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<p>Phytoplankton communities serve as vital indicators of aquatic ecosystem health. This study investigated the relationship between environmental factors and the types of phytoplankton found in three locations (Ode, Osse River, and Downstream) in the Egbe Reservoir, Nigeria, during the wet and dry seasons. Data on phytoplankton species and physicochemical variables such as temperature, pH, total dissolved solids, dissolved oxygen, conductivity, nitrates, and phosphates were analysed using two-way ANOVA, diversity indices, and Canonical Correspondence Analysis (CCA). The results revealed strong spatial heterogeneity in environmental conditions. pH and temperature increased downstream, while dissolved oxygen declined significantly to &lt; 5&#xa0;mg L⁻¹, indicating potential stress for aerobic biota. Conductivity was highest at Ode, suggesting localized ionic loading. Nitrate decreased downstream, whereas phosphate increased, reflecting differential assimilation and internal loading. Chlorophyll-a was markedly elevated at Ode, confirming its role as a productivity hotspot in the region. ANOVA indicated highly significant site effects (<i>p</i> &lt; 0.001) across all variables, with seasonal influences on TDS, temperature, DO, and pH, while Site × Season interactions were non-significant. Phytoplankton exhibited more complex responses, with four dominant genera (Nitzschia, Nitzschia sp. 2, Skeletonema, Rhizosolenia) showed significant site, season, and interaction effects, underscoring site-specific seasonal dynamics. Diversity indices revealed high richness but low evenness at Ode, in contrast to greater evenness at the Osse River. CCA confirmed that phosphate, temperature, pH, conductivity, and DO as key drivers. Chlorella and Nannochloris were linked to nutrient- and temperature-rich conditions, while Cryptomonas and diatoms favoured lower levels; Leptocylindrus exhibited oxygen-driven preferences. These findings underscore the structuring role of physicochemical gradients in phytoplankton communities and highlight the need for continuous monitoring to preserve the ecological integrity of the Egbe Reservoir.</p>

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Ecological Drivers of Phytoplankton Community Structure in Egbe Reservoir, Southwestern Nigeria

  • 期刊论文

  • 发表日期：

    2025年12月4日

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  • Oyewumi Johnson Olalere,
  • Durgesh Kurmar Verma,
  • Oyewumi Folake Funmilayo,
  • Emmanuel Adewumi,
  • Adewumi Patricia Oluwatobi,
  • Ogwuche Blessing,
  • Aminu Kadijah Dolapo

摘要

Phytoplankton communities serve as vital indicators of aquatic ecosystem health. This study investigated the relationship between environmental factors and the types of phytoplankton found in three locations (Ode, Osse River, and Downstream) in the Egbe Reservoir, Nigeria, during the wet and dry seasons. Data on phytoplankton species and physicochemical variables such as temperature, pH, total dissolved solids, dissolved oxygen, conductivity, nitrates, and phosphates were analysed using two-way ANOVA, diversity indices, and Canonical Correspondence Analysis (CCA). The results revealed strong spatial heterogeneity in environmental conditions. pH and temperature increased downstream, while dissolved oxygen declined significantly to < 5 mg L⁻¹, indicating potential stress for aerobic biota. Conductivity was highest at Ode, suggesting localized ionic loading. Nitrate decreased downstream, whereas phosphate increased, reflecting differential assimilation and internal loading. Chlorophyll-a was markedly elevated at Ode, confirming its role as a productivity hotspot in the region. ANOVA indicated highly significant site effects (p < 0.001) across all variables, with seasonal influences on TDS, temperature, DO, and pH, while Site × Season interactions were non-significant. Phytoplankton exhibited more complex responses, with four dominant genera (Nitzschia, Nitzschia sp. 2, Skeletonema, Rhizosolenia) showed significant site, season, and interaction effects, underscoring site-specific seasonal dynamics. Diversity indices revealed high richness but low evenness at Ode, in contrast to greater evenness at the Osse River. CCA confirmed that phosphate, temperature, pH, conductivity, and DO as key drivers. Chlorella and Nannochloris were linked to nutrient- and temperature-rich conditions, while Cryptomonas and diatoms favoured lower levels; Leptocylindrus exhibited oxygen-driven preferences. These findings underscore the structuring role of physicochemical gradients in phytoplankton communities and highlight the need for continuous monitoring to preserve the ecological integrity of the Egbe Reservoir.