Abstract
Measurements of microbial extracellular polymeric substances (EPS) of natural field populations are required to understand the processes of biogenic stabilization and the microbial ecology of intertidal sediments. EPS in sediments can be measured by the phenol‐sulfuric acid assay to measure carbohydrate concentration in sediment samples. We conducted comparative studies of storage and extraction methods for carbohydrate fractions on intertidal estuarine sediments. Measurements of both total and colloidal (material remaining in suspension after aqueous extraction and centrifugation) carbohydrate concentrations were highly dependent on storage conditions, sample size, extraction media, and time. Precipitation (in 70% ethanol) of EPS from saline (25‰) extractions of colloidal carbohydrate (colloidal S) from four different sediment microbial assemblages showed that 20% of colloidal carbohydrate present in extracts consisted of EPS. Concentrations of colloidal S were highly correlated with diatom biomass as determined by chlorophyll a concentrations. Extractions that used 100 mM Na2EDTA as the extracting medium (colloidal EDTA) increased the concentrations of colloidal carbohydrate obtained and, in sediments dominated by bacteria and cyanobacteria, increased the percentage of EPS in the material to 38%. Uronic acids comprised 20% of the total amount of carbohydrate measured in both total sediment and colloidal‐S extracts but increased to 65% in colloidal‐EDTA extracts, suggesting that colloidal‐EDTA extractions remove bacterial capsular EPS and EPS more closely associated with sediment particles.
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