released DOM: Significanceto Stream Detritivores

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Allochthonous inputs of organic matter to woodland streams comprise the principal energy source for diverse groups of detritivores during all, or for various stages of their life cycle. However, this statement only refers to the ability to ingest detritus and it remains poorly understood what components of detritus are assimilated. Associated microbial biomass is known to only contribute 12-45% of the dietary needs of the detritivores examined. Since detritivores lack the enzymes to degrade major plant structural components, it is suggested that other components of detritus are exploited by detritivores. It is proposed that the major dietary requirements of detritivores are provided by dissolved organic matter (DOM) which is associated with and/or released from coarse particulate organic matter (CPOM). The major source of this DOM is derived from organics which are: 1) released from the matrix of ingested detritus; 2) released from extracellular microbial products; or 3) transformed by microorganisms associated with their alimentary tract. It is hypothesized that detritivores have evolved a variety of feeding and digestive strategies to maximize the utilization of these resources. These are 1) physico-chemical properties associated with their midgut to release and digest these compounds; and 2) metabolism by hindgut micro-organisms and assimilation of these metabolites by detritivores. Studies will include: 1) characterization of the temporal qualitative and quantitative nature of DOM which is associated with and/or abiotically released from CPOM; and 2) determining the relative assimilation and fate of these ingested compounds. The significance of these studies not only applies to the basic principles of detritivore nutrition and growth, but to an understanding of carbon sorption, retention and turnover in lotic systems.