Kinetics of microbial mineralization of organic carbon from detrital Skeletonema costatum cells

Abstract

Long-term (6 mo) studies of the mineralization of detrital 14C-labelled Skeletonema costatum cells by coastal microbial communities demonstrated the existence of 4 main pools (G1) of 'utilizable' organic material. The most labile fraction, G0, material, comprised 13 % of the algal biomass and was consumed via first-order kinetics in 14 h. The G02, G03 and G04 fractions (54, 29 and 4 % of the algae respectively) had turnover times on the order of days to weeks, months and years, respectively. Definition of pool size and lability was based on changes in first-order consumption rates of particulate and dissolved organic carbon (POC and DOC) released from intact cells during the experimental period. Sodium azide inhibition of bacterial metabolism resulted in DOC accumulation at rates approximating POC mineralization rates and community metabolism, but problems with incomplete inhibition of the uptake of G01 materials negated conclusions concerning natural DOC release rates from algae. Conflicting opinlons on the response of benthic communities and deep-water bacterioplankton to sedimenting algal blooms may be resolved through consideration of the amount of G01 and G02-organic matter which remain in detrital algae.