Profiles of ectoenzymes in the Indian Ocean: Phenomena of phosphatase activity in the mesopelagic zone

Hoppe, Hans-Georg and Ullrich, Sören (1999) Profiles of ectoenzymes in the Indian Ocean: Phenomena of phosphatase activity in the mesopelagic zone Aquatic Microbial Ecology, 19 . pp. 139-148. DOI 10.3354/ame019139.

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Abstract

Phosphatase (P-ase) activity was determined together with other extracellular enzyme activities, bacterial abundance and production rates during the 2 SW Monsoon process studies of the German JGOFS Arabian Sea Program. Water samples were collected along the cruise tracks from the equator to the upwelling region at the shelf edge off Oman. Depth profiles of P-ase activity were strikingly different from those of the other enzymes. While values of aminopeptidase and β-glucosidase generally decreased below the euphotic zone, P-ase increased by factors of 1 to 7. The relation between peptidase- and P-ase activity was from 4 to 21 at the surface and from 3 to 5 at 800 m depth. Because P-ase production (dissolved and cell-bound) in deep waters is mainly dependent on bacteria, P-ase activities per bacterial cell were calculated: these were, on average, 37 times higher at 800 m than at the surface. We also observed a positive correlation of P-ase activity with phosphate concentrations in the depth profiles below the euphotic zone, while this relationship was much more variable in the mixed surface layer. These observations suggest that C-limited bacteria in the deep strata did not primarily focus on the phosphate generated by their P-ase activity but on the organic C compounds which were simultaneously produced and which could probably not be taken up prior to the hydrolytic detachment of phosphate. It is hypothesised that a considerable part of the measured P-ase activity was dissolved (though it might have originated from bacteria). These enzymes may be important for the slow, but steady regeneration of phosphate and organic C in mesopelagic waters.

Document Type: Article
Keywords: Ectoenzymes; Phosphatase; Aminopeptidase; Glucosidase; Bacteria; Indian Ocean; Arabian Sea; Mesopelagic zone; Deep sea
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MI Marine Microbiology
OceanRep > Institute for Marine Science Kiel
Refereed: Yes
DOI etc.: 10.3354/ame019139
ISSN: 0948-3055
Projects: JGOFS
Date Deposited: 18 Feb 2008 17:24
Last Modified: 26 May 2016 10:19
URI: http://eprints.uni-kiel.de/id/eprint/4294

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