Something very odd seems to be happening in the Southern Ocean, that vast body of cold sea water surrounding Antarctica which absorbs heat and carbon dioxide from the atmosphere.

A new research project led by ocean scientists in South Africa suggests that there has been a significant, five-fold increase in "iron stress" in phytoplankton in the Southern Ocean over the last 26 years.

That might not seem a big deal to most people... until you consider that iron is an essential micronutrient for phytoplankton, which form the base of the entire sea food chain.

Phytoplankton are tiny, single-celled sea plants. They float by the thousands in almost every drop of water close to the ocean surface. Much like trees on the mainland, these microscopic plants take up carbon dioxide, make carbohydrates using energy from the sun, and release oxygen.

Critically, they provide food, directly or indirectly, for many other small sea creatures which eat these plants and eventually nourish much bigger creatures such as fish, seals and whales.

These microscopic sea plants are also responsible for cycling nearly half of the carbon dioxide on Earth through the process of photosynthesis, thereby helping to buffer the planet from the additional carbon loads of the human-driven climate crisis.

These are some of the reasons that the researchers are worried, because iron stress in this vast ocean may lead to a...