engleski

Northern Adriatic mesocosm experiment Rovinj 2003: primary production and total organic carbon

Seasonal accumulation of carbon rich organic matter is thought to be a source of mucilaginous aggregates in the northern Adriatic in condition of marked phosphorus limitation. To assess a possible role of P-limitation in the production of precursors of mucilage aggregates, a mesocosm experiment was designed with different P enrichments. In this paper, a study of the production and fate of organic C during the experiment is presented. Primary production (PP) was measured using the 14C-method. Chlorophyll a was determined fluorimetrically after acetone extraction. DOC was determined using a high-temperature catalytic oxidation method on a TOC analyzer. POC was determined by a CHNS analyzer. Substantially different processes were observed in the two enriched mesocosms regarding primary production. A sustainable orthophosphate concentration, in the "P-deficient" mesocosm, maintained through enzymatic regeneration by induction of alkaline phosphatase (APA), was sufficient to almost equalize the primary production efficiency in both enriched mesocosms. In contrast, in the "nutrient balanced" mesocosm no alkaline phosphatase induction to maintain an appropriate primary production rate were involved. Differences between the "P-deficient" and "nutrient balanced" enriched mesocosm indicated that during bloom events in the northern Adriatic C-rich organic matter can be produced and act as a sustainable source for mucilage production, due to selective enzymatic phosphorus regeneration (APA mediated).

chlorophyll a; primary production; organic carbon; mesocosm experiment; northern Adriatic

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