MARINE MACROPHYTE COMMUNITIES ON THE REEF FLAT AT AGATTI ATOLL (LAKSHADWEEP, INDIA)

The distribution, abundance and standing stock of macrophytes on the i ntertidal reef flat at Agatti atoll (Lakshadweep, India) were recorded in a total of 1234 quadrats in October 1993 and April 1994. Eighty se ven species of macrophytes, including 16 new records, were observed on the different islands. The reef flat at Agatti can be divided into th ree zones partly correlated with physical factors. The upper zone is c haracterized by Thalassia hemprichii, Boergesenia forbesii, Gracilaria edulis and Valoniopsis pachynema, the middle zone by Gelidiella acero sa, Laurencia papillosa and Ceramium sp., and the lower zone by Ulva l actuca, Turbinaria ornata and Codium arabicum. Halimeda gracilis is do minant in both the middle and lower zone. The majority of algae exhibi ted patchy distributions, with seasonal fluctuations in their abundanc e. Species diversity increased with distance from the shore while perc entage cover and species richness exhibited the reverse trend. Herbivo ry appeared significant with sea urchins as the major grazers. Algal a bundance was reduced to one third in April mainly because of periodici ty;governed by the monsoon. Macrophyte wet weight standing stock of Ag atti reef flat was estimated to be 835 +/-: 59 t (October 1993) and 68 6 +/- 77 t (April 1994).