Qualitative and quantitative analysis of carrageenan content in gametophytes of Mastocarpus stellatus (Stackhouse) Guiry along Galician coast (NW Spain)

Qualitative and quantitative differences in carrageenan composition of gametophytes of the rhodophyte Mastocarpus stellatus (Gigartinales) were observed in this study. Carrageenans in gametophytes belong to the kappa family (kappa-, iota-, nu-, mu-carrageenan). The dominant fractions were kappa- and iota-carrageenan (more than 80 % of the total carrageenans). Mean total carrageenan content in gametophytes was of 37.32 +/- 1.21 % DW. Spatial and seasonal variations were observed, mainly related to changes on environmental and oceanographic factors and the role of carrageenans in adapting the fronds to these changes. Maximum values in carrageenan content were observed for San Roman (Biscay Bay) in May and for Laxe and Mougas (Atlantic coast) in June. The results of this study indicated that spatial differences in carrageenan content were due to interactions of different factors, rather than the effect of a single factor. Fronds from San Roman had higher carrageenan content (43.23 +/- 1.87 % DW) than those collected at two sites of the Atlantic coast, Mougas and Laxe (32.20 +/- 1.14 % DW). San Roman is exposed to the open sea, windy and oriented to the north, and the water temperature is higher in summer than in the Atlantic coast. However, seasonal variations in carrageenan content resulted to be more related to other factors directly correlated with the input of energy in the ecosystems (irradiance, sunshine hours and insolation). Thus, carrageenan content began to increase in early spring when the number of sunlight hours increased. Maximum values were reached in late spring or early summer, just before maximum values of irradiance and air temperature were achieved.