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Offshore benthic survey begins in Algoa Bay, revealing exciting images of deeper seafloor

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The ACEP marine platform’s remotely operated vehicle (ROV) has lighting and lasers for image scaling. It is operated by a pilot on board the research vessel and is capable of diving to approximately 200 metres

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The ROV is retrieved at the stern of the ACEP research vessel uKwabelana after a successful dive in Algoa Bay

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

 

Following a successful pilot study in November last year, a much needed broad-scale survey of offshore benthic habitats and epifaunal biodiversity has begun in the Agulhas ecoregion. The project is a collaborative effort between SAEON’s Egagasini and Elwandle nodes, with technical and infrastructural support through the African Coelacanth Ecosystem Programme (ACEP) marine platform.

Using ACEP’s remotely operated vehicle (ROV) to film and photograph the seafloor assemblages, the study area encompasses Algoa Bay and the adjacent continental shelf. Sampling at depths of between 40 m and at least 200 m, the project aims to provide geo-referenced data on epibenthic species occurrence, richness and abundance, as well as information about the nature of species-habitat associations and biophysical interactions occurring on the shelf.

The first field sampling, aboard the ACEP research vessel uKwabelana, took place at the end of February, and despite concerns over the influence of the ongoing red tide, visibility at the seafloor was good. The ROV, piloted by Ryan Palmer, was successful in getting excellent images and video footage from 10 stations, working down to a maximum depth of 88 m.

Remarkable diversity of epifauna

The majority of the areas sampled were typical sandy habitats, but held a remarkable diversity of epifauna. Surprisingly, several patches within these sandy areas supported an abundance of reef-associated organisms including sponges, feather stars, hydroids and soft corals, possibly due to the presence of underlying low-profile reef or highly compacted sediment.

The importance of this survey work becomes clear when these observations are viewed in the wider context. For example, recent international molecular work done in conjunction with staff at Nelson Mandela Metropolitan University (NMMU) distinguishes several new and endemic species of soft coral in Algoa Bay (see McFadden & Ofwegen 2012). Gathering these unique images and video is therefore a key step in establishing species distributions, identifying hotspots and allowing us, through long-term sampling, to track these little understood assemblages.

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Diverse assemblages of epibenthic invertebrates were observed throughout the sandy habitats examined thus far in Algoa Bay

Unusually abundant patches were seen in certain areas, including reef-associated species

 

Many thanks are due to uKwabelana’s skipper, Koos Smith and the ACEP technical co-ordinator and ROV pilot, Ryan Palmer.

Reference

  • McFadden, C.S. and Van Ofwegen, L.P. (2012). A revision of the soft coral genus, Eunephthya Verrill, 1869 (Anthozoa: Octocorallia: Nephtheidae), with a description of four new species from South Africa. Zootaxa 3485: 1–25
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