Effects of tides on the zooplankton of the Great Kwa River, Calabar, Nigeria

Abstract

This study investigated the tidal effects on the composition, diversity, abundance and distribution of zooplankton species in the Great Kwa river, Nigeria. Zooplankton samples were collected fortnightly between July 2019 and September 2019 at low, mid and high tidal regimes. A total of 59 zooplankton species belonging to 41 taxa (genera) and 16 classes groups were identified and recorded during the study. Zooplankton comprised of 199 individuals of which 49 were recorded in low tide, 95 (mid tide) and 55 (high tide). Generally, Rhizopoda (37.19%) were dominant, followed by Copepods (25.13%) while invertebrate, Lepidoptera and Malacostracan were less than 1% each. Copepods were dominant at low tide, while Rhizopoda were dominant at mid-tide and high-tide. Weiner Index (H) showed that zooplankton species was high at low tide (3.95), followed by high tide (2.95) and least in mid tide (2.22). The absence of some zooplankton species at Mid tide and High tide suggests that zooplankton species had vertically migrated downward the river before high tide and mid tide. Despite the highest number of individuals recorded at mid-tide, an evenness value of 0.49 compared to 0.74 (high-tide) and 0.85 (low-tide), suggests that the numerical abundance was less evenly distributed among species.