ABSTRACT Pelagic elasmobranchs are usually underreported in tropical coastal ecosystems, particularly in urbanized regions where long-term monitoring is lacking. This study presents six confirmed records of two pelagic species-Isurus oxyrinchus and Pteroplatytrygon violacea-documented between 1999 and 2025 near the MoNa Cagarras Hope Spot (a no-take Marine Protected Area) off the Rio de Janeiro coast, Brazil. These records combine opportunistic observations, artisanal fishery captures, and a stranding event. All three I. oxyrinchus individuals were identified as immature, whereas all P. violacea specimens were adults. Although occasional, these occurrences suggest that the area may function as a temporary refuge or foraging ground for broadly moving elasmobranchs at different life stages. Spatial proximity of the records to the Cagarras Archipelago reinforces the potential conservation value of this region, even for species not specifically targeted by local management plans. Our study highlights the importance of integrating unusual records into marine biodiversity assessments and recommends future research efforts focused on oceanographic influences, habitat use, and community-based monitoring strategies for threatened marine megafauna.
Mangroves provide coastal protection, nursery habitat, nutrient retention and long-term carbon storage, yet national-scale mangrove information remains incomplete in many Small Island Developing States (SIDS), where forests are often narrow, fragmented and difficult to resolve using medium-resolution satellite products alone. This study presents a comprehensive national mangrove atlas for mainland Mauritius, developed from island-wide ground surveys, GPS-referenced site documentation, manually digitised mangrove polygons and district-level geospatial synthesis. Mangrove coverage maps were baseline-validated using 2019 field data and Google Earth Pro imagery. Subsequent 2026 update integrated latest available remote sensing data with sporadic field-truthing visits. The atlas identifies 244.5 ha (~2.445 km²) of mangroves distributed across the seven coastal districts, with strong spatial concentration in the eastern coastal areas, namely, Riviere du Rempart and surrounding islets (~92.80 ha; ~38.0%), Flacq and surrounding islets (~60.62 ha; ~24.8%) and Grand Port (~55.73 ha; ~22.8%). Boundary sensitivity analysis produced an indicative boundary-derived area envelope of ±24.9 ha (~10.2%). Field validation confirmed that mangroves occur as estuarine stands, lagoon fringes, hypersaline or saltpan-associated patches, islet mangals and restored stands. The atlas provides a reproducible spatial baseline for environmental impact assessment, restoration prioritisation, post-disaster monitoring and future national blue carbon accounting. We show that field-validated ecological atlases remain essential scientific infrastructure for SIDS, where mangrove systems are small in area but disproportionately important for coastal resilience and climate governance. Recent mapping upgrade indicates that the mapped mangrove extent increased by ~12.81% as compared to data captured in 2019. Using stable, mature stands as a predictive proxy, the mangrove extent yields an overall screening-level estimate of approximately 21,829.3 t AGB, corresponding to ~33,617.5 t CO₂e, and ~10,234.3 t BGB, corresponding to ~15,775.2 t CO₂e. Surface sediment carbon was estimated separately at ~0.25 t organic C per tonne of surface sediment, corresponding to ~0.71 t CO₂e.
Microplastics are ubiquitous in aquatic ecosystems and raise concerns due to their persistence and potential toxicity. Given their known impacts on marine species and the use of bivalves as sentinel species for contamination monitoring, this study aimed to experimentally investigate the selectivity of the brown mussel Perna perna (Linnaeus, 1758) when exposed to the chlorophyte microalga Tetraselmis sp. F. Stein, 1878 and plastic microbeads of similar morphology and size. The study hypothesis is that when microplastics resemble natural food in shape and size, P. perna can discriminate between particles, preferentially ingesting microalgae and rejecting microplastics. Experiments included three treatments in triplicate: microalgae only (MA), polystyrene microbeads only (MB), and a 1:1 mixture of microalgae and polystyrene microbeads (MA+MB). Aliquots were collected at the beginning and end of the incubation period and quantified using an optical microscope. Clearance and ingestion rates were calculated for each replicate, and mean values were determined. Although ingestion rates did not differ significantly among treatments, the clearance rate was significantly higher in the MB treatment (627.07 mL g dw-1 h-1) than in MA (270.59 mL g dw-1 h-1) and MA+MB (518.39 mL g dw-1 h-1), suggesting increased filtering activity. Ingestion rates ranged from 6.80 x 104 to 1.22 x 105 particles g dw-1 h-1 across treatments. Mussels ingested microbeads regardless of microalgal availability, indicating no particle selectivity. Hence, the study hypothesis was not supported. Ecologically, this inability to discriminate among particles may have detrimental consequences for mussels. A similar pattern may occur in natural environments, where microplastics are present in the water column of coastal areas and interact with plankton and suspended organic particles, facilitating ingestion and subsequent contamination.
This study employed a comprehensive approach involving field sampling, grain-size analysis, physicochemical measurements, CT scanning and three-dimensional reconstruction in order to investigate the intertidal flats of the Pearl River Delta (PRD). As Perinereis is an important group of bioindicators in relation to environmental factors, sedimentological and ichnological analyses were conducted at 6 out of 63 stations. These analyses aimed to clarify the composition and distribution characteristics of Perinereis traces, reveal their response relationships with physicochemical factors including sediment grain size, salinity, turbidity and total organic carbon (TOC) content, and further illustrate their environmental significance. The results showed that: (1) Perinereis traces are predominantly composed of grazing and dwelling burrows. These burrows display diverse morphologies, including simple cylindrical, Y-shaped, U-shaped and complex branching networks. Some branches exhibit swellings at junctions. (2) Salinity has a significant influence on the burrow diameter of Perinereis, exhibiting a positive correlation in the low to moderate salinity range (0.28–3.97 PSU). Perinereis growth plateaus when salinity exceeds a threshold of approximately 18 PSU, indicating a physiological tolerance limit. (3) Burrow diameter and sediment bioturbation exhibit no significant correlations with sediment grain size, salinity, turbidity or total organic carbon content. This may be attributed to infaunal interactions (e.g. associations with Macrophthalmus japonicus) and the combined influence of multiple environmental factors. This study improves our understanding of the biology and ichnology of modern Perinereis traces. It provides a quantitative basis for interpreting the interactions between infauna and their environment in intertidal flat ecosystems.
This study investigated the growth patterns, mortality rates, and exploitation rate of the short-necked clam Paratapes undulatus (Born, 1778) in Ba Lua Archipelago, An Giang Province, Southwestern Sea of Viet Nam, using biological data. It was conducted from November 2022 to September 2023. A total of 1,140 individuals were randomly sampled from clam dredge landings for biological analysis. The length-weight relationship showed a negative allometric growth (b < 3), indicating that shell length increased proportionally faster than the body weight. The estimated von Bertalanffy Growth parameters were Loo = 53.6 mm, K = 0.91 year(-1), t(0) = -0.149, and tmax = 4.2 year and the growth performance index Phi ' = 3.417. The estimated mortality rates were Z = 3.80 year(-1), M = 1.47 year(-1), F = 2.34 year(-1). The exploitation rate (E = 0.61) indicates that the stock is currently fully exploited. These findings emphasize the need for management measures to ensure the sustainable exploitation of this commercially valuable species.
