People have sailed the world’s oceans for thousands of years, but not all of them have yet made it to port. Researchers estimate that there are approximately three million shipwrecks found worldwide in shallow rivers and bays, coastal waters, and deep oceans. Many sank during disasters; some sank during storms or after running aground, others in battle or in collisions with other ships.
Shipwrecks such as the RMS Titanic, RMS Lusitania and USS Monitor evoke human courage and sacrifice, sunken treasure and unsolved mysteries. But there is another perspective in their story that does not involve humans.
I have been studying the biology of shipwrecks in the United States and internationally for 14 years. From this work, I learned that shipwrecks are not only cultural icons, but can also be biological treasures that provide habitat for diverse communities of underwater life.
Recently, I led an international team of biologists and archaeologists trying to unravel the mysteries of how this transformation occurred. Drawing on the scientific advances of our team and international colleagues, our new study describes how wrecked ships can have second lives as seabed habitats.
A new home for underwater life
Ships are usually made of metal or wood. When a ship sinks, a foreign, artificial structure is added to the seabed.
For example, the World War II tanker EM Clark sank on a relatively flat, sandy seabed when it was torpedoed by a German submarine in 1942. To this day, the intact metal wreck stands above the North Carolina seafloor like an underwater skyscraper, creating an island oasis in the sand.
The creatures that live on and around sunken ships are so diverse and abundant that scientists often colloquially refer to these areas as “living shipwrecks.” Marine life, ranging from microscopic creatures to the largest animals in the sea, use shipwrecks as homes. Brightly colored corals and sponges cover the surfaces of the wreck. Schools of silvery baitfish dart and shimmer around structures, chased by sleek, fast-moving predators. Sharks sometimes wander around wrecks, possibly resting or looking for prey.
Origin of a second life
The transformation of a ship from a ship in service to a thriving metropolis of marine life may seem like a fairy tale. There is an origin story like once upon a time, the destruction event, and a sequence of life arriving at the sunken structure and beginning to blossom.
Tiny microbes, invisible to the naked human eye, initially settle on the surface of the debris, forming a carpet of cells called a biofilm. This coating helps make the submerged structure suitable for larval animals such as sponges and corals to settle and grow there.
Various sea creatures living on the 19th-century wooden-hulled Ewing Bank wreck, located 610 meters deep in the Gulf of Mexico. NOAA
Larger animals, such as fish, sometimes emerge within minutes after a ship sinks. Large sharks glide around the structure while small fish hide in the cracks and crevices of the structure. Marine mammals such as sea turtles and fur seals have also been spotted in the shipwrecks.
Biodiversity hotspots
Shipwrecks host an abundance and variety of marine life that can make them biodiversity hotspots. Microbes that transform the debris structure into a living space also enrich the surrounding sand. Evidence from wrecks deep in the Gulf of Mexico shows that the halo of increased microbial diversity extends anywhere from 650 to 1,000 feet (200-300 meters) from the wreck. In the Atlantic Ocean, thousands of groupers, a reef fish species highly prized by fishermen, congregate around and inside shipwrecks.
Groupers and eels from the wreck of the German submarine U-576 off the coast of North Carolina, bottom center. NOAA
Shipwrecks can also serve as stepping stones on the ocean floor, which animals use as temporary homes as they move from one place to another. This has been documented in shipwreck-prone areas, such as off the coast of North Carolina, where storms and war sank hundreds of ships.
In this part of the ocean, popularly known as the “Graveyard of the Atlantic,” reef fish likely use island-like shipwrecks as corridors as they move north or south from the equator to find suitable water temperatures as climate change warms the oceans. Scientists have also observed sand tiger sharks traveling from one wreck to another, possibly using shipwrecks as resting places during migration.
Life growing on shipwrecks in the depths of the sea can even produce energy. Tube worms that grow on organic shipwreck materials such as paper, cotton and wood host symbiotic bacteria that produce chemical energy. Colonies of such tube worms have been documented aboard the luxury steel yacht Anona in the Gulf of Mexico.
Biological mysteries abound
Despite their biological value, shipwrecks can also threaten underwater life by altering or destroying natural habitats, causing pollution, and introducing invasive species.
When a ship sinks, it can damage existing seafloor habitats. In one well-documented case off the Line Islands in the central Pacific, an iron shipwreck sank onto a healthy coral reef. Iron infusion significantly reduced coral cover and the reef became covered by algae.
Ships can carry pollutants as fuel or cargo. As shipwrecks deteriorate in seawater, there is a risk that these contaminants will be released. The level of risk depends on how much pollutants the ship is carrying and how intact the wreckage is. A recent study found that the effects of contaminants in shipwrecks could be detected in microbes up to 80 years after the wreck.
Shipwrecks may also inadvertently help spread invasive plants and animals that cause biological damage. Debris are new structures in which invasive species can establish, grow, and use as a hub to spread into other habitats. Invasive cup corals from World War II off the coast of Brazil. World War II spread to shipwrecks. On Palmyra Atoll in the Pacific, a species of anemone called corallimorph has quickly invaded a shipwreck and is now threatening healthy coral reefs.
The future of shipwreck searching
Shipwrecks create millions of study sites that scientists can use to ask questions about marine life and habitats. One of the biggest challenges is that many wrecks are found in unexplored or remote locations. Advances in technology can help researchers see the most inaccessible parts of the ocean, not only finding shipwrecks but also better understanding their biology.
Maximizing discoveries will require biologists, archaeologists, and engineers to work together to explore these special habitats. Ultimately, the more we learn, the more effectively we can protect these historical and biological values.
This article is republished from The Conversation, an independent, nonprofit news organization providing facts and analysis to help you understand our complex world.
Written by Avery Paxton National Oceanic and Atmospheric Administration.
Read more:
Avery Paxton is affiliated with NOAA National Centers for Coastal Ocean Science.
We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.OkNoPrivacy policy