Enhanced carbon overconsumption in response to increasing temperatures during a mesocosm experiment

[摘要] Increasing concentrations of atmospheric carbon dioxide are projected to leadto an increase in sea surface temperatures, potentially impacting marineecosystems and biogeochemical cycling. Here we conducted an indoor mesocosmexperiment with a natural plankton community taken from the Baltic Sea insummer. We induced a plankton bloom via nutrient addition and followed thedynamics of the different carbon and nitrogen pools for a period of one monthat temperatures ranging from 9.5 °C to 17.5 °C, representinga range of ±4 °C relative to ambient temperature. The uptake ofdissolved inorganic carbon (DIC) and the net build-up of both particulate(POC) and dissolved organic carbon (DOC) were all enhanced at highertemperatures and almost doubled over a temperature gradient of 8 °C.Furthermore, elemental ratios of carbon and nitrogen (C : N) in bothparticulate and dissolved organic matter increased in response to highertemperatures, both reaching very high C : N ratios of > 30 at+4 °C. Altogether, these observations suggest a pronounced increasein excess carbon fixation in response to elevated temperatures. Most of thesefindings are contrary to results from similar experiments conducted withplankton populations sampled in spring, revealing large uncertainties in ourknowledge of temperature sensitivities of key processes in marine carboncycling. Since a major difference to previous mesocosm experiments was thedominant phytoplankton species, we hypothesize that species composition mightplay an important role in the response of biogeochemical cycling toincreasing temperatures.

[学科分类] 地球化学与岩石