Ife Journal of Science vol. 17, no. 3 (2015) 565 STUDY OF HEAVY METALS IN THE GASTROPOD, AURITA (MULLER, 1774), SEDIMENT AND WATER FROM OLOGE LAGOON, SOUTH- WESTERN NIGERIA

*Samuel, O. B., Osibona, A. O. and Chukwu, L. O.

Department of Marine Sciences, Faculty of Science, University of Lagos, Akoka – Yaba, Lagos, Nigeria *Corresponding Author: [email protected]; [email protected] (Received: 5th June, 2015; Accepted: 22nd June, 2015) ABSTRACT

The levels of Cu, Fe, Pb, Mn and Zn in the gastropod, Pachymelania aurita in relation to heavy metal contaminations in sediments and surface water of Ologe Lagoon, Nigeria were investigated over a twelve- months period. The mean concentration of metals in whole tissue of P. aurita and sediment collected from Ologe Lagoon was in the descending order; Fe > Mn > Zn > Cu > Pb while the mean concentration in the surface water of the site where P. aurita was collected was in the descending order; Fe > Zn > Cu > Mn > Pb. The computed metal pollution index (MPI) (46.76 - 99.03) indicated that there was high level of heavy metal load in the whole tissue of P. aurita, and Iron contributed the highest concentrations of metal load. Based on the bio- sediment accumulation factor (BSAF) and bio-water accumulation factor (BWAF), the amount of Cu, Fe, Pb, Mn and Zn accumulated by P. aurita was found to be about 1.49, 1.46, 1.87, 0.69 and 1.28 times higher than the level detected in the sediment respectively while it was about 4.34, 55.19, 1.67, 83.11 and 20.94 times higher than the level detected in the surface water respectively. Based on the concentrations of Cu and Fe exceeding World Health Organisation (WHO) permissible limits in fish food, P. aurita from Ologe Lagoon may be said to be unsafe for human consumption.

Keywords: Heavy metals, Mollusc, Pachymelania aurita, Bioaccumulation, Sediment, Surface water INTRODUCTION 2007). Moreover, there is a growing concern The accumulation of heavy metals in our among citizens about chemicals and metals that environment has intensified in recent years due to are suspected of disrupting reproduction in population growth, industrialization and new aquatic organisms. These are tied to observations technological developments. This phenomenon is in humans and wildlife over the last 40 years of of great concern because heavy metals constitute worrying trends of adverse effects (Almeida et al., considerable hazards to human health due to their 2001; Licata et al., 2003; Berkun, 2005). toxicities, accumulative tendencies and persistence in the environment (Ayenimo et al., 2005). The Biological communities respond constantly to aquatic environment is the ultimate sink of toxic physical forces, chemical dynamics, and chemicals generated by man's industrial, ecosystem processes that change minute-to- agricultural and domestic activities. Pollutants minute and year-to-year but the difficulty is discharged into streams and rivers are transported establishing to what degree these changes affect over long distances affecting ecosystems miles an ecosystem, how much they are outside the away from the point of discharge. In view of the natural range of variability or disturbance above-mentioned, environmental managers are frequency (Nedeau et al., 2003). constantly faced with having to determine the extent of environmental contamination and Ologe Lagoon meets several socio-economic identifying localities and habitats at risk (Galloway needs (aquaculture, fishing, sand dredging and et al., 2002). drainage) of the various towns and villages bordering it. More importantly, it drains river The fact that heavy metals cannot be destroyed Owo, into which partially treated/untreated through biological degradation and have the effluents from the Agbara industrial estate is ability to persist in the environment make them discharged (Clarke et al., 2004). These discharges deleterious to aquatic environment and coupled with domestic inputs from the Agbara consequently to humans that depend on aquatic residential estates and satellite communities cause products for sources of food (Farombi et al., significant levels of pollution (Clarke et al., 2008). 566 Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita A previous study (Kusemiju, 2010) has revealed dominant gastropod molluscs in Ologe Lagoon the predominance of heavy metals in industrial and other south-western lagoon systems effluents discharged into this environment. With (Oyenekan, 1987; Ajao, 1990; Brown, 2002; respect to Ologe Lagoon, data exist on algal Uwadiae, 2009) of Nigeria. It is endemic to West composition (Clarke et al., 2008; Onuoha, 2009), Africa (Egonmwan, 2007) and is sought after by the fish and fisheries (Anetekhai et al., 2003) and natives of coastal towns and villages in Nigeria as heavy metal concentrations in fish (Kumolu- a staple source of protein. Johnson et al., 2010). However, there is a dearth of information on the heavy metal level of benthic MATERIALS AND METHODS macro-invertebrates in Ologe Lagoon. Description of Study Area The Ologe Lagoon (Figure 1) transverses Lagos Benthic macro-invertebrates are an integral and Ogun States, in Nigeria and is one of the nine component of the aquatic ecosystems. In addition lagoons in south-western Nigeria (Nwankwo, to some being a source of protein to humans, they 2004). It is a freshwater lagoon system that lies play important roles in energy flows, nutrient between latitudes 6° 27′ N and 6° 30′ N and cycling and maintaining community balances in longitudes 3° 02′ E and 3° 07′ E and has a surface these ecosystems. This study therefore area of 9.4 km2 (Anetekhai et al., 2007). Rivers investigates the level of heavy metals (Cu, Fe, Pb, Imede, Owo, Oponu and Ilo are major rivers Mn and Zn) in the gastropod, Pachymelania aurita of emptying into Ologe Lagoon. Its main outlet Ologe Lagoon in relation to heavy metal levels in empties into Elete creek through which it sediment and surface water. Pachymelania aurita connects with other creeks and lagoons such as (; ; ; Iyagbe lagoon, Badagry lagoon and the Lagos Melaniidae) commonly known as periwinkle in Lagoon. Nigeria is one of the commonest and most

Figure 1: Description of the Study Area Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita 567 Collection of Pachymelania aurita for Heavy Sediment Heavy Metal Analysis Metal Analysis Sediment samples (10 g) were oven-dried at 50 0C. Pachymelania aurita samples were collected for a After drying, visible remains of organisms and period of 12 months (January – December, 2008). debris were removed. The dried sample was The were collected by handpicking at the crushed in a mortar and sieved through a 200 mm edge (latitude 060 29.496'N, longitude 030 sieve to normalize particle size. From the dried 03.722'E) of the lagoon at depth less than 0.75 m. sieved sediment sample, 2 g was placed in a The collection was done in three replicates each kheljahl flask and 10 ml aqua regia (HCl: HNO3) month and three individual animals were added. The mixture was digested at 60 0C for combined to serve as a replicate. The collected about two hours. The digest was cooled and samples were taken to the laboratory and stored in transferred to a 50 ml standard flask and made up the freezer prior to digestion for analysis of the to mark with distilled water. The resulting digest heavy metal content. Collection of P. aurita from solution was subsequently filtered using this station was based on its availability throughout Whatman© filter paper into acid pre-washed the year. All samplings were carried out between polyethylene bottles. The metal content of the the hour of 10.00 and 15.00. digest was then determined by Flame Atomic Absorption Spectrophotometry on Perkin Elmer Collection of Water Samples AAnalyst 200. Water samples for physicochemical analysis were collected using acid washed and distilled water Heavy Metal Analysis of Pachymelania cleaned 2-Litre polyethylene containers by dipping aurita them 10 cm below the water surface. Water Whole tissue of collected P. aurita was samples for heavy metal analysis were collected extracted from the shell and dried in an oven at 50 into fresh 120 ml plastic bottles. To prevent 0C for several hours until constant weight was adsorption of metals into the walls of the 120 ml achieved. The dried tissue was crushed and containers, the samples were acidified with 2 homogenised using a domestic blender. Two drops of concentrated HNO3 (APHA, 1998) and 0 grams (2 g) of each sample was then digested with stored in a refrigerator (4 C). Water samples were concentrated nitric acid for 180 minutes in a collected for the duration of 12 consecutive Kheljahl flask at 60 oC on a hot plate. The digest months. was transferred into a 50 ml standard flask and made up to volume with distilled water. The Collection of Sediment resulting mixture was subsequently filtered Sediment samples were taken for a period of 12 2 through a Whatman© filter paper into an acid months, using a 0.1m Van Veen grab. The pre-washed polyethylene bottles. The metal samples were placed in a labelled polythene bags content of this digest was determined using for preservation in the laboratory deep freezer (0 Flame Atomic Absorption Spectrophotometer 0 C) prior to sediment analysis. (AAS) (Perkin Elmer AAnalyst 200).

Heavy Metal Concentrations of Water (mg/l) Statistical Analysis The metals analysis was determined by the Atomic One way analysis of variance (ANOVA) and Absorption Spectrophotometric (AAS) method. comparison of means by Duncan Multiple Range 100 ml of the sample was placed in an Erlenmeyer Test (DMRT) was used to test for significant flask and 10ml concentrated nitric acid added. The differences in the level of heavy metals in the o resulting solution was heated at about 60 C for whole tissue of periwinkle samples collected two hours. The remaining volume was then from Ologe Lagoon. Pearson correlation (r) transferred into a 50 ml standard flask and made to analysis was used to test for significant mark with distilled water. This was then filtered relationship among heavy metal levels in P. aurita, into an acid pre-washed polyethylene bottle. The water and sediment of Ologe Lagoon. metal content of this digest was then determined by flame AAS against known standards using the Metal pollution index (Usero et al., 1997; Adeniyi Perkin Elmer Analyst 200. et al., 2008) was used to compare the total metal 568 Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita level in P. aurita at the different months of RESULTS sampling. The MPI equation is as given below: Copper level in P. aurita 1/n The monthly mean concentrations of copper MPI = (Cf1 x Cf2 x Cf3...... Cfn) (Cu) in the whole tissue homogenates of P. aurita where Cfn = concentration of the metal n in the sample are presented in Figure 2. The highest monthly mean concentration of Cu (21.68 ± 1.52 mg/kg) Bioaccumulation factor was estimated as the ratio in P. aurita was recorded in February while the of the concentration of heavy metal in animal lowest monthly mean (1.03 ± 0.94 mg/kg) was tissue to the concentration of heavy metal in the recorded in November. Analysis of Variance sediment (BSAF = bio-sediment accumulation (ANOVA) showed that the mean concentrations factor) or as the ratio of the concentration of of Cu in P. aurita varied significantly (p<0.05) heavy metal in animal tissue to the concentration among months of collection. Further analysis of heavy metal in water (BWAF = bio-water using Duncan Multiple Range Test (DMRT), accumulation factor) revealed that the mean level of Cu measured in P. aurita collected in February was significantly Heavy metal concentration in animal tissue BSAF = (p<0.05) different from the mean level of Cu in P. Heavy metal concentration in sediment aurita collected in every other month but not significantly (p>0.05) different from that of Heavy metal concentration in animal tissue January (Figure 2). There was no significant BWAF = Heavy metal concentration in water (p>0.05) difference in the concentration of Cu measured in P. aurita tissue in June, July, August, September, October, November and December (Figure 2).

Means (± SE bars) with the same letter on the same bar plots are not significantly different (p>0.05; Duncan)

Figure 2: Temporal variations in the mean level of copper in whole tissue of P. aurita collected from Ologe Lagoon. Table 1: Pearson correlation co-efficient (r) matrix for relationship among heavy metal levels in Pachymelania aurita, water and sediment of Ologe Lagoon

P. aurita Water Sediment Parameters

Cu Fe Pb Mn Zn Cu Fe Pb Mn Zn Cu Fe Pb Mn Zn Samuel etal.: P. aurita Cu 1 Fe -0.442 1 Study of Pb 0.126 0.249 1 Mn -0.504 0.459 0.097 1 Hea Zn 0.550 0.187 -0.164 -0.196 1 vy MetalsintheGastropod, Water Cu 0.654* -0.210 0.079 -0.361 0.244 1 Fe 0.447 -0.007 0.141 -0.338 0.403 0.543 1 Pb -0.230 0.439 0.267 0.246 -0.028 -0.424 0.023 1 Mn 0.446 -0.268 -0.015 -0.653* 0.410 0.328 0.417 -0.162 1 Zn 0.572 -0.202 -0.036 -0.121 0.161 0.557 0.495 -0.132 0.242 1

Sediment P ach

Cu -0.515 -0.008 -0.221 0.471 -0.392 -0.437 -0.055 -0.110 -0.445 -0.034 1 ymelania aurita Fe -0.534 0.223 -0.632* 0.370 0.036 -0.390 -0.191 0.186 -0.220 -0.294 0.182 1 Pb -0.022 -0.038 -0.148 -0.250 0.076 -0.383 -0.434 -0.313 -0.090 -0.174 0.134 -0.254 1

Mn 0.322 -0.366 -0.294 -0.604* 0.195 0.657* 0.295 -0.490 0.648* 0.047 -0.403 -0.061 -0.252 1 Zn -0.472 0.101 -0.480 0.480 -0.208 -0.688* -0.523 0.361 -0.385 -0.115 0.366 0.699* 0.075 -0.511 1

* Correlation is significant at the 0.05 level 569 570 Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita Analysis of relationship between Cu in P. aurita P. aurita was recorded in October while the lowest and that of sediments and water using Pearson monthly mean (408.87 ± 87.71 mg/kg) was correlation coefficient (r) revealed that Cu in P. recorded in March. Analysis of Variance aurita exhibited a positive significant correlation (ANOVA) showed that the mean concentrations with Cu in water column while it was found to be of Fe in P. aurita varied significantly (p<0.05) negatively but not significantly correlated with the among months of collection. Duncan Multiple concentration of Cu in the sediment (Table 1). Range Test (DMRT), revealed that the mean level The concentration of Cu measured in the P. aurita of Fe measured in P. aurita collected in October whole tissue correlated positively with the was significantly (p<0.05) different from the concentration of Pb and Zn but negatively with mean level of Fe in P. aurita collected in January, the concentration of Fe and Mn. February, March, September and December (Figure 3). However, the mean concentration of Iron level in P. aurita Fe in whole tissue homogenates of P. aurita The monthly mean concentrations of iron (Fe) in collected in October was not significantly the whole tissue homogenates of P. aurita are (p>0.05) different from the concentration of Cu presented in Figure 3. The highest monthly mean measured in P. aurita tissue in April, May, June, concentration of Fe (1036.04 ± 196.48 mg/kg) in July, August and November (Figure 3).

Means (± SE bars) with the same letter on the same bar plots are not significantly different (p>0.05; Duncan) Figure 3: Temporal variations in the mean level of iron in whole tissue of P. aurita collected from Ologe Lagoon.

Analysis of relationship between Fe in P. aurita and Lead level in P. aurita that of sediments and water using Pearson The monthly mean concentrations of lead (Pb) in correlation revealed that Fe in P. aurita exhibited a the whole tissue homogenates of P. aurita are positive non-significant correlation with Fe in the presented in Figure 4. The highest monthly mean sediment while it was found to be negatively but concentration of Pb (0.08 ± 0.049 mg/kg) in P. not significantly correlated with the concentration aurita was recorded in August while the lowest of Fe in the water column (Table 1). The monthly mean (0.02 ± 0.023 mg/kg) was concentration of Fe measured in the P. aurita recorded in June. Lead was only detected in the whole tissue correlated positively with the whole tissue homogenates of P. aurita in the concentration of Pb, Mn and Zn but negatively month of January, June and August. Analysis of with the concentration of Cu. variance (ANOVA) showed that the mean concentrations of Pb in P. aurita varied insignificantly (p>0.05) among months of collection. Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita 571

Means (± SE bars) with the same letter on the same bar plots are not significantly different (p>0.05; Duncan) Figure 4: Temporal variations in the mean level of lead in whole tissue of P. aurita collected from Ologe Lagoon

Correlation of Pb level in P. aurita with that of Manganese Level in P. aurita sediment and water using Pearson correlation The monthly mean concentrations of manganese revealed that Pb in P. aurita exhibited a positive (Mn) in the whole tissue homogenates of P. aurita non-significant correlation with Pb in water while are presented in Figure 5. The highest monthly it was found to be negatively but not significantly mean concentration of Mn (191.78 ± 59.50 correlated with the concentration of Pb in the mg/kg) in P. aurita was recorded in November sediment (Table 1). However, Pb in P. aurita while the lowest monthly mean (39.06 ± 3.00 correlated negatively and significantly with Fe in mg/kg) was recorded in March. Analysis of the sediment (Table 1). The concentration of Pb variance (ANOVA) showed that the mean measured in the P. aurita whole tissue correlated concentrations of Mn in P. aurita varied positively with the concentration of Cu, Fe and insignificantly (p>0.05) among months of Mn but negatively with the concentration of Zn. collection.

Means (± SE bars) with the same letter on the same bar plots are not significantly different (p>0.05; Duncan)

Figure 5: Temporal variations in the mean level of manganese in whole tissue of P. aurita collected from Ologe Lagoon 572 Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita Correlation of Mn level in P. aurita with that of aurita was recorded in April while the lowest sediments and water using Pearson correlation monthly mean (36.29 ± 0.71 mg/kg) was revealed that Mn in P. aurita exhibited a negative recorded in November. Analysis of variance significant correlation with Mn in water column (ANOVA) showed that the mean concentrations and with the concentration of Mn in the sediment of Zn in P. aurita varied significantly (p<0.05) (Table 1). The concentration of Mn measured in among months of collection. Further analysis the P. aurita whole tissue correlated positively with using DMRT, revealed that the mean level of Zn the concentration of Fe and Pb but negatively with measured in P. aurita collected in April was the concentration of Cu and Zn. significantly (p<0.05) different from the mean levels of Zn in P. aurita collected in March, Zinc level in P. aurita August, September and November but not The monthly mean concentrations of zinc (Zn) in significantly different from the means of Zn in the whole tissue homogenates of P. aurita are the P. aurita tissue collected in other months presented in Figure 6. The highest monthly mean (Figure 6). concentration of Zn (88.44 ± 7.54 mg/kg) in P.

Means (± SE bars) with the same letter on the same bar plots are not significantly different (p>0.05; Duncan)

Figure 6: Temporal variations in the mean level of zinc in whole tissue of P. aurita collected from Ologe Lagoon

Analysis of relationship between Zn in P. aurita water accumulation factors) are presented in and that of sediments and water using Pearson Table 2. The computed MPIs (lead level not correlation coefficient (r) revealed that Zn in P. included) indicated that there was high level of aurita exhibited a negative non-significant heavy metal load in the whole tissue of P. aurita. correlation with Zn in sediment and with the The highest MPI (99.03) was recorded in the concentration of Zn in the water column (Table month of July while the lowest (46.76) was 1). The concentrations of Zn measured in the P. recorded in the month of November. Iron aurita whole tissue exhibited a positive non- contributed highest concentrations of metal load. significant correlation with Cu and Fe while it With the inclusion of lead (Pb) concentration exhibited a negative non-significant (p>0.05) detected in whole tissue of P. aurita, the MPI correlation with Pb and Mn. reduced in the month of January from 79.36 to 17.38, in June (from 75.10 to 14.48) and in August Metal Pollution Index and Bioaccumulation from 83.39 to 20.77 (Table 2). Factors of P. aurita The metal pollution index (MPI) and the The mean concentration of metals in whole tissue bioaccumulation factors (bio-sediment and bio- of P. aurita and sediment collected from Ologe Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita 573 Table 2: Metal pollution index and bioaccumulation factors of Pachymalania aurita collected from Ologe Lagoon

Heavy metals (mg/kg) Sampling months MPI Cu Fe Pb* Mn Zn 79.36 Jan 16.76 463.58 0.04 66.59 76.67 (17.38) Feb 21.68 511.59 0.00 81.73 76.61 91.29 Mar 11.76 408.87 0.00 39.06 45.20 53.98 Apr 12.27 709.33 0.00 58.59 88.44 81.95 May 9.11 677.63 0.00 59.12 65.00 69.79 75.10 Jun 8.21 867.07 0.02 85.12 52.51 (14.48) Jul 7.82 934.81 0.00 179.17 73.42 99.03 83.39 Aug 8.57 953.97 0.08 136.79 43.24 (20.77) Sep 4.81 577.19 0.00 56.04 31.20 46.94 Oct 6.01 1036.04 0.00 97.50 84.08 84.53 Nov 1.03 666.73 0.00 191.78 36.29 46.76 Dec 5.98 617.16 0.00 145.23 51.23 72.39 Mean level in P. 9.50 702.00 0.0125 99.73 60.32 aurita Mean level in 6.36 482.26 0.0067 144.51 47.24 sediment Mean level in 2.19 12.72 0.0075 1.20 2.88 water BSAF 1.49 1.46 1.87 0.69 1.28 BWAF 4.34 55.19 1.67 83.11 20.94

Lagoon was in the decreasing order; Fe> Mn> Pachymelania aurita collected from Ologe Lagoon Zn> Cu> Pb while the mean concentration in the varied significantly (p<0.05) for all the sampled water column of the site of P. aurita collection was months with no particular seasonal trend. in the order; Fe> Zn> Cu> Mn> Pb (Table 2). On Kumolu-Johnson et al. (2010) had attributed low the basis of computed bio-sediment accumulation levels of heavy metals in fish, Cynothrissa mento factor (BSAF), Pb has the highest BSAF of 1.87 during the wet season at Ologe Lagoon to the and Mn has the least BSAF of 0.69. Highest bio- dilution of the metals as a result of increase in water accumulation factor (BWAF) of 83.11 was rainfall and runoff. In contrast, Nussey et al. recorded for Mn and the lowest BWAF of 1.67 (2000) attributed high concentrations of heavy was recorded for Pb. Based on the BWAF, the metals in tissues of moggel, Labeo umbratus from amount of Fe, Mn and Zn accumulated by P. aurita Witbank dam, Mpumalanga, South Africa during was found to be about 55.19, 83.11 and 20.94 summer to higher rainfall causing pronounced times higher than the level detected in the water leaching of metals into water. Otitoloju (2001) sample respectively. Generally, the levels of Mn also attributed slight increase in metal levels of the detected in P. aurita was less than the ones detected gastropod, Tympanotonus fuscatus collected from in the sediment (BSAF = 0.69). Lagos lagoon during the wet season (study based on selected months) to the increased influx of DISCUSSION fresh inland waters from the adjoining water The levels of all the investigated heavy metals bodies such as River Majidun, Ogun, Ona, Sasa (except Pb and Mn) in the whole tissue of and Osun which drain the neighbouring states 574 Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita and discharges its contaminants including heavy (Otitoloju, 2001; Aderinola et al., 2009) for T. metals into the Lagos lagoon. The monthly heavy fuscatus in Lagos lagoon. However, in the present metal variations in P. aurita observed in this study study, the levels of heavy metals (except Mn) in were largely influenced by the industrial and the sediment and water of Ologe Lagoon were domestic activities of the study area rather than lower than that in the tissue of P. aurita. This is in rainfall. Manganese, zinc, lead, iron have been agreement with the trends reported by Davies et reported to be rainfall independent (Egborge, al. (2006) for Tympanotonus fuscatus radula in Elechi 1991). creek, Niger Delta. The ability of molluscs to accumulate heavy metals to levels higher than the The computed metal pollution index (MPI) (46.76 acceptable minimum metal concentration - 99.03) indicated that there was high level of without any detectable adverse effect has been heavy metal load in the whole tissue of P. aurita widely reported and led to their inclusion in with Fe contributing highest concentrations of monitoring programmes of environmental metal load. The recorded mean concentrations of pollution (Rainbow et al, 2002). The sediment Cu (9.50 mg/kg) and Fe (702 mg/kg) in P. aurita accumulated more heavy metals than water in this were higher than the maximum allowable limits study as have been observed by Otitoloju (2001), (Cu = 3.0; Fe = 100.0 mg/kg) in food fish set by Chindah and Braide (2003), Davies et al. (2006) the World Health Organization while the mean Zn and Aderinola et al. (2009). Sediment is the major and Pb was lower than the permissible limits of depository of metals in some cases, holding more 75.0 and 2.0 mg/kg respectively (WHO, 2008). than 99 % of total amount of a metal present in The levels of Cu (1.03 – 21.68 mg/kg), Fe (408.87 the aquatic system (Odiete, 1999). – 1036.04 mg/kg) and Zn (36.29 – 88.44 mg/kg) observed in P. aurita in the present study were Based on the bio-sediment accumulation factor higher than these values reported by Kumolu- (BSAF), the amount of Cu, Fe, Pb, and Zn Johnson et al. (2010) for Cynothrissa mentho of the accumulated by P. aurita was found to be about same water body while the observed Pb (0.00 – 1.49, 1.46, 1.87 and 1.28 times higher than the 0.08 mg/kg) and Mn (39.06 - 191.78 mg/kg) was level detected in the sediment respectively. The lower and higher respectively than the reported level of Mn detected in P. aurita was less than the (Biney et al., 1994) Nigeria's freshwater fish level detected in the sediment (BSAF = 0.69). The levels. The recorded concentrations of Pb and Cu exposure of the edible periwinkle, Tympanotonus in P. aurita were lower than those of the periwinkle, fuscatus to sublethal concentrations of Zn, Pb, Cu Tympanotonus fuscatus (Pb = 8.1 – 17.2; Cu = 21.4 – and Cd compounds of heavy metals by Otitoloju 40.2 mg/kg) reported by Otitoloju (2001) while and Don-Pedro (2002) resulted in the the recorded concentrations of Zn, Mn and Fe bioaccumulation of higher concentrations of Zn were higher. The implication of these findings and Pb ions that were about 2 – 6 times higher based on the concentrations of Cu and Fe than the levels accumulated in control animals. exceeding WHO (2008) limit is that the Comparisons between the concentration of consumption of the periwinkle, P. aurita from heavy metals in whole body tissues of T. fuscatus Ologe Lagoon can be said to be unsafe. and the sediment of the media reported by this author showed that the concentration of the The mean concentration of metals in whole tissue metals accumulated in tissues of T. fuscatus were of P. aurita and sediment collected from Ologe about 2 – 729 times higher than that in the Lagoon was in the descending order: Fe> Mn> sediment. Likewise, field experiment employed by Zn > Cu > Pb while the mean concentration in the Otitoloju and Don-Pedro (2004) in assessing the water body of the site of P. aurita collection was in impact of metal-laden effluents on the tissue the descending order: Fe> Zn > Cu > Mn > Pb. concentration of heavy metals in Lagos lagoon Of all the metals examined, Fe was found to be the showed that T. fuscatus accumulated Zn and Pb most abundant. This agrees with the findings of about 10 times higher than the concentrations Aderinola et al. (2009) in Lagos lagoon. Higher detected in control animals. The termination of heavy metals levels in sediment than those in the metal-laden effluent discharges into the surface water and organisms have been reported experimental creek, after 150 days of Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita 575 contamination, resulted in a rapid and significant REFERENCES decline in the concentrations of the metals Adeniyi, A.A., Yusuf, K.A. and Okedeyi, O.O. detected in the sediment. However, the 2008. Assessment of the exposure of two concentrations of metals accumulated in tissues fish species to metals pollution in the Ogun of the periwinkles remained high. river catchments, Ketu, Lagos, Nigeria. Environment Monitoring and Assessment 137(1- Based on the bio-water accumulation factor 3): 451-458. (BWAF), the amount of Cu, Fe, Pb, Mn and Zn Aderinola, O.J., Clarke, E.O., Olarinmoye, O.M., accumulated by P. aurita was found to be about Kusemiju, V. and Anatekhai, M.A. 2009. 4.34, 55.19, 1.67, 83.11 and 20.94 times higher Heavy metals in surface water, sediments, than the level detected in the water body fish and periwinkles of Lagos Lagoon. respectively. Despite the relatively low American-Eurasian Journal of Agriculture and concentrations of trace metals in the surrounding Environmental Science 5(5): 609-617. medium, aquatic organisms take up and Ajao, E.A. 1990. The influence of domestic and accumulate them in soft tissues to concentrations industrial effluents on populations of above ambient environmental levels that are sessile and benthic organisms in Lagos capable of exerting biological effects (Ekweozor et Lagoon. Ph.D Thesis, University of al., 2003). Ibadan, Ibadan, Nigeria. 413pp. Almeida, J.A., Novelli, E.L.B., DalPai Silva, M. Copper (Cu) and Pb in P. aurita exhibited a positive and Alves, R., Jr. 2001. Environmental correlation with Cu and Pb in water while it was cadmium and metabolic responses of Nile found to be negatively correlated with the tilapia. Environmental Pollution 114: 169-175. concentration of Cu and Pb in the sediment American Public Health Association (APHA) respectively. Iron (Fe) in P. aurita exhibited a 1998. Standard Methods for the Examination of positive correlation with Fe in the sediment while Water and Waste Water. 20th Edition, APHA, it was found to be negatively correlated with the New York. 1270pp. concentration of Fe in the water sample. Anetekhai, M.A., Akin-Oriola, G.A., Aderinola, Manganese (Mn) and Zn in P. aurita exhibited a O.J. and Akintola, S.L. 2007. Trace metal negative correlation with Mn and Zn in water concentration in Macrobrachum vollenhoevenii column and sediment respectively. from Ologe Lagoon, Lagos, Nigeria. Journal of Afrotropical Zoology, Special Issue: 25-29. The bioaccumulation of pollutants to toxic levels Anetekhai, M.A., Akin-Oriola, G.A., Jimoh, A.A., especially heavy metals is detrimental to organisms Akintola, S.L. and Kumolu-Johnson, C.A. generally, including plants and animals as they may 2003. Preliminary report on fish and be biomagnified through the food chain and fisheries of Ologe Lagoon, Lagos, Nigeria. transmitted to man. The BSAF and BWAF values In: Proceedings of the Third International obtained in this study showed that Conference of African Fish and Fisheries, bioaccumulation occurred. Therefore periodic Association., Cotonou, 10-14 November, heavy metal monitoring of Ologe Lagoon is 2003, Cotonou, Benin. pp1-5. recommended in view of the socio-economic Ayenimo, J.G., Adeeyinwo, C.E. and Amoo, I.A. importance of the lagoon. 2005. Heavy metal pollutants in Warri River, Nigeria. Kragujevac Journal of Science 27: 43-50 ACKNOWLEDGEMENTS Berkun, M. 2005. Effects of Ni, Cr, Hg, Cu, Zn, This study was partly supported by the University Al, on the dissolved oxygen balance of of Lagos Graduate Fellowship. The authors are streams. Chemosphere 59: 207-215. grateful to Dr. B.E. Emmanuel for his assistance Biney, C., Amuzu, A.T., Calamari, D., Kaba, N., during the field trips. The assistance of Mr. Ben Mbome, I.L., Naeve, H., Ochumba, P.B., Begusa and Dr. Abayomi Akeem of the Osibanjo, O., Radegonde, V. and Saad, Department of Chemistry, UNILAG is highly M.A.H. 1994. Review of heavy metals in appreciated. the African aquatic environment. Ecotoxicology and Environmental Safety 28(2): 576 Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita 134-159. Galloway, T.S., Sanger, R.C., Smith, K.L., Brown, C.A. 2002. The diversity and density of Fillmann, G., Readman, J.W., Ford, T.E. and macrobenthic fauna in the western part of Depledge, M.H. 2002. Rapid assessment of Lagos Lagoon and adjacent creeks. Ph.D. marine pollution using multiple biomarkers Thesis, University of Lagos. 246pp. and chemical immunoassays. Environmental Chinda, A.C. and Braide, S.A. 2003. Cadmium and Science and Technology 36: 2219-2226. lead concentrations in fish species of a Kumolu-Johnson, C.A., Ndimele, P.E., Akintola, brackish wetland/upper Bonny estuary, S.L. and Jibuike, C.C. 2010. Copper, zinc Niger Delta. Journal of Nigerian Environmental and iron concentrations in water, sediment Society 1(3): 399-405. and Cynothrissa mentho (Regan 1917) from Clarke, E., Olarinmoye, O.M., Owodeinde, F.G., Ologe Lagoon, Lagos, Nigeria: a Adeboyejo, A.O., Jimoh, A., Akintola, S.L. preliminary survey. African Journal of and Aderinola, O.J. 2008. The dynamics of Aquatic Science 35(1): 87-94. Desmidacean populations in Ologe Lagoon, Kusemiju, V.O. 2010. Impact of industrial Lagos, Nigeria. Journal of Cell and Animal e f f l u e n t s o n p h y s i c o c h e m i c a l Biology 2(2): 021-030. c h a r a c t e r i s t i c s o f R i ve r O wo, Clarke, E.O., Anetekhai, M.A., Akin-Oriola, G.A., macrobenthic composition and its Onanuga, A.I.S., Olarinmoye, O.M., toxicological effects on Tilapia zillii. Ph.D Adeboyejo, O.A. and Agboola I. 2004. The Thesis, University of Lagos, Lagos, Diatom (Bacillariophyta) diversity of an Nigeria. 216pp. open access lagoon in Lagos, Nigeria. Licata, P., Bella, G.D., Dugo, G. and Naccari, F. Nigerian Journal of Research and Review in Science 2003. Organochlorine pesticides, PCBs. 3: 70-77. and heavy metals in tissues of the Mullet Davies, O.A., Allison, M.E and Uyi, H.S. 2006. Liza aurata in Lake Ganzirri and straits in Bioaccumulation of heavy metals in water, Messina (Sicily, Italy). Chemosphere 52: 231- sediment and periwinkle (Tympanotonus 238. fuscatus var radula) from the Elechi creek, Nedeau, E.J., Merritt, R.W. and Kaufman, M.G. Niger Delta. African Journal of Biotechnology 2003. The effect of an industrial effluent on 5(10): 968-973. an urban stream benthic community: water Egborge, B.M. 1991. Industrialisation and heavy quality vs. habitat quality. Environmental metal pollution in Warri river. University of Pollution 123: 1-13. Benin 32nd Inaugural Lecture, University of Nussey, G., van Vauren, J.H.J. and du Preez, H.H. Benin, Benin City, Nigeria. 32pp. 2000. Bioaccumulation of chromium, Egonmwan, R.I. 2007. Reproductive cycle of the manganese, nickel and lead in the tissues of mangrove prosobranch, Pachymelania fusca the moggel, Labeo umbratus (Cyprinidae), (Gmelin, 1791) var. quadriseriata (Gray) from Witbank Dam, Mpumalanga. Water (Gastropoda: Melaniidae) in Lagos, Nigeria. South Africa 26(2): 269-284. Pakistan Journal of Biological Sciences 10(4): Nwankwo, D.I. 2004. The microalgae: Our 649-653. indispensable allies in aquatic monitoring Ekweozor, I.K.E., Dambo, W.B. and Daka, E.R. and biodiversity sustainability. University 2003. Zinc and cadmium levels in Crassostrea of Lagos Inaugural Lecture Series, gasar from the lower Bonny Estuary, University of Lagos Press. 44pp. Nigeria. Journal of Nigerian Environmental Odiete, W.O. 1999. Environmental Physiology of Society 1(1): 31-40. Animals and Pollution. Diversified Resources Farombi, E.O., Adelowo, O.A. and Ajimoko, Y.R. Ltd., Lagos. 261pp. 2007. Biomarkers of oxidative stress and Onuoha, C.P. 2009. Phytoplankton biomass and heavy metal levels as indicators of diversity in relation to environmental environmental pollution in African catfish parameters at Ologe Lagoon, Lagos. Ph.D (Clarias gariepinus) from Nigeria Ogun River. Thesis, University of Lagos, Nigeria. International Journal of Environmental Research 391pp. and Public Health 4(2): 158-165. Otitoloju, A.A. 2001. Joint action toxicity of Samuel et al.: Study of Heavy Metals in the Gastropod, Pachymelania aurita 577 heavy metals and the bioaccumulation Biological Association of the United Kingdom 82: benthic animals of the Lagos Lagoon. Ph.D 793-799. Thesis, University of Lagos, Lagos. Nigeria. Usero, J. Gonzalez-Regalado, E. and Graccia, I. 225pp. 1997. Trace metals in the bivalve molluscs Otitoloju, A.A. and Don-Pedro, K.N. 2002. Ruditapes decussatus and Ruditapes Bioaccumulation of heavy metals (Zn, Pb, philippinarum from the Atlantic coast of Cu and Cd) by Tympanotonus fuscatus var. southern Spain. Environment International 23: radula (L.) exposed to sublethal 291-298. concentrations in laboratory bioassays. West Uwadiae, R.E. 2009. An ecology study on the African Journal of Applied Ecology 3: 17-29. macrobenthic invertebrate community of Otitoloju, A.A. and Don-Pedro, K.N. 2004. Epe Lagoon, Lagos. Ph.D Thesis, Integrated laboratory and field assessments University of Lagos, Lagos, Nigeria. 253pp. of heavy metal accumulation in edible WHO (World Health Organisation) 2008. periwinkle, Tympanotonus fuscatus var radula Guidelines for Drinking Water Quality: (L.). Ecotoxicology and Environmental Safety 57: Third Edition Incorporating the First and 354-362. S e c o n d A d d e n d a ( V o l . 1 : Oyenekan, J.A. 1987. Benthic macrofauna Recommendations). World Health communities of Lagos Lagoon. Nigerian Organisation, Geneva. 515pp. Journal of Science, 21: 45-51. Rainbow, P.S., Smith, B.D. and Lau, S.S.S. 2002. Biomonitoring of trace metal availabilities in the Thames estuary using a suite of littoral biomonitors. Journal of the Marine