Authors: Namiha Yamada Masahiro Suzumura
Publish Date: 2010/03/25
Volume: 66, Issue: 2, Pages: 233-241
Abstract
We have investigated the effects of seawater acidification on the activities of leucine aminopeptidase LAPase βglucosidase BGase phosphatase Pase αglucosidase AGase and lipase Lase which are important promoters of degradation of marine organic matter including proteins carbohydrates organic phosphorus compounds and lipids Seawater samples were collected from a eutrophic coastal area from Tokyo Bay and from oligotrophic pelagic waters outside the Kuroshio Current Enzyme activities were measured using fluorogenic substrates added to the seawater samples which were acidified from pH 82 to 56 by a chemical buffer Spontaneous hydrolysis of the substrates was shown to be negligible in heatinactivated control samples thus validating our results LAPase was the most sensitive to acidification enzyme activity rapidly decreased from pH 82 to 78 corresponding to a realistic scenario of ocean acidification Lase activity also decreased with acidification Activities of Pase and BGase were relatively constant across the pH levels examined suggesting that their activity is not appreciably influenced by acidification The effect of acidification on Pase activities differed between the coastal and semipelagic samples and this was likely due to freshwater influence at the nearshore station Because of the low activity of AGase in the sample the effect of acidification on this enzyme could not be examined The effects of acidification on enzyme activity appear to vary depending on enzyme type and location but we conclude that acidification will cause changes in the cycling of organic matter in marine ecosystems in particular to proteinous and lipid substances
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