Phytoplankton Composition, Abundance and Diversity in Some Selected Parts of Lagos Lagoon

Akhiromen Iniobong, J.A. Adedipe, A.S. Yakub, K.J. Balogun, B.O. Bello and O. Abiodun

Background and Objective: Phytoplankton is the primary producer of any aquatic ecosystem and functions as a suitable indicator for water quality evaluation. Phytoplankton growth and division are tightly linked to their diet cycle. The density and diversity of phytoplankton are influenced by the quality of water. Lagos Lagoon is one of the major nine lagoons located in the southwestern region of Nigeria. The study investigated phytoplankton composition and diversity in Lagos Lagoon between January and October, 2017. Materials and Methods: Samples for the phytoplankton studies were collected using a standard plankton net of 55 μm mesh size and preserved with 4% unbuffered formalin and analysed using the microscope. Surface water samples were collected and analysed for the physicochemical parameters (temperature, dissolved oxygen, turbidity, total dissolved solids, salinity, pH, BOD, nitrate, sulphate, phosphate and silicate) using standard procedures and instruments. Results: A total of 68 species, spread out into six classes, Cyanophyta constituted 50.79% of the total phytoplankton abundance, Bacillariophyta constituted 47.64%, Dinophyta was 1%, Euglenophyta, 0.36%, Charophyta 0.14% and Chlorophyta, 0.07% were identified. Ecological indices were used in the assessment of pollution and productivity of a water body. Shannon-Wiener index ranged between 0.83-2.79. Margalef value ranged between 1.13-5.54, Berger Parker range was between 0.22-0.82, while Equitability values ranged between 0.3-0.91. The dominance of the blue-green algae in terms of phytoplankton density in the study, interplayed with the values of Shannon Weiner diversity index and Margalef, showing the study area is under pollution threat. Conclusion: Based on the result of the study, proper frequent monitoring of the study area is recommended, to avoid enhanced depreciation of the water body.

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