Sciences marines : recherche et développement

Abstrait

An Assessment of Seaweeds Diversity and Distribution at the Beach of Nathia Gali, Karachi, Pakistan

Rashida Qari

The seaweeds resources were sampled from exposed shore of Nathia Gali beach, Karachi coast at low tide. The present data of diversity and biomass of seaweeds provide a comparison of two different periods i.e., from 1989 to 1991 and 2012. A total of 60 taxa were recorded in the coastal area of Nathia Gali; 14 belonging to chlorophyta, 15 to Phaeophyta and 31 to Rhodophyta. The green seaweeds viz, Caulerpa racemosa, Codium iyengarii and Halimeda tuna; brown seaweeds, Cystoseira indica, Iyengaria stellata Padina pavonica and Sargassum boveanum and red seaweeds Gracilaria corticata and Scinaia fascicularis were found to be the dominant species of Nathia Gali. The total biomass 66056.18 g. m-2 was recorded during the study period and the highest biomass was recorded in January (16551.79 g m-2) and the lowest in July (1276.3 g. m-2). In winters, seaweeds biomass and growth increased due to low temperature of air and seawater with low intensity of light and high dissolved nutrients. The richness of seaweed resources in the studied area is due to the intertidal rocks available on the coast but nowadays, there is lot of disturbance due to anthropogenic activities such as discharge of domestic and industrial waste; tanneries effluents; rainfall and associated pollutant from runoff; shipping and agricultural sources. These disturbances play vital role in changing the ecosystem which effects flora and fauna of the coast.