Climate change impacts on marine mammals

The Great Barrier Reef's mammals are most vulnerable to the impacts of climate change that alter their habitats and food sources. The dugong, dolphins and whales of the Great Barrier Reef are ecologically, economically and socially important. 

Whales

There are 15 species of whales that inhabit the Great Barrier Reef at some point through the year. Most whales migrate north during the Southern Hemisphere winter months to breed, so their time on the Great Barrier Reef is especially important to their species' survival.

Ocean acidification is expected to significantly alter marine ecosystems around the world, so the migratory patterns of whales may change as food becomes harder to find in their regular feeding habitats.

Due to their migratory nature and thus exposure to a range of sea temperatures, it is unlikely a rise in the Reef's sea temperature will impact whales.

Most whales are not present in the Great Barrier Reef during cyclone and monsoon seasons, so they are not particularly vulnerable to effects of these events caused by climate change.

Dolphins

Dolphins on the Great Barrier Reef mostly inhabit tropical waters. Therefore a rise in sea temperature may only affect dolphins by increasing their spatial range. For example, as water temperature rises across the Reef, dolphins will find more areas to their liking.

Cyclones, storms and heavy rainfall will affect dolphins in coastal areas by bringing large amounts of nutrients and sediments into the inshore regions. High concentrations of heavy metals and organic compounds have damaging effects on marine mammals.

Dugong

Sea temperatures are likely to increase dugong spatial range. As evidence suggests seagrass beds (their food source) will grow further south out of the Great Barrier Reef. It is likely dugong will be able to live in southern Australian areas also. They are tolerant of high water temperatures, so while food is available they will remain in their favoured habitats of the Reef, including Moreton Bay.

While there is the possibility of dugong strandings after a major cyclone or storm, this is not the main risk posed by extreme weather events. Floods, cyclones and heavy rainfall often destroy seagrass beds, meaning less food is available to dugong. This scenario is likely to occur more often, and across larger areas, as climate change increases the frequency of severe weather events.

The other threats to seagrass populations are rising sea level and ocean acidification. The impacts of these on seagrass will have flow-on effects for dugong populations and could result in population migration or starvation.