Photosynthetic carbon fixation by tropical coral reef phytoplankton assemblages: a UVR perspective

doi:2013.28.3.281

Algae > Volume 28(3); 2013 > Article

Algae 2013;28(3): 281-288. doi: https://doi.org/10.4490/algae.2013.28.3.281

Gang Li¹^,2, Zhiwei Che³ and Kunshan Gao¹^,*

¹State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361005, China
²Key Laboratory of Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, CAS, Guangzhou, Guangdong 510301, China
³Sanya Marine Environment Monitoring Station, SOA, Sanya, Hainan 572000, China

*Corresponding Author

Email: ksgao@xmu.edu.cn

ABSTRACT

Photosynthetic carbon fixation regulates air-sea CO2 fluxes in the waters of coral reefs. However, little has been documented on the effects of solar UV radiation (UVR, 280-400 nm) upon photosynthetic behaviors of phytoplankton dwelling in these ecosystems. In order to evaluate the aforesaid, surface dwelling tropical coral reef phytoplankton assemblages collected from the South China Sea were exposed to solar radiation (i.e., photosynthetically active radiation [PAR] + UV radiation A [UVA] + UV radiation B [UVB], 280-700 nm; PAR + UVA, 320-700 nm; and PAR, 400-700 nm) under static or simulated-mixing conditions. Under the static condition, UVA and UVB significantly reduced the carbon fixation with the maximum of 22.4 and 15.3%, respectively; while lower UVR-related photosynthetic inhibition was observed in case of phytoplankton samples being subjected to mixing. At a moderate level of mixing (i.e., circulation time 80 min), the UVA and UVB caused inhibition were lowered by 52.1 and 79.6%, respectively. Based on this it could be stated that vertical mixing induced by winds and/or tides in the natural environments could reduce the inhibitory effect of solar UVR on phytoplankton productivity in the coral reefs water.

Key words: carbon fixation; coral reefs; phytoplankton; South China Sea; UVR