Time to fight for ocean health – Fellows’ seminar by Stephanie Plön

28 September 2020

“I don’t want to see more extinction. We need to change something. I’m not sure of the exact path but we need to change. Part of the solution is in talking to people. We need to get out of our comfort zone and start talking to change the trajectory,” said Stephanie Plön of the Bayworld Centre for Research and Education.

“The big marine mammals like whales and dolphins are the sentinels of ocean health.  Happy healthy whales equal happy healthy humans.”

“Some populations are surviving but others are not doing well. We are seeing more sick animals and more animals injured by human activities. Environmental anxiety is very real – you feel helpless if you can’t do anything.”

STIAS Visiting Scholar Stephanie Plön during her seminar on 22 September 2020.

Plön described her over 25 years of research in this area starting at the Port Elizabeth Museum in the Eastern Cape – “The waters off the Eastern Cape have a very high biodiversity with close to 40% of all whale and dolphin species found in its waters.”

“Although whales and dolphins (collectively known as cetaceans) are increasingly recognised as indicators of ocean health, they are inherently difficult to study. A combination of different aspects of cetacean biology is needed to gain a good understanding of their ecology and health status.”

Most of the research is done on specimens found in museum collections allowing access to species not readily available in the wild. The PE Museum, for example, houses the Graham Ross Marine Mammal Collection, the third-largest collection in the world – 5500 specimens representing 43 dolphin and whale species, as well as seals and sea lions, and the dugong (sea cow). These specimens are all from strandings or bycatch (unintentional net capture) and necropsies started as far back as the late 1970s.

Plön explained that bycatch in fishing gear is a huge global issue. Off South Africa, the main bycatch occurs in shark nets deployed along the KwaZulu-Natal coast after a series of fatal shark attacks in the 1950s. In the early days this accounted for the death of about 40 animals per year, but now with new management of the nets and the use of drumlines this has been reduced to about 15 animals per year.

“Obviously we don’t condone the use of shark nets but we make the most of the information from the animals who die in them in the interest of furthering science,” she said.

As an example, she described research undertaken by a student who analysed stomach contents to determine the fish species eaten. This showed that from the 1970s to 1990s, 48% of the diet was sardines, but in the 2000s this switched to mackerel – with 65%.

“This is probably due to ocean warming – sardines move deeper to cooler water and therefore become less accessible to the dolphins feeding on them.”

Cause of death

A large part of Plön’s work also deals with stranded animals, for which the cause of death is usually unknown, as opposed to the animals accidentally caught in the shark nets.

Describing much of the work as “Dolphin CSI or Crime Scene Investigation” she explained that it’s about trying to figure out why the animals had died. While the assumption is that those accidentally caught in nets are generally representative of the wild population, which is assumed to be healthy, those that strand are usually sick animals – possibly from chemical pollutants, but also caused by viruses or bacteria.

The work also provides valuable information on population genetics. Plön referred to her own research on dugongs – in which she sourced 177 samples from Western European natural history museums. Doing historical DNA allowed her to map a Western Indian Ocean lineage and to identify an isolated population off Madagascar thus adding to global data on the species.

Since 2010 international collaboration and funding has allowed more detailed systematic investigations particularly in bottlenose and humpback dolphins.

“Detailed analysis of these specimens from 2009/10 onwards provided the first systematic health assessment of dolphins caught in shark nets providing valuable information on their general biology, life history, feeding patterns, population structure and the human impact. Applying a range of research techniques assists us in determining the health of individuals and populations, both in the veterinary and ecological sense.”

The initial work focused on re-establishing basic structures for research in this global biodiversity hotspot. The international collaboration has facilitated training and research outputs at an internationally recognised level and allowed the (re)establishment of basic knowledge.

To take the work further, Plön and her collaborators formed the South African Ocean Health Network in 2019. This is a consortium of scientists from various institutions and backgrounds who are interested in elucidating baseline parameters of the health of marine mammals from south-eastern South Africa. Partnering with the Veterinary University of Hannover, Germany, they are also aiming to train a cohort of South African and German students.

Reliable baseline data will make it possible to ascertain the impact of future developments like ‘Operation Phakisa’ which is the South African government’s strategy to develop the Blue/Oceans Economy and includes increased shipping, coastal construction, oil and gas exploration, but also fishing and ocean tourism.

Blue lives matter

However, Plön emphasised that it’s critical for research evidence to feed into the global picture.

“In 2021 we will enter the UN Decade of Ocean Science for Sustainable Development,” she said. “It’s becoming clear that such initiatives have not only local and regional implications, but increasingly need to be seen in a global context of the ‘extinction crisis’ and the current state of emergency that ‘ocean health’ is in.”

“It’s time to seriously consider ocean health, and our relationship with and stewardship of the oceans,” she added.

Using a film clip, she highlighted the major role that whales play in climate change. Whales keep the fish and krill alive by fertilising the plankton which they feed off. The whales, in turn, feed off the fish and krill. More plankton thus lead to more fish and krill and thus more whales. Whale movements also move the plankton allowing it to transport carbon to the deeper ocean – removing carbon from the atmosphere.

“Restoring whale populations could play a huge role in reversing climate-change, making them a valuable economic commodity,” she explained.

“We are seeing increasing accumulation of pollutants in the oceans – plastic and chemical pollutants, but also underwater sound from seismic surveys and shipping. Whales and dolphins are increasingly recognised as acoustic creatures who use sound for communication and navigation as well as finding food and mates– and this is causing massive stress.”

“These are marine mammals at the top of the food chain,” she added. “We are losing species and need urgent action to save these populations. This is our last chance.”

“South Africans tend to identify their connection with nature to the veld. There is a lack of acknowledgement of the marine environment. We are unique with three different oceans, but we need more ownership and appreciation.”

She pointed to the urgency of scientists working across disciplines and learning to communicate better with governments, industry and the public about these issues.

“We need to stop only documenting and start actively doing something to restore ocean health. It’s vital to our survival. What goes into the ocean goes into you.”

Michelle Galloway: Part-time media officer at STIAS
Photograph: Noloyiso Mtembu

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