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Uncovering the secrets of the deep

By Grant van der Heever and Charles von der Meden, SAEON Egagasini Node
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In October 2016 Grant van der Heever joined SAEON’s Egagasini Node as an offshore instrument technician.

Grant jumped into the proverbial deep-end, taking up his post early in order to participate in the African Coelacanth Ecosystem Programme (ACEP) Deep Secrets research cruise alongside National Research Foundation (NRF) Innovation postdoc, Charles von der Meden.

The cruise presented an excellent opportunity for Grant to learn the operations, protocols, procedures and troubleshooting of SAEON’s benthic deep-sea camera, SkiMonkey III.

Study the first of its kind

The ACEP Deep Secrets cruise, led by Dr Kerry Sink from the South African National Biodiversity Institute (SANBI), set out to fill in gaps and shed light on the priority areas and research questions identified during the recent Marine Protected Area and Marine Spatial Planning Initiatives of Operation Phakisa’s Marine Protection and Governance Lab. The study is the first of its kind to be conducted in the Agulhas Ecoregion, and a combined effort between fifteen institutions and international collaborators including Dr Lisa Levin (Scripps Institution of Oceanography, University of California at San Diego, USA).

Broadly, the cruise aimed to improve our knowledge of marine offshore habitats, as well as to build understanding of the effects of the expanding fishing and petroleum industries on marine offshore communities.

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The benthic community off Knysna at a depth of between 105 and 137 metres. Here, three jacopever (Helicolenus dactylopterus), anemones and several soft and hard corals can be seen.

 

The Agulhas sandy outer shelf at a depth of between 500 and 536 metres. Here, four brightly coloured orange brisingids and a pumpkin urchin can be seen, with scattered assemblages of other soft corals. Notable is the tail of the rare deepsea cod, Lepidion natalensis, seemingly seeking refuge under a boulder.

Departing the morning of 26 September, the RV Algoa was met with gusting winds and heavy swells. Despite these adverse weather conditions, the team’s goals were clear. The scientists on board, from nine of the collaborating institutions, aimed to sample 48 stations in four main study areas, extending from Browns Bank to Dwesa-Cwebe in the 100-700 m depth range.

The plan was to visually sample the seabed using the Department of Environmental Affairs (DEA) and SAEON SkiMonkey towed camera systems up to 700 m, with the South African Institute for Aquatic Biodiversity (SAIAB) drop-camera system being used to scope, supplement and survey deeper than 700 m and in very rough grounds. In-situ samples were to be obtained using the cone dredge, benthic sled and/or the benthic grab.

Although operations were hampered by a number of consecutive cold fronts, most of the planned activities were completed (some reduction in replication), with the team managing to conduct research at 61 offshore stations, stretching from Robben Island on the west coast to Kei Mouth on the east coast. A total of 15 habitat types were examined, with the team uncovering a number of undocumented features, including a rocky ridge off Port Elizabeth, submarine canyons in the Amathole area and coral habitats at Browns Bank on the west coast and between Knysna and Port Elizabeth on the east coast.

Surveys

A total of 59 tow-camera surveys and 26 drop-camera surveys were conducted, yielding over 3 000 seabed images, from which approximately 34 fish species were observed from nine families. The team also managed to conduct epi-benthic sleds at 16 stations and benthic grabs at 18 stations, collecting over 550 benthic specimens that will be used for taxonomy and genetic barcoding.

Sediment samples were collected using the benthic grab for the most part, attaching the cone dredge onto the towed camera enabled sediment to be collected from the exact visual track being surveyed. Through the further attachment of a novel plankton net to the towed camera, fish larvae and invertebrate plankton from 24 stations were collected, with 287 of these fish and invertebrate samples being taken to the laboratory for stable isotope analysis.

By the end of the survey, the SAEON SkiMonkey III camera system was sampling four different components of the ecosystem simultaneously: visuals from the seabed for fauna; physical variables through the attached microCAT-CTD; sediment samples with the cone dredge; and fish larvae and invertebrate plankton from the plankton net!

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The Deep Secrets cruise team, which included scientists from the Department of Environmental Affairs (DEA), Eastern Cape Parks and Tourism Agency (ECPTA), South African Institute for Aquatic Biodiversity (SAIAB), South African National Biodiversity Institute (SANBI), South African Environmental Observation Network (SAEON) and the Scripps Institution of Oceanography in the USA.

Achievements

A number of achievements characterised this cruise, including the deepest visual biodiversity ‘dive’ in South Africa thus far, with the drop-camera system being plunged down to a depth of 1 035 m off Knysna. In addition, SAEON’s SkiMonkey III camera obtained stills and videos from a depth of 667 m, which is its deepest ‘dive’ to date.

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Grant van der Heever (L) and Charles von der Meden dismantle SAEON’s SkiMonkey camera to locate a disconnected modem.

Other highlights from the survey include the first photographs of South African deep cold-water corals, the collection of live coral specimens that will be used for taxonomic research, discovery of fish eggs and larvae nestled in octocorals and also the first known images of a number of species, including the Cape chimaera, Hydrolagus notafricana, and the King crab, Lithodes ferox.

The cruise was a resounding success despite poor sea conditions and technical difficulties. The outcomes will certainly increase our understanding of outer shelf, shelf edge and slope ecosystems along the Agulhas Ecoregion.

“Grant has shown himself to be a passionate and highly capable team member, rising to the challenge of several technical crises including a full dismantling of SAEON’s SkiMonkey camera to locate a disconnected modem,” says colleague Charles von der Meden. “The Egagasini Node team wishes him an exciting and productive time at SAEON.”

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