Ecosystems

A new scientific study has revealed that World War II ammunition dumps on the seabed—long regarded solely as hazardous legacy sites—also support surprisingly rich marine biodiversity. 

The findings suggest that, in addition to posing management and safety concerns, these munitions fields may now function as unintentional artificial reefs hosting complex ecological communities.

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.

The Descent into Blue

A whale’s body sinks slowly through the water, passing layer after layer of drifting life. Small fish, sharks, and seabirds may feed briefly at the surface, but soon the great shape slips out of sight, falling into deeper, quieter realms.

As it sinks, it becomes a kind of travelling oasis — shedding nutrients, attracting small creatures, and nourishing life as it goes. This falling world can take hours or even days to reach the abyssal plain, thousands of metres below.

In this dim layer, life has taken extraordinary forms. Many creatures are small and transparent, some studded with lights of their own. Lanternfish, hatchetfish, and comb jellies shimmer like stars, using bioluminescence to confuse predators or to signal one another in the gloom. Shrimp flash warning pulses, squid glow along their arms, and gelatinous drifters flow through beams of pale blue light.

The birth of a brinicle

When seawater begins to freeze at the surface, pure ice crystals form and push out the salt, leaving behind pockets of extremely cold, salty brine. This dense brine seeps downward through cracks in the ice. Because it is much colder and heavier than the seawater around it, it sinks—freezing the water it touches as it falls.

These giants are born of fire. Most seamounts began as volcanoes, formed where molten rock burst through the oceanic crust at weak points or along tectonic boundaries. Over time, many became dormant, sculpted by currents and covered in marine life. Others, like those in the Pacific “Ring of Fire,” remain active, still growing and occasionally shaking the sea above them with tremors.

A snowstorm of life

Marine snow is made of tiny particles drifting down through the ocean—bits of plankton, algae, faecal pellets and other organic material that begin their journey near the surface. To the deep-sea world, it is as vital as sunlight is to a coral reef. Every flake carries the remains of life from above, feeding creatures that live where light never reaches.

Coral reefs are among the planet’s most vital ecosystems, yet they face increasing threats from climate change, including bleaching events and destructive storms. A new study by the Australian Institute of Marine Science (AIMS) sheds light on the crucial role of connectivity between coral communities in helping reefs recover and adapt to environmental challenges.

Their groundbreaking study, published in 2022, marks a significant milestone in understanding and preserving vital marine ecosystems that are crucial for mitigating climate change.