Alvin P. Monotilla^1,, Serafin M. Geson¹, Paul Isaac O. Dizon¹, Danilo T. Dy¹

Endogenous coordination between light, temperature and other factors by different species of algae would be vital in the production of several proteins needed for growth and adaptations, and therefore will affect their productivity. Among plant activities that are governed by daily light-dark cycles (i.e. 12L:12D and 12L:12L) among calcareous algae (Halimeda simulans, Mastophora rosea and Padina australis) were conducted by monitoring the dissolved oxygen (DO) concentration inside incubating bottles with algal samples for 24h and the features of the resulting DO curves were determined by measuring the number of pixel under the curve through image analysis. There was no significant difference among algae during the initial 12L:12D cycle suggesting their normal response to light-dark cycles. However, after six days under continuous light, M. rosea showed a significant decrease in the DO curve (lesser number of pixel under the curve) compared to DO curves during the initial 12L:12D cycle. The decrease in the DO concentration during the continuous L:L treatments might be attributed to the photoinhibitory effect of the red alga being less adoptive to subsequent high intensities. Although an increase in DO concentrations is expected with continuous light, not all algae responded to it. Only Padina exhibited circadian rhythm in our 24h observation under continuous light.

Coral reef, Padina, Halimeda, Mastophora, circadian rhythm