Detrital microbial community development and phosphorus dynamics in a stream ecosystem

Detrital microbial community development and phosphorus dynamics in a lotic system were investigated in non-recirculating laboratory streams contains leaf detritus. Temporal patterns of microbial colonization, as determined by scanning electron microscopy, indicate leaf species dependency and that bacteria were the first colonizers followed by fungi. An extensive glycocalyx layer developed. Phosphorus incorporation rates of both the whole community and intracellular components were determined by time-course measurements of 33PO4 or 32PO4. Phosphorus turnover rates were determined by a sequential double-labeling procedure using 33PO4 and 32PO4, in which the microbiota were labeled with 33P until in isotopic equilibrium, then 32P was added. The turnover rate was determined by time-course measurements of the ratio 32P to 33P. Snail grazing resulted in an increase in phosphorus metabolism per unit microbial biomass; however, per unit area of leaf surface no increase was observed. Grazing also caused a two-fold reduction in microbial biomass. The results indicate that microbiota associated with decomposing leaves slowly recycle phosphorus, are slowly growing, and have a low metabolic activity. The spiraling length is shortened by microbiota on a short-term basis; however, it may increase on a long-term basis due to hydrological transport of detritus downstream