Polycyclic aromatic hydrocarbons (PAHs) and estrogenic compounds in experimental flue gas streams

The importance of combustion processes as a source of substances with estrogenic activity in the environment was investigated. Wood (nontreated and treated with wood preservatives), barbecue charcoal, meat, and kitchen waste were combusted in a laboratory-scale incinerator. Flue gas emissions (particulates and gaseous pollutants) were trapped in polyurethane foam cartridges. The cartridges were subjected to Soxhlet extraction and part of the extracts redissolved in dimethylsulfoxide (DMSO) for analyses of estrogenic activity by means of the yeast-based human estrogen receptor (hER) bioassay. A synthetic estrogen, 17-alpha-ethinylestradiol (EE2), was used as the reference estrogenic compound. Part of the extracts was analyzed for the 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs). Estrogenic compounds in the flue gas (wood) were as high as 234 +/- 25 ng m(-3) EE2 equivalent compared with 27 to 81 ng m(-3) EE2 equivalent in flue gas from combustion of barbecue charcoal. Concentrations of polycyclic aromatic hydrocarbons in both flue gas streams were in the range of 21000 +/- 2000 and 240 +/- 110 ng m(-3), respectively. In general, the concentrations of EE2 equivalent in the flue gas samples were at least a factor of 1000 lower than total PAH concentration. The EE2 levels were not related to the concentration of PAHs in any flue gas sample

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

Phenology of mangroves and its implication on forest management: a case study of Mida Creek, Kenya

Mangrove forest decline has continued despite establishment of protected areas, restoration and other conservation efforts. This is due to anthropogenic pressure, and phenological traits that together with adverse environmental factors derail natural and artificial regeneration. An understanding of phenological traits can inform planning and management of mangrove forests with benefits to restoration and increased mangrove area cover. Phenological traits of Rhizophora mucronata, Ceriops tagal, Bruguiera gymnorrhiza and Sonneratia alba, were studied in Mida Creek. Litter fall data was collected monthly on 10 m × 10 m plots from July 2010 to July 2012, oven dried, sorted into leaves, stipules, flowers and propagules, and weighed. Results obtained showed that leaf production occurred throughout the study period for all the species. Propagule fall occurred in the dry season for Ceriops tagal and Bruguiera gymnorrhiza, and during the wet season for Rhizophora mucronata and Sonneratia alba. Immature propagules accounted for 99 %, 86 % and 67 % of the cumulated propagules for R. mucronata, B. gymnorrhiza and C. tagal respectively. The longest propagule for R. mucronata was 40.5 cm. This indicates the need for nursery propagation of propagules of these species for seed availability. The findings of this study are discussed in relation to mangrove forest management

Nematodes as bio-indicators of physical disturbance of marine sediments following polychaete bait harvesting

Sediment disturbance in marine environments is caused by activities including polychaete bait harvesting, trawling, dredging, sediment erosion and treading. These activities affect the benthic communities by changing the densities, community assemblage and diversity. The aim of this study was to evaluate the potential of nematodes as indicators of sediments disturbance following polychaete bait harvesting. The study was conducted in three sites experiencing different bait harvesting intensities in Mida Creek, Kenya. Sediment samples were collected from the mudflats during low tide, preserved in 5% formalin and transported to the laboratory for processing and identification of nematodes. The highly disturbed site recorded the lowest nematode genus richness while the less disturbed sites had the highest. Overall, the most abundant nematode genera in the non-disturbed (Dabaso) and less disturbed sites (Kirepwe) were selective deposit feeders (Spirinia and Terschellingia), while most disturbed sites (e.g. Mayonda) had predators/omnivores (Pheronus, Aporcelaimellus) and selected members of the genus Spirinia. The disturbed site was characterised by low nematode diversity (H’) and low dominance (D) while the non-disturbed and less disturbed sites had higher diversity and dominance. Clearly, nematode community assemblage, diversity and feeding guilds changed following disturbance to a low diversity that favoured higher proportions of predator/omnivore taxa