The study of diversity, distribution and abundance of Zooplankton in the southern of Caspian Sea

Abstract

This survey was carried out by R/V Gilan with a conical plankton net of 100 micron mesh by vertical hauls at 8 transect in the southern Caspian sea. Transects were located at Astara, Anzali, Sefid roud, Tonekabon, Noshahr, Babolsar, Amirabad and Torkman in depths of 5, 10,20,50and 100m. Samples were taken in 4 seasons ( in each season 64 samples) in 2009. In this study 23 species formed the zooplankton community including 4 species of Copepoda, 8 species of Rotatoria, 2 species of Protozoa and 8 species of Cladocera. The meroplankton blonged to 2 species of Balanus sp and Lamellibranchiata larvae. The annual results revealed that the maximum abundance of Copepoda were 3612±4839 ind/m3 and 35/75 ±42/81 mg/ m3 in summer and decreased gradually since autumn and reached to minimum value in winter. The maximum abundance of Cladocera was 300± 383 ind/m3 in spring and reached to less than 4 ind/m3 in summer and autumn. The Rotatoria had high population (3775± 8632 ind/m3) in winter which consisted the zooplankton population with Copepoda. The Protozoa had no efficient role in zooplankton population of Caspian sea during the year. The zooplankton population was affected by Meroplankton and Lamellibranchiata larvae in spring and winter. The Copepoda contributed in zooplankton population only in summer and autumn. The maximum zooplankton abundance and biomass were in 5m depth which included 10209±8352 ind/m3 and 43/56±26/08mg/ m3 in spring, 8545±7127 ind/m3 and 73/59±56/65mg/ m3 in summer(10 m depth), 8427±6711 ind/m3 and 43/15± 29/59 mg/ m3 in autumn and 24426 ±26975 ind/m3 and 334/25±392/21 mg/ m3 in winter which decresed from surface to depth. The maximum abundance and biomass of zooplankton were 5119±6018 ind/m3 in east and 28/59±24/79 mg/ m3 in central area in spring, 6628±7117 ind/m3 in west area and 50/73±59/52 mg/ m3 in central area in summer, 5248 ±5489 ind/m3 and 31/16 ±31/22 mg/ m3 in west area in autumn and 11588±16191 ind/m3 and 131/02±193/61 mg/ m3 in west area in winter. The annual statistical analysis reveals that there is significant difference between Copepoda and Cirripedia population among seasons, sampling stations, depth and sampling layer (Kruskalwallis test, p<0.05) and the total zooplankton populatin had no significant difference only between seasons (Kruskal-wallis test, p>0.05). The Cladocera, Lamellibranchiata larvae and the Rotatoria had significant difference between seasons only (Kruskal-wallis test, p<0.01).