Factors controlling bacterial production in marine and freshwater sediments

We collected benthic bacterial production data measured by ³H thymidine incorporation (TTI) (25 studies), frequency of dividing cells (FDC) (3 studies), dark-C0₂ assimilation (1 study) and ³H-adenine uptake (2 studies) from the literature, which included 18 marine, 6 river, and 2 lake studies. In all of the studies that used the TTI method, ³H-DNA was isolated and incubations were carried out at in situ temperatures. Most of the researchers also determined ³H-DNA extraction efficiencies and isotope dilution, thus interpretable estimates of bacterial production were used in the analysis. In marine sediments, bacterial production rates were linked to bacterial biomass, bacterial abundance, sediment organic matter, temperature, and sediment chlorophyll a, with these variables explaining between 40% and 68% of the variation in production rates. Simple relationships between production and bacterial biomass or bacterial abundance, or between production and sediment organic matter, were improved by also including temperature in the analysis of marine sediments. Sediment organic matter explained an appreciable fraction (58%) of the observed production in freshwater sediments. Temperature was the most powerful predictor of the observed variability in specific growth rates (r² = 0.48 and r² = 0.58) in marine and freshwater sediments, respectively. Thus, bacterial production and specific growth rates are most closely linked to substrate supply and temperature in marine and freshwater sediments.Offprint requests to: B. C. Sander.