Do shipwrecks help or harm marine life?


Accidental wrecks are often laden with toxic materials that seep into the environment where they are difficult to dispose of. Shipwrecks also occur frequently when a ship crashes into hidden coral reefs, damaging particularly important marine habitats. While many wrecks damage the marine environment, some wrecks are intentionally placed underwater to create new habitats. Although the intentional sinking of ships is criticized by some as greenwashing, research suggests that “artificial reefs” can be created by sinkings under the right conditions. By creating new habitats for fish and other marine species, shipwrecks could help mitigate the loss of reef ecosystems.

Pollution and habitat destruction

When ships are abandoned in the ocean or sink due to catastrophic breakdowns, they inevitably have an impact on the environment around them. When large ships scrape the seabed, they can easily damage over 10,000 square feet of ocean habitat. Additional long-term effects can arise from the contents of a sunken ship, such as the ship’s cargo, fuel, and even paint.

Wreck of the sea diamond

In 2007, the cruise ship MS Sea Diamond ran aground on a volcanic reef in the Aegean Sea. Less than a day later, the ship sank in the caldera of Santorini’s ancient underwater caldera.

On board the wrecked Sea Diamond was carrying about 1.7 tons of batteries and 150 CRT televisions. Together, these manufactured products and the ship’s electrical equipment contain approximately 80 grams of mercury, 1,000 grams of cadmium and over a ton of lead. Other heavy metals, such as copper, nickel and chromium, are present in the hull of the sunken ship. Over time, these heavy metals will leach into the surrounding seawater or turn into salts that can contaminate the sand below.

Although low concentrations of heavy metals occur naturally in seawater, a survey of the area around the wreck of the Sea Diamond three years after the cruise ship ran aground found levels of lead and cadmium that exceed safe limits set by the Environmental Protection Agency. Given the time it takes for the metals to corrode, the study authors predict that heavy metal concentrations will continue to rise in the region.

The Sea Diamond remains underwater today, where it continues to harm the environment. While a pollution barrier is in place, critics say it’s not enough to mitigate the damage from the sinking. In December 2019, the Greek government began moving forward with a plan to remove the wreckage before quickly halting all efforts weeks later.

Wreck of the Rena

In October 2011, a container ship known as MV Rena ran aground on Astrolabe Reef off New Zealand. Shortly after the collision, the 700ft vessel began leaking oil. Four days after the sinking, enough oil had spilled out to form a 3-mile slick. Oil from the container ship killed around 2,000 seabirds. More than 300 oil-coated penguins have been rehabilitated by wildlife rescue teams following the oil spill.

While the oil spill resulting from the sinking of the MV Rena was relatively minor overall, Astrolabe Reef, where the sinking occurred, today remains severely damaged by the ship’s cargo. Studies of the area in the years following the sinking found heavy metals, petroleum products and toxic chemicals in reef sediments, surrounding seawater and in marine life. While much of the oil has been cleaned up or degraded in the environment, the contaminants stored in the ship’s cargo will remain in the environment much longer. For example, one of the containers aboard the Rena carried more than 20 tons of granulated copper pieces that piled up on Astrolabe Reef when the ship’s hull ruptured. Copper is known to be toxic to marine life, but fine pieces have been impossible to clean entirely.

The ship itself also has a lasting effect on the reef. The MV Rena is coated with chemical paint used to prevent marine life from growing on the boats and damaging them. While “anti-fouling” paint is still commonly used today, the type of deterrent chemical paint used by the MV Rena includes tributyltin, or TBT, which is particularly effective at killing marine life. The chemical was so effective that its use in antifouling paints was banned in 2008. Ships already coated with TBT, such as the MV Rena, can continue to operate as long as they do not reapply the banned TBT-containing paint. As the MV Rena skims the reef, more TBT is released into the environment.

New habitats

Coral reefs and kelp forests teem with marine life due, in part, to their complex landscapes. Compared to areas with just a sandy bottom, reefs and kelp forests provide plenty of nooks and crannies for marine life to live and hide. Shipwrecks can have a similar effect on the underwater world by adding new structures to sea life.

The benefits a shipwreck can bring to the marine environment vary greatly depending on where a ship sinks and the composition of the ship. For example, while a shipwreck that lands on top of an existing reef can damage large areas of existing marine habitat, a shipwreck near an existing reef can provide new habitat for marine life in the area.

In addition to creating habitat for marine life, wrecks can also create new places for divers to visit. If divers visit wrecks instead of natural reefs, the reefs and their inhabitants could benefit.

Bellucia Wreck

A Goliath Grouper hanging around a shipwreck.

Stephen Frink/Getty Images

The Bellucia, a steel-hulled freighter, sank in 1903 near the Rasas Islands off the coast of Brazil after accidentally hitting a reef. The vessel remains in place in two pieces at approximately 85 feet depth. Today the vessel is considered an important fish feeding and spawning area and is used locally by artisanal fishers.

A second steel-hulled wreck, the Victory, is located near the Bellucia, but sank in 2003. Unlike the Bellucia, the Victory was intentionally sunk to create habitat. The ship was stripped before sinking, removing almost all materials on board that could harm marine life.

Even though the Bellucia sank 100 years before the Victory, a 2013 study comparing fish diversity at the two wreck sites to nearby natural reef ecosystems found that neither wreck hosts a similar fish diversity. to that of natural reefs. The study showed that even a 100-year-old wreck cannot provide habitat of equal quality to much older reefs. Although it is possible that the Bellucia and the Victory will continue to support a greater diversity of marine life over time, the creation of artificial reefs by shipwrecks cannot quickly replace the loss of natural reefs.


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