TY - JOUR T1 - Phytoplankton and bacterial alkaline phosphatase activities in relation to phosphate and DOP availability within the Gironde plume waters (Bay of Biscay) A1 - Labry,Claire A1 - Delmas,Daniel A1 - Herbland,Alain AD - IFREMER, CNRS, Ctr Rech Ecol Marine & Aquaculture, F-17137 LHoumeau, France. AD - IFREMER/Laboratoire Aquacole de Calédonie (LAC Saint Vincent) BP 2059 98846 Nouméa cedex, France UR - https://archimer.ifremer.fr/doc/00000/608/ DO - 10.1016/j.jembe.2004.12.017 KW - Phytoplankton KW - Phosphate KW - Gironde KW - DOP KW - Bacteria KW - Alkaline phosphatases N2 - Previous studies conducted on the continental shelf in the Southeast Bay of Biscay influenced by Gironde waters (one of the two largest rivers on the French Atlantic coast) showed the occurrence of late winter phytoplankton blooms and phosphorus limitation of algal growth thereafter. In this context, the importance of dissolved organic phosphorus (DOP) for both algae and bacteria was investigated in 1998 and 1999 in terms of stocks and fluxes. Within the mixed layer, although phosphate decreased until exhaustion from winter to spring, DOP remained high and phosphate monoesters made up between I I to 65% of this pool. Total alkaline phosphatase activity (APA, V-max) rose gradually from winter (2-8 nM h(-1)) to late spring (100-400 nM h-1), which was mainly due to an increase in specific phytoplankton (from 0.02 to 3.0 nmol mu gC(-1) h(-1)) and bacterial APA (from 0.04 to 4.0 nmol mu gC(-1) h(-1)), a strategy to compensate for the lack of phosphate. At each season, both communities had equal competitive abilities to exploit DOP but, taking into account biomass, the phytoplankton community activity always dominated (57-63% of total APA) that of bacterial community (9-11%). The dissolved APA represented a significant contribution. In situ regulation of phytoplanktonic APA by phosphate (induction or inversely repression of enzyme synthesis) was confirmed by simultaneously conducted phosphate-enrichment bioassays. Such changes recorded at a time scale of a few days could partly explain the seasonal response of phytoplankton communities to phosphate depletion. Y1 - 2005/05 PB - Elsevier JF - Journal of Experimental Marine Biology and Ecology SN - 0022-0981 VL - 318 IS - 2 SP - 213 EP - 225 ID - 608 ER -