Significance of exoenzymatic activities in the ecology of brackish water: measurements by means of methylumbelliferyl-substrates

Abstract

The rates of hydrolysis of glucosides, protein-like compds., glucosaminides, and org. phosphorus compds., as well as hydrolyzation rates of naturally occurring substrate analogs were measured using fluorogenic methylumbelliferyl (I) compds. in 2 eutrophic Baltic Sea fjords and adjacent offshore waters. The activity of protease [9001-92-7] was dominant in all water samples. The activity of .alpha.-D-glucosidase [9033-06-1] and glucosaminidase [76199-21-8] varied significantly between fjords and offshore waters. An expt. with I compds. and radioactively labeled substrates indicated there is a discrepancy between the amt. of substrate hydrolyzed by exoenzymes and the amt. incorporated by bacteria. This suggests that there are medium-scale changes in the dissolved org. C (DOC) pool and the mode of equilibration of small mols. and macromols. in the DOC pool.