Temperature and irradiance effects on growth and photosynthesis of Caulerpa (Chlorophyta) species from the eastern Mediterranean

We evaluated the effects of temperature and irradiance on growth and photosynthetic activity of Caulerpa prolifera, C. mexicana and C. scalpelliformis, all common species in the eastern Israeli Mediterranean. The growth of these species was negative at 15 °C but optimal at 23–26 °C, averaging 16% at 23 °C and 48% at 26 °C. For all species, the effect of irradiance on growth was seen by a large number of buds (regeneration of new thalli from mother leaves), particularly at the high (120 μmol photons m−2 s−1) experimental irradiance. The species most sensitive to high irradiance was C. scalpelliformis, for which growth was negative from 60 μmol photons m−2 s−1 and above. Photosynthetic rates and photosynthetic parameters generally correlated with growth, irradiance, and temperature conditions found in the natural environments for all three species.

► Growth of C. prolifera, C. mexicana, and C. scalpelliformis was negative at 15 °C and optimal in 23–26 °C temperature range. ► With increasing irradiances, all three species responded by developing a large number of buds (new thalli from old leaves). ► C. scalpelliformis was most sensitive to increasing irradiance, with growth negative from 60 μmol photons m−2 s−1 and above. ► Photosynthetic rates and parameters correlated with growth, irradiance, and temperature conditions in all three species.