Document of bibliographic reference 404440

BibliographicReference record

Type

Bibliographic resource

Type of document

Reports

BibLvlCode

MS

Title

A description of the ecosystem on and around the breakwater in Benin (Arrondissement Avlékété)

Abstract

This study has the aim to give a description of the ecosystem on and around a nearshore breakwater in Benin (Arrondissement Avlékété). The benthic and fish fauna around the submerged breakwater and a sandy reference location were investigated, respectively with Van Veen grab samples, fishnet surveys and eDNA monitoring. The fauna on the breakwater was investigated by taking scrape samples.
Taxonomic identifications of the Van Veen Grab and scrape samples revealed over 200 benthic morpho-species, including 90 at species level. The benthic infauna in the sediment around the breakwater is more diverse compared to the sandy reference location. The seaward side Van Veen samples host the highest number of taxa (60 taxa), compared to the leeward site of the breakwater (47 taxa) and the reference (28 taxa). The most dominant taxa groups are the Crustacea, Mollusca, and Polychaeta. Polychaeta are clearly dominating at the reference location, while Mollusca dominate at the seaward site. At the leeward side of the breakwater the Mollusca and Polychaeta are equally dominating. The species found on the hard substrates of the breakwater depict a different community composition compared to the benthos in the sediment. A total of 127 morpho species were identified of which 50 at species level. On the breakwater, sponges, soft corals, and oysters are the most abundant of the larger taxa. Associated with these reef-building species are a range of smaller organisms such as polychaetes, crustaceans (amphipods, tanaidaceans, isopods, crabs, and shrimps), a few brittle stars, flatworms, mollusks (bivalves and gastropods) and minor groups (sipunculid worms, pycnogonids).
Of the 50 fish species morphological recorded in the area over time (2021-2024), 22 were also detected by eDNA metabarcoding and in addition to that eDNA detected an additional 30 species. The lower comparability is due to a lack of reference sequences. The majority of the detected fish species were shared between breakwater and reference locations. Seven species were exclusively detected in leeward locations, six species were detected exclusively in seaward locations, and two species were exclusively detected in reference locations. Following the IUCN red list classification, from the species found exclusively near the breakwater, one species was near threatened, three species were vulnerable, and one species was endangered.
This study shows that the breakwater has successfully established a thriving new habitat, supporting a wide range of marine species across various taxa. By providing essential hard substrates, the breakwater has encouraged the growth of diverse reef building communities, resulting in significantly greater biodiversity compared to the reference location, which lacks such substrates. These findings highlight the ecological benefits of the breakwater as it not only fosters habitat creation but also contributes to enhancing species diversity in the area.

Bibliographic citation

Hillewaert, H.; Derijcke, S.; Dukan, N.; Geldhof, R.; Midinoudewa, H.; Sohou, Z.; Van Acker, J.; Zounon, Y.; Van Hoey, G (2024). A description of the ecosystem on and around the breakwater in Benin (Arrondissement Avlékété). ILVO Mededeling, D/2024/08. Flanders Research Institute for Agriculture, Fisheries and Food: Merelbeke. 68 pp.

Topic

Marine

Access rights

open access

Is accessible for free

true