April 26, 2024

Ozone hole brings new threat to Antarctic life

Animals and plants battling increased UV radiation exposure

A new paper released this week has brought together data on ozone depletion over Antarctica with startling findings for biodiversity.

Published today in Global Change Biology, the paper - Extended ozone depletion and reduced snow and ice cover – consequences for Antarctic biota – explores changes in the pattern of ozone levels over Antarctica and how plant and animal life may be adapting.

The paper is written by University of Wollongong (UOW) climate change biologist Distinguished Professor Sharon Robinson AM, who is Deputy Director of Securing Antarctica’s Environmental Future (SAEF), and three other members of the United Nations Environmental Effects Assessment Panel (EEAP); Associate Professor Laura Revell (University of Canterbury), Dr Roy Mackenzie (Universidad de Magallanes-CHIC and Millenium Institute BASE) and Dr Rachele Ossola (Colorado State University).

Ozone depletion over Antarctica has typically peaked in September and October when most land-based plants and animals are dormant and protected under snow cover, and marine life is protected by sea ice. Recently, ozone cover has remained depleted through to December, the start of summer, meaning Antarctic life has been more exposed to UV radiation.

“Previously, the highest ozone depletion would happen in September and October. That's very different to what's been happening for the last four years where the depletion has been extending right through to December,” Professor Robinson said.

“Once we get to December, in the Southern Hemisphere the sun is much higher in the sky and the radiation coming down to earth is higher. We’re seeing a UV index of 14 in Antarctica in December, up from pre-ozone hole levels of 6. A UV index of 14 is extreme – what we’d experience during summer in Sydney or San Diego.

“That means that Antarctica’s animals and plants are exposed to more than twice as much UV radiation as they were in the 1970s.”

The start of summer is peak breeding season for penguins and seals and extreme UV exposure comes at a vulnerable time in their lifecycle. An increase in UV radiation in early summer could be particularly damaging to young penguin chicks and seal pups who are on the ice in late spring.

Increased UV-B radiation increases risk for skin cancer and cataracts in humans but we do not know if the same is true for Antarctic mammals and birds.

The extent that Antarctic organisms are susceptible to UV damage depends on their natural defences. Birds and mammals have outer coverings of fur and feathers that reflect UV radiation or act as a barrier, whereas adult fish may have less physical protection. Macaroni and rockhopper penguins have melanin and carotenoid pigments in their irises that may protect their eyes from UV damage, while magellanic, rockhopper and king penguins produce oil droplets in their eyes that may protect their cells.

“For most organisms, increased UV exposure means they have to invest more into sun protection and repair of any damage,” Professor Robinson said.

“Plants do that by making their own sunscreen compounds. But if they're putting energy into sunscreen, they're putting less energy into growing – there is a cost to making your own sunscreens. There’s always a cost to sun protection.

“If krill are exposed to high UV radiation they tend to move down deeper into the ocean. We also know that the phytoplankton they feed on will have to make sunscreens in order to avoid damage from the UV.

“If the phytoplankton need to make sunscreens, then there may be less plankton, or they may be less palatable. This then changes the behavior of the animals that feed on them.

“The extended UV radiation may not kill things, but we know that there's a cost to creating sun protection and that takes away from the other things the animals and plants are able to do.”

Since the Montreal Protocol was established in 1987, phasing out the global use of ozone-depleting chemicals, many have assumed that the ozone layer is repaired. However, numerous factors can still delay ozone recovery, including increased incidence and intensity of wildfires, major volcanic eruptions and a range of human activities.

“The Montreal Protocol is working – the ozone is recovering. It's just taking time for all the ozone damaging compounds humans have put into the stratosphere to dissipate,” Professor Robinson said.

“The biggest thing we can do to help Antarctica is to act on climate change – reduce carbon emissions as quickly as possible so we have fewer bushfires and don't put additional pressure on ozone layer recovery.

“The best way to protect animals in the Southern Ocean is to keep global heating as low as possible so that we keep as much sea ice as possible. The best thing that we can do for the environment is to take action on climate change by reducing carbon emissions.”

This research highlights the need for a rapid transition to Net Zero, underscoring collective and individual responsibility to preserve the environment and climate for current and future generations.

UOW is committed to addressing the United Nations Sustainable Development Goals (SDGs), which provide a shared blueprint to achieve a better and more sustainable future for everyone. Antarctic research addresses SDG 13: Climate Action, SDG 14: Life Below Water and SDG 15: Life on Land.