State of mangrove biodiversity assessment in Kenya and the prospect of environmental DNA in strengthening surveys

Abstract

Assessing and monitoring biodiversity in mangrove ecosystems remains challenging, with most studies relying on proxy indicators to infer biodiversity status. This limit understanding of biodiversity dynamics and constrains evidence-based mangrove management. In the Western Indian Ocean region, biodiversity assessments in mangrove forests remain scanty, with no clear information on spatiotemporal and taxonomic coverage. Addressing these gaps requires examining existing biodiversity records and exploring complementary approaches that can broaden the scope and efficiency of biodiversity monitoring. This study assessed the current state of biodiversity assessments in mangrove forests in Kenya and evaluated the feasibility of environmental DNA (eDNA) as a complementary biodiversity monitoring tool. A systematic literature review was conducted by retrieving published sources from major academic databases using defined search terms to extract and compile taxonomic information. In addition, a snapshot eDNA survey was carried out in selected mangrove forests, where sediment and water samples were collected, processed, and analyzed using established molecular and bioinformatics pipelines. The literature review identified 26 sources documenting biodiversity across 15 mangrove forest areas, with 68% of the studies concentrated in four sites representing about 6% of mangrove cover in Kenya. A total of 1,044 unique taxa belonging to 255 families were identified, with the classes Teleostei, Aves, Chromadorea, and Malacostraca accounting for 84.5% of documented taxa. The eDNA survey detected heterogeneous taxa from multiple ecosystems, including 502 taxa belonging to 305 families. Only 67 families were common to both datasets, highlighting the complementarity of literature-based inventories and eDNA detection. While eDNA showed considerable potential to expand biodiversity detection, its application is constrained by a number of factors. Integrating eDNA as a core biodiversity monitoring tool in mangroves will require combining conventional surveys with molecular tools, developing curated regional DNA reference databases, and adopting standardized analytical frameworks.