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Whales as indicators of ocean health
The health of whale populations can tell us much about the health of our oceans. Watch Stephanie Plon explain why South Africa is a research hotspot.
STEPHANIE PLON: My name’s Stephanie, and I’m with the African Earth Observation Network at Nelson Mandela University. And the scientists they are really interested in Earth stewardship science. My specific interest is in ocean health and the role that marine mammals, or whales and dolphins in particular, play as indicators of ocean health. South Africa is really exciting in that respect because a lot of the research we’re currently doing is very novel. We’re doing a lot of baseline research because we don’t really know what is happening in the oceans of South Africa. And yet, it’s a biodiversity hotspot so there’s a lot of different species and a lot of research to be done.
Yet, at the moment, we’re also facing a lot of changes. There are a lot of anthropogenic impacts potentially happening. We have a lot of coastal development, ports being built or expanded. And we have a lot of deep sea exploration, specifically for oil and gas. So in that context, it is really important to understand what the ocean off South Africa is like before we, as humans, go and have a potential impact on them. When I started working in Algoa Bay, there were a lot of planned developments or ongoing developments in the Bay. There was a plan for a big new deep water port. For a large marine protected area. And also, a number of fish farms in the Bay.
And yet, we didn’t have a good understanding of the distribution, both in space and time, of the whales and dolphins in that bay. So after a three year survey to really find out the distribution of these animals, one of the surprising results was that we found a large number of baleen whales with their calves. So it appeared that we had found a new nursery area. This might be a result of the recovering whale populations off South Africa. Post the ban on whaling, our humpback whale and southern right whale populations are growing, at 9% and 7% respectively. And they are re-colonizing old areas where they were previously found.
Now the question then arose that how could all this development, what kind of impact could it have on these whales? We know that whales are very sensitive to shipping noise because of the low frequency, but we knew very little about how mother whales and their babies were bonding. We don’t know if they bond by vocalisation or with some more of a physical phase that they bond initially before they go on their migrations down to the Antarctic feeding grounds. But the research question really was, what potential impact could this new deep water port have on these baleen whale mothers and their calves? And if it didn’t have a negative impact, would that potentially lead to an increased risk of ship strikes?
So we set out to really examine the soundscape of Algoa Bay with all the shipping that was going on there in comparison to the next bay to the west of Algoa Bay, St. Francis Bay, which has very little commercial shipping and some recreational boats and fishing boats, but nothing in the scale of the large port. So I’m on the beach here in Port Elizabeth, you can see Algoa Bay behind me. And the port of Port Elizabeth, to my right. And the new port development with all the ships lying in front of it, the Port of Coega, the far end of the Bay.
And the reason the research we’re doing here is so interesting at the moment is that we are now able to combine the historical aspect using the marine mammal collection at the Port Elizabeth Museum and really looking at global change over the last few decades. And combining that with the work we’re doing in Algoa Bay and in eastern cape waters on current new developments and anthropogenic impacts that result from that on the marine mammals and our waters.
So the combination of these two scenarios using material from the collection and data from the field studies, allows us to then really look at cumulative or multiple impacts on the marine mammal populations in our waters and to tease apart what is really affecting them. So some of these impacts, for example, are the changes in prey over the last few decades. Looking at stomach contents and isotopes, we can determine if there’s been a substantial change in the prey base for these animals in relation to global change. We’re also starting to look more at pollutants in conjunction with that, and parasites, and looking at the interplay of parasites and pollutants with the prey and the predator, so the dolphin.
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You’ve heard a little about the smallest and most numerous life forms in the oceans from Jon and Verity. But what about some of the most endearing (and largest) inhabitants? What can apex predators such as whales and dolphins tell us about the health of our oceans?
Stephanie Plön is a cetacean researcher based in the Africa Earth Observatory Network at Nelson Mandela University. In this video Stephanie visits the Bayworld Museum in Port Elizabeth, which is home to one of the largest marine mammal collections in the world. At least 30 different species of whales and dolphins are represented there by over 5,000 specimens. Stephanie explains why the Algoa Bay area around Port Elizabeth is so important for research and describes some recent studies which include the general ecology, diet, reproduction and taxonomy of whales and dolphins. The ocean off the coast of South Africa is recognised as a biodiversity hotspot. Every year the phenomenon of the sardine run sparks a mass feeding frenzy in Algoa Bay. In addition, the area is undergoing major changes with increasing coastal development and deep water ports being built or expanded. Parts of the deep sea are also being explored for oil and gas. One of the results of a 3 year survey to understand whale distribution in space and time through the Algoa Bay was the discovery of new nursery area for whale mothers and calves. As whale populations start to grow after the whaling ban, old areas are being recolonised but little is known about the bonding processes between mothers and their babies. Whales are sensitive to shipping noise due to low frequencies (more about that in the next step) so what potential impact could a new deep water port have on mothers and calves? It could drive them away from these nursery areas or, if the whales aren’t sufficiently undisturbed by the port activity, it could lead to an increased risk of shipstrike. Stephanie’s research uses a combination of the extensive Bayworld marine mammal collection and studies of the live whales and dolphins in the bay to establish what is normal variability in a population. In doing so, researchers are able to then study multiple and cumulative impacts such as pollutant levels, parasites and availability of prey.“From the poles to the equator, marine mammals such as seals, dolphins, and whales, play an important role in global ecosystems as apex predators, ecosystem engineers, and even organic ocean fertilisers. They occupy a diverse range of habitats, from deep sea environments to the Earth’s rivers and coastlines, and continue to astound us with their natural beauty.” Dr Jon Tennant.
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The Ocean Data Viewer also includes data about whale and dolphin distributions in 2013. This time you can choose the filter for the cetacean species that interest you most. You can choose from:- Sperm whales
- Sei whales
- Bowhead whales
- Northern Bottlenose whales
- Atlantic Spotted dolphins
- Melon-headed whales
- Hector’s dolphins
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