70 years of helping people to care for our ocean

Exploring Submarine Canyons and Deepwater Coral Reefs

Dr Sean Porter

The Deep Connections project recently completed its first research expedition on board the vessel Phakisa, to Sodwana Bay and Maputaland in the iSimangaliso Wetland Park World Heritage Site. This is a multidisciplinary project led by Professor Kerry Sink of the South African National Biodiversity Institute with aspects investigating coelacanth ecology, the use of environmental DNA, natural products chemicals, and pollutants. The Oceanographic Research Institute’s involvement focused on the latter, specifically organochlorine pesticides and microplastics in canyon and deep reef corals and sponges. This component will compliment shallower pollutant work already being undertaken on the coral reefs.

A remotely operated vehicle (ROV) was used to collect the samples and record what types of organisms occur in the canyons and on the deep reefs. Several coelacanths were found too, and a higher number of sponge and coral samples collected than expected for pollutant analyses. Previous work by the author has shown that the shallow coral reef organisms carry high pesticide burdens of DDT and various agricultural chemicals (https://doi.org/10.1016/j.marpolbul.2018.10.028). Therefore, the samples just collected will be used to determine how far offshore and deep these pollutants may move from the land. Furthermore, the project plans to sample deep reefs and canyons further south in KZN to get an understanding of how widespread these contaminants may be in the province. The analysis of micro-plastics is being done by measuring the concentration of pthalate esters. This is novel and will provide a more accurate way of quantifying organismal exposure to plastics as what is being measured is that which is assimilated by the organism over a period of several months rather than just the quantity of plastic pieces in the gut at any one moment in time.

The results from this work will have important implications for the management of reefs in the region. This is particularly so in view of maintaining the most resilient reef communities possible to give them the best chance to resist the impacts of climate change as much as possible. KZNs reefs are the backbone of the dive tourism and fishing industries and without them thousands of livelihoods would be lost and millions of rands worth of ecosystems services unrealised.