Effects of sea surface warming on the production and composition of dissolved organic matter during phytoplankton blooms: Results from a mesocosm study

• Published in: Journal of Plankton Research
• Language: English
• Published: Oxford University Press 2011
• Subjects: Life Sciences; Alfred Wegener Institute
• Online Access: http://hdl.handle.net/2262/59642; https://doi.org/10.1093/plankt/FBQ122

Abstract An experimental study was conducted to test the effects of predicted sea surface warming (according to the IPPC scenarios) on the accumulation and composition of dissolved organic matter during marine phytoplankton blooms in cold areas (<4?C). Eight mesocosms (~1400 L) were filled with natural seawater and two replicate mesocosms were incubated at +0, +2, +4, and +6?C, respectively. The mesocosms were initially fertilized with inorganic nutrient to induce the development of phytoplankton blooms, which were dominated by diatoms. Over a four week period, dissolved combined carbohydrates (DCCHO) and dissolved amino acids (DAA) were determined as major components of freshly produced, labile to semi-labile dissolved organic matter. In all mesocosms, the increase in DCCHO concentration occurred sharply after the peak of chlorophyll a concentration, when nutrients became depleted. Rising temperature resulted in an earlier, faster and higher accumulation of DCCHO, and of combined glucose predominantly. DCCHO yielded a maximum percentage of 35, 40, 49 and 59% of total polysaccharides in the +0, +2, +4, and +6?C treatment, respectively. Accumulation of DAA occurred more continuously and at an average rate of 0.79?0.20 nmol L-1 h-1, but was not affected by rising temperature. Due to the higher accumulation of DCCHO, the C:N ratio of DOM increased strongly in the course of the bloom, with higher ratios in the warmer treatments. Our study suggests that warming increases the extracellular release of carbohydrates from phytoplankton, and therewith may affect the bottom-up control of the microbial loop in cold seas in the future. [e-mail] (Engel, Anja) [e-mail] (Handel, Nicole) [e-mail] (Wohlers, Julia) [e-mail] (Lunau, Mirko) [e-mail] (Grossart, Hans-Peter) [e-mail] (Sommer, Ulrich) [e-mail] (Riebesell, Ulf) Alfred Wegener Institute for Polar and Marine Research, Polar Biological Oceanography - Am Handelshafen 12--> - 27515 - Bremerhaven - GERMANY (Engel, Anja) Alfred Wegener Institute for Polar and Marine Research, Polar Biological Oceanography - Bremerhaven - GERMANY (Handel, Nicole) Leibniz Institute of Marine Sciences, IFM-GEOMAR, Marine Biogeochemistry - Kiel - GERMANY (Wohlers, Julia) Alfred Wegener Institute for Polar and Marine Research, Polar Biological Oceanography - Bremerhaven - GERMANY (Lunau, Mirko) IGB-Neuglobsow, Limnology of Stratified Lakes - Stechlin - GERMANY (Grossart, Hans-Peter) Leibniz Institute of Marine Sciences, IFM-GEOMAR, Marine Biogeochemistry - Kiel - GERMANY (Sommer, Ulrich) Leibniz Institute of Marine Sciences, IFM-GEOMAR, Marine Biogeochemistry - Kiel - GERMANY (Riebesell, Ulf) GERMANY