COS 79-2 - CANCELLED - Efficacy of MPA network along the Wild Coast of South Africa: Using invertebrate communities associated with Ecklonia radiata and environmental parameters as indicators

Abstract: Marine protected areas (MPAs) are tools used worldwide for safeguarding marine biodiversity. There is compelling evidence for MPA effectiveness, but their capacity to refill nearby unprotected sites still need to be studied, particularly in South Africa's southeast coast where their establishment is contested by local residents. We compared the patterns of variation in invertebrate communities associated with the holdfast of Ecklonia radiata across Nqabarha (non-MPA), Dwesa (MPA), and Cwebe (MPA). Ecklonia radiata holdfasts (n= 15) were collected from three replicate rock pools per site, at 50 meters apart. Invertebrate species richness and abundance were calculated per holdfast. Field measurements of physicochemical parameters were made. In the lab, holdfasts were dissected and cleaned on a 1 mm sieve after being measured using the water displacement method. Invertebrates that remained on the sieve were identified to the highest taxonomic resolution possible. The richness and abundance of invertebrate species were then calculated per holdfast. Principal component analysis was used to link environmental variables to variance in species richness and abundance. Data were analysed using the Permutations of Multivariate Analysis of Variance. There were 2.53 species and 27.7 individuals per holdfast. The invertebrate species abundance (F= 2.42; df = 2; p = 0.001) and richness (F=2.80; df = 2; p = 0.001) differed considerably between sites, but there was no dispersion in the community structure. On the large holdfasts, species abundance generally appeared to be declining, with most individuals living in holdfasts between 5- and 100-ml volume. The source-sink idea was supported by our findings. However, different environmental factors had different effects on holdfast-associated invertebrate communities. As a result, additional research is required to identify the key drivers of this pattern between studied sites. We recommend the prioritization of areas containing E. radiata for MPA coverage due to their capacity to accommodate various invertebrate communities. Despite using a community ecology approach, these results are comparable to other studies testing the source-sink theory on South Africa's southeast coast. More research is needed to determine the role of E. radiata holdfast in connecting populations of species with low dispersal potential across large geographical ranges.