Jabulani Ndaba1, 2, Phumlile Cotiyane-Pondo3, 4, 5, Xolani Nabani1, Lucienne Human3, 4, Eleonora Puccinelli6, Paula Pattrick3, Francesca Porri2, 1
1Rhodes University, South Africa - 2South African Institute for Aquatic Biodiversity (SAIAB), South Africa - 3South African Environmental Observation Network (SAEON), South Africa - 4Nelson Mandela University, South Africa - 5University of Western Cape, South Africa - 6Royal Netherlands Institute for Sea Research (NIOZ), Netherlands
Microphytobenthos aggregate to form biofilm, consisting of different taxonomic groups (i.e., bacteria, diatoms and fungi) ubiquitous across aquatic ecosystems, including for instance intertidal environments. In these systems, biofilm play an important role in the biogeochemical cycling of nutrients and serve as a “middleman” for chemical cues that mediate larval recruitment of coastal fish and invertebrates into adult habitats. Diatoms, as dominant primary producers, are vital in primary productivity, carbon sequestration and food-web dynamics. Monitoring diatom successional changes in coastal eco-engineering studies becomes therefore fundamental for understanding early successional processes. Despite their ecological importance, such processes on eco-engineered substrates remain incorporated. This study aimed to assess diatom successional changes on an Indigenous knowledge-based 30 x 30 cm eco-engineered structure, termed “Imizi”, deployed at four sites along the Southeast coast of South Africa. At each site, three treatments included a control (burnt and scraped rock), flat and a seeded treatment, with the latter incorporating the addition of the native mussel Perna perna. Monthly sampling was conducted for six months. A circular area of 10 cm2 of biofilm was scraped and processed, and diatom valves were identified to the lowest possible taxon (genus/species level). Preliminary results indicated higher diatom species richness and diversity on the seeded treatments, followed by the flat and the control treatments. Dominant taxa observed were centric diatoms (i.e., Melosira and Actinocylcus), with seasonal variations influencing species diversity. The seeded treatment consistently supported higher biodiversity, likely due to the structural complexity and biological interactions facilitated by P. perna species. This finding aligns with the hypothesis that biophysical complexity (structural and biotic interactions) promotes biofilm development and successional processes in intertidal habitats. In conclusion, this study indicated the potential of the Imizi structures to promote diatom richness and support ecosystem functionality and restoration in impacted intertidal zones.
Biography
Mr Jabulani Ndaba is a PhD candidate at the South African Institute for Aquatic Biodiversity in Grahamstown, South Africa. As part of the Indigenous Marine Innovations for Sustainable Environments and Economies project, he focuses on rehabilitating impacted urban coastal habitats while integrating Indigenous Knowledge systems. His work involves designing eco-engineered prototypes that enhance ecosystem services, including primary productivity and water quality improvement and trophic dynamics.