The effects of phosphate on physiological responses and carbohydrate production in Ulva fasciata (Chlorophyta) from two populations

Bioproducts derived from Ulva species have received increasing attention in several biotechnological fields due to their economic potential and cosmopolitan distribution. This study assessed the influence of different phosphate concentrations (0, 2 and 4 µM PO43-) commonly found in eutrophic environments on carbohydrate production, growth rate, tissue phosphorus, phosphate uptake and photosynthetic response in U. fasciata from two distinct sites (Arraial do Cabo, an upwelling site, with cold and nutrient rich water, and Niterói / Rio de Janeiro – Brazil, a non-upwelling site). After fifteen days of the experiment, the carbohydrate content increased in both populations and in all treatments (p < 0.05) at approximately 136 and 264 % for Arraial do Cabo and Niterói, respectively. In Arraial do Cabo individuals, the carbohydrate content was high in all treatments (71 % DW), while Niterói individuals cultivated in the highest phosphate concentration presented the lowest carbohydrate content (46 % DW). Individuals cultivated in the absence of phosphate (control) presented the lowest tissue P and a progressive decline in the maximum quantum yield (Fv/Fm) over the experimental period (p < 0.05). Altogether, the results indicate that phosphate concentrations in the culture medium influenced the carbohydrate content of U. fasciata and that populations from sites with broad environmental variations can present higher productivity.