STUDIES ON ASPECTS OF LIMNOLOGY OF YARDANTSI RESERVOIR, GUSAU, ZAMFARA STATE, NIGERIA
STUDIES ON ASPECTS OF LIMNOLOGY OF YARDANTSI RESERVOIR, GUSAU, ZAMFARA STATE, NIGERIA
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Date
2018-08
Authors
JABBI, AMINU MUHAMMAD
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Abstract
Yardantsi Reservoir, Gusau, Nigeria serves multitude of purposes for the Gusau populace. It is the main source of water for domestic purpose, irrigation, and fishing. The reservoir receives both organic and inorganic waste through runoffs and seepage from the catchment area. The physico-chemical parameters of surface water and sediment, plankton composition, distribution and abundance, fisheries potentials and presence of some trace metals in the reservoir, were investigated on a monthly basis between May, 2015 and April, 2017. Surface water, sediment and plankton samples were collected from five sampling stations and analysed using standard procedures for examination of water and wastewater. Trace and alkali-alkaline earth metals concentrations in water and sediment samples were analysed using Shimadzu AA6800 Atomic Absorption Spectrophotometer. The data obtained from this study was subjected to multivariate analysis using Microsoft Office Excels, SPSS and PAST packages. The results from this study showed that surface water temperature ranged from 25.98±0.09– 32.41±0.11ᴼC, Transparency (12.00±0.33-59.90±1.44cm), Mean depth (1.86±0.04-2.97±0.06m), pH (6.84±0.39-9.57±0.70), Electrical conductivity (64.20±5.25- 197.90±10.14μS/cm), Total dissolved solids (41.60±6.18- 109.30±1.9408mg/L), Dissolved Oxygen (5.97±0.10-8.86±0.09mg/L), Biological Oxygen Demand (1.79±0.08-3.58±0.08mg/L), Alkalinity (22.60±0.64– 47.80±0.88mg/L), Hardness (23.10±0.66–67.50±0.98mg/L), NO3-N (1.64±0.05-5.19±0.10mg/L), PO4-P (106.50±2.60-197.90±4.44mg/L) and Chloride (29.45±0.62- 89.90±0.90mg/L). As for the trace and alkali-alkaline earth metals concentrations in the reservoir, results showed that Ca ranged from 0.52±0.03-4.49±0.26mg/L, K(1.84±0.05-4.46±0.13mg/L), Mg (0.19±0.01-2.83±0.07 mg/L), Na (29.85±0.73-84.06±1.71mg/L), Cd (0.03±0.00-0.29±0.05mg/L), Cr (0.73±0.03-1.62±0.15mg/L), Cu (0.05±0.00-0.25±0.04mg/L), Fe (0.68±0.03-5.74±2.51mg/L), Ni (0.09±0.02-0.18±0.05mg/L), Pb (0.02±0.00-0.07±0.01mg/L) and Zn (0.66±0.03-1.75±0.19mg/L). Most of the values for surface water parameters with the exception of Fe, Cr, Cd, Mg, Ni, and Pb are within threshold levels set by NSDWQ, WHO and FAO. Analysis of variance showed significant seasonal variation between stations with surface water temperature, mean depth, electrical conductivity, Dissolved oxygen, phosphate, chloride, chromium and iron (p<0.05), while total dissolved solids, sulphate, calcium, magnesium and sodium showed highly significant seasonal variation (p<0.01). The concentrations of metals in surface water throughout the study period revealed the following decreasing order of magnitude; Na > K > Ca > Mg > Fe > Cu > Zn > Cr > Cd > Ni > Pb; and Na > K > Fe > Zn > Cu > Ca > Mg > Cr > Ni > Cd > Pb for dry and rainy season respectively, while Fe > Zn > Cu > Ca > Mg > Cd > Cr > K > Ni > Na > Pb was observed for sediment. Four groups of phytoplankton (viz; Bacillariophyta, Chlorophyta, Cynophyta and Dinophyta) comprising of eleven different species were observed in this study, with Chlorophyta having the highest abundance for both dry and rainy seasons (40.42% and 41.33% respectively) of the total phytoplankton population. Bacillariophyta ranged from 73 to 360 individuals per litre, Chlorophyta (105 to 529 individuals per litre), Cynophyta (31 to 131 individuals per litre) and Dinophyta (76 to 289 individuals per litre) Phytoplankton showed significant positive correlation with temperature, mean depth, nitrate-nitrogen, phosphate-phosphorus, sulphate and zooplankton (p<0.01). Phytoplankton showed the following order of abundance: Chlorophyta > Bacillariophyta > Dinophyta > Cyanophyta in both seasons. Three groups of zooplankton (viz; Copepoda, Cladocera and Rotifera) comprising of thirteen different species were observed in this study, with Rotifera having the highest abundance for both dry and rainy seasons (35.79% and 43.18% respectively) of the total zooplankton population. Copepoda ranged from 94 to 204 individuals per litre, Cladocera (70 to 203 individuals per litre) and Rotifera (80 to 300 individuals per litre). Zooplankton exhibited significant positive correlation with dissolved oxygen, alkalinity and chloride (p<0.05), and with phosphate phosphorus and phytoplankton at 0.01 level. Zooplankton showed the following order of abundance: Rotifera > Copepoda > Cladocera in both seasons. Fisheries potential was found to be higher in dry season for all stations. This coincides with higher abundance of certain zooplankton species (Daphnia sp., Macrothrix sp., Cyclops sp., Brachionus patulus Müller, and Chromogaster sp.) in dry seasons. This could be attributed to distortion of the aquatic habitat during water discharge. Morpho Edaphic Index exhibited significant positive correlation with transparency, total dissolved solids, electrical conductivity, dissolved oxygen, alkalinity, hardness, and chloride (p<0.05). Based on Shannon and Margalef diversity index, the water surveyed throughout the study period was found to be slightly polluted. The result of this survey has shown that the multitude of reservoir users and its catchment have negatively impacted on its water quality. Various management strategies such as restricting cultivation on steep slopes and periodic limnological assessment should be employed to monitor and track trend of changes to water quality and quantity, periodicity and biodiversity of the reservoirs.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY (PhD) IN BIOLOGY DEPARTMENT OF BIOLOGY, FACULTY OF LIFE SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA.
Keywords
STUDIES ON ASPECTS OF LIMNOLOGY OF YARDANTSI RESERVOIR,, GUSAU,, ZAMFARA STATE,, NIGERIA,