Seasonal variation in phytoplankton diversity, distribution, composition and chlorophyll-A at Yewa Lagoon, Nigeria
Adedipe, J.A.; Onyema, I.C.; Emmanuel, B.E.; Adesalu, T.A. (2025). Seasonal variation in phytoplankton diversity, distribution, composition and chlorophyll-A at Yewa Lagoon, Nigeria. J. Appl. Sci. Environ. Manage. 29(7): 2246-2260. https://dx.doi.org/10.4314/jasem.v29i7.25
In: Journal of Applied Sciences & Environmental Management . National Agricultural Research Programme (NARP): Port Harcourt. ISSN 2659-1502; e-ISSN 2659-1499, more
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| Keywords |
Bioindicators
Periodicity > Seasonality
Water quality
Microcystis aeruginosa (Kützing) Kützing, 1846 [WoRMS]
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| Author keywords |
Carlson’s Trophic State Index; organic pollution |
| Authors | | Top |
- Adedipe, J.A.
- Onyema, I.C.
- Emmanuel, B.E.
- Adesalu, T.A.
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| Abstract |
Yewa Lagoon, part of the Lagos Lagoon complex on the Guinea coast of West Africa, is subject to intense anthropogenic activity, necessitating regular monitoring of its water chemistry and biological properties. Hence, the objective of this paper was to evaluate the seasonal variation in phytoplankton diversity, distribution, composition and chlorophyll A at Yewa Lagoon, Nigeria using various standard methods, over an 18-month period (August 2017 – January 2019). Monthly sample collections revealed seasonal fluctuations influenced by rainfall and runoff, affecting water quality parameters. Air and water temperatures were high (24.0 – 34.0 °C and 26.5 – 37.5 °C), with salinity ranging from 0.0 – 9.0 ‰ and pH (5.7 – 7.9). Dissolved oxygen (1.0 – 9.6 mg/L) and biochemical oxygen demand (1.1 – 12.3 mg/L) indicated variable pollution levels, with chemical oxygen demand (≤478 mg/L). Chlorophyll A levels (1.04 – 16.8 μg/L) were higher in the dry season. Heavy metal concentrations were low, while nutrient levels (reactive nitrogen, phosphorus, sulphate, and silica) were high. Calcium and magnesium concentrations were higher in the rainy season. Significant differences (p<0.05) across stations were only observed for sulphate and COD in the rainy season, and air temperature and water depth in the dry season. Phytoplankton diversity included 315 species from 112 genera across 11 classes and 7 divisions, with notable taxa such as Microcystis aeruginosa, Nitzschia, Navicula, and Cyclotella. Seasonal changes and pollution affected phytoplankton diversity and abundance. Carlson’s Trophic State Index classified the lagoon as eutrophic (60–80), supported by the dominance of cyanophytes (44%) and diatoms (40%) and low ecological index values (Shannon ≤1.929, Margalef ≤8.436, equitability ≤0.477), indicating moderate biodiversity and potential ecological stress. |
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