Pigment levels, chemical constituents, and photosynthetic responses of two estuarine populations of Gracilaria verrucosa and one neretic population of G. tikvahiae were monitored before, during and after culturing in nutrient-enriched seawater. Chlorophyll a and
phycoerythrin, protein, soluble carbohydrate, lipid, and energy content did not change in both species cultured for 5 weeks in nutrient-enriched seawater and then for another 5 weeks without nutrients. Productivity (Pm) remained high after culture with and then without nutrients
and no photoinhibition was evident at irradiances of 1200 μE m–2s–1 after culture in any of the populations. An increase in the initial slope of the photosynthesis-irradiance curve (alpha) with no change in the compensation point irradiances (I) suggests
an increase in photosynthetic efficiency after culture in nutrient-enriched seawater. Exposure to enriched and then non-enriched seawater did not result in any shift in tolerance to 12 combinations of temperature and salinity based on photosynthetic and respiratory responses. The study extends
previous findings regarding nutrient storage by seaweeds by demonstrating the ability of Gracilaria to tolerate stress after nutrient deprivation.
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