The effect of xylene on the biochemical and physicochemical properties and algal dynamics in a culture

Thesis Overview

<p> </p><p><b>1.0 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; INTRODUCTION</b></p><p>Algae<br>are autotrophs in many aquatic ecosystems and are well represented in fresh<br>waters. Many factors contribute to algal diversity and reproduction, including<br>variation in nutrient supply and temperature (Turpin and Harrison, 1979). It is<br>known that microalgae respond with physiological alterations to the<br>environmental conditions where they grow (Scragg <i>et. al</i>., 2002, Valenzuela-Espinoza <i>et. al.</i>, 2002). This behaviour can be viewed as biotechnological<br>attribute that can be manipulated in order to control the algae biochemical<br>composition and growth.</p><p>The<br>influence of physical and chemical environment on a water body together with<br>the rate of growth of individual species play important roles in algae<br>diversity. Among the physical factors, light and temperature are the major ones<br>that control the algal dynamics (Emeka <i>et.<br>al., </i>2011). Physicochemical parameters are the major factors which controls<br>the dynamics and structure of the phytoplankton of aquatic ecosystems (Huyal<br>and Kaliwa, 2009). Changes in the physicochemical parameters may positively or<br>negatively affect the biota of water body in a number of ways which increases<br>the survival and growth rate and these may eventually result in the<br>disappearance of some species of organisms or its reproduction (Edward and<br>Ugwumba, 2010).</p><p>Temperature<br>has major structuring effects at all levels of biological organization. The<br>rate at which biochemical reactions occur is temperature dependent (Brown <i>et. al.</i>, 2005). Temperature is important<br>because the rate of chemical reactions increases at high temperature which in<br>turn affects biological activities and growth of aquatic organism (Waziri <i>et. al., </i>2012). The increase in water<br>temperature is an important factor when toxic substances are present in the<br>water. Most of the substances (cyanides, Xylene) exhibit increased toxicity at<br>elevated temperature. These toxicities and other physiological interactions are<br>also influenced by increased temperature and history of the species In an algal<br>culture, the optimal temperature for algal survival is generally between 200C<br>and 240C, although may vary with the composition of the culture<br>medium and the strain culture.</p><p>Most<br>phytoplankton isolates originating from alkaline lakes reach their optimum<br>growth rate and photosynthetic capacity at a neutral and alkaline pH and are<br>unable to survive in acidic conditions. Whether a species can grow at neutral<br>pH or not defines it as acid-tolerant or acidophilic specie (Gross, 2000).<br>Maintaining an alkaline, cystolic pH is one of the major problems these<br>organisms are faced with as many enzymes are highly pH dependent and become<br>inactive at acidic pH values (Gimmer, 2004). The pH in water governs biological<br>processes while temperature in water governs the availability of oxygen<br>(Kowalkowski <i>et. al.</i>, 2006).</p><p>Both<br>aquatic plant and animals depend on dissolved oxygen (DO) for survival. DO is<br>important in aquatic ecosystem because it determines the types and abundance of<br>species that can survive and flourish there (Huyal and Kalliwa, 2009). The<br>maximum concentration of oxygen that can be dissolved in water is a function of<br>temperature and therefore, dissolved oxygen of water may vary from place to<br>place and from time to time (Prasad and Patil, 2008). Fluctuations in dissolved<br>oxygen are due to fluctuations in water temperature and addition of sewage<br>waste demanding oxygen (Koshy and Nayar, 2000). The dissolved oxygen of water<br>is greatly affected by the content of Biochemical oxygen demand (BOD). BOD<br>determination is used to measure the amount of organic material of an aquatic<br>system, which supports the growth of organisms (Keramat, 2008).</p><p>The<br>persistence of organic pollutants introduced into the environment through<br>industrial discharges, or improper waste disposal practices poses a chronic<br>threat to the health of human and wildlife (Pavlostathis <i>et. al., </i>2001). Depending on biogeochemical processes, many organic<br>pollutants like hydrocarbon are involved in adsorption, desorption and<br>transformation processes and can be made available to benthic organisms as well<br>as organisms in the water column through the sediment-water interface (Perele,<br>2010). Investigations on organic xenobiotics bioaccumulation/ biodegradation in<br>green algae are of great importance from environmental point of view because<br>widespread distribution of these compounds in agricultural areas has become one<br>of the major problems in aquatic ecosystems (Jin <i>et. al.</i>, 2012). The algae proved to be effective in hyper<br>accumulation of heavy metals as well as degradation in xenobiotics (Suresh and<br>Ravishankar, 2004).</p><p>The<br>impact of xylene on the biochemical and physicochemical properties and algal<br>dynamics are presently unknown as there is no documented information. Thus,<br>this study was structured with the following aims:</p><p>1. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br>To determine the effect of xylene on<br>physicochemical properties of water.</p><p>2. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br>To determine the effects of xylene on<br>biochemical properties of water.</p><p>3. &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br>To determine the effect of xylene on<br>algal dynamics.</p><h3></h3><br> <br><p></p>