Forces joined in documenting marine biodiversity in South African kelp forests

The Great African Seaforest is a unique large-scale marine ecosystem that covers about 1000 kilometres of the South African coast line. PICTURES: JANNES LANDSCHOFF

Marine researchers at Stellenbosch University (SU) have teamed up with Cape Town-based not-for-profit, Sea Change Project, to research the biodiversity of the Great African Seaforest.

A recent MoU has formalised a two-year working relationship that will support several student research projects focussing on kelp forest ecosystems in South Africa.

Kelp forests cover approximately 1000km of the South African coastline. This vast, unique marine ecosystem is highly biodiverse, however, biodiversity and ecology research in the space has dwindled since the 1970s.

Despite these forests being recognised for their intrinsic socio-ecological value, large knowledge gaps on the biodiversity they hold still exist. As all marine ecosystems are under threat from climate change and anthropogenic pressures, it is crucial to understand not only which species live where, but also their interactions with each other.

Researchers at SU are collaborating with Sea Change to fill these knowledge gaps on South African kelp forests by not only recording their biodiversity but also investigating the processes that have allowed kelp forests to become such biodiverse spaces.

Students undertaking this research are jointly co-supervised by Dr Nasreen Peer, marine biologist and lecturer at SU’s Department of Botany and Zoology, Professor Sophie von der Heyden, a marine molecular ecologist at SU’s Department of Botany and Zoology & School of Climate Studies and Dr Jannes Landschoff, marine biologist at Sea Change and Research Associate at SU’s Department of Botany and Zoology.

Dr Landschoff leads Sea Change’s 1001 Seaforest Species project which aims to document the distinctive species living in South Africa’s kelp forests, dubbed the ‘Great African Seaforest’ by the organisation. Funded by the Save Our Seas Foundation, the 1001 project balances both scientific research and storytelling.

“Together with Sea Change co-founder and filmmaker, Craig Foster, I dive the Great African Seaforest to uncover and share 1001 stories of the unique species that live there,” Dr Landschoff says.

“We combine marine biological research with the art of underwater tracking and storytelling (as seen in the Oscar-winning film My Octopus Teacher) to inspire a renewed appreciation for the wonder and fragility of this special ecosystem.”

SU is partnering with Sea Change on two projects: a taxonomic investigation of the biodiversity present in kelp holdfasts led by Peer, and a further investigation of large-scale patterns of kelp-associated biodiversity using DNA-based molecular tools led by Professor Von der Heyden.

The holdfasts of kelp are root-like structures that anchor the kelp firmly to rocks, helping them to weather turbulent conditions like the winter storms that periodically hit the Cape. Peer and Landschoff had long wondered if the network of sturdy holdfasts offered a shelter to animals, and devised student projects to study the invertebrate biodiversity of kelp holdfasts.

BSc Honours students Chaitanya Katharoyan (2022) and Jean-Pierre Joubert’s (2023) work on holdfasts has shown that these micro-habitats are teeming with life.

Dr Landschoff says that even he was shocked at the sheer number and diversity of species they found. In just one holdfast they found more than 50 different species of small crustaceans alone – that’s not even counting the array of sponges, worms and other animals that also make holdfasts their home.

“Even though we expected large numbers of species from the start, two years later, each holdfast sample still leaves us astounded at the new and wonderful things we find,” says Peer.

“It’s a testament to the life and colour, often hidden or small in size, that keeps our planet going. Without this solid partnership, our holdfast project would have been an extremely overwhelming and near-impossible task.”

Given the scale of the findings, a new cohort of students will continue this work in 2024. The holdfast project is supported by a Foundational Biodiversity Information Programme grant, through the National Research Foundation of South Africa.

Complementing the taxonomic holdfast project, Professor Von der Heyden’s students have been using DNA-based tools to provide genetic clues about species present in the kelp forest. Organisms naturally shed DNA into their environment; this ‘free DNA’ is termed environmental DNA (eDNA). By sequencing the eDNA filtered from a single sample of seawater, the team can identify entire marine communities from the genetic signatures they leave behind.

“Environmental DNA metabarcoding provides a powerful tool for detecting marine biodiversity, ranging from single-celled species to sharks,” Professor Von der Heyden explains.

“With repeated sampling we can build an entire inventory of marine life from just a few litres of water, without needing to disturb the ecosystem.”

BSc Honours student Emma Rossouw (2022) analysed the eDNA present in seawater samples from a single kelp forest site in False Bay and found more than 900 different species representing nearly 100 different taxonomic families. Current MSc student, Kira Courtaillac, is continuing this work, supported by an NRF grant held by Professor Von der Heyden.

The group plans to expand their partnership further into molecular ecology studies by building a genetic barcode library of invertebrate kelp forest species. By enabling DNA samples retrieved to be matched to sequences of known organisms in the reference library, this library will open the door to further molecular studies in the ecosystem.

“Knowing which species live where and when is crucial to designing conservation actions, which makes eDNA metabarcoding an important tool in our conservation toolbox,” Professor Von der Heyden says.

The Department of Botany and Zoology will also be rolling out a new marine biology module next year. This development will give undergraduate students an opportunity to learn about South African marine systems, including kelp forests. The module will be offered at a third-year level.

“Working with the 1001 Seaforest Species project is a unique opportunity to unite diverse skillsets that together strengthen not only our ability to research the biodiversity of kelp forests, but to communicate our findings and raise awareness of the importance of the Great African Seaforest to humanity,” says Professor Von der Heyden.

“This collaboration has been an influence and inspiration for us at Sea Change and for the 1001 Seaforest Species project. To see the passion and motivation that SU students bring to their projects has been a great experience,” says Dr Landschoff.

“I am confident that this is the start of a well-aligned, mutually beneficial research programme that will really make a difference to our understanding of South Africa’s kelp forests.”

Holdfasts of the Bamboo kelp Ecklonia maxima provide a habitat for diverse and understudied invertebrate communities.
A postgraduate student at Stellenbosch University, Chaitanya Katharoyan, is sorting through large numbers of invertebrates sampled from kelp holdfasts together with her study leader Dr Nasreen Peer and 2022 research intern of the 1001 Seaforest Species project Zara Prew.
Stellenbosch University MSc student Kira Courtaillac snorkelling in shallow waters of False Bay during eDNA sampling.