Quantification and characterization of microplastics ingested by mangrove oysters across West Africa.

Microplastic ingestion by marine organisms presents a challenge to both ecosystem functioning and human health. We characterized microplastic abundance, shape, size, and polymer types ingested by the West African mangrove oyster, Crassostrea tulipa (Lamarck, 1819) sampled from estuaries and lagoons from the Gambia, Sierra Leone, Ghana, Benin, and Nigeria using optical microscopy and Fourier transform infrared (FTIR) techniques. A total of 780 microplastics were isolated in the whole tissues of the 250 oysters (n = 50 oysters per country). The abundance and distribution of microplastics in the oysters followed the pattern: the Gambia > Ghana > Sierra Leone > Nigeria > Benin. The Tanbi wetlands in the Gambia recorded the highest average of 10.50 ± 6.69 per oyster while the Ouidah lagoon in Benin recorded the lowest average of 1.80 ± 1.90 per oyster. Overall, microplastic numbers varied significantly (p < 0.05) among the five countries. Microfibers, particularly those within 1001-5000 µm size, dominated the total microplastic count with a few fragments and films. No spherical microplastics were isolated in the oysters. In the Sierra Leone and Benin oysters, fragments and films were absent in the samples. Microplastic between the 1001 and 5000 µm size class dominated the counts, followed by 501-1000 µm, 101-500 µm, and 51-100 µm. Five polymer groups namely polyethylene, polyester, nylon, polypropylene, and polyamide were identified across the five countries, with polyethylene occurring in oysters from all five countries and polyester occurring in all but the oysters from Nigeria. This diversity of polymers suggests varied sources of microplastics ingested by the studied oysters. The absence of microspheres across the five supports findings from other studies that they are the least ingested and highly egested by the oysters.

Ecotoxicological and health risks associated with sediment-bound polycyclic aromatic hydrocarbons in peri-urban closed and open coastal lagoons.

Coastal urbanisation has ramifications for the sustainable development of developing nations. There are often unquantified ecological and health risks associated with urbanisation. Sixteen polycyclic aromatic hydrocarbons (PAHs) were analysed in surface sediment from three peri-urban coastal lagoons in southern Ghana. We found significant spatial variations of sediment PAHs. These variations were attributed to physiography of the lagoons and diverse anthropogenic activities surrounding them. Total PAHs ranged from 20.81 to 24,801.38 µg/kg (dry weight), underscoring a low to very high pollution level. Diagnostic ratios revealed both pyrogenic and petrogenic origins. Over 50 % of individual PAHs were of moderate ecological risk to benthic organisms, and cancer risk to humans was above the World Health Organisation's recommended safety limit (1 × 10-6). These ecological and health risks should be wake-up call for a more integrated urban planning approach to coastal urbanisation as coastal communities largely depend on natural ecosystems for food and livelihood opportunities.

Effects of coastal protection structures in controlling erosion and livelihoods.

The fiscal and social cost of ameliorating the impact of coastal erosion resulting from climate change is an increasing burden for coastal states, and in developing nations the physical interventions implemented may present a double agony - increasing debt levels and potentially obstructing livelihoods in the rural coasts. Against this background, this study was conducted to explore the impact of hard-engineered coastal protection on coastal vulnerability and community livelihoods in Ghana using a combination of Unmanned Aerial Vehicles (UAV), geographic information system tools and social survey. Shoreline change analysis by the application of the Digital Shoreline Analysis System (DSAS) with aerial photographs from 2005 to 2022 reveals an average statistical rate of change of -1 m/year in shoreline erosion of the beaches. A computation of coastal vulnerability indices for fourteen beaches, incorporating coastal protection as an additional parameter shows that from east to west, hard-engineered coastal protection structures slowed the rate of erosion, whereas unprotected beaches have highly eroded, stressing the importance of coastal protection. In consequence, coastal protection has dire livelihood-reduction implications for coastal inhabitants who are predominantly artisanal fishers. A lack of acceptable consultation with the communities exacerbates the effects from these hard-engineering interventions. The beaches of high vulnerability concerns are Dzita, Ada, Sakumono, Glefe, Apam, Anlo, and Busua. To safeguard the livelihoods of vulnerable coastal communities, we support a shift from hard engineering to more integrated and nature-based coastal management approaches on a national scale since most parts of the coast are now susceptible to erosion in contrast to what was previously observed that only the eastern part of the coast was highly vulnerable.