Seasonal variations in the rate of photosynthetic activity and chemical composition of the seagrass Cymodocea nodosa (Ucr.) Asch.

Abstract

Temporal changes in biomass, rate of photosynthetic activity and chemical composition of the seagrass Cymodocea nodosa (Ucr.) Asch., under the influence of various environmental factors, were followed in the Faborsa Bay, Northern Adriatic. Throughout the year the estimated average biomass was about 130 g dry wt m^-2 with annual production of 80 g C m^-2. In general, leaf length, biomass and production showed clear seasonality, with maximum values during the summer period (July-September) and clear minima in winter. Net oxygen production was closely related to biomass, leaf length, chlorophyll concentration, water temperature and incident light intensity. No clear seasonality was observed in the chemical composition (protein, fats, total phosphorus) of C. nodosa. Over the annual cycle, the range of measured variables was 10-16% for protein, 1.7-3.1% for fat, 0.3-0.8% for phosphorus, 1.6-2.6 for nitrogen in leaves, and 5-17% for protein, 0.9-3.2% for fat, 0.1-0.6% for phosphorus and 0.9-2.8 for nitrogen in roots.