Deep Seacrets: the outer shelf and slope ecosystems of the Eastern Cape

This project aims to develop multi-disciplinary offshore research capacity and knowledge to support improved management of poorly studied outer shelf, shelf edge and upper bathyal ecosystems of the Agulhas Ecoregion. The study area is Knysna to Port Alfred in the 200-700 m depth range, within an Ecologically and Biologically Significant Area (EBSA), a Focus Area for Offshore Protection and the Phakisa Proposed Port Elizabeth Coral Marine Protected Area (MPA). Research includes geoscience, oceanography, biodiversity, molecular research, Marine Spatial Planning (MSP), Marine Protected Area (MPA) and fisheries science.

The project is motivated by the poor state of knowledge and expanding threats in offshore habitats, the current lack of human and technical capacity to build the knowledge base to manage these threats and by the opportunities provided by ACEP IV and the Phakisa Ocean cruise in particular, to address these limitations.

Marine Spatial Planning, Marine Protected Area (MPA) establishment and offshore environmental assessment and management in South Africa are constrained by the poor state of knowledge for many ecosystem types. The situation is worse for deeper, less accessible ecosystem types, particularly those that have never been sampled. Such habitats include hard ground ecosystems such as deep reefs, cold water coral communities and submarine canyons, rare habitats such as gravel and shelf edge muds and potentially undiscovered offshore ecosystems such as chemosynthetic communities. Seep ecosystems have never been recorded in South Africa despite the existence of museum records of known seep clams on the Agulhas shelf edge. This area is within the hake trawl grounds.

This multi-disciplinary project addresses priority research questions about physical habitats, their evolutionary history, ecology, connectivity, vulnerability to impact and current state. Knowledge frontiers in geoscience, oceanography, biodiversity, taxonomy and molecular science will be advanced. The knowledge is urgently needed for application in habitat mapping and assessment, understanding potential industry impacts on biodiversity, ecosystem based fisheries management and Marine Spatial Planning including the implementation of Phakisa Proposed MPAs and the identification of further areas for protection in South Africa’s representative MPA network.

This project will advance the marine geoscience and oceanographic understanding of the Eastern Cape, research deep habitat types for the first time generating knowledge of their biodiversity and state, and improve understanding of the role of wind-driven and shelf-break upwelling driven by the Agulhas Current. The oceanography will support an understanding of connectivity of deep water ecosystems, knowledge that is important for MPA design, and will investigate how currents influence food transport for benthic communities. Priority habitats listed in the ACEP IV call that will be tackled in this project include hard grounds, specifically cold water corals, deep reefs and submarine canyons. There is a focus on the identification of potential habitat types that are not currently included in the habitat map including cold water coral reefs, lace and bamboo coral grounds (identified from museum records off Cape St Francis and Tsitsikamma), gravels and a possible cold seep. The coral component builds on the work of Sink and Samaai (2009) in mapping potential Vulnerable Marine Ecosystems. Offshore multi-disciplinary research will assess the presence, physical requirements and state of cold water coral reefs in the Agulhas ecoregion and verify the coral record that drove the selection of the Port Elizabeth Coral Phakisa Proposed Marine Protected Area. The gravel component is new with no gravels sampled in South Africa to our knowledge. Gravel habitats are very difficult to sample by grab with a high grab failure rate for this very coarse sediment. Verification of this rare habitat type is important because such habitats of limited extent tend to drive MPA planning due to their scarcity. The canyon work builds on previous research by project members on submarine canyons in KwaZulu-Natal (Sink, Roberts, Green and Samaai) but represents the very first sampling of an Agulhas canyon ecosystem.

The area between Algoa Bay and Port Alfred is considered to be a transition zone for the Agulhas Current dynamics as it flows from the northern narrow shelf area onto the wider south coast shelf, where wind-driven upwelling and alongshore coastal currents become more important. These different upwelling mechanisms are likely to have substantially different nutrient inputs, resulting in potentially different ecosystem drivers and responses, especially for species that rely on filtering food supply from the water column. This project will advance this knowledge through detailed oceanographic profiling across the region, combined with investigating phytoplankton and zooplankton communities. The composition of the nutrient rich water, and the vertical profile of the water column, will have significant influence on determining appropriate habitat for colonisation of filter-feeders. Oceanographic and geological data will be used to understand habitat requirements for cold water coral communities and to predict their occurrence.

Although early marine scientists such as John Gilchrist sampled the outer shelf and shelf edge of South Africa in the early 1900s, little in-situ sampling has taken place since this time and modern techniques have yet to be applied in this challenging deep water research area. Most deep hard ground ecosystems cannot and should not be sampled by trawling as these habitats are frequently colonized by sensitive, slow growing species such as corals and bryozoans. This project will enable the first surveys of at least 8 unsampled ecosystems. The investigation of a seep habitat could unlock very interesting and relevant further microbial research. Elsewhere in the world seep ecology has led to biotechnological discoveries.

Many of these unsampled habitats support important offshore economic activities yet the ecosystem impact of these activities has never been examined. This is all the more challenging as no offshore MPAs exist to serve as reference areas. Some are expected to be very vulnerable to physical damage from activities such as demersal trawling, petroleum exploration and mining. This research will provide data that can be used to validate and improve the ecosystem condition and threat status in the next National Biodiversity Assessment, a further Key Research Area listed in the Phakisa Ocean Cruise component of the ACEP call. This project aims to provide insight into potential impacts on cold water corals, other hard grounds and gravel habitats by exploring both trawled and untrawled areas.

Because the gaps in our knowledge of outer shelf and shelf edge ecosystems span fundamental ecology, quantitative and predictive understanding, through to ecosystem management, a multidisciplinary approach is required to meaningfully change the status quo. The proposed research will advance geological, oceanographic and ecosystem knowledge with anticipated new species discoveries, possible new ecosystem discoveries and a new understanding of geological and oceanographic dynamics to support habitat predictions. The research is needed to provide new information to support environmental impact assessment; Marine Protected Area establishment, zonation, monitoring and management. This knowledge is critical for sustainable development of the mining and petroleum sectors, sound fisheries management and access to lucrative markets through fisheries eco-certification, and optimal development of South Africa’s ocean economy.

Last updated on 30 March 2017
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