Search for: All records

Abstract We conducted a mesocosm experiment to examine how ocean acidification (OA) affects communities of prokaryotes and eukaryotes growing on single‐use drinking bottles in subtropical eutrophic waters of the East China Sea. Based on 16S rDNA gene sequencing, simulated high CO 2 significantly altered the prokaryotic community, with the relative abundance of the phylum Planctomycetota increasing by 49%. Under high CO 2 , prokaryotes in the plastisphere had enhanced nitrogen dissimilation and ureolysis, raising the possibility that OA may modify nutrient cycling in subtropical eutrophic waters. The relative abundance of pathogenic and animal parasite bacteria also increased under simulated high CO 2 . Our results show that elevated CO 2 levels significantly affected several animal taxa based on 18S rDNA gene sequencing. For example, Mayorella amoebae were highly resistant, whereas Labyrinthula were sensitive to OA. Thus, OA may alter plastisphere food chains in subtropical eutrophic waters.

Abstract. Trichodesmium species, as a group of photosynthetic N2 fixers(diazotrophs), play an important role in the marine biogeochemical cycles ofnitrogen and carbon, especially in oligotrophic waters. How ongoing oceanwarming may interact with light availability to affect Trichodesmium is not yet clear. Wegrew Trichodesmium erythraeum IMS 101 at three temperature levels of 23, 27, and 31∘C undergrowth-limiting and growth-saturating light levels of 50 and 160 µmol quanta m−2 s−1, respectively, for at least 10 generations and thenmeasured physiological performance, including the specific growth rate, N2fixation rate, and photosynthesis. Light availability significantly modulatedthe growth response of Trichodesmium to temperature, with the specific growth ratepeaking at ∼27∘C under the light-saturatingconditions, while growth of light-limited cultures was non-responsive acrossthe tested temperatures (23, 27, and 31∘C). Short-term thermalresponses for N2 fixation indicated that both high growth temperatureand light intensity increased the optimum temperature (Topt) forN2 fixation and decreased its susceptibility to supra-optimaltemperatures (deactivation energy – Eh). Simultaneously, alllight-limited cultures with low Topt and high Eh were unable tosustain N2 fixation during short-term exposure to high temperatures (33–34∘C) that are not lethal for the cells grown underlight-saturating conditions. Our results imply that Trichodesmium spp. growing under lowlight levels while distributed deep in the euphotic zone or under cloudyweather conditions might be lessmore »sensitive to long-term temperature changesthat occur on the timescale of multiple generations but are more susceptible toabrupt (less than one generation time span) temperature changes, such asthose induced by cyclones and heat waves.« less