Dolphins are recognized by their ‘smiley’ faces. They are small-toothed cetaceans, and there are 36 different species of them. Dolphins are aquatic mammals. Dolphins are found in every ocean. There are also four different species of dolphins in the Greek Sea. Most of the dolphins live in salty water, however, there are a few species that are found in freshwater, for example, the Amazon River dolphin. Dolphins feed mainly on fish and squid. Echolocation is a sonar system that bounces sound waves. Dolphins use it for communication and also for tracking their prey. With these waves, the dolphins get information like location (of the prey and other species), size, and shape.
The only enemies for dolphins are humans. Like for all marine mammals, their lives are endangered because of oil pollution, contamination by synthetic chemicals that are accumulating in their tissues, noise pollution, military drills, climate change, and accidentally getting caught in commercial fishing nets. Dolphins need to rise to the surface regularly to breathe. If they can’t do it, they drown. Warming climates and warming oceans are causing their primary food source to move deeper, where the cooler water is. Scientists have also noticed that the warmer water has a negative impact on dolphins’ reproductive rates and, therefore, their ability to survive.
Dolphins are mostly marine animals, and therefore they are affected by climate change in many ways. Firstly, the rising water temperature has forced the dolphins to look for different geographical locations to find cooler temperatures. That causes stress to them. Secondly, the rising water temperatures are causing an increase in harmful algae growth. This has led to a mass extinction of bottlenose dolphins.
Like already said, climate change is affecting dolphins’ primary food source. The Mediterranean has experienced an increase in sea surface temperature, together with salinity, upwelling intensity, and sea level. This has led to a decrease in prey abundance, which has caused a sharp decline in the Mediterranean subpopulation of short-beaked dolphins, which was declared endangered in 2003. This species is currently found only in the Alboran Sea due to its high productivity, special ecosystem, and different conditions from the rest of the Mediterranean. The other example would be the pilot whale. Between 1982 and 1983 in California, El Niño warming caused the near-bottom spawning market-squid to leave southern California. Therefore, their predator also had to leave. And there are many more examples like these.
Scientists have noticed after long research that after the heatwave in 2011, dolphins’ survival rates have decreased by 12%. In 2011, Shark Bay in Western Australia was experiencing a heat wave that raised the water temperature by more than four degrees. The area is famous for the seagrass and is important for the ecosystem. The rising temperature caused a big loss of the seagrass. Therefore, changes in the ecosystem affected all the other animals that were also living there.
Scientists still don’t know why the survival rate has decreased that much and has lasted more than six years. They bring out many different reasons for this phenomenon. For example, they think that the adults have abandoned their calves. They have also noticed that there have been more deaths among newborns, late sexual maturity, or all the previous things combined. Also, scientists noticed that female dolphins give birth less often because they don’t have enough food to feed their calves. Luckily, not all the dolphins were affected by this heatwave. Some dolphins in Shark Bay use sponges as tools to hunt. With the help of sponges, dolphins detect the location of food in deep waters.
This phenomenon really worries the scientists because, usually, when things like this happen the next year, they are back to normal. The thing that worries the scientist the most is that so far, we haven’t been able to stop the temperature from rising. This means that this kind of phenomena in the future are not phenomena’s any more, but our everyday problems.
Sources:
https://contentarchive.wwf.gr/en/endangered-species/marine-mammals/dolphin
https://www.nationalgeographic.com/animals/mammals/facts/dolphins
https://en.wikipedia.org/wiki/Dolphin
https://givingcompass.org/article/climate-change-impact-on-dolphins
https://www.futurity.org/dolphins-climate-change-2023222/
https://edition.cnn.com/2019/04/01/world/warm-oceans-kill-dolphins-scn/index.html
