Asian Journal of Environment & Ecology

Shellfish as Bio-indicators of Petroleum-related Pollution in a Tropical Oil-producing Estuarine Ecosystem of the Niger Delta, Nigeria

Christian Livingstone Otiasah, Ohanuna, Chukwudi, Sampson, Adonis Perron — Sat, 03 Oct 2026 00:00:00 +0000

Petroleum-producing estuaries of the Niger Delta support shellfish harvesting while receiving complex, spatially variable mixtures of hydrocarbons and other contaminants. Shellfish can integrate biologically accessible exposure, but their interpretation is complicated by differences in habitat, taxonomy, physiology and analytical practice. This critical narrative review evaluates the conditions under which shellfish provide reliable evidence of petroleum-related contamination, biological effects and potential dietary exposure. Search-engine-assisted scholarly retrieval, bibliographic verification and thematic appraisal covered literature published from 2000 to 30 July 2026, with emphasis on regional field investigations and experimentally supported mechanisms. The evidence supports sediment-associated periwinkles and locally verified mangrove oysters as complementary sentinel candidates, rather than interchangeable monitors. Niger Delta studies demonstrate hydrocarbon and metal occurrence, heterogeneous tissue burdens and biological disturbance, but frequently provide weaker evidence for source-specific attribution, causal injury or population-level consequences. Apparent disagreements among seafood risk assessments arise partly from different analyte panels, tissue-weight bases, consumption assumptions, treatment of non-detects and interpretation of screening values. Petroleum hydrocarbon totals, individual biochemical responses and tissue-to-sediment ratios cannot independently establish ecological impairment or consumer safety. Recent molecular and rapid-screening approaches improve investigative capacity, although local calibration and independent validation remain necessary. An integrated monitoring framework is proposed that combines taxonomically verified organisms, paired environmental chemistry, exposure and effect measurements, seasonally matched comparisons, and separately conducted dietary assessments. Its central requirement is to preserve distinctions between contaminant detection, source attribution, biological injury, ecological recovery and human exposure. Immediate priorities are harmonised regional sampling, reproducible analytical quality assurance, experimentally validated biomarker panels and transparent reassessment of published risk calculations. Shellfish are defensible bio-indicators when embedded within this chain of evidence; they are not self-sufficient forensic tools or substitutes for representative food-safety surveillance.

Coastal Groundwater Sustainability in Keralam, India: A Critical Review of GIS-and Remote Sensing-based Seawater Intrusion Vulnerability Assessment

Arjun Ram Gopi, Pottepaka Shravan, Rachcha Arun — Tue, 06 Oct 2026 00:00:00 +0000

Keralam's 590-kilometre coastline hosts nine of the state's fourteen districts, an exceptionally dense coastal population, and a hydrogeologically distinctive combination of narrow lateritic and alluvial coastal aquifers, an extensive 1,500-kilometre backwater and estuarine network centred on the Vembanad, Ashtamudi and Kallada systems, and intense monsoon-driven recharge that alternates seasonally with acute groundwater stress. This critical review synthesises evidence from studies published predominantly between 2018 and 2026 in peer-reviewed and indexed journals to assess how Geographic Information Systems (GIS), satellite remote sensing, and parametric vulnerability indices, principally GALDIT and DRASTIC together with locally modified variants such as GALDIT-U, have been applied to characterise seawater intrusion (SWI) risk across Keralam's coastal aquifers. The review finds that district-level research coverage is markedly uneven: Ernakulam, Kozhikode and, more recently, Thiruvananthapuram have been investigated using different combinations of vulnerability indexing, hydrochemical analysis, electrical resistivity and numerical modelling, while Kollam, Thrissur, Kannur and Kasaragod remain comparatively underexamined despite documented salinity problems. Keralam's laterite-dominated hydrogeology and strong monsoonal recharge generally suppress GALDIT-index vulnerability relative to deltaic coasts elsewhere in India, but urbanisation, backwater proximity, groundwater over-extraction and coastal erosion produce sharply localised high-vulnerability pockets, particularly around Kochi, Kozhikode and Thiruvananthapuram's urban and harbour fringes. Sea-level-rise projections under RCP4.5 and RCP8.5 scenarios have also been incorporated into groundwater and seawater-intrusion modelling, while explainable machine learning and Monte Carlo uncertainty frameworks are only beginning to be applied within the state. The review concludes by identifying priority gaps: uneven district-level and seasonal monitoring coverage, limited hydrochemical or geophysical validation of GIS-based vulnerability maps, minimal integration of dynamic land-use changes into index parameterisation, and an absence of state-wide, standardised comparative assessment across Keralam's full coastal gradient.

Mitigating the Ecological Consequences of Urban Renewal for Floral and Faunal Diversity in Nigeria: A Critical Narrative Review

Wed, 07 Oct 2026 00:00:00 +0000

Nigerian cities are being remade through slum clearance, road and waterfront redevelopment, land reclamation and master-planned expansion, yet the ecological consequences of these renewal processes for plants and animals have rarely been examined as a coherent body of evidence. This critical narrative review synthesises and appraises literature on how urban renewal and associated redevelopment affect floral and faunal diversity in Nigeria and evaluates the strategies available to mitigate those effects. Peer-reviewed studies, together with essential institutional documents, were identified through structured keyword and Boolean searches of multidisciplinary scholarly indexes, supplemented by backward and forward citation tracing, and were appraised for design, scale, measurement validity and transferability. The evidence consistently shows that redevelopment and expansion in Lagos, Abuja, Ibadan and other cities have converted vegetated land, mangroves, swamps and floodplains into built surfaces, fragmented remaining green space and intensified urban heat. Field studies of birds, trees, amphibians and stream invertebrates indicate that urban sites generally lose species richness, particularly among forest-dependent and specialist taxa, while functional diversity and total abundance may be partly maintained by tolerant generalists. Vegetation structure, native tree cover and reduced human disturbance emerge as the most consistent local correlates of faunal diversity. Confidence in causal attribution to renewal specifically remains limited, because most studies are cross-sectional, rely on land-cover proxies rather than species data, concentrate on birds and trees, and rarely measure outcomes before and after identifiable renewal projects. Evidence on mitigation is largely transferred from other regions; avoidance of wetland and large-tree loss, native-dominated planting, connectivity planning and integrated impact assessment are the best-supported options, whereas offsetting and ornamental greening remain weakly evidenced in the Nigerian context. Governance failures, fragmented environmental assessment and displacement-driven renewal constrain implementation and raise equity concerns. Mitigating the ecological costs of renewal in Nigeria will depend less on novel techniques than on enforcing avoidance, embedding biodiversity baselines into project approval and generating longitudinal, multi-taxon evidence from Nigerian cities.

Impacts of Crop Residue Burning on Ambient Particulate Matter and Soil Properties: A Case Study from Chandrakona, West Bengal, India

Sukla Nandi, Partha Roy Chowdhury — Sat, 03 Oct 2026 00:00:00 +0000

Crop residue burning (CRB) is widely used for rapid field clearing after harvest and can produce short-term particulate pollution as well as changes in soil properties. This study examined these effects in Chandrakona-II, Paschim Medinipur, West Bengal, using two complementary datasets. A portable, auto-calibrated, laser-scattering particle monitor was used to record location-specific PM2.5 and PM10 concentrations during field-burning events in December 2025. Hourly PM2.5 and PM10 observations from the Chandrakona Continuous Ambient Air Quality Monitoring Station (CAAQMS), operated by the West Bengal Pollution Control Board (WBPCB), were also analysed for the November–January post-monsoon periods of 2024–2025 and 2025–2026. Daily and monthly means were calculated. In addition, paired soil samples collected before and after burning at four locations were analysed for pH, electrical conductivity (EC), organic carbon (OC), available N, P and K, and selected micronutrients. During a representative burning event, PM2.5 increased from about 25–30 to approximately 1000 µg/m³, while PM10 increased from about 40 to nearly 400 µg/m³. Elevated concentrations persisted after burning. CAAQMS records showed that daily and monthly particulate concentrations remained above the WHO 24-h guidelines and the Indian NAAQS during the study periods, with the highest monthly means recorded in December 2025. All four paired soil sites showed lower OC and available N, P and K after burning, together with declines in the measured micronutrients. The findings provide a local baseline for Chandrakona and support residue-management approaches that avoid open-field burning.

Fish Species Composition, Diversity and Community Structure of Ibikpe Creek, a Tropical Freshwater System in the Niger Delta, Nigeria

IdopiseAbasi E. Asuquo, Gwendoline I. Asuquo — Fri, 09 Oct 2026 00:00:00 +0000

The ichthyofauna of Ibikpe Creek, a previously unsurveyed tropical freshwater system in Uruan Local Government Area, Akwa Ibom State, Niger Delta, Nigeria, was investigated monthly from June to December 2025 at three sampling stations. Sampling was conducted using unbaited gill nets (mesh sizes of 25–75 mm and approximately 30 m in length) set overnight at vegetated marginal zones by experienced local artisanal fishers. Specimens were identified using regional keys (Idodo-Umeh, 2003; Olaosebikan & Raji, 1998). A total of 60 fish specimens belonging to 16 species, 13 genera and 7 families were recorded. Cichlidae was the most speciose family (8 species; 26 specimens, 43.5% of total abundance), followed by Alestidae (3 species; 6.5%); Anabantidae, Notopteridae, Polypteridae, Cyprinidae and Hepsetidae were each represented by a single species. Ctenopoma kingsleyae was the single most abundant species (20 specimens; 33.3% frequency of occurrence), while seven species were each represented by a single specimen (1.7%). Monthly abundance was highest in July and August (12 specimens each) and lowest in November and December (5 each); the four highest-abundance months fell within or immediately adjacent to the wet season. Species diversity, the Shannon-Wiener index and Margalef’s richness index were highest in June (7 species; H′ = 1.846; d = 2.502). These findings provide the first documented species checklist and community-structure baseline for Ibikpe Creek, indicating a species-poor, wet-season-favoured assemblage dominated numerically by a single air-breathing anabantid, and establish a reference point for future monitoring and conservation planning.

Assessment of Life Forms and Biological Spectrum of a Grassland Community of Baripada, Odisha, India

Ananta Kumar Nayak, Kamal L. Barik — Sat, 10 Oct 2026 00:00:00 +0000

Aims: To assess the life forms and biological spectrum of a grassland community at Baripada, Mayurbhanj, Odisha, and compare the observed spectrum with Raunkiaer’s normal spectrum and selected grassland communities.

Study Design: A field-based ecological assessment using floristic identification, herbarium preparation, and life-form classification. Place and Duration of Study: Maharaja Purna Chandra Autonomous College, Takhatpur, Baripada, Mayurbhanj, Odisha, India, from July 2022 to July 2023.

Methodology: Plant specimens were collected and identified using regional floras. Herbarium specimens were prepared following standard field and herbarium procedures, and the recorded species were classified according to Raunkiaer’s life-form system as modified by Dansereau and Rao. Soil characteristics and meteorological conditions during the study period were also documented to describe the environmental context of the grassland.

Results: Thirty-six species were recorded, comprising 8 chamaephytes (22.22%), 11 hemicryptophytes (30.56%), 2 cryptophytes/geophytes (5.55%), and 15 therophytes (41.67%). Phanerophytes were absent. Relative to Raunkiaer’s normal spectrum, therophytes, chamaephytes, and hemicryptophytes showed higher representation, whereas cryptophytes showed slightly lower representation.

Conclusion: The observed biological spectrum indicates a distinctive life-form composition at the Baripada grassland. The pattern may be associated with local species composition, soil characteristics, climatic conditions, topography, and biotic interference. The findings provide baseline information for future ecological assessment and comparative evaluation of grassland vegetation in the region.

Assessing Illegal Hunting Activities in and Around Deng-Deng National Park, East Region of Cameroon

Sat, 10 Oct 2026 00:00:00 +0000

Protected areas in Central Africa face sustained hunting pressure that can affect wildlife populations, local livelihoods, and the functioning of forest ecosystems. This study assessed hunting practices and bushmeat distribution networks in and around Deng-Deng National Park (DDNP), Cameroon, using interviews with 146 respondents from 20 villages, conservation-service records, and spatial observations collected primarily during February-July 2023. Respondents reported subsistence and commercial hunting, with trapping included in 120 of 146 technique profiles (82.19%); firearm use and hunting with dogs were also reported. Survey-derived annualised harvest projections indicated that blue duiker, African brush-tailed porcupine, and bay duiker were among the most frequently reported taxa. Woutchaba ZIC was identified by respondents as the largest reported bushmeat supply basin, while road, rail, and water routes supported movement towards regional markets. Patrol records showed marked differences in several indicators between 2022 and 2023; however, because comparable patrol-effort and detectability metrics were not available, these differences are interpreted descriptively rather than as direct evidence of temporal change in underlying poaching intensity. The findings support strengthened effort-standardised monitoring, targeted protection of access corridors and hunting hotspots, participatory management, and livelihood alternatives that reduce dependence on illegal wildlife harvest.

Waterbirds as Wetland Sentinels: Assessing Avian Diversity in Relation to Soil and Water Quality in the Kole Wetlands

Anamika Babu, P. O. Nameer, M. Vishnu Sreejith, Malik Fasil Madala, M. Shaji — Wed, 14 Oct 2026 00:00:00 +0000

The Kole wetlands of Thrissur, Kerala, support resident and migratory waterbirds within a seasonally flooded agricultural landscape. This study examined associations between waterbird assemblages and soil and water conditions at five sites: Palakkal, Pullu, Pullazhi, Adat and Puzhakal. Field surveys conducted from August 2025 to March 2026 documented bird abundance, species richness, diversity and feeding-guild composition. Water and soil samples were analysed for selected physicochemical characteristics, and water and soil quality indices were assessed alongside canonical correspondence analysis (CCA). Water quality differed among sites, with Adat showing the most favourable index category and Pullazhi the least favourable. Soil quality was classified as good at Palakkal, medium at Pullu and poor at Pullazhi, Adat and Puzhakal. Pullazhi had elevated turbidity (19.8 NTU) and the lowest recorded dissolved oxygen concentration (2.4 mg/L), accompanied by large congregations of Glossy Ibis and Little Egret. Puzhakal had strongly acidic soil (pH 3.75) and relatively low organic matter (7.94%), alongside reduced avian community evenness. CCA indicated associations between piscivores and dissolved oxygen; insectivores and omnivores and soil moisture and organic matter; and carnivores and more acidic soil conditions. These findings suggest that waterbird assemblages reflect local gradients in soil and water quality. Integrated assessment of avian communities and physicochemical conditions may therefore inform site-specific wetland monitoring and management.

Groundwater Quality Assessment of Eket Local Government Area, Akwa Ibom State, Nigeria: Physicochemical Profiling, WHO-Referenced Suitability, and a Multivariate Assessment of Saline Intrusion and Petroleum Related Impact

Fri, 16 Oct 2026 00:00:00 +0000

Groundwater is the primary domestic water source for communities in Eket Local Government Area (LGA), a coastal, oil-producing area of Akwa Ibom State located along the Qua Iboe River estuary near the Atlantic Ocean. This study assessed the quality and drinking-water suitability of groundwater from eight hand-dug wells and boreholes across Eket LGA using physicochemical profiling of pH, electrical conductivity (EC), total dissolved solids (TDS), oxidation-reduction potential (ORP), salinity, iron (Fe), sodium (Na), potassium (K), total hardness, and total alkalinity. Drinking-water suitability was evaluated against World Health Organization (WHO) guideline values and quantified using the Weighted Arithmetic Water Quality Index. A complementary Integrated-Weight Water Quality Index (IWQI), based on entropy-derived weights, was combined with Pearson correlation analysis, Ward’s hierarchical cluster analysis, one-way ANOVA, great-circle distance analysis, and Moran’s I spatial autocorrelation analysis to distinguish localised saline intrusion from broader groundwater-quality problems. Statistical analyses were performed in Python using pandas and SciPy. The results show that groundwater across the LGA is predominantly acidic (pH 4.0–6.6; seven of the eight sites below the WHO lower limit of 6.5) and iron-enriched (0.89–1.26 mg/L; all eight sites above the 0.3 mg/L guideline). Weighted Arithmetic WQI values ranged from 291 to 412, classifying all sampled sources as “very poor” to “unsuitable for drinking” without treatment. EC, TDS, and salinity were nearly perfectly intercorrelated (r = 1.00) and varied by more than an order of magnitude across sites (20–258 µS/cm). Cluster analysis separated a high-conductivity/high-salinity group (E3, E5, and E8) from a lower-conductivity group, with ANOVA confirming significant differences for EC, TDS, and salinity (p = 0.001), but not for pH, iron, hardness, or alkalinity. Spatial analysis showed that the saline-influenced sites were geographically closely clustered (mean separation 1.21 km, compared with 5.36 km among the remaining sites), indicating a localised intrusion hotspot rather than a uniform LGA-wide gradient; however, Moran’s I tests did not show statistically significant LGA-wide spatial autocorrelation at the current sample size (n = 8). Overall, the findings indicate a localised saline-intrusion signature superimposed on a broader acidity and iron problem. Groundwater across Eket LGA therefore requires treatment, including pH correction and iron removal at minimum, before consumption; sources nearer the estuarine and coastal fringe also require additional safeguards against saline intrusion.