Wohlers J, Engel A, Zollner E, Breithaupt P, Jurgens K, Hoppe HG, Sommer U, Riebesell U
biological feedbacks, carbon cycle, climate change, global warming, Marine bacteria, mesocosm, Kiel indoor, 1.4 m3, Germany
It is responsible for approximately half of global primary production,sustains worldwide fisheries, and plays an important role inthe global carbon cycle. Ocean warming caused by anthropogenicclimate change is already starting to impact the marine biota, withpossible consequences for ocean productivity and ecosystem services.Because temperature sensitivities of marine autotrophic andheterotrophic processes differ greatly, ocean warming is expectedto cause major shifts in the flow of carbon and energy through thepelagic system. Attempts to integrate such biological responsesinto marine ecosystem and biogeochemical models suffer from alack of empirical data. Here, we show, using an indoor-mesocosmapproach, that rising temperature accelerates respiratory consumptionof organic carbon relative to autotrophic production in anatural plankton community. Increasing temperature by 2–6 °Chence decreased the biological drawdown of dissolved inorganiccarbon in the surface layer by up to 31%. Moreover, warmingshifted the partitioning between particulate and dissolved organiccarbon toward an enhanced accumulation of dissolved compounds.In line with these findings, the loss of organic carbonthrough sinking was significantly reduced at elevated temperatures.The observed changes in biogenic carbon flow have thepotential to reduce the transfer of primary produced organicmatter to higher trophic levels, weaken the ocean’s biologicalcarbon pump, and hence provide a positive feedback to risingatmospheric CO2.