A marine collaboration gets underway in the bay

By Charles von der Meden, Anthony Bernard and Elodie Heyns, SAEON Tweet

Photo 1:  The collaborative Egagasini and Elwandle nodes team - Dr Elodie Heyns (left), Dr Charles von der Meden (right) and Dr Anthony Bernard (not in frame) - undertake a photographic survey of the benthos in Algoa Bay Photo 2:  Soft-sediment habitats in Algoa Bay often hold an impressive fauna, including seastars, brittle stars and many feathery crinoids Photo 3:  Sampling closer to the rocky reef sees increasing numbers of species associated with hard-substratum habitat

Starting this October, SAEON’s Egagasini and Elwandle nodes are collaborating on a project to survey and map the benthic biodiversity of key reef and soft-sediment habitats of Algoa Bay.

The work falls under a wider ACEP (African Coelacanth Ecosystem Programme) IV programme led by Prof. Rosemary Dorrington at Rhodes University (RU), with collaborators from RU.

Mapping benthic biodiversity

The SAEON-led portion of the project aims to provide a ‘bay-scale’ spatial description of benthic biodiversity and habitat characteristics. This spatial inventory of the benthos, and the ecological understanding gained along the way, will complement targeted taxonomic and bio-discovery components of Prof. Dorrington’s team.

The benthic survey work is done largely photographically from SAEON’s research boat Honckenii, using the Elwandle Node’s GoPro drop-camera frame and dive lights (Photo 1). The drop-camera is used to photograph a set of transects over the reefs, and large grids (100-m scale) on the soft-sediment habitats such as mud, sand and gravel.

This is time-consuming work, with the boat manoeuvring between sampling points with the drop-camera suspended off the sea-floor before being lowered to rest on the bottom to capture a sample image of the habitat of interest. Conditions in the bay are often poor in terms of visibility and surge, making sampling difficult, especially on the soft-sediment habitats where the camera has to be left in position to allow disturbed sediment to settle.

The bay was bustling with ACEP activity as both research teams found themselves on the water on the same day, with SAEON scientists Charles von der Meden (SAEON Egagasini Node), Anthony Bernard and Elodie Heyns (SAEON Elwandle Node) working off Honckenii and Shirley Parker-Nance (RU) and team undertaking delicate ROV work off R/V uKwabelana to collect reef specimens for the molecular studies.

Examining benthic habitats

Charles and the SAEON Elwandle team managed to get three days of work done in the western sector of the bay, which included acoustically mapping Evan’s reef, sampling the adjacent soft-sediment habitat and sampling two other soft-sediment locations. Sediment samples are taken at the non-reef sites to allow quantitative classification of the substratum types.

With good visibility on day one, the team got excellent photographs, highlighting the impressive presence of invertebrate assemblages in areas that are often assumed to be barren sands (Photo 2). Sampling towards Evan’s reef showed nicely the striking change to reef habitat (Photo 3).

As difficult as field sampling at sea can be, it is nearly always rewarding and the team looks forward to next year when more of these benthic habitats can be examined. Thanks go to Dr Anthony Bernard and Koos Smith who took on skippering duties, often in less than optimal conditions.