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When people hear about underwater coral reefs, they usually imagine colorful gardens made of coral. However, some coral reefs are anchored to even more unusual foundations.
For more than a century, people have placed various objects on the ocean floor off the coast of the United States to provide habitat for marine life and recreational opportunities such as fishing and diving. Artificial reefs are made from decommissioned ships, chicken cages, concrete pipes, railroad cars, and more.
We study the ecology of fish living in the sea. use artificial reefs inside US and beyond. Through our research, we found that artificial reefs can become hotspots for large predatory fish such as groupers and groupers. jack. It can also function as stepping stones Coral reef fish are expanding their range northward as water temperatures rise. Rest area For the sharks.
Artificial coral reefs are strategically designed and placed Optimize fish habitat. But even though they provide valuable ecological services, no one has investigated how many of these structures exist in U.S. waters or how much area of the ocean floor they occupy. No one is here.
To fill this knowledge gap, we led a team of scientists and artificial reef managers from 17 U.S. states to conduct an artificial reef construction program that was the first to calculate the area of artificial reefs nationwide.our new research These reefs cover a total of about 7 square miles (19 square kilometers) of the U.S. ocean floor, the equivalent of 3,600 football fields. We also discuss the diversity of materials used to form coral reefs and the patterns of artificial reef formation over time.
Creation of modern artificial reefs
Modern reef fishing is not the same as dumping trash into the water. Regulated at the federal and state level. A rigorous permitting and approval process ensures that any proposed object or material is suitable for deployment at sea.
For example, retired ships are thoroughly Clean and drain fuel and other contaminants before settling to minimize environmental risks. Some materials once used to make artificial reefs, such as rubber, fiberglass, wood, and plastic, can migrate from their place of installation, damaging nearby habitat, or degrade quickly in salt water. This is now prohibited due to the possibility of
Reef-covered objects can only be sunk in pre-designated areas of the U.S. ocean floor. These zones, which are usually sandy seabed, total about 2,200 square miles (5,800 square kilometers), or about the size of the state of Delaware.
Each zone can support the formation of many individual reefs over decades. Within a given zone, reef-covered objects are usually separated by large sand bands and located far apart from each other. This maximizes the amount of sand habitat that some reef fishes forage on.
The extent of artificial reefs in these zones has increased by about 2,000 percent over the past 50 years. However, since 2010, the area of artificial reefs has increased by only 12%. This is probably due to difficulties in obtaining and sinking acceptable reef material. It is also Structure development Especially suitable for use as artificial reefs.
airplanes, trains, cars
Our study shows that artificial reefs have occurred offshore in U.S. coastal states dating back to 1899, excluding six states without artificial reef programs: Maine, New Hampshire, Connecticut, Oregon, Washington, and Alaska. Records of intentional reef formation were collected.
For some of these phenomena, especially in recent decades, we have detailed records of the size and quantity of sunken objects and ocean floor maps from which these measurements can be derived. These reefs were easy to quantify.
Other records, including those from the early 20th century, had few details. For these, we developed an approach to estimate how much seafloor is covered by coral reefs, based on similar developments with better records.
Our research uncovered a huge variety of reef-covered objects on the ocean floor of the United States. They included decommissioned tugboats, fishing boats, barges, ferries, and warships. Reefs have also been created from railroad boxcars, aircraft, vehicles, chicken transport cages, voting machines, missile platforms, concrete pipes, radio towers, tires, limestone, and objects intentionally designed as artificial reefs.
Objects that make up the most parts of the ocean floor include limestone, large concrete modules specifically designed for reef fishing, metal rigs and towers, and long, narrow pieces of concrete recycled from previous uses, such as culverts and bridges. It is included.
Potential impact
Once a reef forms, fish may appear within minutes to hours. The order in which the fish arrive is sometimes follow the pattern. Ephemeral fish such as horse mackerel and barracuda come first, followed by bottom-dwelling fish such as grouper and small reef fish. Over time, plants and animals grow on the hard surface of the artificial reef, helping to provide food and sanctuary for the fish.
However, these reefs can also harm the ecosystem. Invasive species such as plants and other animals that grow on hard structures can be removed using artificial reefs. spread to new locations.
Artificial reefs may also attract fish from nearby natural reefs. Constructed reefs are often located in prime recreational fishing locations, which can increase catches of these species.
Another risk is that if artificial reefs are improperly installed or anchored to the ocean floor, they can move to unintended locations, especially in the aftermath of a storm, and cause damage to sensitive habitats.For example, Florida One to two million tires were sunk offshore. Attempts were made to create artificial coral reefs in the 1970s, but marine life did not colonize the reefs as intended. Now the tires are scouring the area and suffocating the coral.
Learning from artificial coral reefs
Monitoring how fish and other species use artificial reefs, especially in comparison to naturally occurring reefs, is key to understanding the benefits and risks of these structures.as climate change As marine ecosystems continue to change, we believe there is an opportunity to learn which types of artificial reefs are best suited to enhance habitat for specific types of fish.
For example, we know that large predators that live in open waters, such as horse mackerel, barracuda, and sharks, tend to prefer open waters. High artificial reefs than low artificial reefs.This is similar to insights from oil rigs, where these vertical, complex structures Habitat for valuable fish. Over 500 decommissioned oil rigs turned into a reef. Our calculations included only reefs managed by state artificial reef programs.
Other structures underwater Offshore wind turbine basicsintention Likely to form a habitat for marine life It’s the same as an artificial coral reef. Insights into what types of structures different fish prefer could help guide the design and location of offshore wind farms.
Humanity depends on the ocean for many benefits, including food, commerce, energy, and a stable climate. Measuring the footprint of artificial reefs is the first step in understanding their positive and negative impacts on marine wildlife and human use of the ocean.
Brendan Lundea marine scientist at The Nature Conservancy, contributed to this article.