World Bank assisted National Agricultural Research Project (NARP) - University of Port Harcourt
Abstract
The composition and distribution of planktonic fauna (adult form of
zooplankton and planktonic juvenile forms of higher animals) within the
eastern part of the Lagos Lagoon were investigated in July, 2008 and
March, 2009 representing rainy and dry season respectively. Samples of
water and planktonic fauna were collected from twelve stations within
the eastern axis of the Lagoon and analyzed using standard methods. The
study area had brackish water characteristics with fresh water
condition (0\u2030 salinity across the 12 stations) in the rainy
season whereas the salinity ranged from 11.4\u2030 to 30.5\u2030 in
the dry season. The adult forms zooplankton recorded in the rainy
season were mainly Crustaceans, Chaetognathans and Rotifers while those
collected during dry season belonged to Crustacean, Cnidaria and
Chordata. Crustaceans dominate both adult zooplankton and planktonic
juvenile fauna in the two seasons. The rainy season adult zooplankton
count (515) was lower than that of dry season (580) but the reverse was
the case for the juvenile stages count (520 and 325 in rainy and dry
season respectively). Higher species abundance was recorded for both
adult zooplankton (20) and juvenile stages (10) in rainy than dry
season when 14 and 8 were recorded for the two groups respectively.
Higher values were also of community structure indices (Margalef
species richness and Shannon-Wiener species diversity) were recorded in
the rainy than dry season for the two groups of planktonic fauna. The
findings show the influence of salinity gradients on distribution of
planktonic fauna of the Lagos Lagoon