Influence of the Agulhas Current oceanography on the biodiversity of the Transkei Shelf

Principal Investigator: Ray Barlow

Project Abstract:
There is limited knowledge of the distribution of biodiversity on the shelf between Algoa Bay and Port Edward. Such Knowledge is not only important to assess the effectiveness of existing MPAs but is also relevant to the newly proposed expanded Phakisa MPA network. The biodiversity on this shelf must be influenced by the oceanography which is strongly dominated by the fast, warm, southward flowing Agulhas Current. The interaction of the Current with slope topography, as well as inshore boundary perturbations is thought to induce upwelling of cold, nutrient-rich water up the slope and onto the shelf. How close to the coast this water moves is unknown. These mechanisms, together with increased plankton productivity, strongly impact the pelagic and benthic environments on the slope and shelf. This project will investigate the effect of these processes on the benthic biodiversity. It is proposed to undertake a research cruise on the Transkei coast in summer to investigate the effect of current flow and associated hydrography on pelagic plankton communities and benthic biodiversity. A series of stations across the continental shelf and slope will be occupied for ADCP, hydrographic and bio-optical profiling, visual benthic biodiversity surveys, seawater sampling for various chemical and microscopic analyses, and net hauls for zooplankton and ichthyoplankton. It is envisaged that this project will (1) provide greater insight into the oceanographic environment, planktonic and benthic communities associated with the inshore shelf, slope and oceanic Agulhas Current, (2) explore cross-shelf connectivity between these domains, including potential biotic inputs into MPAs, (3) explore along-shore flow and biotic connectivity between the southern and northern limits of this under-explored but biodiversity-rich shelf region, and (4) survey the benthic habitats in three focus areas linking with existing or proposed MPAs.