Assessment of benthic macroinvertebrate fauna as bio-indicator and physicochemical characteristics in the Gulf of Guinea off western Nigerian shor

Abstract

Benthic macroinvertebrates are helpful bio-indicators providing better understanding of modified and perturbed aquatic ecosystems. This study seeks to determine the ecological status and diversity of the macroinvertebrate community in relation to environmental variables in western Nigerian offshore waters within the Gulf of Guinea. Macroinvertebrate samples were collected from five (5) sampling stations using a Van-veen grab following standard protocols. Water samples were collected and the physico-chemical parameters measured onboard using a multi-parameter checker, HORIBA-U53. The physico-chemical parameters of the water varied significantly (p<0.05) between stations. Macoma litoralis (13.71%), Tellina gilchristi (13.71%), and Tellina trilateri (11.71%) were the dominant macroinvertebrate species, while Nassarius cuvierii, Oxystele tigrina Tritia lanceolata Turritella communis, Turritella communis and Orbinia angrapequensis (0.33% each) were the least abundant. Axis 1 (63.73%) and axis 2 (22.32%) of the Canonical Correspondence Analysis (CCA) explained macrobenthic fauna-environmental variables association. Gastropoda showed strong relationship with salinity, silicate, sulphate, TDS and conductivity in Stations 1, 2 and 3. Bivalvia and Scaphopoda showed strong relationship with pH, BOD, water temperature, phosphate and nitrate in Stations 4 and 5. The AZTI Marine Biotic Index (AMBI, 0.85), multivariate AZTI Marine Biotic Index (M-AMBI, 0.80), Bentix Index (5.46) and Biotic Index (BI, 1.00) showed that this section of the Gulf of Guinea is undisturbed.