Microbial mechanisms coupling carbon and phosphorus cycles in phosphorus-limited northern Adriatic Sea

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• 作者：F. Malfatti ; V. Turk ; T. Tinta ; P. Mozeti膷 ; M. Manganelli ; T.J. Samo ; J.A. Ugalde ; N. Kova膷 ; M. Stefanelli ; M. Antonioli ; S. Fonda-Umani ; P. Del Negro ; B. Cataletto ; A. Hozi膰 ; N. Ivo拧evi膰 DeNardis ; V. 沤uti膰 ; V. Svetli膷i膰 ; T. Mi拧i膰 Radi膰 ; T. Radi膰 ; D. Fuks ; F. Azam ; et al.
• 关键词：Marine carbon biogeochemistry ; Bacterial alkaline phosphatase ; ELF-enzyme ; Hydrolyses ; DOC accumulation ; Laser Scanning Confocal Microscope
• 刊名：Science of the Total Environment
• 出版年：1 February, 2014
• 年：2014
• 卷：470-471
• 期：Complete
• 页码：1173-1183
• 全文大小：1274 K

文摘

The coastal northern Adriatic Sea receives pulsed inputs of riverine nutrients, causing phytoplankton blooms and seasonally sustained dissolved organic carbon (DOC) accumulation鈥攈ypothesized to cause episodes of massive mucilage. The underlying mechanisms regulating P and C cycles and their coupling are unclear. Extensive biogeochemical parameters, processes and community composition were measured in a 64-day mesocosms deployed off Piran, Slovenia. We followed the temporal trends of C and P fluxes in P-enriched (P +) and unenriched (P 鈭? mesocosms. An intense diatom bloom developed then crashed; however, substantial primary production was maintained throughout, supported by tightly coupled P regeneration by bacteria and phytoplankton. Results provide novel insights on post-bloom C and P dynamics and mechanisms. 1) Post-bloom DOC accumulation to 186 渭M remained elevated despite high bacterial carbon demand. Presumably, a large part of DOC accumulated due to the bacterial ectohydrolytic processing of primary productivity that adventitiously generated slow-to-degrade DOC; 2) bacteria heavily colonized post-bloom diatom aggregates, rendering them microscale hotspots of P regeneration due to locally intense bacterial ectohydrolase activities; 3) P_i turnover was rapid thus suggesting high P flux through the DOP pool (dissolved organic phosphorus) turnover; 4) Alpha- and Gamma-proteobacteria dominated the bacterial communities despite great differences of C and P pools and fluxes in both mesocosms. However, minor taxa showed dramatic changes in community compositions. Major OTUs were presumably generalists adapted to diverse productivity regimes.We suggest that variation in bacterial ectohydrolase activities on aggregates, regulating the rates of POM 鈫?#xA0;DOM transition as well as dissolved polymer hydrolysis, could become a bottleneck in P regeneration. This could be another regulatory step, in addition to APase, in the microbial regulation of P cycle and the coupling between C and P cycles.