The measurement of lipid phosphate is proposed as an indicator of microbial biomass in marine and estuarine sediments. This relatively simple assay can be performed on fresh, frozen or frozen-lyophilized sediment samples with chloroform methanol extraction and subsequent phosphate determination. The sedimentary lipid phosphate recovery correlates with the extractible ATP and the rate of DNA synthesis. Pulse-chase experiments show active metabolism of the sedimentary phospholipids. The recovery of added 14C-labeled bacterial lipids from sediments is quantitative. Replicate analyses from a single sediment sample gave a standard deviation of 11%. The lipid extract can be fractionated by relatively simple procedures and the plasmalogen, diacyl phospholipid, phosphonolipid and non-hydrolyzable phospholipid content determined. The relative fatty acid composition can be readily determined by gas-liquid chromatography. The lipid composition can be used to define the microbial community structure. For example, the absence of polyenoic fatty acids indicates minimal contamination with benthic micro-eukaryotes. Therefore the high content of plasmalogen phospholipids in these sediments suggests that the anaerobic prokaryotic Clostridia are found in the aerobic sedimentary horizon. This would require anaerobic microhabitats in the aerated zones.

Determination of the sedimentary microbial biomass by extractible lipid phosphate.

Use of fluorochromes for direct enumeration of total bacteria in environmental samples: past and present.

Deposit-feeding animals acquire food by swallowing large volumes of sediment. Possible food sources include organic debris and sediment-associated microbes. The relative importance of these classes of food is currelty an area of active research. The idea that microbes attached to sediment and detritus particles constitute the major food source for deposit feeders is being replaced by more complex models that incorporate interactions between animals and the food sources in the sedimentary matrix. Many deposit feeders appear to require both microbial and detrital foods. Deposit feeders display many adaptations appear to be cosistent with the energy maximization principle of optimal foraging theory, but rigorous testing of foraging models has proven to be difficult. Elucidation of deposit-feeding strategies may develop as optimal foraging theory is integrated with physiological energetics.

Ecology of Deposit-Feeding Animals in Marine Sediments

Microbial lipids of an intertidal sediment—I. Fatty acids and hydrocarbons

Fatty acids of bacterial origin in contemporary marine sediments

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1974.19.3.0509

Norman G. Dale

Papers

Bacteria in intertidal sediments: Factors related to their distribution1