Distribuição, biomassa e diversidade dos bancos de ervas marinhas na ilha de bazaruto

Abstract

The study of seagrass distribution, diversity and biomass was carried out from January to April 2003 in the intertidal zone on the west coast of Bazaruto Island, Inhambane province, 25 km from Inhassoro District. The study also estimated the area covered by seagrass beds, and compared the biomass of the grass species between areas used and areas not used by the human population for subsistence purposes. The study area was divided into square spaces; in each space the coordinates were registered and 5 samples were extracted; in each sample, the species present were identified and the species were weighed separately. Seagrass species identified in the Bazaruto intertidal zone are: cymodocea rotundata, cymodocea serrulata, Halophila ovalis, Nanozostera capensis, thalassodendron ciliatum and Thalassia hempríchii. As for the distribution, the species cymodocea rotundata, nanozostera capensis, Thalassodendron ciliatum and Thalassia hempríchii had wide distribution; the species cymodocea serrulata and Halophila ovalis had a restricted distribution. The species identified in Bazaruto formed 2 communities dominated by thalassodendron ciliatum and Thalassia hempríchii. In total 53 seagrass beds were recorded and the average coverage area of ​​each bed was 0.058 km2. The total coverage area of ​​the seagrass beds was 11.6 km2 (23.1% of the Bazaruto intertidal zone). The mean total biomass of the aerial part of the seagrass species was 47.3g/m2 (dry weight) and the mean total biomass corresponding to the underground part was 73g ps/m2 . The estimated total seagrass biomass at Bazaruto was 580.3 tonnes dry weight/m2. There are no differences in the aboveground and total biomass of species in used and unused areas. There were differences in the biomass of the underground part. (TRADUÇÃO NOSSA)