Using benthic macroinvertebrates as bioindicators to evaluate the impact of anthropogenic stressors on water quality and sediment properties of a West African lagoon

A systematic review on distribution, sources and impacts of heavy metals in mangrove ecosystems

Mangrove ecosystems play a vital role in providing habitat for numerous plant and animal species, protecting coastlines from erosion and storm damage, and supporting coastal communities with natural resources. Several studies have been conducted on heavy metals due to advancements in technology, which have improved the accuracy in detecting, identifying, and quantifying the metals. However, our understanding on the distribution, sources, and impacts of heavy metals on mangrove ecosystem health and productivity is currently scattered and unorganized. This review aims to bridge knowledge gaps, inform conservation strategies, and promote interdisciplinary collaboration by synthesizing ecological, socio-economic, and policy-related insights. We reviewed 139 publications from 2003 to 2024 across 20 countries, sourced from four databases (Scopus, Web of Science, PubMed, and EBSCO) and one search engine (Google Scholar). The results revealed a rapid increase in publications on this topic globally, particularly during the period between 2010 and 2023. China (29%) and India (22%) emerged as the leading contributors to research on mangrove heavy metal contamination. The most frequently studied heavy metals were Cadmium followed by Lead, Copper, Zinc and Chromium. The major sources of heavy metals contamination in mangrove ecosystems were industrial effluents (36 %) and rapid land-use conversion (31 %) and sediments (51 %) were the most commonly investigated component of mangrove ecosystem. Heavy metals have negative effects on human health (44 %) and reduce mangroves growth and development (25 %). Future studies should prioritize investigating the interactions among heavy metals contamination, and mangrove productivity and health, as well as the resilience of associated species over time.

Assessment of ecological health using benthic macroinvertebrates and physico-chemical parameters in Gilgel Abay River, Ethiopia

Biomonitoring is currently given due attention as it appropriately reflects the health of aquatic ecosystems. There is little research on the Gilgel Abay River to assess its ecological status using biological organisms. The aim of this study was to assess the ecological health of the Gilgel Abay River using benthic macroinvertebrates and physico-chemical parameters. Five sampling sites were selected based on major stressors and accessibility of the sites for sampling. In situ physico-chemical parameters measurement and nutrient analyses were conducted in 2023. Benthic macroinvertebrate samples were collected following a multi-habitat sampling approach and identified to the family level except Chironomidae were species level. Highest concentrations of NO3- (4.25 mg/L) and TSS (0.065 mg/L) were recorded at the Telifa site, while lowest levels of NO3- (1.23 mg/L) and NO2- (0.008 mg/L) and highest concentration of dissolved oxygen (7.74 mg/L) were recorded at the slightly impacted site. Absence of pollution intolerant taxa, fewer numbers of tolerant taxa and collector-gatherer functional feeding groups are evident of the impacted sites. While sensitive to modestly tolerant taxa and scrapers functional feeding groups were frequently encountered in upstream sites. According to ETHbios; 2 (S1, S2) sites were classified as slight ecological disturbance, 3 (S3, S4, S5) as significant ecological degradation. Redundancy analysis indicated that pH, DO, CD, NO3-, NO2-, and TSS significantly impacted the distribution of macroinvertebrates. This finding highlights the ecological degradation of the Gilgel Abay River, underscoring the need for watershed conservation and stabilization of riverbanks with active participation of local communities to safeguard the river's health.

Multidimensional aspects of riverine biodiversity can vary in response to nutrient pollution and environmental dynamics across climatic watersheds

The concurrent impact of anthropogenic and bioclimatic factors on biodiversity is a key focus in macroecological and biogeographical considerations in conservation programs within riverine ecosystems. However, there is still a lack of understanding about how multidimensional alpha and beta diversity measures respond to anthropogenic and bioclimatic drivers. Here, we assess the variations in taxonomic, phylogenetic, and functional alpha and beta diversity of riverine macroinvertebrate communities across different watersheds in China. Our results show significant declines in most facets of alpha diversity across watersheds with low environmental heterogeneity, reflecting the loss of species with unique traits and evolutionary legacies. Both functional and phylogenetic beta-diversity values reveal a decreasing pattern along low heterogeneity environments, whereas taxonomic beta-diversity shows a contrasting pattern, which highlights the influence of microhabitat variation. Moreover, our findings identify nutrient levels, organic matter, water quality indicators, climatic variation, and geographic and habitat characteristics as key determinants of diversity patterns that are indicative of broader water pollution challenges. These factors jointly influence functional and phylogenetic alpha diversity and contribute to spatial homogenization, which is reflected in decreased functional and phylogenetic beta diversity. These trends highlight the complex interactions of chemical and physical factors in shaping biodiversity characteristics across watersheds. Based on the null model, macroinvertebrate communities primarily show random patterns, whereas clustering and overdispersion were sporadically observed in specific communities. We propose that conservation and restoration efforts should be aimed at enhancing aquatic biomes by managing extreme environmental conditions and amplifying spatial spillover, thereby supporting the intrinsic dynamics within natural metasystems and thus preserving the multidimensional aspects of biodiversity.

Habitat sensitivity in the West African coastal area: inferences and implications for regional adaptations to climate change and ocean acidification

This study focuses on assessing coastal vulnerability and habitat sensitivity along the West African coast by delineating hotspots based on surface temperature, pH, chlorophyll-a, particulate organic carbon, and carbonate concentrations between 2018 and 2023 depending on data availability. Initial exploration of these variables revealed two distinct focal points i.e., the Togo-Nigerian coastal stretch and the stretch from Sierra Leone to Mauritania. Lower pH trends (acidification) in surface waters were observed off the West African coast, particularly in areas around the south-south Niger Delta in Nigeria and the coastal regions of Guinea and Guinea Bissau. Sea surface temperature analysis revealed highest temperatures (27-30°C) within Nigeria to Guinea coastal stretch, intermediate temperatures (24-27°C) within the Guinea Bissau and Senegal coastal stretch, and the lowest temperatures off the coast of Mauritania. Furthermore, correlation analysis between sea surface temperature and calcite concentration in the Mauritania-Senegal hotspot, as well as between overland runoff and particulate organic carbon in the Togo-Nigeria hotspot, revealed strong positive associations (r>0.60) and considerable predictive variability (R2 ≈ 0.40). From the habitat sensitivity analysis, certain regions, including Cape Verde, Côte d'Ivoire, Nigeria, Senegal, and Sierra Leone, exhibited high sensitivity due to environmental challenges and strong human dependence on coastal resources. Conversely, Gambia, Guinea, Guinea-Bissau, Liberia, and Togo displayed lower sensitivity, influenced by geographical-related factors (e.g. coastal layout, topography, etc.) and current levels of economic development (relatively lower industrialization levels). Regional pH variations in West African coastal waters have profound implications for ecosystems, fisheries, and communities. Addressing these challenges requires collaborative regional policies to safeguard shared marine resources. These findings underscore the link between ecosystem health, socioeconomics, and the need for integrated coastal management and ongoing research to support effective conservation.