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SAEON Egagasini goes to the Southern Ocean

By Dr Charles von der Meden, Postdoctoral Researcher, SAEON Egagasini Node

All breaths were held at SAEON’s Egagasini Node as the first sea deployment of the SkiMonkey III benthic camera was attempted during the April-May 2013 annual Marion Island relief voyage.

The towed camera system (Sea Technology Services), which is mounted on weighted skis, is a new equipment addition for SAEON aimed at enabling non-destructive research and monitoring of deep (up to 700 metres) benthic epifauna. As part of a multi-disciplinary team comprised of scientists from the University of Cape Town (UCT), the Department of Environmental Affairs (DEA) and Rhodes University, SAEON’s Dr Charles von der Meden was aboard the SA Agulhas II to lead the camera work.

Due to daytime island logistics, the first nerve-wracking deployment of the camera was made at night. Although this first deployment resulted in the camera repeatedly landing incorrectly, adjustments made for the second deployment produced a near-perfect landing and much excitement in the small crowd gathered in the operations room.

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SAEON’s SkiMonkey III camera is deployed at the Prince Edward Islands during the April-May 2013 annual Marion Island relief voyage.

Inter-island benthic survey

With the deployment technique well in hand, work began on the long-planned inter-island benthic survey. The objective of the survey was to re-sample sites around the Prince Edward Islands (PEI) originally photographed by Professor George Branch, Dr Colin Attwood and colleagues in 1988.

Primarily, this was to investigate long-term change in benthic biodiversity around the islands. With the recent proclamation of the PEI Marine Protected Area, the survey also looked to provide an up-to-date assessment of the ecological state of the area’s benthic community; a hugely important and timely reference point for future monitoring of this sensitive region.

During a patchwork of nine days spent around the two volcanic islands (Prince Edward and Marion), the camera was towed slowly along transects, capturing around 130 still photographs at each of the 28 stations, as well as video footage. The characteristically clear water of the region made things easier, and images were gathered from depths of between 40 and 380 metres, covering substratum types ranging from sparsely populated volcanic pebble to densely covered fine mud.

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The inter-island stations surveyed at the Prince Edward Islands. Images show the four key benthic communities found around the islands during the 2013 survey.

Diversity encouraging

The photographs show an encouraging diversity of invertebrate fauna, with even the barest areas having hardy and surprisingly diverse populations including polychaetes, anemones and starfish. While preliminary observations suggest that the diversity of the inter-island region remains very similar to what was seen in the survey over two decades earlier, several stations showed striking differences.

Most apparent was a change in some previously sparsely populated communities consisting of the tubeworm (Lanice marionensis) and isolated sponges and algae, to habitats densely covered by hydroids, octocorals and sponges (see comparative photos). Of course, only detailed image processing and data analyses will tell whether these observations are significant. 

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An example of the striking differences seen in the benthic community at some of the inter-island survey stations: the sparsely populated benthos photographed in 1988 (left) and the far more densely covered substratum in 2013 (right)

With the SkiMonkey III camera having had a baptism of cold weather (and even a little snow), the Egagasini Node’s researchers are excited to see a lot more work done in waters closer to home where the camera is set to contribute to a wide range of SAEON monitoring efforts.The experience gained on this cruise is invaluable and a huge debt of thanks goes to the Department of Environmental Affairs as well as Captain Gavin Syndercombe and his excellent crew for making the voyage possible. SAEON would also like to sincerely thank the Chief Scientist, Dr Hans Veryheye (DEA) and Dr Isabelle Ansorge (UCT) for facilitating such a diverse team of scientists.

It goes without saying that a research cruise is a collaborative effort and the tireless work and assistance of Herman Engel, Dr Margaux Noyon, Keshnee Pillay, Marco Worship, Gavin Tutt, Henry Kakora and all the others on board, whose encouragement and enthusiasm kept the research team going, is gratefully acknowledged.

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