Spatial uptake of dissolved organic carbon in river beds

Abstract

The uptake of dissolved organic carbon by three stream bed components ; surface stones, underlying gravel and organic floc was measured in three rivers in North Wales, U .K . Overall, surface stones and underlying gravel appeared to be the major sites of uptake but the relative importance of these two components varied both temporally and spatially . Organic floc was found to be relatively unimportant as a site of dissolved organic carbon uptake .

Aquatic protists modulate the microbial activity associated with mineral surfaces and leaf litter

“…We suggest that the discrepancy between the community respiration associated with a mineral surface and leaf litter was related to the available carbon and nutrient resources. Initial biofilms grown at mineral surfaces receive nutrients and organic carbon mainly from the overflowing water (Lock 1979, Mickleburgh et al 1984, Battin et al 1999). In our experiments, the growth of young biofilms at mineral surfaces was controlled by the dissolved organic carbon of the medium.…”

“…In streams, these sites are hot spots of carbon turnover (Geesey et al 1978). The microbial activity of biofilms at mineral surfaces is nourished by the dissolved organic carbon (DOC) in the surrounding water during the initial biofilm development (Mickleburgh et al 1984, Sobczak 1996, Romaní et al 2004). To gain their required carbon, microbial communities on organic substrates utilize the organic substances of the wood or leaf tissue itself.…”

The biofilm polysaccharide matrix: A buffer against changing organic substrate supply?

“…First, analog approaches have studied the responses of stream bacteria to the addition of radiolabeled model monomeric compounds such as amino acids (Ladd et al 1982;Fiebig and Marxsen 1992). Second, biofilm bacteria have been challenged with added nondefined DOC mixtures such as leaf extracts and their metabolic responses recorded (Kaplan and Bott 1985;Mickleburgh et al 1984). Third, studies have been made of the impacts on the microbes of the removal of components of the DOC pool such as phenolics (Freeman et al 1994) and specific molecular weight fractions (Lock and Ford 198 5;Ford and Lock 1987).…”

Hyporheic biofilm development on artificial substrata, as a tool for assessing trophic status of aquatic systems : first results

“…Biofilms are mixed assemblages of bacteria, fungi, and algae that develop on all surfaces in contact with water (Trulear & Characklis 1982, Lock et al 1984, Characklis & Marshall 1990). As they grow, microbial.…”

“…organisms secrete a polysaccharide matrix, the glyeocalyx. This matrix displays adsorption and diffusion properties that favour the retention of dissolved organic matter from the water column (Mickelburg et al 1984, Jones & Lock 1989, Fiebig & Lock 1991, Fiebig 1992, Flemming 1995, Freeman et al 1995. Thus, biofilms play a major role in biogeochemical processes such as nutrient cycling (Liu et al 1993).…”