Ship anchors are doing great harm to protected ocean life on the Antarctic seafloor

When ships travel to the ends of the Earth, their anchors leave more than temporary marks – they create lasting scars on fragile marine life and ecosystems.

From tourism vessels to research ships, maritime traffic is growing even in the far reaches of Antarctica. And with every anchor dropped, the seafloor is at risk.

Undersea cables, pipelines, and sensitive wildlife habitats can all be damaged by this simple act. Yet, anchoring remains almost completely unregulated in polar waters.

Anchors leave their mark in Antarctica

Scientists have recorded new underwater footage that reveals the impact of ship anchoring in Antarctica’s remote marine environments. Their findings offer a rare look into an underreported environmental issue that’s hidden from view.

“This is the first time the impacts of ship anchoring and chain damage are documented in Antarctic waters,” explained Matthew Mulrennan, a marine scientist and founder of KOLOSSAL, an ocean exploration and conservation nonprofit in California.

“Activities in Antarctica have a lot of strict rules around conservation, yet ship anchoring is almost completely unregulated.”

Study co-author Dr. Sally Watson, a marine geophysicist from New Zealand’s National Institute of Water and Atmospheric Research, emphasized the urgency of the situation.

“Documentation is way overdue, given the importance of these ecosystems and the protections we place on them. Anchoring impacts are understudied and underestimated globally. It’s so important to recognize and mitigate the impacts across all industries and limit planned anchoring,” said Dr. Watson.

What the cameras revealed

During the austral summer of 2022-23, researchers recorded underwater footage across 36 sites near the Antarctic Peninsula and South Georgia Island.

Cameras were positioned at various depths – close to the surface, midwater, and just one meter above the seabed. What they captured was alarming.

In areas where ships had dropped anchor, the ocean floor was visibly disturbed. Grooves and striations crisscrossed the seabed, and patches of mud covered the habitat.

At these sites, marine life was sparse or entirely absent. Sponge colonies were crushed, and overall benthic biomass was nearly nonexistent. Yet, just meters away, life thrived – showing that the destruction was highly localized and recent.

“The observed damage was a near miss to three giant volcano sponges, believed to be the oldest animals on the planet, which may live up to 15,000 years,” said Mulrennan.

The team also observed other species at risk, including Antarctic sun stars, giant Antarctic octopuses, sea spiders, and various fish, all of which dwell at depths that make them vulnerable to anchoring.

Chain reaction across ecosystems

According to the researchers, the impacts of ship anchors to marine life extend beyond individual species.

“The weird and wonderful animals that are impacted, like sponges, are important for filtering water, carbon sequestration, and providing shelter, food, and complex habitats which benefit the whole marine ecosystem, including penguins and seals – the animals tourists come to see,” noted Mulrennan.

This ripple effect could alter the food web, and affect iconic Antarctic wildlife that draws attention and resources for conservation.

Slow recovery in cold waters

Life in Antarctica is tough, slow, and highly adapted. That makes it especially vulnerable to disruption. Many organisms in anchor zones are slow-growing and can’t relocate. Recovery could take decades – or more.

“We know that anchor impacts in tropical reefs can last a decade. In muddy sediment the scours can still be visible over a decade later,” said Dr. Watson.

“Ecological recovery is really site specific. Things in cold waters are much slower growing than in warmer temperatures so I expect that recovery would take longer the higher the latitude.”

Anchor impacts on marine life

The researchers say more work is needed. Studies should examine both short- and long-term effects of anchoring, recovery timelines, and how broader ecological functions are disrupted.

But a major hurdle remains: there is no global database tracking where and how often ships anchor in polar regions.

“Anchoring is likely the most overlooked ocean conservation issue in terms of global seafloor disruption; it is on par with the damages from bottom trawling,” Mulrennan concluded. “It’s a pressing environmental issue, but it’s out of sight, out of mind.”

The full study was published in the journal Frontiers in Conservation Science.

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