Ocean News

Sharks Use Movement to Ease the Effects of Climate Change

Coral reefs are synonymous with stunning natural beauty and an incredible amount of biodiversity.

But sadly, corals are becoming ever more associated with the damaging effects of climate change. The milky-white skeletons of the coral left behind after a bleaching event reveals a baron wasteland depleted of its former color and life. Therefore, it is easy to understand why scientists are trying to study exactly how these ecologically and economically important habitats will be affected under future climate conditions.

One reef inhabitant, the epaulette shark, may have developed a behavioural response to help alleviate the effects of climate change, according to a team of researchers from various worldwide institutions including James Cook University, Australia and The University of Copenhagen, Denmark. The study, published in the journal Marine Biology, discovered that epaulette sharks actively sought out to control their exposure to higher temperatures on reef flats by moving towards cooler areas.

EMBED GBR coral coverBleached corals off Heron Island in the Great Barrier Reef shows the damaging effects climate change can have on entire ecosystems. Credit: The Ocean Agency / XL Catlin Seaview Survey.

Coral reef flats are often the warmest areas of the entire reef ecosystem and temperatures can fluctuate by as much as 12°C over a 24-hour period depending on the season and duration of low tide. Consequently, residents of reef flats can often be exposed to conditions that may alter temperature-dependent processes such as swimming, digestion, and reproduction. The researchers feel that understanding how the species living here adapt to extreme temperatures is essential if we are to assess their distribution and ability to survive in the future.

Using the epaulette shark as a model organism, the team sought out to investigate how the predicted end-of-century conditions of 32°C affected the shark’s growth, survival, and behaviour in comparison to the current average summer temperatures of 28°C. Individuals were placed in a chamber aquarium with a passage in between which allowed the sharks to move freely between the different temperatures. The team found that after 90 days, 33 percent of sharks kept at 28°C did not survive in comparison to 100 percent of sharks kept at a higher temperature. Furthermore, individuals that were kept at 32°C experienced a decrease in growth as they were unable to eat the amount of food necessary to meet the energy demands needed to live at higher temperatures.

When allowed to move freely between the chambers, the researchers found that the epaulette sharks preferred to live at approximately 30°C. They believe this will be an important strategy for many marine organisms if they are to offset the effects of climate change on coral reefs. Moving to cooler waters may slow down digestion and increase the number of nutrients the shark can uptake, allowing the energy demands of a challenging environment to be met.

Epaulette sharks are already known for their ability to adapt under harsh conditions. At low tide, the sharks can ‘walk’ on land in order to find deeper rock pools that are cooler and contain more oxygen. And so, the ability to swim away from elevated temperatures may just be another feather in the cap of the epaulette shark. The authors of the study concluded the paper by saying, “As conditions in coral reefs and other tropical habitats decline, the use of these behaviours may become more frequent and could ultimately lead to entire populations redistributing as species move to deeper waters or towards the poles”.

By Ellis Moloney

Gervais, C., Nay, T., Renshaw, G., Johansen, J., Steffensen, J. and Rummer, J. (2018). Too hot to handle? Using movement to alleviate effects of elevated temperatures in a benthic elasmobranch, Hemiscyllium ocellatum. Marine Biology, 165(11).

This work was supported by an Australian Research Council (ARC) Super Science Fellowship, ARC Early Career Discovery Award, and ARC Centre of Excellence for Coral Reef Studies.

ECO Magazine is a marine science publication committed to bringing scientists and professionals the latest ground-breaking research, industry news, and job opportunities from around the world.

Corporate

8502 SW Kansas Ave
Stuart, FL 34997

(772)-221-7720

Newsletter Signup

Please type your full name.

Please type your full name.

Invalid email address.

All emails include an unsubscribe link. You may opt-out at any time. Clicking subscribe confirms your acceptance of our privacy policy.