ALGAL DIVERSITY AND WATER QUALITY OF ASATA RIVER ENUGU STATE, NIGERIA

ABSTRACT

An assessment of the physicochemical, parameters, algal diversity and bacterial flora of Asata River Enugu, Enugu State, Nigeria was carried out for six months. Water samples and periphyton were collected fortnightly from four locations namely: Okpara Coal Mine, University of Nigeria Teaching Hospital (UNTH) Old Site, Ogbete market and Ogui and analysed using standard procedures. Algal diversity and species richness were determined using Shannnon – Wiener index. Spread plate method on Macconkey agarwasusedforbacterialcount.Resultsshowedmonthlyvariations.(P≤0.05) inair temperature, velocity, alkalinity, aluminum, dissolved  oxygen, biological oxygen demand, chemical oxygen demand, calcium, pH, total suspended solids, iron, lead andn zinc,atthevariouslocations.Significant(P≤005) positive (colour and  depth, transparency, iron and Bacillariophyta) and negative (pH and algal divisions; lead and Bacillariophyta; mercury and Cyanophyta) correlations were also observed among some parameters investigated. Thirty-four algal taxa belonging to four divisions in the following decreasing order: Bacillariophyta (33 %), Chlorophyta (32 %), Euglenophyta (21 %), and Cyanophyta (14 %) were encountered. Some pollution tolerant algae such as Gomphonema, Nitzschia, Navicula, Surirella, Euglena and Oscillatoria were dominant. Based on Shannon–Wiener index, the water at UNTH and Ogbete were classified as mesoptrophic whereas, Okpara coal mine and Ogui were classified as eutrophic. The diversity index showed no complete evenness in the river. The lowest and highest enteric bacterial counts (1.029 × 10⁴ ± 1.174 and 5.05 × 10⁴ ± 1.472) were observed in August and November respectively. Gram – positive and gram – negative bacteria such as Escherichia, Salmonella, Micrococcus, Proteus and Enterobacter were isolated. Escherichia was dominant indicating fecal pollution. pH was within the permissible limit; iron, lead and phosphate beyond the limit; and calcium, magnesium, biological oxygen demand, chemical oxygen demand, dissolved oxygen below WHO standard for drinking water, indicating that the river was eutrophic.

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CHAPTER ONE

INTRODUCTION

Rivers are important pathways for flow of energy, matter and organisms through the landscape. They have always provided a focus of attraction for environmental studies. They offer a number of benefits and services to man. A wide range of human activities at the catchment areas may lead to environmental deterioration of river quality (Kagalou et al., 2002). The increasing environmental pollution is alarming and is on a global scale by anthropogenic activities.

The productivity of the river is determined by the water quality parameters, the aquatic species composition and abundance are affected, hence there is the need to monitor the water quality (Agboola et al., 2011). Rivers are useful in multiple ways such as source of water for man and for domestic animals, in fisheries, agriculture and generation of hydroelectric power. Also tropical rivers play crucial role in the epidemiology of several tropical diseases (Kadiri, 2007).

The river system presents interesting feature for aquatic organisms, in relation to extended periods of dryness, land use practices and intense human activities, all of which influence water quality (Papastergradou and Babalonas, 1993). Knowledge of specific relationships between particular organisms and environmental factors enable a quick look and fairly reliable evaluation of the essential features of a given biotope (Fytainos et al., 2001).

Pollution of fresh water bodies such as rivers, streams, lakes and ponds is mostly experienced as a result of industrial discharge, municipal waste disposal and surface runoff. Indiscriminate and uncontrolled discharge of waste into river impact negatively on river ecosystem and human health (Chima et al., 2009).

Water quality is crucial in order that man can benefit from river through series of users (Oliveira et al., 2006). Water quality deals with physical, biological and chemical characteristics in relation to all other hydrological properties. Any characteristics of water that affect survival, reproduction; growth and production of aquaculture species; influence management decisions; cause environmental impact or reduce product quality and safety can be considered a variable quality. The use of physicochemical properties of water to assess water quality gives a good impression of the status, productivities, and suitability of such water body. The change in physical characteristics like depth, temperature, transparency and chemical element of water such as dissolved oxygen, chemical oxygen demand, nitrate, phosphate provides valuable information of the quality of the water, the source (s) of the variation and biodiversity (Mustapha, 2006, 2008; Sumita et al., 2010).

Nutrients play major role in growth and development of plants in tropical water where there is enough light for photosynthetic activities throughout the year, resulting in light and temperature probably not being limiting. Aquatic autotrophs have nutritional and energetic requirement for their photosynthetic carbon function and growth. Nutrient limitation is important in the regulation of phytoplankton abundance (Hirose et al., 2003). Phytoplankton diversity with the seasonal fluctuation indicates the condition of ecological niches.

Algae are simple plants that vary considerably in size, shape and colour and are found in a range of habitats (Christi et al., 2011). Algae are frequently found in polluted and unpolluted waters and due to this behavior they are considered useful in determining the quality of water. They are very suitable organisms for the determination of the impact of toxic substances on the aquatic environment because any effect on the lower level of the food chain will also have consequences on higher levels (Joubert, 1980; Jafari and Gunale, 2006). Algae are used for assessing the degree of pollution or as indicators of water pollution of different water bodies (Trivedy, 1986; Sudhaker et al., 1994; Dwivedi and Pandey, 2002). Due to their short life cycle, algae respond quickly to environmental changes and are thus a valuable indicator of water quality (Hotzel and Croome, 1999). Pollution stress reduces the number of algal species but increases the number of individuals hence species diversity of fresh water habitats are very much affected by eutrophication (Christi et al., 2011) As sunlight driven cell factories micro - algae convert carbon dioxide to potential biofuels, food and feeds (Chisti, 2008). These photosynthetic microorganisms are also useful in bioremediation (Navid, 2005; Kadiri 2010).

The anthropogenic inputs of complex mixtures from neighboring communities and agricultural waste such as runoff of manures and fertilizers could lead to alteration of water quality (Mustapha, 2006; Garg et al., 2009). Of primary concern of these anthropogenic activities are their effects on the water quality and aquatic life. Depending on the quality and quantity of waste input, the physical, chemical and biological balance of the receiving water may be significantly modified resulting in pollution and its associated consequences (Akpan et al., 2002; Osondu, 2007).

Water quality deterioration may also be as a result of acidification, heavy metals, organic pollution and obnoxious fishing practices. The effects of these “imports” bring loss of structural biodiversity of the water (Mustapha, 2008). Water quality monitoring is of immense importance in the use of water bodies in the management of fisheries (Mustapha, 2006; Nweze, 2009b; Agboola et al., 2011). However, the overall condition of this complex and dynamic system where biotic and abiotic components are constantly interacting with each other brings structural and functional changes in an ecological unit such as aquatic ecosystems (pond, lake, river or ocean) (UNESCO, 2006; Chia et al., 2011).

Water quality assessment may be determined by physical, chemical and biological attributes in relation to standards developed by U.S. Environmental Protection Agency (USEPA, 1976), World Health Organization (WHO, 1993) and American Public Health Association (APHA, 1995), The water required for domestic consumption should possess a high degree of purity and it should be free from suspended and dissolved impurities and bacteria (Alexander, 2008). Whatever the source of water, it is expected to be less contaminated depending upon management and temperature gradient of the water environment ( Radojevic and Bashkin, 1999; APHA, 2005).

1.1 Statement of the Problem

Biological assessment is useful alternative for assessing the ecological quality of aquatic ecosystems since biological communities indicate the environmental effect of water chemistry. The impact of increased environmental pollution in recent times has become a global menace and even much devastating at regional levels. This is often constituted by anthropogenic activities. The diversity of algae in water bodies shows the pollution status of water bodies including that of River Asata. This necessitated this study on physicochemical parameters of Asata River to determine those factors that affect the water quality and algal diversity. Enugu being a metropolitan city where River Asata is located experiences increase in population due to urbanization and industrialization. As the population increases, the introduction of waste into the river also increases, and this leads to contamination of the river, thereby constituting environmental and health hazards to the inhabitants of the urban area.