STUDIES ON MICROBIOLOGICAL AND HEAVY METALS CONCENTRATION OF PERIWINKLE (Tympanotonus fuscatus and Pachymelania aurita) HARVESTED FROM AQUATIC ECOSYSTEM IN AKWA IBOM STATE, NIGERIA
1.1 Background of the Study
The environment is perceived to be at risk from thousands of toxic substances and chemicals of both anthropogenic and natural origin. When hazardous substances are released into the environment, an evaluation is necessary to determine the possible impact of these substances on human health and other biota (Adams, Kimerle and Barnett, 1992; Ogeleka, Ezemonye and Okieimen, 2010). An important process through which chemical substances can affect living organisms is bioaccumulation. Bioaccumulation is a process by which chemicals or substances are taken up by an organism either directly from exposure to a contaminated medium or by consumption of food containing the chemical or substance. Bioaccumulation means an increase in the concentration of a chemical or substance in a biological organism over time, compared to its concentration in the environment (Corl, 2001; Relyea and Diecks, 2008). Thus understanding the dynamic process of bioaccumulation is very important in protecting humans and other organisms from the adverse effects of chemical exposure and has become a critical consideration in the regulation of chemicals (DPR, 2002; OECD, 2003). The natural aquatic ecosystems may extensively be contaminated with heavy metals released from industrial and other anthropogenic activities.
Heavy metal pollution is a global issue, although its severity and the levels of pollution differ from place to place. At least twenty metals are classified as toxic with half of them emitted into the environment in concentrations that pose great risks to human health (Deb and Fukushima, 1999). Contamination of the environment with toxic heavy metals has become one of the major causes of concern for human kind. Heavy metals are intrinsic, natural constituents of water (Asaolu, Ipinmoroti, Olaofe and Adeeyinwo, 1997). They are generally present in small amounts in natural aquatic environments. In recent times, industrial activities have raised natural concentrations causing serious environmental problems. The biota that inhabits contaminated sites is generally exposed to very high concentrations of these pollutants (Woo, Sin and Wong, 1993). Heavy metals are non-biodegradable and are considered as major environmental pollutants causing cytotoxic, mutagenic and carcinogenic effects in animals (Ajayi and Osibanjo, 1981; Hayat, Javed and Razzaq, 2007; Hussain, Javed, Javid, Javid and Hussain, 2011). Heavy metals generally enter the aquatic environment through natural (atmospheric deposition, erosion of geological matrix) or anthropogenic activities (caused by industrial effluent, domestic sewage, mining and agriculture wastes (Connell and Miller, 1984; Vautukuru, 2005). Heavy metal contamination may have devastating effects on the ecological balance of the recipient environment and a diversity of aquatic organisms (Ashraj, 2005; Waqar, 2006; Farombi, Adelowo and Ajimoko, 2007; Tawari-Fufeyin and Ekaye, 2007; Yilmaz, Ozdemir, Demirak and Tuna, 2007).
The study of toxic heavy metals in Akwa Ibom is more important in comparison with other pollutants due to their non-biodegradable nature, accumulative properties and long biological half-lives. It is difficult to remove them completely from the environment once they enter into it. With the increased use of a wide variety of metals and petrochemicals in industries coupled with African lifestyle of dumping of wastes indiscriminately, there is now a greater awareness of toxic metal pollution of the environment, (CIFA, 1994 and Ukpebor, Ndiokwere and Ukpebor, 2005).
Many aquatic organisms for examples, periwinkles have the ability to accumulate and bio-magnify contaminants like heavy metals, polycyclic aromatic hydrocarbons (PAHs) and PCB which are mutagenic and carcinogenic in the environment. The ingestion of these contaminants may affect not only the productivity and reproductive capabilities of these organisms, but ultimately affect the health of man that depends on these organisms as a major source of protein (Davies, Alison and Uyi, 2006).
Periwinkles are mollusks of high economic value in Niger Delta. They are deposit feeders and bio-indicator of heavy metals and hydrocarbon pollutions in the marine environment. Periwinkles are mass consumer products (Ekanem and Otti, 1997). They are very cheap source of protein in Akwa Ibom state, South-south Nigeria. Periwinkles are shellfishes dominantly found in brackish waters of the riverine areas of Nigeria, where they are highly prolific. This feature had made them a cheap source of protein in many homes when compared to other conventional protein sources (Bassey and Ayuk, 2007; Ekpo and Uzegbu, 2004). They are also transported to many non-riverine towns and cities, where they are used to prepare various palatable dishes in hotels and restaurants, across the country, Nigeria. Some are found mostly in shallow waters and sometimes in inter-tidal zones where they burrow into the mud in the beds of the river which serves as their habitat (Nwiyi and Okonkwo, 2013). The best method to process periwinkles before consumption differs among the populace. Some believe that the shell should be removed and the meat washed thoroughly before cooking, others believe that the periwinkle should be thoroughly washed; its pointed end cut off and then cooked with its shell because of its perceived medical and nutritive value. However, studies on the microbiological quality of shell fishes have shown that they harbour many pathogenic microorganisms (Ukpong and Efuk, 1992; Ekpo, Nyandu, Ating and Anele, 2010). Most times, the accumulation and concentration of pathogenic microorganisms and other toxic materials are usually from untreated human waste and industrial effluents that find their way into the water bodies that are inhabited by these shellfishes (Montgomery and Needselman, 1997).
1.2 Statement of the Problem
All over the country pollution is on the increase. Many of the rivers in the country are dying because toxic chemicals are constantly being dumped into them. Consuming aquatic life forms from these water bodies could be a risk. Wastes are discharged in the environment due to lack of awareness concerning the health implications associated with it.
During rains, pollutants find their ways into drainage systems resulting to pollution of water resources and increase in health problems such as typhoid, cholera, dysentery and hepatitis. Again constant consumption of polluted water especially polluted with heavy metals results to health problems like kidney failure, cancer, and deformity of the unborn babies, malfunctioning of the organs of the body and at higher rate led to death.
Unplanned and unorganized waste disposal habit, indiscriminate digging of mine tailings in search of the economic mineral, mine waste dumping, disposal of chemical wastes in the environment all brings about ecological changes to the environment. Again, in the area, geologic and hydrologic factors are often neglected during planning and execution of waste disposal projects coupled with the fact that these activities are carried out in recharge zone which makes the pollutants to easily find their ways into the cities drainage system. Considering the concept of impact analysis, resultant pollutants easily get to man through consumption of food and water from such zones.
Based on the above problems in the Riverine Area, the study on microbiological and heavy metal concentrations by periwinkle from aquatic ecosystem was embarked on.
1.3 Objectives of the Study
The general objective of this study is to evaluate the Microbiological contamination in water, sediments and periwinkle as well as the concentration of five heavy metals by the periwinkle from aquatic ecosystem in Akwa Ibom State. Specifically this study seeks to determine:
- Microbiological loads of water, sediment and periwinkle.
- The level of heavy metal accumulation in the water, sediment and periwinkle.
- Physicochemical properties of water and sediment.
- The effect of processing of the periwinkle on the heavy metals and microbial levels.
- The effects of heavy metals concentration and microbial loads on water and sediment quality, and
- Antibiotic resistance pattern of the isolated organism.
1.4 Justification of the Study
Heavy metals are non-biodegradable and undergo a global eco-biological cycle in which natural waters are the main pathways (CIFA, 1994; Ukpebor, et al., 2005) and periwinkle, like all molluscs can accumulate these heavy metals in their tissues at concentrations greater than the ambient water and pose a health threat to humans who consume them.
The applications of sewage sludge, sewage water, pesticides and fertilisers to agricultural lands contribute to the accumulation of the heavy metals in top soil layers and their subsequent spreading to large areas of water bodies through surface run-off. The smelting activities of the small scale metal fabricating industries activities not only release the target metals but also metals which are associated in the ores (Madkour, Obirikorang, Amisah, Otchere, and Adjei-Boateng, 2011). Anecdotal information suggests that the river might be receiving a considerable range of polluting effluents, particularly heavy metals from these sources. The health risks associated with heavy metal poisoning in man and the environment are of concern to environmentalists and government agencies locally and globally and underscores the need for continuous research with a view to ameliorating the problems of environmental pollution by heavy metals. It is, therefore, very important for studies to be conducted on the levels of these heavy metals in the tissues of periwinkle, and in sediments and water of study sites, and to ascertain whether or not the concentrations in the seafood are within the permissible limits for human consumption in comparison to Safety Reference Standards for the Consumption of Molluscs.