EVALUATION OF PHYSICOCHEMICAL PARAMETERS AND PHYTOPLANKTON ASSEMBLAGE OF LAKE ASA, ILORIN, NIGERIA
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Date
2025-03-12
Journal Title
Journal ISSN
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Publisher
Animal Research International
Abstract
A limnological investigation of Lake Asa was conducted from November 2023 to October
2024, encompassing three sampling stations, to assess its physicochemical properties and
phytoplankton composition. Measured values of physicochemical parameters were
evaluated against established water quality standards. The lake's water quality was
assessed through three analytical approaches: (1) analysis of phytoplankton taxonomic
structure; (2) multimetric assessment using diversity indices; and (3) multivariate
ordination of taxonomic group distribution to environmental variables. Thirteen
physicochemical parameters were analyzed. Comparative analysis revealed that nine
parameters met acceptable limits for domestic water supply and aquaculture, while four
parameters were deemed unsuitable. Specifically, transparency, total nitrogen, organic
matter, total organic carbon, and total phosphorus concentrations indicated a
hypereutrophic state across all sampling stations, a hallmark of eutrophication. However,
taxonomic analysis suggested a mesotrophic status for the lake. Phytoplankton community
composition consisted of six taxonomic groups, with Cyanophyta dominating (83.20%).
Other groups present, in descending order of abundance, were Bacillariophyta (diatoms
8.4%), Dinophyta (4.20%), Chlorophyta (2.70%), Euglenophyta (1.00%), and
Chrysophyta (0.41%). Phytoplankton diversity indices ranged as follows: Shannon-Wiener
(H = 0.26 – 0.98), Simpson (D = 0.46 – 0.90), and Pielou's evenness (J = 0.22 – 0.44).
Canonical Correspondence Analysis (CCA) demonstrated the influence of environmental
variables on phytoplankton assemblage structure, while Non-metric Multidimensional
Scaling (NMDS) revealed spatial and temporal differences in phytoplankton assemblages.
The observed Cyanophyta dominance and low diversity index values collectively indicate
that Lake Asa is heavily polluted and in poor ecological condition.