We are 5 days into sampling environmental DNA of the Knysna seahorse (Hippocampus capensis) and I continue to be impressed by the landscapes and nature of South Africa. After sampling at the southern Eastern Cape we traveled to the Knysna estuary in the Western Cape. We not only collected water samples along our way, but also passed through a national park to get a look at some of the wildlife.
And oh my, how lovely that was. I might be a marine scientist, but seeing the impressive wildlife here is pretty amazing as well. Obviously seeing elephants, zebras, lions and all the other cool animals roaming around is awesome, but there is so much more than that. There’s all the different kinds of gazelles, the warthogs (might be a personal favourite) and the very diverse birdlife. Unfortunately there won’t be enough time this trip to really experience it all, so I will just have to come back!
The focus of the trip is still very much on the endangered Knysna seahorse. But what does it mean when we say that an animal is endangered? And why are the Knysna seahorse and the estuarine pipefish endangered?
The easiest way to explain what “Endangered” means, is that an animal or plant has a high chance of becoming extinct in the near future. This can be caused by directly killing the animals/plants, such as overfishing or hunting (think rhinos and the ivory trade), but also by more indirect threats. For example: if you cut down the rainforest, the animals that need the forest to live in will disappear as well, even if you do not kill the animal directly.
In the case of the two species we are working on, two big factors are responsible for their high extinction risk. Both the Knysna seahorse and the Estuarine pipefish only occur in a very, very small area of the world. The seahorse only lives in 3 estuaries and the pipefish in 4 estuaries in the southern tip of South Africa. They do not live in the ocean or the rivers, but only in the small area of mix salt and fresh water where the rivers go into the ocean.
The other big factor is that both species only live in a particular habitat. That is, they don’t just live anywhere in those estuaries, that would be too easy! No no, the species we study aren’t happy anywhere else than in areas where there is enough seagrass. So even though there might be a lot of space in the estuaries they live, they only live in a very small area in that space.
What this means is that small changes to the seagrass can have a very big effect on the seahorses or pipefishes. As you may or may not know, seagrass is disappearing all over the world, including South Africa. Some of the most important causes are poor water quality, coastal development, and climate change (Here is a great site for more info on threats to seagrass meadows).
For our two species, even a small, localised decrease of seagrass means they can go extinct in those estuaries where the seagrass is affected. The estuarine pipefish has in fact already disappeared from two estuaries where it used to live. This might also already have happened to the Knysna seahorse, but there is very little information about where it used to live and where it lives now, so it is hard to be certain about this.
Hopefully our work will help to protect these beautiful, but vulnerable animals. How the results of our research might help is for one of the next mini-blogs.