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 remove. Shipwrecks also frequently occur 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 wrecks under the right conditions. By creating new places to live for fish and other marine life, wrecks could help mitigate the loss of reef ecosystems.
Pollution and habitat destruction
When ships are abandoned in the ocean or sink due to catastrophic failures, they inevitably have an impact on the environment. When large ships scrape the seabed, they can easily damage over 10,000 square feet of ocean habitat. Additional long-term effects can result from the contents of the sunken ship, such as the ship’s cargo, fuel and even paint.
Shipwreck of the Diamond of the Sea
In 2007, the MS Sea Diamond cruise ship ran aground on a volcanic reef in the Aegean Sea. Less than a day later, the ship sank in the caldera of the ancient submarine caldera of Santorini.
On board the castaway, the Sea Diamond was carrying around 1.7 tonnes 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 one tonne 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 seep into the surrounding seawater or turn into salts that can contaminate the sand below.
While low concentrations of heavy metals are naturally present 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 exceeding safe thresholds set by the Environmental Protection Agency. Given the time it takes for 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 is not enough to mitigate the damage from the sinking. In December 2019, the Greek government began to move forward with a project to remove the wreckage before stop quickly all efforts weeks later.
In October 2011, a container ship known as MV Rena ran aground on Astrolabe Reef off the coast of New Zealand. Shortly after the collision, the 700-foot vessel began to leak oil. Four days after the sinking, enough oil had spilled to form a 3-mile slick. The oil from the container ship killed around 2,000 seabirds. More than 300 oil-coated penguins have been rehabilitated by wildlife rescue teams in the aftermath of 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, remains severely damaged by the ship’s cargo today. Studies of the area in the years following the sinking found heavy metals, petroleum products, and toxic chemicals in the reef sediments, surrounding seawater, and marine life. While much of the oil has been cleaned up or degraded in the environment, contaminants stored in the ship’s cargo will remain in the environment much longer. For example, one of the containers aboard the Rena was carrying more than 20 tonnes of pelletized pieces of copper that piled up on Astrolabe Reef when the ship’s hull ruptured. Copper is known to be toxic to marine life, but the fine pieces were impossible to clean up 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 causing them to deteriorate. While “anti-fouling” paint is still commonly used today, the type of chemical deterrent paint used by the MV Rena includes tributyltin, or TBT, which is particularly effective in killing marine life. The chemical was so effective that its use in anti-fouling paints was banned in 2008. Vessels already coated with TBT, such as the MV Rena, can continue to operate as long as they do not reapply the prohibited paint containing TBT. As the MV Rena scrapes the reef, more TBT is released into the environment.
Coral reefs and kelp forests teem with marine life in part because of their intricate landscapes. Compared to areas with just a sandy seabed, reefs and kelp forests provide plenty of nooks and crannies for marine life to live and hide. Wrecks can have a similar effect on the underwater world by adding new structures for marine life.
The benefits that a wreck can bring to the marine environment vary widely depending on where a ship sinks and the makeup of the ship. For example, while a wreck that lands on top of an existing reef can damage large areas of existing marine habitat, a wreck 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 rather than natural reefs, the reefs and their inhabitants could benefit.
Sinking of the Bellucia
The Bellucia, a steel-hulled cargo ship, 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 approximately 85 feet deep. Today the vessel is considered an important area for feeding and spawning fish and is used locally by artisanal fishermen.
A second steel-hulled wreck, victory, is located near the Bellucia, but sunk in 2003. Unlike the Bellucia, the Victory was intentionally sunk to create habitat. The ship was stripped before sinking, removing almost any material on board that could harm marine life.
Even though the Bellucia sank 100 years before Victory, a 2013 study comparing the diversity of fish at the two wreck sites to nearby natural reef ecosystems found that none of the wrecks were home to a similar diversity of fish. to that of natural reefs. The study showed how even a 100-year-old wreck cannot provide habitat of a quality equal to much older reefs. While 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 through wrecks cannot quickly replace the loss of natural reefs.