Response of natural phytoplankton assemblage to two emerging environmental treats (ocean acidification and warming) using controlled mesocosm experiments

Seminar by Dr. Ja-Myung Kim from Pohang University of Science and Technology

08 December 2022
KST 15:00 – 16:00

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

A third of CO2 released by burning fossil fuels since the industrial revolution has ended up in the ocean. The absorbed CO2 subsequently lowers the pH level, and the temperature of the surface ocean has discernibly increased. The impact on marine biology appears to be inevitable. This talk will cover the results of mesocosm experiments that mimicked ocean acidification and warming in the coming decades. The experiment testing the effect of pCO2 concentration (250, 400, and 900 μatm) on the growth rate of a natural phytoplankton assemblage suggested that ubiquitous diatom, Skeletonema costatum, showed an increase in growth rate (40%) with increasing seawater pCO2 concentration. The different responses of S.costatum and other diatom species to pCO2 manipulation imply that future pCO2 increases in the surface ocean could potentially change the structure of the diatom population. Another experiment investigating the combined effects of pCO2 concentration (900 μatm) and temperature (~3oC) elevation showed that the elevated CO2 and temperature conditions disproportionately enhanced dissolved organic carbon production and its contribution to total organic matter production, while the total organic carbon production remained constant. The experimental condition significantly stimulated the grazing and the growth rate of micrograzers, which resulted in considerable dimethylsulfide (biogenic gas oxidized to aerosols exerting a cooling effect by scattering solar radiation) production. The results from the mesocosm studies indicated the active feedback of marine phytoplankton on climate change. The knowledge gained from the studies can provide a better understanding to predict the response of marine ecosystems to elevated pCO2 concentrations and enable scenarios of future impacts on ecosystem function and biogeochemical cycles to be developed.