ABSTRACT

The effect of xylene on the biochemical and physicochemical properties and algal dynamics in culture were investigated ex-situ between May, 26th and July 9th, 2017. The biochemical and physicochemical parameters Viz: Temperature, Dissolved oxygen, Biochemical oxygen demand, and volume were analyzed. Air temperature ranged between 25 – 310C, Water temperature ranged between 28 – 340C, Dissolved oxygen ranged between 42 – 90mg/l, Biochemical oxygen ranged between 9 – 72 and Volume ranged between 1000 – 4000 ml. There was no significant difference on all the parameters analyzed. The algal species present include Chlorella vulgaris, Scenedesmus acuminatus, Cladphora spp, Oedogunium grande, Sururella spp and their pattern of colonization is of the order Chlorella vulgaris whichwas the pioneer species, followed by Scenedesmus acuminatus followed by Oedogonium grande followed by Sururella spp followed by Cladphora spp. The division Chlorophyta represented by Chlorella vulgaris, Scenedesmus acuminatus, Cladphora spp, Oedogunium grande and Sururella spp were the dominant group. The result obtained in this study could be a useful tool in understanding the bioremediation potential of various algal species.

CHAPTER ONE

1.0                                                   INTRODUCTION

Algae are autotrophs in many aquatic ecosystems and are well represented in fresh waters. Many factors contribute to algal diversity and reproduction, including variation in nutrient supply and temperature (Turpin and Harrison, 1979). It is known that microalgae respond with physiological alterations to the environmental conditions where they grow (Scragg et. al., 2002, Valenzuela-Espinoza et. al., 2002). This behaviour can be viewed as biotechnological attribute that can be manipulated in order to control the algae biochemical composition and growth.

The influence of physical and chemical environment on a water body together with the rate of growth of individual species play important roles in algae diversity. Among the physical factors, light and temperature are the major ones that control the algal dynamics (Emeka et. al., 2011). Physicochemical parameters are the major factors which controls the dynamics and structure of the phytoplankton of aquatic ecosystems (Huyal and Kaliwa, 2009). Changes in the physicochemical parameters may positively or negatively affect the biota of water body in a number of ways which increases the survival and growth rate and these may eventually result in the disappearance of some species of organisms or its reproduction (Edward and Ugwumba, 2010).

Temperature has major structuring effects at all levels of biological organization. The rate at which biochemical reactions occur is temperature dependent (Brown et. al., 2005). Temperature is important because the rate of chemical reactions increases at high temperature which in turn affects biological activities and growth of aquatic organism (Waziri et. al., 2012). The increase in water temperature is an important factor when toxic substances are present in the water. Most of the substances (cyanides, Xylene) exhibit increased toxicity at elevated temperature. These toxicities and other physiological interactions are also influenced by increased temperature and history of the species In an algal culture, the optimal temperature for algal survival is generally between 200C and 240C, although may vary with the composition of the culture medium and the strain culture.

Most phytoplankton isolates originating from alkaline lakes reach their optimum growth rate and photosynthetic capacity at a neutral and alkaline pH and are unable to survive in acidic conditions. Whether a species can grow at neutral pH or not defines it as acid-tolerant or acidophilic specie (Gross, 2000). Maintaining an alkaline, cystolic pH is one of the major problems these organisms are faced with as many enzymes are highly pH dependent and become inactive at acidic pH values (Gimmer, 2004). The pH in water governs biological processes while temperature in water governs the availability of oxygen (Kowalkowski et. al., 2006).

Both aquatic plant and animals depend on dissolved oxygen (DO) for survival. DO is important in aquatic ecosystem because it determines the types and abundance of species that can survive and flourish there (Huyal and Kalliwa, 2009). The maximum concentration of oxygen that can be dissolved in water is a function of temperature and therefore, dissolved oxygen of water may vary from place to place and from time to time (Prasad and Patil, 2008). Fluctuations in dissolved oxygen are due to fluctuations in water temperature and addition of sewage waste demanding oxygen (Koshy and Nayar, 2000). The dissolved oxygen of water is greatly affected by the content of Biochemical oxygen demand (BOD). BOD determination is used to measure the amount of organic material of an aquatic system, which supports the growth of organisms (Keramat, 2008).

The persistence of organic pollutants introduced into the environment through industrial discharges, or improper waste disposal practices poses a chronic threat to the health of human and wildlife (Pavlostathis et. al., 2001). Depending on biogeochemical processes, many organic pollutants like hydrocarbon are involved in adsorption, desorption and transformation processes and can be made available to benthic organisms as well as organisms in the water column through the sediment-water interface (Perele, 2010). Investigations on organic xenobiotics bioaccumulation/ biodegradation in green algae are of great importance from environmental point of view because widespread distribution of these compounds in agricultural areas has become one of the major problems in aquatic ecosystems (Jin et. al., 2012). The algae proved to be effective in hyper accumulation of heavy metals as well as degradation in xenobiotics (Suresh and Ravishankar, 2004).

1.1       Objectives of the Work

The impact of xylene on the biochemical and physicochemical properties and algal dynamics are presently unknown as there is no documented information. Thus, this study was structured with the following aims:

1.                  To determine the effect of xylene on physicochemical properties of water.

2.                  To determine the effects of xylene on biochemical properties of water.

3.                  To determine the effect of xylene on algal dynamics.

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