The impact of climate change on dolphins

Since dolphins live in the water, they can't sweat or pant like other mammals when they're too hot. Instead, they have to send warmer blood to the periphery of their bodies-like their bellies, which is why they sometimes appear pink-and allow it to be cooled by the ocean. However, when ocean temperatures start to warm to the level of dolphins' body temperatures, dolphins can no longer cool themselves down.

In addition to these immediate effects of increased temperatures, researchers have also found that marine heat waves impact dolphin reproduction and calf survival in the long term. The survival rate for some dolphin species fell by 12% post-heatwave compared to pre-heatwave. It's theorised that this could be due to lower prey availability.

Reduction in the ocean's oxygen content

Rising temperatures also affect the level of dissolved oxygen in the ocean. There is an inverse relationship between temperature and dissolved oxygen-as temperatures increase in the ocean, dissolved oxygen levels decrease.

Since the 1960s, global oceanic oxygen content has declined by more than 2%. But in some tropical waters, the loss is as high as 40%.

Dolphins themselves do not take in dissolved oxygen-they breathe oxygen from the air when they swim to the ocean's surface. However, dolphin prey is negatively impacted by these changes, as fish take in dissolved oxygen through their gills.

As a reduction in dissolved oxygen puts stress on other marine species-impacting the abundance, quality, and distribution of prey-food chains are disrupted, and it becomes harder for dolphins to find the food they need.

Changes in ocean noise

Changes in the ocean's chemistry-such as acidification that results from increased CO2 in the ocean-can impact how sound travels through the water. Dolphins rely on sounds for communication and echolocation, which they use to hunt. As the ocean's pH decreases, it grows noisier, impacting dolphins' ability to travel, hunt, and locate each other.

Ocean noise pollution is already a major issue impacting dolphins, as boats send vibrations through the water that impede the communication channels of marine mammals. If this issue is not mitigated by changing vessel speed regulations, ocean noise will only be further exacerbated by changes in the ocean's chemistry.

Habitat loss and degradation