A global horizon scan of issues impacting marine and coastal biodiversity conservation

The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5–10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems

Taxon-related diversity patterns from the continental shelf to the slope: a case study on nematodes from the Western Indian Ocean

A study was carried out across the continental shelf and slope in the Western Indian Ocean along the Kenyan margin to unravel depth-related species diversity patterns portrayed by different nematode families. Sediment samples were collected along four bathymetric transects at 20, 50, 200, 500, 1000 and 2000 m. Three nematode families were selected for species analysis, based on their general occurrence with relatively high numbers and diversity from shelf to slope. All three families exhibited a distinctly different shelf and slope nematode species community. However, all three families also had a significant proportion of species that displayed a eurybathic distribution. Coincidentally, Microlaimidae, the least species-rich family had the most eurybathic species (75%) compared to Comesomatidae (39%) and Chromadoridae (32%). Total number of species per depth zone along the sampled area (gamma diversity) was three to four times the average number of species (alpha) per station. The difference was more pronounced at the slope than at the shelf. The species turnover was also higher at the slope than at the shelf stations. Each of the three families had a different diversity pattern: Comesomatidae showed a peak at mid-depth, Chromadoridae increased with depth, and Microlaimidae showed no prominent change with depth. When the three families were combined, the shelf maintained a lower diversity compared to the slope (both local and regional). There was no consistency between genus and species diversity patterns with depth, indicating that genus diversity data may not be a proxy for species diversity. At the lowest taxonomic level (species), the slope showed a higher diversity than the shelf, whereas at higher (genus) taxonomic level the diversity was comparable between the slope and the shelf. The number of species encountered increased with the number of samples analysed and did not reach asymptote, meaning that the area was still under-sampled. This situation points to the possibility of an even higher regional diversity

Presence of microplastics in benthic macroinvertebrates along the Kenyan coast

Microplastics (MPs) are plastics less than 5 mm in diameter. Their small size renders them invisible to deposit- and filter-feeding fauna, leading to unintentional ingestion. This study investigated the presence of MPs in an oyster (Saccostrea cuccullata) and three species of brachyuran crabs (Tubuca dussumieri, Cranuca inversa and Gelasimus vocans) along the Kenyan coast. Sampling was carried out at eight stations distributed between three sites: Tudor, Port Reitz and Mida creeks, in January and February 2018, during low spring tide. The sample comprised 206 crabs and 70 oysters. Samples were digested using 10% KOH at 60 °C for 24 hours and then passed through 38-µm sieves. Sieved products (<38 µm) were filtered through Whatman filter membranes (0.8 µm) and viewed under a dissecting microscope for MPs. The study identified mainly MP fibres, which were of different colours: red, yellow, black, pink, orange, purple, green, blue and colourless. Colourless fibres were the most prevalent, comprising at least 60% of the total MPs. Mean lengths of MPs fibres of different colours were between 0.1 and 4.2 mm. The mean concentration of MPs (MPs g−1 wet tissue) was 0.65 (SE 0.13) in crabs and 3.36 (SE 0.53) in oysters, and the difference between the two taxa was significant (independent two-sample t-test: t = 5.61, df = 14, p = 0.01). The higher mean concentration in oysters was attributed mainly to their filter-feeding habit. This study exposes MP pollution along the Kenyan coast and its uptake by marine fauna, and thus strengthens the case for better control ofplastic wastes in the ocean. Keywords: deposit feeders, East Africa, filter feeders, genus Uca, ingested microplastics, marine fauna, plastic pollution, Saccostrea cuccullat

Microplastics pollution in the sediments of creeks and estuaries of Kenya, western Indian Ocean

Microplastic pollution has been recognised as a global threat in marine environments and a danger to prey, predators and humans. Yet, there have been few studies in the western Indian Ocean, specifically along the Kenyan coast, which makes it difficult to estimate the extent of such pollution in the region. This is the first study on microplastics (MPs) in the sediments within creeks and estuaries (Tudor, Port Reitz and Mida creeks) on the Kenyan coast. In January/February and September 2018 sediment samples were collected for MPs analysis. The concentration of MPs differed between the sampling seasons and was distinctively higher in the second sampling season across particle sizes, suggesting that there were more MPs from larger terrestrial discharges due to increased runoff. The concentrations of total MPs, and the occurrence of different sizes, shapes and colours, were established under a microscope. The overall mean concentration was highest for the large size category of MPs (500–4 999 μm) at 9.1 (SE 0.8) particlescm−2, with Tudor Creek being more polluted with MPs than Port Reitz and Mida creeks. We recommend formulation of policies on proper plastic waste management and disposal to protect nearshore ecosystems which are rich in marine biodiversity