Study on Water Quality Parameters and Benthic Fauna Diversity of Otamiri River in Owerri, Imo State, Nigeria
Chapter One
Objective of the Study
The general objective of this study is to evaluate the water quality variables and the benthic organisms in Otamiri River.
Specific objectives of this study were to
- determine the benthic organisms diversity of Otamiri River;
- assess the water quality of Otamiri River;
- determine the relationship between water quality parameters and composition of benthic fauna in Otamiri River and
- determine the effect of season on physico-chemical parameters of the water and composition of benthic organisms.
Chapter Two
Literature Review
Water quality parameters
Several studies had dealt with the relationship between the aquatic macrobenthos diversity, water sediment and physico-chemical status of the aquatic ecosystem (Quasin et al., 2009; Garg et al., 2009 and Edokpayi et al., 2010). Water quality plays a vital role in the distribution, abundance and diversity of aquatic organisms. A short-term exposure of benthic organisms to water of poor quality causes an alteration in the community structure due to the elimination of the species that are intolerant to stress and proliferation of stress tolerant species (Woke and Wokoma 2007). The physical and chemical characteristics of water are important parameters as they may directly or indirectly affect its quality and consequently its suitability for the distribution and production of fish and other aquatic organisms (Obot et al., 2014). Important physical and chemical parameters influencing aquatic environment are temperature, rainfall, pH, salinity, dissolved oxygen, Biological Oxygen Demand, Turbidity (Adakole and Annune 2003).
The following guide defines each variable, discusses the importance of the variable to the aquatic environment and lists potential anthropogenic sources.
Temperature
This is a measurement of the intensity (not amount) of heat stored in a volume of water. Surface water temperatures naturally range from 0°C under ice cover to 40°C in hot springs. Natural sources of heat include: solar radiation, transfer from air, and condensation of water vapor at the water surface, sediments, precipitation, surface runoff and groundwater. Temperature is the primary influencing factor on water density (Integrated Land Management Bureau, 2010).
Importance: Temperature affects the solubility of many chemical compounds and can therefore influence the effect of pollutants on aquatic life. Increased temperatures elevate the metabolic oxygen demand, which in conjunction with reduced oxygen solubility, impacts many species. Vertical stratification patterns that naturally occur in lakes affect the distribution of dissolved and suspended compounds (ILMB, 2010).
Anthropogenic sources: industrial effluents, agriculture, forest harvesting, urban developments, mining.
Turbidity
This is a measurement of the suspended particulate matter in a water body which interferes with the passage of a beam of light through the water. Materials that contribute to turbidity are silt, clay, organic material, or micro-organisms. Turbidity values are generally reported in Nephelometric Turbidity Units (NTU). Pure distilled water would have non-detectable turbidity (0 NTU). The extinction depth (for lakes), measured with a Secchi disc, is an alternative means of expressing turbidity (ILMB, 2010).
Importance: High levels of turbidity increase the total available surface area of solids in suspension upon which bacteria can grow. High turbidity reduces light penetration; therefore, it impairs photosynthesis of submerged vegetation and algae. In turn, the reduced plant growth may suppress fish productivity. Turbidity interferes with the disinfection of drinking water and is aesthetically unpleasant. (ILMB, 2010).
Anthropogenic sources: forest harvesting, road building, agriculture, urban developments, sewage treatment plant effluents, mining, industrial effluents.
pH
This is the measurement of the hydrogen-ion concentration in the water. A pH below 7 is acidic (the lower the number, the more acidic the water, with a decrease of one full unit representing an increase in acidity of ten times) and a pH above 7 (to a maximum of 14) is basic (the higher the number, the more basic the water), (ILMB, 2010).
Importance: Higher pH values tend to facilitate the solubilization of ammonia, heavy metals and salts. The precipitation of carbonate salts (marl) is encouraged when pH levels are high. Low pH levels tend to increase carbon dioxide and carbonic acid concentrations. Lethal effects of pH on aquatic life occur below pH 4.5 and above pH 9.5, (ILMB, 2010).
Anthropogenic sources: mining, agriculture, industrial effluents, acidic precipitation (derived from emissions to the atmosphere from cars and industry).
CHAPTER THREE
MATERIALS AND METHODS
Study Area
The Otamiri River is one of the main rivers in Imo State, Nigeria and Located on latitude 70 06 ̍E and longitude 50 30 ̍N and at an elevation of 152 meters above sea level. The river takes its name from Ota Miri, a deity which owns all the waters that are called by its name, and who is often the dominating god of Mbari houses (Basden, 1966). The river runs south from Egbu past Owerri, Nekede, Ihiagwa and through Ozuzu Etche, in Rivers State, from where it flows to the Atlantic Ocean (Anyanwu, 2009). The length of the river from its source to its confluence at Emeabiam with the Uramiriukwa River is 30 kilometres (19 mi) (Anyanwu, 2009).
The vegetation of the sampled area is rain forest with the watershed is mostly covered by depleted rain forest vegetation, with mean temperatures of 27 °C (81 °F) throughout the year. Conversion of the tropical rainforest to grassland with slashes and burn practices is degrading soil quality.
Three sampling stations will be used. Sampled Station 1 is located at Owerri urban along Nekede road, where the state’s refuse dump site is located and sand mining activities, while Station 2 is at No 8 Bus stop Umugwueze, Nekede, where sand mining activities take place and Station 3 is at Umuezerokam village which is the home of vegetable farming. The activities of sampled Stations 1 and 2 are, sand dredging and sand mines, farming and waste management dump station whereas, at Station 3 farming activities such as fishing, vegetable farm and cultivation. The seasons in these sampled areas are dry and wet seasons.
Sampling Method
Six consecutive months of fieldwork (once in a month) were carried out in Lower River Niger, Idah which covered both dry and rainy seasons. Water and sediment samples were collected from the three sampling stations (Station 1, Station 2 and Station 3) within the River. Each sampling station was subdivided into three sub-stations such that water and sediment samples were randomly collected in triplicates from each station. Dugout canoe with paddle was used for sampling within the River. All sample containers were washed and soaked overnight with 5% nitric acid and rinsed with distilled water prior to sampling. At the sampling site plastic containers for water sample collection were rinsed several times with the river water. This is in accordance with the methods of Wangboje and Oronsaye (2001).
Sample Collection
Water samples were collected from the three stations (Stations 1, 2 & 3) within the river for six months (June – August and October – December, 2015). The samples were collected in triplicates from each sampling stations. Dugout canoes with paddles were used during sampling within th river. At the sampling stations, BOD and DO containers to store water samples were rinsed several times with the river water. Vertebrates and macro invertebrate samples were stored in 30 – 40% ethanol for vertebrates and 10% formal saline for macro-invertebrates (Wangboje and Oronsaye, 2001).
CHAPTER FOUR
RESULTS
Species Composition, Abundance and Diversity of Benthic Organisms in Otamiri River. The results of species composition, abundance and diversity yielded 229 benthic organisms belonging to 15 species and 14 families. Station 3 recorded more species and had highest abundance of benthic organisms than the other sampled stations while Station 1 had the least with only six benthic species. Station 2 had 11 species while Station 3 had 13 species of benthic organisms. Majority of the sampled benthic organisms were recorded in Station 3
The abundance of benthic organisms in Otamiri River were favoured by season as more benthic organisms were recovered in the dry season than in rainy season. Chrysichthys nigrodigitatus (32.65%) was the most abundant species recorded in the present study as against the least that was Paleamon. serratus (1.25%). Both occurred only in Station 3.
The diversity indices yielded high diversity in Station 3 than the other two studied stations. More species were recorded and with high diversity index in the dry season than the wet season in all the sampled Stations.
CHAPTER FIVE
DISCUSSION AND CONCLUSION
Species Diversity and Composition of Otamiri River
Total of (13) families of benthic fauna were recorded in Otamiri River. This can be said to be high compared to the (4) families reported by Ogidiaka et al., (2012) in Ogunpa River in Ibadan and the (10) families reported by Adjarho et al (2013) in Omna River, Ibadan but close to the families reported by Obot et al.,(2014) in Ediene Stream, Akwa Ibom and the 20 families reported by Hart, and Zabbey (2005) in Woji Creek in the upper reaches of Bonny River in the lower Niger Delta. The difference in the Woji Creek may be attributed to the fact that it is a larger and brackish water system. Otamiri River being a freshwater body was dominated by Calroteidae (36.25%) with (1) species; other benthic fauna family had one species each except Mochokidae which recorded two species. The distribution pattern of Calroteidae showed that they were more abundant in Station 3. The dominance of nigrodigitatus at Station 3 compared to other stations indicated pollution, stress and high level of anthropogenic activities such as dredging in Stations 1 and 2.
Nwankwo and Akinsoji (1992) had attributed the low species abundance and diversity of some sites of a river to the pollution of such sites. The relative abundance of benthic fauna in each station of the present study is a reflection of the level of pollution of each station. Burger and Gochfeld, (2009) related the abundance and diversity of the benthic fauna to the health of the water body. Stations 1 and 2 in Otamiri River recorded relatively lower taxa and this could be attributed to the resultant effect of the bridge construction among other human activities ongoing at these stations.
Anthropogenic activities such as dredging often result in substratum instability and increased siltation. Edokpayi and Nkwoji (2007) had reported in a previous study that suspended silt has the ability of reducing light penetration and primary productivity and could clog the gills o aquatic fauna thereby smothering them. The occurrence of relatively higher taxa and individuals in station 3 may be an indication of lower degree of anthropogenic activities at the station compared to other stations. Overall diversity had been reported to be the product of all dynamic spatial and temporal changes affecting an urban stream community in nigeria(Victor and Ogbeibu 1991). It could also be a reflection of the extent to which the ecosystem has been perturbed by human activity.
The abundance and diversity of benthic fauna are generally affected by the physical and chemical characteristics of water, availability of food and substrate occupation (Odo, et al., 2007). In this study, such parameters like temperature, depth, BOD, DO, Alkalinity, turbidity and TSS were observed to have influenced the community composition of Otamiri River. This is in agreement with earlier reports of Ajao and Fagade, (1990a), Edokpayi and Nkwoji, (2007) and Brown and Oyenekan (1998).
Conclusion
The study revealed that Stations 1 and 2 of Otamiri River were influenced by anthropogenic activities which have influenced the fauna diversity of the area. Anthropogenic activities had caused severe stress to aquatic life in these two stations and had also led to erosion that drained into the river. It is concluded that the river is suitable for drinking having met WHO standards and also suitable for aquatic life with the range of DO recorded.
Recommendation
It is recommended that proper management of the river should be put in place to preserve its water quality and biodiversity for sustainable development. Government should make laws restricting dredging and sand mine activities in the study area.
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