EFFECTS OF POLLUTION ON WATER AND FISH PRODUCTION IN IKPOBA RIVER USING MACRO INVERTEBRATES AS BIO-INDICATORS
ABSTRACT
The study of water quality using macro invertebrates as bio indicators of pollution in the Ikpoba river Benin City, Edo State was carried out for a period of 3months (march-may) in 2013. Water and macro invertebrate samples were collected from three stations (Okhoro), Reservoir and the Bridge.) along the river. Physiochemical variables were determined using standard methods. A total of 652 macro invertebrates were collected. Twenty seven (27) taxa were recorded in all the stations. Station 2(Reservoir) had 23 taxa, while station 1(Bridge) and 3(Okhoro) had 16 and 18 taxa, respectively. Also station 1 (Bridge) contributed the highest number (46%) of the total number of individuals and the least number of taxa (16).A total of11 Bulinus spp, 39 Biomphalaria spp and 4 Physia spp represented the Mollusca family in all the stations. Coleopteran was represented by 12 Sphaerodema spp, 6 Hydrous spp and 8 Phithydrus spp. Ditera species collected in the sampling stations were, 18 enstalis larvae, 4 Simulium spp, 283 Chironomus spp, 20 Pentaneura spp, 18 Coatate pupa, 23 Chronomus pupa, 5 pupa type 1 and 2 Anopheles larvae.Only 1 Notonecta specie represented the Hemiptera family. Four (4) Neoperia and 7 Branchythermis spp represented the Plecopera family. The Odonata family was represented by 9 Coenagrion spp, 6 Pseudagnon psp and 3 Enallagma spp. Ephemeroptera was represented by two members of the Pseudocleon spp. Crustacea was represented by 18 astacidae. Annelid was represented by 31 Tubifex spp, 48 Nais spp and 55 Stalaria spp. Hirudinea spp was represented by 15 members of the Glossiphonia spp. The presence of low densities of pollution tolerant macro invertebrate groups, the deteriorating water quality and the physiochemical conditions of the water during Month march was a reflection of organic pollution by decomposing domestic refuse and inorganic fertilizers washed into the river by run-off.
CHAPTER ONE
1.0 INTRODUCTION
Although biologist have been studying the effects of human activities on aquatic systems and its effects on fish production for decades, their findings have only relatively recently being translated into methods suitable for monitoring the quality of water bodies. Mostly, bio-indicators such as benthic macro-invertebrates, phytoplankton and zooplankton are among the common bio-indicator organisms used during bio-monitoring of water to determine the suitability for fish production (Tassi, 2009). Artificial (and in some cases natural) changes in the physical and chemical nature of freshwaters can produce diverse biological effect ranging from the severe (such as a total fish kill) to the subtle (for example, changes in enzymes level or sub-cellular components of organisms) (Pagano et.al., 2006), changes like these indicates that the ecosystem and its associated organisms are under stress or that the ecosystem has become unbalanced (Masona, 2007).
Because flora and fauna of various trophic levels can integrate the effects of water quality or habitat changes over time, they become effective pollution indicators (Fernando, 2002). The concentration of a pollutant in an organism is the result of many variables such as the concentration of the pollutant in the water, the physical-chemical form of the pollutant, the membrane permeability of the organism, the type and quantity of food and its degree of contamination, the physiological state of the organism and the characteristics of the physical environment influencing the organism as well as the pollutant (Rose et.al., 2003). The response of biological communities or of the individual organism can be monitored in a variety of ways to indicate effects on the ecosystem. The co-existence and abundance of certain species at a particular location can indicate for example whether that habitat has been adversely altered (Pearl et al., 2003). The reactions of individual organisms such as behavioral, physiological or morphological changes can also be studied as responses to stress or adverse stimuli (for example caused by the presence of contaminants (Bailey et al., 2001).
If an environment receives a foreign pollutant, the organism living in it will start to take up the pollutant, from the water or food, and concentrate it in its body (Straskraba and Tundisi, 2008). Assuming that the pollutant concentration in the environment is constant overtime and the pollutant concentration in the organism body increases, death will occur after a long period. Conversely, a continuous decrease of the pollutant concentration in the medium produces a corresponding release of the pollutant form the organism, with some delay (Anmtage, 2008).
The kinetics of both pollutant uptake and release by the organism has the same pattern for any substance and animal species, whereas the uptake-and loss-rate are dependent on the characteristics of the organism as well as on those of the pollutant and the environmental conditions.
Bio-monitoring is measuring the conditions and integrity of various sources of water to ensure the health and fitness of the water body for the growth and production of fish species. For lotic (running) water systems, analysis of benthic macro-invertebrate communities provides the principal means of achieving this, particularly since macro-invertebrates are more stationary and less temporal than periphytic or attached microscopic communities (Relyea, 2008).
Biological monitoring refers to the collection and analysis of stream macro-invertebrate communities as indicators of water or habitat quality. Macro-invertebrates are larger than microscopic primary benthic (bottom dwelling) fauna, which are generally ubiquitous in fresh water and estuarine environments and play an integral role in the aquatic food web (Bernard et. al., 2003), they are the most commonly used bio-indicator of water quality among the community of indicator organisms because the presence or absence of certain pollution tolerant or intolerant species can be a great determining factor in ascertaining the level of pollution of the water available for fish production.
Total absence of pollution intolerant species, indicates bad water quality which may have adverse effect on fishes inhabiting such water bodies or in most cases, death of the fishes. They are insects and animals without backbone (invertebrates) that can be seen with unaided eye (without a microscope) that live in and on the bottom of streams, lakes, ponds, reservoirs, estuaries and oceans (Downing and Rigler, 2002). Insects (largely immature forms) are especially characteristics of freshwaters; other major groups include worms, mollusk (snails, clams) and crustaceans (scuds, shrimp etc.) (Lathrop and Markowitz, 2001). They are more readily collected and quantified than either fish or periphyton community. Species comprising the upstream communities occupy various niches, based on functional adaptation or feeding mode (e.g. predators, filter or detritus, feeders, scavenger); their presence and relative abundance is governed by environmental conditions (which may determine available food supply) and by pollution tolerance levels of the respective species (Cardoso et.al., 2006).
Benthic macro invertebrates are of great importance in assessing water quality available for fish culture because they have several characteristics that makes them easy to study and show clear responses when faced with adverse environmental conditions (Davis and Simon, 2005).
