The Measurement of Electron Transport System Activity in Freshwater Benthic and Planktonic Samples

Abstract

The measurement of electron transport system (ETS) activity in freshwater benthic and planktonic samples was examined. Significant improvements in sensitivity were obtained by increasing the concentration of substrates and of Triton X-100 in the extraction buffer and by changing the buffer system. The mechanical homogenization procedures which have been used previously to extract the enzymes were shown to be inadequate yielding, at best, 25% of the activity obtained by ultrasonication. The yield of enzymes from sediments was greatly affected by the degree of dilution used and previously published methods would appear to be inadequate.ETS activity correlated well with biological oxygen uptake and, in individual water and sediment profiles, with microbial numbers and biomass. At a more general level, however, the ETS :biomass ratio showed considerable variation.

A modified method for studies of electron transport system activity in freshwater sediments

“…The maximum activity obtained with mechanical treatment was only 25% of the activity achieved with the sonification method. Similar results are reported by Jones & Simon (1979).…”

“…In ETSA analyses of sediments, a mechanical homogenizer (Olanczuk-Neyman & Vosjan, 1977) grinding in a mortar with quarts sand (Wieser & Zech, 1976) and sonification (Christensen & Packard, 1977;Jones & Simon, 1979), have been used. In this study, different amounts of sediment from Lake Erken were homogenized in an ice bath using both sonification and a mechanical homogenizer (Polytron P T 10, 2.5 min.…”

“…S2 ), INT-formazan was formed very quickly during incubation, thereafter the absorbance of the 'turbidity blank' was relatively stable. Among oth- ers, Jones & Simon (1979) did not include INT in their turbidity blanks, which means that they did not correct for chemical reduction of INT. At low activity in the sample and high absorbance in the turbidity blank the incubation time must be increased in order t o get the necessary accuracy in the measurements.…”

“…Methods described earlier for marine sediments must accordingly be modified to suit the freshwater environment. Such a modification has been performed by Jones & Simon (1979). Their assay is based on that of Owens & King (1975), which was developed to measure the respiratory activity of marine zooplankton.…”

Increased Temperature Due to Global Warming Alters the Respiratory Potential in Aquatic Organisms from an Oligotrophic Lake

“…It has been shown that the respiratory potential of sediment depends on microbial abundance (JONES and SIMON, 1979), depth of the sediment (RELEXANS, 1996a), depth of water column above the sediment (CHRISTENSEN and PACKARD, 1977;RELEXANS, 1996a), temperature (TREVORS, 1984;G.-TÓTH et al, 1994;TÖRNBLOM and PETTERSSON, 1998), availability of organic matter for organisms (TREVORS, 1984;RELEXANS, 1996b), source of food (BROBERG, 1985), protein concentration (CHRISTENSEN and PACKARD, 1977), and trophic level of the lake (G.-TÓTH, 1992;MURI and SIMČIČ, 2004).…”