Taiwanese marine microbenthic algal communities remain similar yet chlorophyll a concentrations rise in mesocosms with elevated CO2 and temperature

Abstract

The effects of increasing CO₂ concentrations and temperature on microalgal assemblages were examined in Taiwan using mesocosms that simulate coral reef ecosystem. We assessed changes in abundance and diversity of benthic algae grown at 25°C and 28°C, under ambient (~400μatm) and at high CO₂ conditions (800-1000μatm). Total alkalinity, pCO₂, and the aragonite saturation state, were all significantly different between control and high CO₂ treatments in both temperature treatments. Chl a concentration increased significantly in CO₂-treated groups at 25°C, but benthic microalgal abundance was not significantly different. The number of microalgal species and the microalgal community structure did not differ between control and CO₂-treated groups at both temperatures. Our results suggest that increasing CO₂ may boost benthic microalgal primary productivity if sufficient nutrients are available, although site-specific responses are difficult to predict.