A new international study, led by researchers at the University of Copenhagen, suggests that rising ocean temperatures may directly interfere with the microscopic cilia that corals use to circulate oxygen-rich water across their surfaces. The findings add a new layer to scientific understanding of why corals become stressed and die during marine heatwaves.

A growing body of research, including a recent study, points to an unexpected vulnerability: Some of the ocean’s fastest and most capable predators may be at risk of overheating as the seas warm.

Built for speed

Unlike most fish, species such as the great white shark, basking shark and Atlantic bluefin tuna are mesothermic. That means that their bodies run warmer than the surrounding water, due to specialised adaptations that trap metabolic heat.

US President Donald Trump has rescinded a series of federal environmental protections, including reversing the long-standing “endangerment finding” that classified greenhouse gas emissions as harmful to public health. The decision has been widely reported as one of the most consequential climate policy reversals in recent years. Environmental organisations have criticised the move, legal challenges are expected, and analysts warn that it could slow US emissions reductions if upheld by the courts.

Recent discussion in the media and scientific community has focused on claims that the world’s coral reefs have already crossed a thermal tipping point—an irreversible threshold beyond which widespread collapse is inevitable. While there is no doubt that reefs face unprecedented thermal stress, three newly published studies offer a more nuanced, cautiously optimistic perspective.

A climate tipping point is a critical threshold in the Earth’s natural systems where a small change can cause significant and irreversible consequences, leading to a cascade of global impacts. Other examples include the melting of polar ice sheets, the dieback of the Amazon rainforest, and the collapse of vital ocean currents. These events have the potential to cause food system breakdowns, rapidly raise sea levels, and accelerate global warming. 

At the heart of this system lies one of the great mysteries of modern oceanography: the global “thermohaline circulation,” also known as the Atlantic Meridional Overturning Circulation, or AMOC. Scientists are still trying to understand just how stable it is.

But a new study suggests that this toothy advantage may be under threat.

Ocean acidification from global warming

A team of German scientists has discovered that ocean acidification—caused by rising carbon dioxide levels in the atmosphere—could interfere with sharks’ ability to regrow their teeth, potentially making it harder for them to hunt and feed effectively.

Unlike human teeth, which are protected by gums, shark teeth are exposed directly to seawater. This makes them especially vulnerable to changes in the ocean’s chemistry, particularly shifts in pH levels.

Founded over ten years ago by US Navy veteran Dr Eric Rasmussen and US Army veteran Alex Hatoum, the group was soon joined by superb documentarian and X-Ray Mag contributor Lorenzo Moscia, who created a video capturing key moments over the past decade.

The latest reports from organisations like the International Union for Conservation of Nature (IUCN) and UN Environment Programme report that about 50% of the world's coral reefs are considered damaged or at risk of collapse, with some estimates suggesting that we could lose up to 90% of coral reefs by 2050 if current trends continue. This is a staggering figure when considering the ecological and economic importance of coral reefs.