DIVERSITY INDICES OF SELECTED BIOTA IN SOMBREIRO RIVER, RIVERS STATE, SOUTH-SOUTH NIGERIA

Abstract

An investigation aimed at ascertaining the species richness, evenness and diversity of phytoplankton, epipelic algae, zooplankton and benthic macro faunal communities ofSombreiro River was carried out over a 24 month period across 10 stations. Samples were collected once monthly and preserved in the field before transporting to the laboratory, where samples were identified and enumerated to the species level using relevant identification keys. Field and laboratory methods followed standard procedures and data generated were subjected to specific ecological statistical analyses using analytical tools fit for natural communities. Margalef’s index for species richness, evenness index and Shannon – Weiner diversity index for phytoplankton varied from 5.638 – 7.423, 0.717 – 0.882 and 1.331 – 1.664 respectively. Those of epipelic algae are 8.796 – 9.302, 0.489 – 0.709 and 0.560 – 0.922 respectively, those of Zooplankton respectively fluctuated from 1.852 – 4.297, 0.748 – 0.921 and 0.920 –1.399 and finally benthic macro fauna values ranged from 0.944 – 2.055, 0.905 – 0.991 and 0.452 – 0.673 respectively. Species richness/ diversity data except for phytoplankton showed that more species were recorded in the lower zone followed by the middle zone and then the upper zone. This is in total agreement with
the generally held consensus that diversity decreases as pollution increases and vice versa.