Enhanced enzymatic activities in seawater surrounding aggregates: Consequences for carbon cycling (2010)

Undergraduates: Analise Jenkins, none none Kai Ziervogel, Ph. D.

Faculty Advisor: Carol Arnosti
Department: Biology

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Microbial activities in the ocean drive the global carbon cycle, remineralizing photosynthetically produced dissolved organic matter through substrate-specific hydrolytic enzymes. High levels of hydrolytic activities are expressed by marine snow associated microbial communities. We investigated enzymatic hydrolysis rates in coastal seawater surrounding aggregates formed on a roller table and in the same seawater that was not placed on the roller table using four fluorescently labeled polysaccharides (extracts from Spirulina, Isochrysis and Thalassiosira, and laminarin). The goal was to determine the extent to which the presence of aggregates affects enzyme activities in the surrounding seawater and to compare rates at which purified polysaccharides and algal-derived extracts were hydrolyzed by natural microbial communities. _x000D_
All four substrates were hydrolyzed in water surrounding aggregates and in stagnant water w/o aggregates with highest rates observed after 48 hours. Laminarin and Isochrysis hydrolysis was higher in roller compared with bench bottles suggesting that aggregate formation affects enzyme production in the water column. Microbial communities on or near aggregates are likely stimulated to produce more (or more active) extracellular enzymes, possibly due to bacterial quorum sensing on aggregates. These elevated enzymatic activities lead to a net increase in substrate hydrolysis, increasing overall rates of carbon cycling. _x000D_