Vol. 2, Issue 1, Part D (2016)

Abstract
Studies on the distribution of macro fauna on tidal flat of Calabar River was investigated at four different stations (Tinapa, Adax Petroleum, Itiat Ekpe and Esuk Nsidung). Sediments samples for macro fauna identification were collected at each station of Calabar River, twice monthly for three month (February- April, 2015) using a quadrant square of 50 by 50 cm² (0.25 m²) in the exposed area and a corer of about 8 cm in diameter and 30 cm long was used in the sub-tidal area. Data obtained from the studies was calculated using biological indices such as; numerical abundance, percentage relative abundance, Margalef’s index, Shannon- wiener index and Species equitability or evenness to estimate abundance and diversity of macro fauna species. A total number of 826 individual’s organisms containing 28 species were encountered and identified in sediments samples using standard identification keys from the four sampling stations. The highest numbers of organisms were recorded at station 1with 318 individuals, followed by station 3 with 313 individuals and the least was station 4 with 60 individuals. Twenty-eight species belonging to four taxa were recorded. These included Mollusca with 8 species and 591 individuals which represented 71.55% of the macro fauna population. Annelida had 10 species with 81 individuals (9.81%), Crustaceans had 8 species with 146 individuals (17.68%) and Echinodermata contained 2 species and 8 individuals which represent (0.97%) of the macro fauna population. Margalef’s diversity index d, ranged between 0.48 and 2.05, while Shannon-wiener index ranged between 0.93 – 2.91, and Evenness ranged between 0.28 – 0.87 indicating that the macro fauna assemblage in Calabar River were densely distributed at the 10 cm depth. The dominance of the group Mollusca in the sediments of Calabar River is understandable because these group of organisms are mainly filter feeders and can survive were other organisms cannot including poor nutrients areas. They filter water and obtain plankton and detritus or burrow through sediments, feeding on other inhabitants.