Photosynthetic Characteristics of Three Cohabitated Macroalgae in the Daya Bay, and Their Responses to Temperature Rises.

Biochemical compositions and photosynthetic characteristics of three naturally cohabitated macroalgae, , and , were comparably explored in the field conditions in Daya Bay, northern South China Sea, as well as their responses to temperature rise. Chlorophyll (Chl ) and carotenoids contents of were 1.00 ± 0.15 and 0.57 ± 0.08 mg g in fresh weight (FW), being about one- and two-fold higher than that of and ; and the carbohydrate content was 20.3 ± 0.07 mg g FW, being about three- and one-fold higher, respectively. Throughout the day, the maximal photochemical quantum yield (F/F) of Photosystem II (PS II) of these three macroalgae species decreased from morning to noon, then increased to dusk and kept steady at nighttime. Consistently, the rapid light curve-derived light utilization efficiency (α) and maximum relative electron transfer rate (rETRmax) were lower at noon than that at morning- or night-time. The F/F of (varying from 0.78 to 0.32) was 38% higher than that of throughout the day, and that of was intermediate. The superoxide dismutase (SOD) and catalase (CAT) activities in were lower than that in and . Moreover, the rises in temperature species-specifically mediated the damage () caused by stressful high light and the corresponding repair () to photosynthetic apparatus, making the / ratio increase with the rising temperature in , unchanged in but decreased in . Our results indicate that may compete with or and dominate the macroalgae community under aggravatedly warming future in the Daya Bay.