Heterotrophic microbial activity in lake sediments: effects of organic electron donors

Abstract

Allochthonous and autochthonous organic matter deposited in benthic sediments are mineralized by microbial communities, resulting in release of nutrients to the water column. Lakes with different trophic states may have sediments with different carbon and nutrient concentration with consequently different microbial communities. Microbial diversity of surface sediments of three subtropical lakes of different trophic state was investigated by measuring catabolic response to a wide variety of carbon-substrates. Basal carbon dioxide and methane production rates were highest in Lake Apopka (hypereutrophic), followed by Lake Annie (oligo-mesotrophic) and Lake Okeechobee (eutrophic) sediments. The oligo-mesotrophic Lake Annie showed the highest metabolic quotient (qCO 2 ; proportion of basal respiration per unit of microbial biomass, 0.008 ± 0.001) indicating inefficient use of energy. The low qCO 2 found in Lake Apopka sediment indicated higher efficiency in using energy. Lake Okeechobee sediments had intermediary values of qCO 2 (M9 0.005 ± 0.001; M17 0.006 ± 0.0003; KR 0.004 ± 0.001) as compared with other lakes (lake Apopka 0.004 ± 0.14). Lake Apopka's sediment catabolic diversity was higher than that observed in other sediments. Addition of organic electron donors to sediment samples from all lakes stimulated heterotrophic activity; however, the extent of the response varied greatly and was related to microbial biomass. The hypereutrophic Lake Apopka sediments had the highest respiration per unit of microbial biomass with the addition of electron donors indicating that these sediments respired most of the C added. These results showed that sediments with different biogeochemical properties had microbial communities with distinct catabolic responses to addition of the C sources.

Stable isotope (δ13C and δ15N) values of sediment organic matter in subtropical lakes of different trophic status

“…Stratigraphic fluctuations in the d 13 C and d 15 N values of Lake Annie sediment OM probably reflect a combination of factors, including a shift in relative contribution of autochthonous/allochthonous OM, changing autochthonous primary productivity, and relative microbial biomass and activity (Torres et al 2011). Small, oligotrophic lakes might be expected to have relatively high proportions of allochthonous C contribution to sediment OM (Gu et al 1996).…”

“…Consequently, 13 C-rich CO 2 is transferred from the sediments to the DIC of the water column (Gu et al 2004). Lake Apopka sediments display high CH 4 production rates (Torres et al 2011). Furthermore, most of the OM generated by primary productivity in this lake is deposited in its sediments (Gale and Reddy 1994).…”

Some Metabolic, Diversity and Toxicity Aspects of Bacterial Communities Life in Aquatic Sediments

“…The oligo-mesotrophic lake sediment microorganisms had lowest efficiency in use of energy [1]. The lack of water circulation in stratified water bodies (with a thermocline and halocline) in conjunction with continuous O 2 -consumption by remineralization leads eventually to complete O 2 depletion.…”

“…Microbial biomass may be significantly in relation to rate of C source consumption in all lake sediments, suggesting that microbial activity is limited by C availability. Findlay (2003) showed that the addition of different carbon sources, i.e., glucose, bovine serum albumin and natural leaf leachate to hyporheic biofilms enhanced microbial activities [1]. Carbon sources may influence nitrate reducing activity of the biofilm.…”

Millennial-Scale Phosphorus Transformations during Diagenesis in a Subtropical Peatland

“…The linkage between nutrient loading, ecosystem trophic status, and sediment properties is not always direct. For example, Torres et al (2011) examined sediment properties of three lakes of widely varying trophic status, ranging from oligotrophic to hypereutrophic. They found the surface sediment of an oligotrophic lake to have the highest total P (1427 mg P kg −1 ), as well as highest labile forms of P, of the lakes they studied.…”