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

Abstract

Phosphatase (P-ase) actlvity 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 striklngly different from those of the other enzymes. While values of aminopeptidase and P-glucosidase generally decreased below the euphotic zone. P-ase increased by factors of 1 to 7. The relation between peptidase-and P-ase actlvity 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 activlty with phosphate concentrations in the depth profiles below the euphotic zone, while this relationship was much more varlable in the muted surface layer. These observations suggest that C-limited bacteria in the deep strata did not primarily focus on the phosphate generated by the11 P-ase activity but on the organic C compounds which were simultaneously produced and whlch could probably not be taken u p prior to the hydrolytic detachment of phosphate. It is hypothesised that a considerable part of the measured P-ase activlty was dissolved (though it mlght have o n g~n a t e d from bacteria). These enzymes may b e important for the slow, but steady regeneration of phosphate and organic C in mesopelagic waters.

Alkaline phosphatase activities in the central Atlantic Ocean indicate large areas with phosphorus deficiency

“…The APA found in our study (between 4 and 50 nmol MF-P l -1 h -1 ) is comparable to that reported by Li et al (1998) and Thingstad et al (1998) for some stations in the Gulf of Aqaba (Red Sea) and the NW Mediterranean, respectively. Nevertheless, our values are somewhat higher than those found in the central north Pacific, Indian, Sargasso and eastern Mediterranean seas (Perry 1972, Cotner et al 1997, Zohary & Robarts 1998, Hoppe & Ullrich 1999. With the exception of the study of Li et al (1998), in which the samples were incubated at 37°C, the remainder of the studies listed in Appendix 1 (available at www.int-res.com/ journals/suppl/vidal_appendix.pdf) derive from APA assays performed at the 'in situ' temperature of the samples.…”

“…1). APA has also been reported for other open-ocean sites such as the subtropical central north Pacific (Perry 1972), the Sargasso Sea (Cotner et al 1997, Guildford & Hecky 2000, the Indian Ocean (Hoppe & Ullrich 1999) and the Mediterranean Sea (Thingstad et al 1998), suggesting that utilisation of P from DOP through APA is probably a characteristic feature of the oligotrophic ocean. The APA found in our study (between 4 and 50 nmol MF-P l -1 h -1 ) is comparable to that reported by Li et al (1998) and Thingstad et al (1998) for some stations in the Gulf of Aqaba (Red Sea) and the NW Mediterranean, respectively.…”

Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific oceans

“…Produced by high primary production in upwelling regions, DOM can accumulate in the euphotic zone with maximum concentrations of 100-300 µmol C L −1 off Peru (Franz et al, 2012a;Romankevich and Ljutsarev, 1990). Due to the vicinity of the DOM-rich surface layer to the shallow and sharp oxycline of the Peruvian OMZ, as well as the O 2 -depleted waters below the oxycline, physical vertical transport may bring large amounts of labile organic matter to the OMZ, where it may be utilized by heterotrophic communities (Hoppe et al, 2000;Hoppe and Ullrich, 1999;Pantoja et al, 2009). DOM supply via (sub)mesoscale vertical transport processes and diapycnal mixing may therefore contribute importantly to sustaining microbial activity in the Peruvian OMZ and may thus largely impact biogeochemical cycles.…”

Vertical Variation in Dissolved Alkaline Phosphatase Activity in a Shallow Eutrophic Lake Determined in Reverse Micelles

“…Stewart and Wetzel(1982) found that alkaline phosphatase tended to be bacterioplanktonic at increased depth, and the high phosphatase (dissolved and cell-bound) production in deep water was thought to be mainly dependent on bacteria. It is hypothesized that a considerable part of the measured phosphatase activity was dissolved, though it might have originated from bacteria (Hoppe and Ullrich 1999). In this context, the different behaviors of dissolved phosphatase of surface and overlying water that we observed might be due to the different origins, with the former being alage and the latter being bacterial.…”