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

Bioproducts derived from <i>Ulva</i> 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 PO₄^3-) commonly found in eutrophic environments on carbohydrate production, growth rate, tissue phosphorus, phosphate uptake and photosynthetic response in <i>U. fasciata</i> 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 (<i>p</i> &lt; 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 (<i>p</i> &lt; 0.05). Altogether, the results indicate that phosphate concentrations in the culture medium influenced the carbohydrate content of <i>U. fasciata</i> and that populations from sites with broad environmental variations can present higher productivity.