TY - JOUR T1 - Effect of P depletion on the functional pools of diatom carbohydrates, and their utilization by bacterial communities A1 - Labry,Claire A1 - Delmas,Daniel A1 - Moriceau,Brivaela A1 - Gallinari,Morgane A1 - Quere,Julien A1 - Youenou,Agnes AD - Ifremer, DYNECO, F-29280 Plouzané, France AD - Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France AD - Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, France UR - https://doi.org/10.3354/meps13297 DO - 10.3354/meps13297 KW - P limitation KW - Phytoplankton KW - Diatom KW - Bacteria KW - Mineralization KW - Carbohydrate KW - Glucosidase N2 - Phosphorus (P) limitation of phytoplankton growth is known to affect the accumulation and release of carbohydrates (CHO) by micro-algae. However, relatively little is known about the fate of algal exudates, notably their bacterial degradation. The CHO chemical characterization is also not exhaustive, especially in ‘functional’ pools relevant for phytoplankton physiology (particulate reserve [R] or structural [S] CHO) and for bacterial degradation (dissolved mono- [MDCHO] and polysaccharides [P-DCHO]). In this study, we investigated how P depletion and repletion affect the CHO composition in diatom Thalassiosira weissflogii cultures, and the shortterm response of free and diatom-attached bacteria in terms of abundance and potential βglucosidase activity (βGlc). The bacterial inoculum was composed of the bacterial consortiums of diatom precultures and a natural bacterial community from the Bay of Brest. P depletion favored CHO accumulation in diatom cells, mainly as R i.e. soluble CHO accumulated in cytoplasm, but also as S, polysaccharides linked to the cell wall. The R:S ratio was high in the present diatom cultures. The high M-DCHO observed in P-deplete cultures (twice that of P-replete cultures) when P-DCHO remained quite similar is explained both by active polysaccharide hydrolysis (very high potential βGlc of attached bacteria) and reduced uptake of M-DCHO by Pdepleted bacteria. P depletion of heterotrophic bacteria favors labile CHO accumulation, which may affect particle potential aggregation. However, the remarkably constant M-DCHO concentration over time for both conditions suggests tight coupling between phytoplankton accumulation, release, polymer hydrolysis and monomer uptake by bacteria. Y1 - 2020/05 PB - Inter-Research Science Center JF - Marine Ecology Progress Series SN - 0171-8630 VL - 641 SP - 49 EP - 62 ID - 74045 ER -