TY - JOUR
T1 - Microbial mechanisms coupling carbon and phosphorus cycles in phosphorus-limited northern Adriatic Sea
AU - Malfatti, F.
AU - Turk, V.
AU - Tinta, T.
AU - Mozetič, P.
AU - Manganelli, M.
AU - Samo, T. J.
AU - Ugalde, J. A.
AU - Kovač, N.
AU - Stefanelli, M.
AU - Antonioli, M.
AU - Fonda-Umani, S.
AU - Del Negro, P.
AU - Cataletto, B.
AU - Hozić, A.
AU - Ivošević DeNardis, N.
AU - Žutić, V.
AU - Svetličić, V.
AU - Mišić Radić, T.
AU - Radić, T.
AU - Fuks, D.
AU - Azam, F.
N1 - Funding Information:
We thank the staff of the Marine Biology Station of Piran and the R/V Sagita crew for the support. DOC analyses were performed by FM in the laboratory of Dr. L. Aluwihare at SIO. We thank Mr. T. Makovec and Dr. M. Grego for their assistance with image processing and Primer Software. This work was supported by grants from NSF CREICO ( 0132677 ) and Gordon and Betty Moore Foundation MMI to FA, by the Ministry of Higher Education, Science and Technology of Slovenia ( PI-0237 ) to VT, and by the Croatian Ministry of Science, Education and Sports (Project No. 098-0982934-2744 ) to VS.
PY - 2014/2/1
Y1 - 2014/2/1
N2 - The coastal northern Adriatic Sea receives pulsed inputs of riverine nutrients, causing phytoplankton blooms and seasonally sustained dissolved organic carbon (DOC) accumulation-hypothesized 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-) 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 186μM 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) Pi 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→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.
AB - The coastal northern Adriatic Sea receives pulsed inputs of riverine nutrients, causing phytoplankton blooms and seasonally sustained dissolved organic carbon (DOC) accumulation-hypothesized 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-) 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 186μM 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) Pi 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→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.
KW - Bacterial alkaline phosphatase
KW - DOC accumulation
KW - ELF-enzyme
KW - Hydrolyses
KW - Laser Scanning Confocal Microscope
KW - Marine carbon biogeochemistry
UR - http://www.scopus.com/inward/record.url?scp=84887704068&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2013.10.040
DO - 10.1016/j.scitotenv.2013.10.040
M3 - Article
C2 - 24246940
AN - SCOPUS:84887704068
SN - 0048-9697
VL - 470-471
SP - 1173
EP - 1183
JO - Science of the Total Environment
JF - Science of the Total Environment
ER -