Qua Iboe Estuary Research Articles

DNA BARCODING OF Caranx senegallus FROM THREE WATER BODIES ADJOINING THE GULF OF GUINEA, NIGERIA

Fish species show astonishing phenotypic and genetic diversity in populations. The delimitation and recognition of fish species are not only of interest to taxonomists but also a requirement in studies of ecology. In this study, the genetic structure of Caranx senegallus collected from three water bodies adjoining the Gulf of Guinea, Nigeria was characterized using the cytochrome c oxidase I (COI) barcode gene region. Fish samples collected from Qua Iboe estuary, Escravos estuary, and Lagos lagoon were identified morphologically, and muscle tissues were used for DNA barcoding using Fish1 and Fish2 primers. Evolutionary analysis showed the formation of diverging clades in the neighbor-joining tree and indicated the presence of multiple species. The result also revealed that morphological identification was not entirely successful, as the Basic Local Alignment Search Tool (BLAST) prediction confirmed the presence of three specimens initially identified as C. senegallus but genetically matching C. fischeri and Trachinotus goreensis. This observation further emphasized the need for an integrative method for species identification.

Aspects of the reproductive biology of <i>Pseudotolithus typus</i> (Bleeker, 1863) from qua Iboe River Estuary, Nigeria

The study was conducted to assess the reproductive biology and condition index of Pseudotolithus typus in Qua Iboe Estuary using standard methods. A total of 580 fish specimen were sampled over a period of 8 months (January – August, 2018). Condition index was generally low with the highest value of 1.03 recorded in the month of April. The overall mean condition index significantly deviated (p<0.05) from the expected value of 1.0. Male-female ratio of the species showed female dominance. Significant variation (p<0.05) were observed in condition and gonadosomatic indices with peak values in the months of March and July for females. Male fish showed no seasonality in gonadosomatic index. The average fecundity ranged from 2140 eggs to 8560 eggs with mean value of 4891±641 eggs. Positive correlation was observed between fecundity and total length, body weight, standard length and gonad weight of the fish. Thus, it could be concluded that P. typus is a dual seasonal spawner having spawning periods early in the year (March) and in the peak of wet season (July).
 Keywords: Pseudotolithus typus, condition index, gonadosomatic index, fecundity, estuary.

Assessment of Heavy Metals Concentrations in Selected Crustaceans and Their Potential Health Risk at Qua Iboe Estuary, Ibeno

Assessment of Heavy Metals Concentrations in Selected Crustaceans and Their Potential Health Risk at Qua Iboe Estuary, Ibeno

Growth and Extracellular Enzyme Activity Responses of a Multi-enzymic Strain of Serratia sp. in a Simulated Diesel-contaminated System

Aim: The present study was aimed at elucidating the alternative metabolic preferences of Serratia sp. strain DW2 that permitted its survival in a diesel-contaminated environment.
 Study Design: We adopted a 4 x 4 x 3 completely randomized design of a full-factorial experiment for the study.
 Place and Duration of Study: The study was conducted at the Department of Microbiology, University of Calabar, Nigeria, during the months of March and June, 2019.
 Methodology: In this study, Serratia sp. strain DW2 was isolated from Douglas Creek water of the Qua Iboe Estuary, along the Qua Iboe terminal at Ibeno, Nigeria, as a significant biological contributor to the decontamination process through inherent ability to utilize diesel oil hydrocarbons. This paper elucidated the growth and responses of the bacterial lipase, caseinase and gelatinase activities to diesel-oil hydrocarbon contamination.
 Results: Range finding test results showed that the bacterium could grow in the presence of water soluble fraction of diesel (wsf-D) concentration between .0042 and .0335 µg/mL, albeit with increasing lag time and decreasing specific growth rate when compared with growth in glucose-Bushnell-Haas broth. Lag time changes were not significantly influenced by exposure time but changes in specific growth rate were. Gelatinase activity was most susceptible to toxicant onslaught but was least affected by exposure time. Conversely, lipase activity was the most affected by exposure time. Toxicant concentration/exposure time interaction of a two-way analysis of variance model for caseinase activity was not significant (P > .05) but those for lipase and gelatinase activities were.
 Conclusion: The bacterium survived diesel toxicity by exploiting its lipase and gelatinase activities for provision of alternative sources of carbon, energy and nitrogen to drive ecosystem decontamination in the event of refined petroleum contamination.

Rainwater Chemistry Within the Vicinity of Qua Iboe Estuary, Nigeria

The Qua Iboe River estuary is one of the most studied ecosystems in the Niger Delta of Nigeria given its proximity to intense industrial activities. There have been concerns regarding possible environmental contamination, which has led to several monitoring studies. In this study, some trace metals (Zn, Mn, Cu, Fe, Cr, Pb, Ni, Cd) in rainwater samples collected around the estuary were investigated using standard analytical methods. Rainwater samples were also analysed for physicochemical characteristics. The results obtained revealed varied levels of trace metals and physicochemical parameters across dry and wet seasons. The average abundance of trace metals in rainwater samples from the study locations is in the order: Fe > Zn > Mn > Cr > Cu > Ni > Cd > Pb. In addition, predominant anions in rainwater samples are in the order >Cl−>>>S2–>CN–. Results from statistical analyses reveal the relationships across parameters as well as the discrimination of monitored sites based on the intensity of industrial activities. Principal component analysis reveals that soil dust, sea salt, and fossil fuel combustion are major factors affecting the rainwater chemistry of the study area. The significant amounts of trace metals and the physicochemical parameters quantified in the rainwater samples indicate some level of contamination. However, these levels do not indicate serious pollution problems at present.

Distribution and risk assessment of trace metals in Leptodius exarata, surface water and sediments from Douglas Creek in the Qua Iboe Estuary

Five trace metals in Leptodius exarata, epipellic sediments and surface water from an intertidal ecosystem in the Niger Delta (Nigeria) were studied to evaluate their spatial distributions, degrees of contamination, and associated ecological and health risks. The results show that the Cd (cadmium), Cr (chromium), Ni (nickel), Pb (lead) and Zn (zinc) concentrations in sediment range from 0.550–1.142, 9.57–15.95, 9.15–13.96, 2.00–8.90 and 91.5–121.6mgkg−1 dw, respectively, while the L. exarata tissue metal content varies from 0.162–0.931, 3.81–8.62, 4.45–17.15, 1.90–7.35, and 125.55–269.75mgkg−1 dw, respectively. The bioconcentration factor ranking for trace metals was found to follow the Zn>Ni>Pb>Cr>Cd sequence. The high biota to sediment accumulation factor (BSAF) found for L. exarata reveals a sentinel metal bioindicator. Sediments from most sites were found to be uncontaminated to moderately contaminated (geoaccumulation, Igeo>0), with Cd and Zn associated with anthropogenic intrusions. Low mean-ERM (effect range-median) and mean-PEL (probable effect level) quotients of sediments were found, indicating low–moderate degrees of contamination with 30% and 21% probabilities of toxicity. The multi-metal potential ecological risk index (RI) for the intertidal ecosystem denotes low–moderate risk. Health risks associated with crab (L. exarata) consumption are more significant for children than for adults.

Distribution of Trace Metals in Water and Sediments of Qua Iboe River Estuary, Nigeria

Surface water and sediments collected from three stations along Qua Iboe Estuary, Niger Delta between January and June 2013 were analyzed for Iron (Fe), Zinc (Zn), Lead (Pb) and Cadmium (Cd). The trace metal concentrations (mg/L) in surface water were 0.08, 0.17, 0.01, 0.004 for Fe, Zn, Pb and Cd, respectively and 0.59, 0.33, 0.04 and 0.02 mg/kg in sediments respectively for the same metals. There were significant differences (p 0.05). Positive significant correlations (p<0.05) exist between the metals in sediments which revealed their co-accumulation potentials. Trace metal concentrations in water and sediment were below the maximum permissible level recommended by national and international standards except for lead in water. Thus Qua Iboe estuary is relatively suitable for fish production and domestic use despite effluent discharges into the estuary.

English

Seasonal variation of the distribution pattern, enrichment and contamination of some heavy metals (Cd, Cr, Fe, Pb, Zn, Ni and Cu) in surface water of Qua Iboe river estuary and adjoining creeks were investigated using physicochemical parameters. The results of wet season mean concentrations (mg/l) were: Cd (0.09 &plusmn; 0.02), Cr (0.05 &plusmn; 0.02), Cu (0.05 &plusmn; 0.01), Fe (10.68 &plusmn; 1.91), Pb (0.06 &plusmn; 0.01), Zn (0.08 &plusmn; 0.03) and Ni (7.4 &plusmn; 1.31) while the dry season mean concentrations (mg/l) revealed Cd (0.06 &plusmn; 0.02), Cr (0.04 &plusmn; 0.02), Cu (0.02 &plusmn; 0.004), Fe (7.36 &plusmn; 1.94), Pb (0.03 &plusmn; 0.008), Zn (0.03 &plusmn; 0.01) and Ni (5.17 &plusmn; 1.73). The wet season mean concentration of heavy metals were higher than the dry season. Concentration data were processed using Pearson correlation matrix to identify the inter-relationships between physicochemical parameters as well as the sources of heavy metals. The results showed that salinity, pH and temperature among others played a significant role in the adsorption/desorption and dissolution of heavy metals in the surface water. The Enrichment factor (EF) calculated during the wet season in surface water ranged from 0.2 to 2.9 while the EF calculated during the dry season ranged from 0.2 to 1.9. During wet season, Cd, Cu, Fe, Pb and Zn showed minor surface enrichments while Cr and Ni showed no enrichment. During dry season, Cd, Fe and Zn were moderately enriched in surface water while Cr, Cu, Pb and Ni were not enriched. Surface enrichment was attributed to atmospheric deposition, released of sediment bound metals to the surface, dissolution/erosion of coastal sediments as well as anthropogenic input. The computed degree of contamination indicated that the river system was moderately contaminated during dry season but highly contaminated during wet season. The implication is that during flooding which is consequent upon climate change, there will be higher degree of contamination of Qua Iboe River estuary and adjoining creeks. &nbsp; Key words: Heavy metals, seasonal variations, surface enrichments and contamination, Qua Iboe estuary.

Evaluation of Status of Heavy Metals Pollution of Sediments in Qua-Iboe River Estuary and Associated Creeks, South-Eastern Nigeria

Sixteen bottom sediment samples collected from Qua-Iboe River estuary and associated creeks were analyzed for Cd, Cr, Cu, Fe, Pb, Zn, Ni, pH, Organic carbon (orgC),and grain size in order to assess the current pollution status in sediment of the study area. Concentration data were processed using Pearson correlation analysis. Sediment pollution assessment was carried out using Enrichment factor, Geo-accumulation index and Modified degree of contamination. The calculated enrichment factor showed that the sediment was enriched with Cd, Zn, Cu and Pb. The results of geo-accumulation index (Igoe) indicated that sediments are unpolluted with Fe, moderately polluted with Cr, Cu, Pb, strongly polluted with Cd and extremely polluted with Ni. This was attributed mainly to oil contaminating wastes and metal scraps. The results of the modified degree of contamination (mCd) revealed that the sediment of Qua Iboe estuary and associated creeks fall between 8 ? mCd ? 16 indicating very high degree of contamination.

Condition factor, hydrocarbons and bacterial burdens of shellfishes from mudflats in the Qua Iboe Estuary, Nigeria

In this article, the condition factor (CF; health status), bacterial burdens and total petroleum hydrocarbons (TPH) accumulating potential of shellfishes harvested from tidal mudflats in the Qua Iboe Estuary mangrove ecosystem, Nigeria, were investigated. The results revealed that most species of shellfishes from the estuary were not healthy. Tympanotonus fuscatus had a healthy status (CF) of 54.6%, while Mytilis edulis, Thais haemostoma and Callinectes latimanus from hydrocarbon-impacted mudflats exhibited poor health statuses with CF values less than 40%. Though unhealthy, they exhibited great propensity to bioaccumulate hydrocarbons and bacteria including hydrocarbonoclastic bacteria from the environment. The mean levels of TPH in the shellfishes were 4.68 mg/g, 7.92 mg/g, 4.86 mg/g and 3.97 mg/g dry weight of T. fuscatus, M. edulis, Th. haemostoma and C. latimanus, respectively, as against 30.36 mg/g dry weight detected in the intertidal sediment. Correlation between levels of TPH accumulated and CF of the shellfishes (at p < 0.05) revealed weak and not definite relationships in T. fuscatus (r = 0.080), M. edulis (r = 0.102) and Th. haemostoma (r = 0.214), while a positive significant relationship was observed for C. latimanus (r = 0.583). The bacteria densities of freshly collected samples varied between the diverse species of shellfish. The relationship between bacterial load and CF was negative and insignificant in C. latimanus (r = − 0.123) but insignificantly positive in M. edulis (r = 0.011), Th. haemostoma (r = 0.347) and T. fuscatus (r = 0.347). These findings have shown that shellfishes from mudflats in the Qua Iboe Estuary are not healthy but have great capability to bioaccumulate hydrocarbons and bacteria. Their bioaccumulating potential is not definitive and health (CF) dependent, but plausibly determined by the availability and nature of contaminants and their feeding mode. Though the role of oil-degrading bacteria within the viscera of shellfishes is uncertain, it is obvious that the commercially valid species investigated could serve as possible bio-indicators of hydrocarbon and bacterial contaminants in the fishing waters.

Activities of hydrocarbon-utilizing and diazotrophic bacteria in crude oil impacted mangrove sediments of the Qua Iboe Estuary, Nigeria

Analysis of the total petroleum hydrocarbons (TPH) and the activities of hydrocarbon-utilizing bacteria (HUB) and diazotrophic bacteria (DB) in mangrove sediments of the Qua Iboe Estuary revealed that the organic-laden sediments have high hydrocarbon repository status. The epipelic sediment was relatively richer in total organic nitrogen (TON) content. Correlation analysis revealed positive relationship between TPH and HUB (r = 0.60) in the epipelic sediment, while no definite relationship (r = − 0.30) was established between the variables in benthic sediment. A strong negative relationship was observed between TPH and TON in the intertidal (r = − 0.746) and benthic (r = − 0.838) sediments. However, weak positive (r = 0.451) relations were established between TPH and log-transformed densities of DB in both the epipelic and benthic sediment. These indicate that although hydrocarbons contamination may have a direct negative effect on nitrogen availability in mangrove sediment, it has variable influence on the activities of nitrogen fixers. The effect on nitrogenase activity was much stronger in the “oxic” epipelic than the “hypoxic” benthic sediments. Of the 21 bacterial species isolated, only 7 – Azotobacter, Bacillus subtilis, Bacillus sp, Chromatium sp, Klebsiella sp, Moraxella sp, and Pseudomonas aeruginosa – have been implicated in nitrogen fixation. Chromatium sp, a microaerophilic nitrogen-fixing bacterium failed to utilize hydrocarbons while Bacillus megaterium, Micrococcus sp, Acetobacterium sp, Flavobacterium, Nocardia, and Alcaligenes species with no nitrogenase activity demonstrated oil-degrading capabilities. Among the free-living, facultative anaerobic nitrogen fixers encountered Bacillus subtilis, Bacillus sp, and Pseudomonas aeruginosa were prevalent, less affected, and exhibited strong ability to degrade hydrocarbons. These species of free-living nitrogen fixers are recommended for the remediation of oil-contaminated ecosystems in the Niger Delta of Nigeria.

Hydrocarbons contamination and microbial degradation in mangrove sediments of the Niger Delta region (Nigeria)

The distribution of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), and their degradability by bacteria in epipelic and benthic sediments from Qua Iboe Estuary mangrove ecosystem and associated creeks were investigated. The research findings revealed that total aliphatic hydrocarbons in sediments ranged from 16.82 mg·kg −1 to 210 mg kg −1, wheras total PAHs ranged from 6.30 to 35.55 mg·kg −1 dry weight of sediment. Low molecular mass (i.e. the 2–3-ring) PAHs were predominant in almost all the sampling points, whereas the higher molecular masses (4-, 5- and 6-ring PAHs) had the lowest concentrations. In general, the sediment samples ES 2 (39.7%), ES 3 (24.8%), BS 1 (46.7%), BS 2 (49.9%) and BS 3 (44.2%) showed<50% contributions of Σ combustion–derived PAH (COMP-PAH) concentration to the Σ PAH concentrations, whereas ES 1 (57%) contained>50% of COMP-PAHs. Our results have also shown that many mangrove bacteria have strong capacity to utilise Qua Iboe Light (QL) crude oil as the sole source of carbon and energy, while lower number of bacterial species including Bacillus sp., Micrococcus sp., Pseudomonas aeruginosa, Alcaligenes sp. and Flavobacterium sp. exhibited detectable PAHs degradability; and as such may serve as efficient degraders of QL crude oil contamination of mangrove ecosystem.

Petroleum hydrocarbons and trace metal loads in the mangrove oyster (Crassostrea rhizophorae) from the Qua Iboe Estuary and adjoining creeks in Nigeria

The mangrove oyster Crassostrea rhizophorae was harvested from clutches associated with mangroves in the Qua Iboe Estuary and adjoining creeks to determine the concentrations of total petroleum hydrocarbons (TPH) and trace metals (Fe, Ni, Pb, Cr, V, Cu and Zn) and to understand their bioaccumulation status. The mean concentrations of trace metals in C. rhizophorae were 36.06 mg·kg− 1 for Fe, 0.58 mg·kg− 1 for Ni, 0.05 mg·kg− 1 for Pb, 0.66 mg·kg− 1 for Cr, 0.32 mg·kg− 1 for V, 6.70 mg·kg− 1 for Cu and 3.93 mg·kg− 1 for Zn. The oysters demonstrated relative affinity for accumulation of Fe, Cu and Zn and the relative status of the metals accumulated, in comparison with the background trace metal load, revealed bio-concentration factors of 0.024, 0.016, 0.004, 0.213, 0.037, 0.302 and 0.036 for Fe, Ni, Pb, Cr, V, Cu and Zn, respectively. The concentrations of TPH in the oyster were highly variable and ranged between 6.37 and 8.44 mg·kg− 1 dry weight of C. rhizophorae. Although the correlation between TPH levels in intertidal (epipelic) sediment and oyster specimens was positive (r = 0.097), it was not significant (p>0.05). However, the relationship between TPH and trace metal levels in C. rhizophorae revealed well-fitting linear models that indicated that the trace metals originated from petrogenic sources. Although the levels of TPH and trace metals in the oyster were within permissible levels, they might affect calcium metabolism and the general productivity of the shellfish. The recorded levels are also indicative of long-term and chronic accumulation of hydrocarbons in the estuarine ecosystem and potential risk to human health.

Effect of Graded Doses of Heavy Metals on the Radial Growth Rate of Hyphomycetous Fungi from Mangrove Sediments of the Qua Iboe Estuary, Nigeria

ABSTRACT Toxicity and heavy metal tolerance potentials of hyphomycetous fungi from epipellic sediments of the Qua Iboe Estuary, Nigeria were investigated ex situ in laboratory microcosms. Indigenous fungi were exposed to Pb, Zn, Ni, Cu and Cr for 90 days following sediment simulation with varying concentrations of the appropriate metallic salts. Growth pattern after acclimation revealed that Aspergillus glaucus ndash; ESM7 exhibited tolerance to Cr, A. repens—ESM4 to Zn and A. niger—ESM10 to Cu. Fusarium semitectum—ESM18 tolerated Ni and Penicillium digitatum—ESM8 resisted toxicity due to Pb. However results of the toxicity assay showed that the radial growth rate of A. glaucus—ESM7 was retarded by 60 mgl−1 of Cr, while that of A. repens—ESM4 in 328 mgl−1 of Zn and Penicillium digitatum—ESM8 in 140 mgl−1 of Pb were apparently enhanced by the metals. On the other hand Ni at 241 mgl−1 was toxic and highly inhibitory to F. semitectum—ESM18 while 83 mglminus;1 of Cu significantly (Students t—test, P = 0.05) enhanced the growth of A. niger—ESM10 when compared with the control. Based on these findings A. niger may be regarded as a promising myco-remediation agent for the removal of Cu from metal contaminated environment. It is also suggestive that because of the growth enhancing effect of Zn and Pb on A. repens—ESM4 and Penicillium digitatum—ESM8 minimal concentrations of the metals may plausibly be incorporated into mycological media for quick recovery of the moulds. On the other hand because of its toxic effect on Fusarium semitectum—ESM18, Ni may be adapted as an excellent biocide component for the formulation of fungicidal preparations against plant diseases caused by fusaria provided that the acceptable background level of Ni is not exceeded. However, more detailed information is required in order to optimize the conditions for maximum utilization of these metals and hyphomycetous fungi in useful environmental and biotechnological activities.

Bioaccumulation of heavy metals by yeasts from Qua Iboe estuary mangrove sediment ecosystem, Nigeria

The effect of heavy metals (Pb, Ni and Zn) on the growth rate, number of generation, generation time and bioaccumulation potential of Saccharomyces-ESY2 andCandida-ESY13 isolated from the epipellic sediment of Qua Iboe mangrove ecosystem was evaluated. The investigation was conducted over a period of 90 days in laboratory microcosms bearing epipellic sediment simulated with 1642.00 mgkg-1of Zn, 208.00 mgkg-1 of Pb and 522.60 mgkg-1 of Ni. The growth attribute of yeasts were determined forth nightly, using the population dynamics of the inocula as an index of response to metal pollution and bioaccumulation capability. Results revealed that Ni and Zn increased the generation time of Candida-ESY13 andSaccharomyces-ESY2 respectively, resulting in a reduced number of generations and decrease in growth rate. Both yeasts exhibited a high Pb accumulating capability. However, Candida-ESY13 with a bioconcentration factor (BCF) of 0.299 accumulated more Pb (41.87 mgg-1) than Saccharomyces-ESY2 with a BCF of 0.296. These findings have demonstrated that yeasts could tolerate and detoxify metals especially Pb in mangrove ecosystem and could be adapted for the detoxification of metals-impacted environments. However, the ability of these isolates to bioaccumulate this metal raises the question of biomagnifications in the food chain within a tropical mangrove ecosystem. Key words: Heavy metals, bioaccumulation, growth rate, sediment.

Heavy metal burdens in patches of asphyxiated swamp areas within the Qua Iboe estuary mangrove ecosystem

This study examined the burden of Zn, Cu, Ni, Pb, Cr and V in patches of asphyxiated mangrove swamp areas within Qua Iboe Estuary mangrove ecosystem by sediments and surface water analysis; in order to establish natural background levels of these metals and to assess anthropogenic influences on them. The analysis shows that the mean concentrations (mg/kg, dw) of Zn, Cu, Ni, Pb, Cr and V in sediments from asphyxiated and healthy mangrove ecosystems of Qua Iboe vary from 36.3-179.4, 29.2-43.2, 3.6-37.4, 39.6-93.8, 0.15-0.53 and 2.9-9.3, with the former exhibiting higher metal accumulating potential. Although heavy metal concentrations in surface water of the asphyxiated swamp were low, their accumulative effect is significant. The concentrations of Cu and Pb in surface water of this ecosystem exceeded the water quality criteria while Ni and Cr were under the maximum concentration for drinking water quality and protection of aquatic life. The values of pollution load index (PLI), which are generally greater than unity, show that the sediments and the surface water from the asphyxiated mangrove ecosystem were polluted with heavy metals, thus suggesting anthropogenic activities as a possible source of these metals. The mean concentrations of Zn, Ni and Pb exceeded the effects range-low (ERL), indicating that there may be some ecotoxicological risk to organisms living in asphyxiated mangrove sediments.

Chromatium species: an emerging bioindicator of crude oil pollution of tidal mud flats in the Niger Delta mangrove ecosystem, Nigeria

Establishing microbiological indices for the monitoring of environmental decay by crude oil pollution in the Niger Delta region has been a major concern of our current researches. Chromatium species, a purple, Gram positive pleomorphic, motile, microaerophlic sulfur bacterium offers a good potential for use in the assessment of the short term effects of oil pollution of tidal mud flats in the Niger Delta mangrove ecosystem. Its response to the November 22, 2003 spillage at the Qua Iboe Estuary and the adjoining Cross River Estuary was investigated. Our results have revealed that the sulphur bacterium is easily identified and widely distributed in the epipellic sediment of the mangrove ecosystem but very sensitive to hydrocarbon pollution. The bacterium was readily detected in the tidal mud flats containing as much as 2.0 mg kg(-1) but not detected in sediment with THC level of 3.65 mg kg(-1) and above. It is thus, suggestive that the threshold and lethal limits of effect of hydrocarbons against the sulfur bacterium lies between 2.04 and 3.65 mg kg(-1). These imply that in any case of crude oil pollution that Chromatium is not detected during monitoring the THC levels of the sediment may have been raised to a level close to or above 3.65 mg kg(-1). Statistical analysis of the relationship between THC level and density of Chromatium in sediment revealed a significant (p < 0.05) negative relationship (r = -0.85) in Qua Iboe mangrove ecosystem as against an insignificant (p > 0.05) relationship (r = -0.41) recorded for the Cross River mangrove ecosystem which served as the control. The result indicates that oil pollution affect the homeostatic status of Chromatium in tidal mud flats despite its even distribution (R2 = 71.4%). The finding though not definitive may contribute to the hierarchical process of oil pollution assessment in the Niger Delta region of Nigeria. However, its effective utilization will require not only the development of a selective medium for enumeration and isolation of the bacterium but also the establishment of a defined dose-response relationship under controlled conditions which requires further research.

Seasonal dynamics of physicochemical properties and heavy metal burdens in Mangrove sediments and surface water of the brackish Qua Iboe Estuary, Nigeria

The physicochemical properties and concentrations of heavy metals were determined in surface water, intertidal mudflats (epipellic) and benthic sediments obtained from the mangrove swamp ecosystem of the Qua Iboe Estuary, Nigeria. The monthly concentrations of the nutritive salts revealed that the sediments are halomorphic. Heavy metal concentrations in benthic sediments and surface water were generally lower than the values recorded for the intertidal mudflats. The mean concentrations of heavy metals obtained from estuarine surface water and intertidal and subtidal sediments were highly variable and seasonally dependent. The levels of heavy metals in the intertidal sediments were comparatively higher in the wet than the dry season. The range of concentration over the months increased by 1.3% (Cr), 1.6% (Pb), 6.0% (V), 7.5% (Ni), 10.5% (Fe), 12.0% (Zn), and 15.0% (Cu). Cr, Pb, Zn, and V concentrations in intertidal and subtidal sediments were below the Sediment Quality Guidelines (SQGs). However, Cu and Ni concentrations exceeded these effect levels, indicating potential ecological effects on local benthic, pelagic and benthopelagic communities of the estuary. Linear relationships and coefficients for concentrations of heavy metals in surface water, intertidal and subtidal sediments during wet and dry seasons were calculated. Moreover, the results indicated a common anthropogenic pollution origin for the heavy metals.

Interseasonal distribution and partitioning of heavy metals in subtidal sediment of Qua Iboe Estuary and associated Creeks, Niger Delta (Nigeria)

An analysis of the distribution and chemical forms of selected metals: cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb) in subtidal sediments of Qua Iboe Estuary and adjourning creeks, collected between June 2000 and January 2001, were studied using a sequential chemical extraction method. The concentration of metals in each extracted fraction was determined using inductively coupled plasma spectrometer (ICP-AES). Pb, Cd and Cu appear to be the most abundant metal in the sediments of the systems, and are predominantly associated with the residual, organic and oxidisable phases. Results indicate that there are also insignificant components that are bound to both the exchangeable and carbonates fractions. Ni is largely associated with bioavailable phases with insignificant bound to organic matter and residual fractions. In general, an insignificant component of Cd and Pb are bound to organic matter phase. Moreover, speciation results indicate that metal contamination in the ecosystems investigated primarily comes from human-mediated sources. Thus, based on index of geoaccumulation calculated, sediments of these ecosystems have been classified as uncontaminated by Cr, Cu and Ni, strongly contaminated by Pb and extremely contaminated by Cd.

Petroleum hydrocarbons and limiting nutrients in Macura reptantia, Procambarus clarkii and benthic sediment from Qua Iboe Estuary, Nigeria

The levels of total petroleum hydrocarbons in two commonly consumed benthopelagic shellfishes, Macura reptantia and Procambarus clarkii, harvested from benthic sediment of Qua Iboe Estuary were determined using a gas chromatography with flame-ionization detector. Seventy-two (72) samples each of benthic sediment and the shellfishes were collected monthly between June 2003 and February 2004 covering the peak periods of the wet and dry seasons. Concentrations of hydrocarbons were highly variable and ranged between 5.00 and 232.00 µg/g dry weight of benthic sediment, 3.05 and 11.30 µg/g dry weight of M. reptantia, 1.62 and 9.00 µg/g dry weight of P. clarkii. Pearson’s correlation analysis of total hydrocarbon concentrations in subtidal sediments with levels in the fauna species yielded positive significant (P < 0.05) correlations in M. reptantia (r = 0.737) and P. clarkii (r = 0.924). This is indicative of a long term and chronic accumulation of hydrocarbons in the estuarine ecosystem, reflecting the potential for exposure of the resident biota and the risk to human health.