Basin-scale variability of phytoplankton biomass,production and growth in the Atlantic Ocean |
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| Institution: | 1. Departamento de Ecolog??a y Biolog??a Animal, Universidad de Vigo, E-36200 Vigo, Spain;2. School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, Southampton SO14 3ZH, UK;3. Instituto Español de Oceanograf??a, Centro Oceanográfico de A Coruña, Apdo 130, E-15080 A Coruña, Spain;4. Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL1 3DH, UK;1. National Research Council of Canada, 1200 Montreal Road, K1A 0R6 Ottawa, Ontario, Canada;2. Consiglio Nazionale delle Ricerche (CNR), Istituto di Chimica dei Composti Organometallici, UOS di Pisa, Via Moruzzi 1, 56124 Pisa, Italy;3. QUASIMEME, NL-6700 EC Wageningen, Bornsesteeg 10, 6721 NG Bennekom, The Netherlands;1. Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901, United States;2. Skidmore College, Saratoga Springs, NY 12866, United States;1. University of Maryland Center for Environmental Science, Horn Point Laboratory, P.O. Box 775, Cambridge, MD 21613, USA;2. Zhejiang University, Department of Ocean Science and Engineering, Hangzhou, China;1. National Oceanography Centre, Southampton, SO14 3ZH, UK;2. School of Environmental Sciences, University of Liverpool, Liverpool, L69 3GP, UK;3. School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, L3 3AF, UK;4. Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, 28570, Germany;5. MARUM and University of Bremen, Bremen, 28359, Germany;6. Dept. of Applied Physics II. ETSIE. universidad de Sevilla, Sevilla, 41012, Spain;1. Department of Parasitology, Medical College of Zhengzhou University, Zhengzhou 450052, PR China;2. Department of Immunology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA |
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| Abstract: | The latitudinal distributions of phytoplankton biomass, composition and production in the Atlantic Ocean were determined along a 10,000-km transect from 50°N to 50°S in October 1995, May 1996 and October 1996. Highest levels of euphotic layer-integrated chlorophyll a (Chl a) concentration (75–125 mg Chl m?2) were found in North Atlantic temperate waters and in the upwelling region off NW Africa, whereas typical Chl a concentrations in oligotrophic waters ranged from 20 to 40 mg Chl m?2. The estimated concentration of surface phytoplankton carbon (C) biomass was 5–15 mg C m?2 in the oligotrophic regions and increased over 40 mg C m?2 in richer areas. The deep chlorophyll maximum did not seem to constitute a biomass or productivity maximum, but resulted mainly from an increase in the Chl a to C ratio and represented a relatively small contribution to total integrated productivity. Primary production rates varied from 50 mg C m?2 d?1 at the central gyres to 500–1000 mg C m?2 d?1 in upwelling and higher latitude regions, where faster growth rates (μ) of phytoplankton (>0.5 d?1) were also measured. In oligotrophic waters, microalgal growth was consistently slow surface μ averaged 0.21±0.02 d?1 (mean±SE)], representing <20% of maximum expected growth. These results argue against the view that the subtropical gyres are characterized by high phytoplankton turnover rates. The latitudinal variations in μ were inversely correlated to the changes in the depth of the nitracline and positively correlated to those of the integrated nitrate concentration, supporting the case for the role of nutrients in controlling the large-scale distribution of phytoplankton growth rates. We observed a large degree of temporal variability in the phytoplankton dynamics in the oligotrophic regions: productivity and growth rates varied in excess of 8-fold, whereas microalgal biomass remained relatively constant. The observed spatial and temporal variability in the biomass specific rate of photosynthesis is at least three times larger than currently assumed in most satellite-based models of global productivity. |
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