TY - JOUR
T1 - Phytoplankton response to a Lagrangian phosphate addition in the Levantine Sea (Eastern Mediterranean)
AU - Psarra, Stella
AU - Zohary, Tamar
AU - Krom, Michael D.
AU - Mantoura, R. Fauzi C.
AU - Polychronaki, Thalia
AU - Stambler, Noga
AU - Tanaka, Tsuneo
AU - Tselepides, Anastasios
AU - Frede Thingstad, T.
N1 - Funding Information:
The authors thank Pre Carbo for contributing to the successful coordination of this experiment. Ms Denise Cummings (PML) is acknowledged for HPLC analyses. We also wish to thank Paraskevi. Polymenakou, Eleni Hatziyanni, and Ourania. Barouta for their indispensable help at sea, as well as George Zodiatis and Panos Drakopolous for CTD operations and data assimilation and of course Cliff Law, Malcolm Woodward and Tim Fileman for the phosphate release/tracer and buoy operations. Special thanks are due to the captain and the crew of the RV “Aegaeo” for their assistance. This work was funded as part of the CYCLOPS—Cycling of Phosphate in the Eastern Mediterranean—Project (EVK3-CT-1999-00037) by the EU Framework V and the Greek General Secretariat of Research and Technology.
PY - 2005/11/1
Y1 - 2005/11/1
N2 - In order to test the hypothesis of P-limitation on primary production and microbial biomass, a mesoscale Lagrangian phosphate-enrichment experiment was performed in the warm core of the Cyprus Eddy (Eastern Mediterranean Sea) in May 2002. This study reports the effects of the phosphate addition on the phytoplankton community, by measuring induced changes in biomass, primary production, and community structure. Prior to the addition, primary production and chlorophyll a were very low (0.107μgCl-1h-1 and 18ngl-1, respectively), typical of the ultra-oligotrophic conditions prevailing in the area. The autotrophic community was dominated in terms of both abundance and biomass (60% of total chl-a) by picoplankton (mostly Synechococcus). More than 90% of the autotrophic biomass was confined to particles <10μm, while larger phytoplankton (diatoms, dinoflagellates, coccolithophores) were very scarce. Unexpectedly, the addition of P resulted in a decrease in phytoplankton biomass. Total HPLC-chlorophyll slightly declined to 11ngl-1 in the P-enriched patch, five days after the P-addition. As the patch was diluted away (7-9 days), chlorophyll concentrations returned to background levels. Similar trends were observed in chlorophyll determined fluorometrically and in primary production. Picophytoplankton and smaller nanophytoplankton abundance declined (by 49 and 65%, respectively) within the first four days of the experiment. At the same time, there was a small increase of larger nanophytoplankton (10-20μm) and microphytoplankton (>20μm) species. Small nanophytoplankton (2-10μm) were the group most affected by the addition. These results together with an onboard microcosm experiment (reported elsewhere in this issue), in which ammonia was added to the P-enriched water, indicate that the system was N and P co-limited for phytoplankton. The decrease in pico and smaller nanophytoplankton was probably caused by increased predation by micrograzers that became more active because of the increased heterotrophic bacterial activity and/or the increased P content of their prey. The immediate decrease in Synechococcus numbers, as the system became temporarily N-limited implies that N-fixation caused by this particular cyanobacteria was unlikely to occur.
AB - In order to test the hypothesis of P-limitation on primary production and microbial biomass, a mesoscale Lagrangian phosphate-enrichment experiment was performed in the warm core of the Cyprus Eddy (Eastern Mediterranean Sea) in May 2002. This study reports the effects of the phosphate addition on the phytoplankton community, by measuring induced changes in biomass, primary production, and community structure. Prior to the addition, primary production and chlorophyll a were very low (0.107μgCl-1h-1 and 18ngl-1, respectively), typical of the ultra-oligotrophic conditions prevailing in the area. The autotrophic community was dominated in terms of both abundance and biomass (60% of total chl-a) by picoplankton (mostly Synechococcus). More than 90% of the autotrophic biomass was confined to particles <10μm, while larger phytoplankton (diatoms, dinoflagellates, coccolithophores) were very scarce. Unexpectedly, the addition of P resulted in a decrease in phytoplankton biomass. Total HPLC-chlorophyll slightly declined to 11ngl-1 in the P-enriched patch, five days after the P-addition. As the patch was diluted away (7-9 days), chlorophyll concentrations returned to background levels. Similar trends were observed in chlorophyll determined fluorometrically and in primary production. Picophytoplankton and smaller nanophytoplankton abundance declined (by 49 and 65%, respectively) within the first four days of the experiment. At the same time, there was a small increase of larger nanophytoplankton (10-20μm) and microphytoplankton (>20μm) species. Small nanophytoplankton (2-10μm) were the group most affected by the addition. These results together with an onboard microcosm experiment (reported elsewhere in this issue), in which ammonia was added to the P-enriched water, indicate that the system was N and P co-limited for phytoplankton. The decrease in pico and smaller nanophytoplankton was probably caused by increased predation by micrograzers that became more active because of the increased heterotrophic bacterial activity and/or the increased P content of their prey. The immediate decrease in Synechococcus numbers, as the system became temporarily N-limited implies that N-fixation caused by this particular cyanobacteria was unlikely to occur.
KW - Chemotaxonomic pigments
KW - Chlorophyll
KW - Eastern Mediterranean
KW - P-addition
KW - Phytoplankton
KW - Primary production
UR - http://www.scopus.com/inward/record.url?scp=27844585234&partnerID=8YFLogxK
U2 - 10.1016/j.dsr2.2005.08.015
DO - 10.1016/j.dsr2.2005.08.015
M3 - Article
AN - SCOPUS:27844585234
SN - 0967-0645
VL - 52
SP - 2944
EP - 2960
JO - Deep-Sea Research Part II: Topical Studies in Oceanography
JF - Deep-Sea Research Part II: Topical Studies in Oceanography
IS - 22-23
ER -