Caulerpa paspaloides (Bory) Greville were collected during the winter and summer (1978 to 1979) from the Florida Keys, USA. Thalli collected during the winter photosynthesized more efficiently at low light intensities (Ic<1, Ik=38 μExm-2xs-1) than did thalli collected in the summer (Ic=13, Ik=111 μExm-2xs-1). Summer thalli exhibited higher Pmax values (2.20 mgO2xg-1 dry wtxh-1) than winter thalli (1.70 mg O2xg-1 dry wtxh-1). Rates of rhizome elongation and frond initiation were strongly inhibited by winter temperatures. The maximum lethal temperature for summer thalli was 37° to 38°C as measured by both growth and photosynthesis. No evidence of nitrogen or phosphorus limitation was found. Relatively minor reductions in salinity (3‰S) resulted in significant increases in rhizome apex motality. Results indicate that low winter temperatures are responsible for reduced winter growth rates previously reported for the Key Largo population. Increased photosynthetic efficiency at low light intensities and preferential maintenance of rhizome elongation over frond initiation appear to allow this tropical macroalga to optimize growth and survival during the winter.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Aquatic Science