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

Soil Macroinvertebrate Response to Paddy Rice Farming Pathways in Mpologoma Catchment, Uganda

Agricultural practices play a major role in influencing soil fauna abundance and diversity. Interest in these practices has increased owing to the growing need for sustainable agricultural systems in this era of increasing agricultural intensification. In this study, two paddy rice farming pathways (smallholder and large-scale commercial) and an adjacent natural wetland in Mpologoma catchment were studied to determine the response of soil macroinvertebrates to paddy rice farming pathways. Eighteen macroinvertebrate taxa were observed, some of which were not the usual soil taxa (Hirudinea, Decapoda, Ephemeroptera, Trichoptera, and Odonata). SIMPER analysis showed that Oligochaeta, Gastropoda, and Coleoptera were the major taxa responsible for dissimilarity among sites. Macroinvertebrate richness and diversity also varied among sites. Some taxa showed habitat exclusivity: Diptera, Odonata, and Trichoptera were exclusive to both rice paddies; Decapoda, Chilopoda, Diplopoda, and Blattodea to natural wetland; Diplura and Ephemeroptera were exclusive to large-scale commercial paddies. NMDS ordination showed that macroinvertebrate distribution among sites was strongly correlated with soil pH and calcium and moderately correlated with phosphorus. These results indicate that wetland conversion to rice paddies could affect macroinvertebrate richness and diversity and underscore the importance of soil environment in influencing the macroinvertebrate community in rice paddies

Microplastic pollution in the surface waters of creeks along the Kenyan coast, Western Indian Ocean (WIO)

Microplastic pollution has been recognized as a global threat in marine environments and a danger to prey, predators and humans. Yet there have been limited studies in the Western Indian Ocean (WIO) and along the Kenyan coast making it difficult to estimate the extent of such pollution. This is the first study on microplastics (MPs) in the surface waters within creeks (Tudor, Port-Reitz and Mida creeks) in Kenya. Sampling was done in January/ February and September 2018 to collect microplastics from surface water. Neuston nets of 500 μm (large) and 250 μm (medium) size were towed for ten minutes and 50 litres of seawater sieved through a 20 μm net (small) in three replicates. The samples were digested in 10 % Potassium Hydroxide, sieved, and then filtered with cellulose nitrate membrane microfilters. Concentrations of total microplastics, different shapes and colours were established under a microscope. High concentrations of small size (20-250 μm) MPs were encountered and Tudor and Port Reitz had higher concentrations compared to Mida Creek. The study provides data on microplastic concentrations within the creeks and recommends focussing on small size microplastics for monitoring purposes, which due to their high concentrations can be hazardous to organisms

A review of marine invertebrates used as fishing baits and the implications for national and regional management in the Western Indian Ocean

In the Western Indian Ocean (WIO), more than 76 records from peer-reviewed and grey literature identified approximately 60 invertebrate taxa harvested for bait and food. The most diverse phyla were Mollusca, followed by Arthropoda and Annelida, with few records of Porifera, Nemertea and Echinodermata. Importance of each phylum differs according to country, with arthropods (Upogebia africana and Kraussillichirus kraussi), and annelids (Marphysa mossambica) being most important in South Africa and Kenya, respectively. Of the taxa utilised, only 42 are reliably identified to species level, suggesting that the diversity of species utilised in the region is greatly underestimated. Most of the data on biology and exploitation were for species from South Africa. Less data were available from Kenya with minimal to none being available from the remaining WIO countries. This limits the understanding of biology and trends in exploitation of most bait taxa, and consequently information required for developing national and regional management policies. Bait management guidelines are available only for South Africa, but require updating in view of changes in use of bait resources. We recommend the development of coordinated multidisciplinary, multicountry research aimed at increasing data and information to feed into policy development and support national and regional bait resource management

A decade to study deep-sea life

The United Nations Decade of Ocean Science for Sustainable Development presents an exceptional opportunity to effect positive change in ocean use. We outline what is required of the deep-sea research community to achieve these ambitious objectives