Summer and Winter Comparisons in the Nutritional Value of Marine Macroalgae from Hong Kong

Abstract

The chemical composition of common marine macroalgae from Hong Kong was determined both in the winter (cool and dry) and the summer (hot and wet) of 1994. During the winter, macroalgal diversity was high and variation in chemical composition between the species was great. In contrast, during the summer, algal diversity was reduced and the shores were dominated by only a small number of comparatively nutrient rich encrusting algae. Multivariate analysis indicated that the nutritional value of algal species (in terms of ash, lipid and soluble carbohydrate content) was related to their systematic position and that, overall, the Phaeophyta had the highest levels of nutrients, while the Chlorophyta and the Corallinaceae were of comparatively low nutritional value. The chemical composition of the species varied temporally as did the abundance and diversity of algae on the shore. Overall, however, seasonal differences in algal availability appeared to be more important in determining total nutrient availability than temporal changes in the nutritional value of the species. Local macroalgae are the main food source for a large number of marine herbivores and variation in algal availability and chemical composition are likely to effect the ecology of these grazers and subsequently community organization.