| Summary: | Four species of benthic macroalgae belonging to Rhodophyta namely Palmaria decipiens (Reinsch) Ricker, Phyllophora antarctica A. et. E. S. Gepp, Porphyra endiviifolium (A.et. E. S. Gepp.) Chamberlain and Iridaea cordata (Turner) Boerg. collected from beneath the sea-ice from the coast of the Vestfold Hills, Antarctica were cultured under different temperature regimes (- 4, -1.8, +4, +12, +20°C). The algae were cultured at each of these temperatures and Chlorophyll a concentrations of the algae were measured after every 24 and 96 h of exposures. The Chlorophyll a concentration in endemic Antarctic macroalgae P. decipiens and P. antactica showed peak at 4°C and at 12°C in 24 h respectively, while the cold temperate macroalgae P. endiviifolium and I. cordata showed peak at 4°C in 96 h and 24 h respectively. Among the four macroalgal species evaluated, a maximum Chlorophyll a of 750 mg g-1 was recorded in P. endiviifolium. This alga showed 38% higher Chlorophyll a concentration than the control and concentration remained same till the end of the experiment. I. cordata and P. decipiens recorded a maximum Chlorophyll a concentration at 4°C in 24 h and declined thereafter, while in P. antarctica Chlorophyll a concentration showed an increasing trend with a peak (680 mg g-1) at 12°C in 24 h and thereafter, alga started to bleach and degenerated. The experiment indicated that time period was found necessary for optimum Chlorophyll a concentration and time required to adapt to each temperature regime.
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