Kinetics and Trophic Role of Bacterial Degradation of Macro-Algae in Antarctic Coastal Waters
Aerobic formation of detritus from debris of the Antarctic Kelp, Himantothallus grandifolius, yielded amounts of carbon and nitrogen 2 and 4 times higher, respectively, than fresh algae, and a concomitant decrease of the carbon:nitrogen ratio from 19 to approximately 10. These changes were achieved only in the presence of the indigenous Antarctic bacterio-flora. During formation of detritus from the Antarctic red alga, Leptosomia simplex, C:N ratios may drop even below the Redfield ratio reported for phytoplankton. The increases in the C and N contents of the debris and its colonization by epiphytic bacteria were characterized by saturation kinetics, which showed an initial lag, subsequent steep increment, and a final stationary phase. During its exponential phase, rates of bacterial colonization of debris from brown and red algae were comparable to those calculated for kelp in areas of temperate climates. There is preliminary evidence that some of the enzymes, which participate in the decomposition of the particulate detrital matter, are optimally adapted to the temperature regime of a permanently cold environment. The results obtained favour the idea that the formation of macro-algal detritus in Antarctic coastal waters is as efficient as in temperate regions. Preliminary assessments indicated that partly degraded thalli from both the brown and red algae were preferred over fresh thalli, as a food source, by intertidal amphipods.
KeywordsRedfield Ratio Epiphytic Bacterium Algal Debris Detrital Food Chain Benthic Macrophyte
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