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.

Unlike many animals, oysters do not have sex chromosomes. Instead, their gender is dependent on environmental factors—a process known as environmental sex determination. 

With rising carbon dioxide levels leading to the increased acidification of the oceans, a team of researchers led by Xin Dang and Vengatesen Thiyagarajan sought to find out how the gender ratio of oysters across generations is affected as a result.

Seashells come in various shapes and sizes. And it appears that the seashells from the tropics tend to be larger than those found in the temperate regions.

Far from being just a coincidence, it seems that there is a rational explanation for it. Simply put, this is because the sea snails in the tropics have to devote relatively less energy to shell growth, compared to those in the cold-water regions.

For two years, the researchers from University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science collected water samples along the 200-kilometre (124-mile) stretch of the Florida Reef Tract north of Biscayne National Park to the Looe Key National Marine Sanctuary. The data provide a snapshot on the health of the reefs, and establish a baseline from which future changes can be judged.

Coral reefs are particularly vulnerable to the ocean acidification process, because reef architecture is built by the accretion of calcium carbonate, called calcification, which becomes increasingly difficult as acid concentrations increase and the surrounding water's pH decreases.

Image at the top:  Great Barrier Reef, Australia. An intertidal 'micro-atoll'. Photo: Isobel Bennett.

Coral colonies of P. cylindrica have a unique internal solution to the problem of forming their skeletons and building reef structures in the face of rising ocean acidification.

Australian Institute of Marine Science (AIMS) scientist Dr Katharina Fabricius has led two research expeditions, with researchers from six countries including Papua New Guinea (PNG), to study three natural CO2 seeps in Milne Bay Province, PNG. This unique location is the only presently known cool, CO2 seep site in tropical waters containing coral reef ecosystems. The study has given scientists unprecedented insights into what coral reefs would look like if greenhouse gas emissions and resulting ocean acidification continues to increase at present rates.