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Marine Debris as a Potential Pathway for Invasive Species: A New MDP Report

The NOAA Marine Debris Program (MDP) is proud to announce the release of our new report detailing the potential of marine debris to act as a pathway for the introduction of invasive species.

There is mounting concern over the increase in debris in our ocean and the potential for that debris to assist in the spread of non-native species. While the pathways associated with global shipping draw the greatest amount of attention regarding marine invasives, the purpose of this paper is to consider the potential role that marine debris may play in introducing non-native species that may become invasive. This report reviews the scientific literature that exists on the subject and identifies areas where more research is needed.

Check out the new invasive species report, which joins our reports on entanglement, ingestion, ghost fishing, modeling, and habitat on our website.

Cover of Marine Debris as a Potential Pathway for Invasive Species report.

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Impacts of Marine Debris: the Struggle for Marine Animals

A plastic bag may look flimsy, but in a fight against a sea turtle, it often wins. Unfortunately, the marine debris that we find floating in our oceans and waterways all too often impacts marine life.

There are many ways that marine debris can impact marine animals. For instance, the accidental ingestion of debris is a big problem! Animals may unintentionally eat debris along with their meal, or intentionally ingest trash due to its resemblance to real food. For example, a plastic bag can win a fight with a sea turtle using its resemblance to a jellyfish when it’s floating in the water. Jellyfish are a favorite snack of sea turtles and the plastic bag is often swallowed before the turtle knows the difference. Since plastic is not real food, the turtle is not getting the nutrients it needs, and once that plastic is in its gut, it can sometimes get stuck there, making the turtle very sick. All sea turtle species eat debris and unfortunately, turtles aren’t the only animals that mistake plastic for food. Many marine animals ingest marine debris. This is an especially big problem in seabirds. A recent study by Wilcox et al. estimated that 90% of seabirds have ingested plastic and predicted that number would increase substantially by 2050.


Unfortunately, the impact of marine debris doesn’t stop there. Entanglement and ghostfishing also pose a threat. Marine life can get entangled in marine debris such as plastic bands or fishing line. For an animal, this is a situation that can range from slightly uncomfortable to lethal. Derelict fishing gear such as nets and crab pots can also be a big problem. These materials can continue to capture marine life but no longer have a person responsible for setting captured animals free. This is called “ghostfishing.”


Marine debris can also harm animals indirectly by impacting their habitat. Large or heavy debris can smother or crush sensitive habitats, such as coral reefs and sea grass. Non-native species can also hitch a ride on marine debris from one region to another. This might simply sound like a convenient way to travel, but invasive species can wreak havoc on an ecosystem by depleting food sources or destroying habitat.


Don’t like the sound of all this? Let’s change it! It might seem hopeless, but it’s not. There are many ways to reduce this threat, such as improving waste management techniques and disposing of trash items properly, but we need your help! Remember to reduce, reuse, and recycle to decrease the amount of trash that is adding to our marine debris problem. Help with a cleanup in your area—the 30th International Coastal Cleanup is Saturday, September 19th, and there are cleanup locations all over the country. If everyone made an effort, think of the difference it would make! It’s up to us.


Aboard the transoceanic invasive species mobile

By guest blogger Rebeka Ryvola, Ecologic Institute

When introduced into new environments, invasive species can be a major problem.  Invasives – species living in a certain area where they don’t belong – can harm the native species present or out-survive them and cause dramatic ecosystem changes. The changes are usually for the worse.

Humans are often unwittingly instrumental in helping these species infiltrate new territories, and we’re finding more and more evidence that marine debris is a culprit.

Invasive species stage their “invasions” in a number of ways. They can float through the air, travel by water currents, or cling to migrating animals. On land, species such as insects and plants can hitchhike by lurking in suitcases, in and on cars, on bicycles, and even on your clothing. Oceanic species – such as barnacles, mollusks, algae, and fish – can attach themselves to boats or stow away in ship ballast water.

When it comes to the ocean, ships are not the only means of transportation for invasives; efforts to stop these species are challenged by marine debris in our oceans and seas. It turns out that ocean-bound marine litter often offers potential invaders free round-the-world trips to entirely new territories and areas that may not be prepared for the influx of strange and competitive species.

In 2009, researcher David Barnes studied the remote Seychelles Islands and found that over 60 percent of marine litter he inspected harbored potentially invasive species. In the even-more-isolated Antarctic, home to many species found nowhere else on earth, the influx of invasive species-hosting debris has been found to be more common than previously thought.  In less remote regions, new species arrive frequently, and with few barriers.

Journalist Lindsey Hoshaw traveled to the “Great Pacific Garbage Patch” and captured how species can get creative with their modes of garbage transportation:

Invasives can attach to chunks of trash like foamed plastic. Credit: Lindsey Hoshaw

Nets tangled in debris

A floating mat of debris. Credit: Lindsey Hoshaw

Crate, barrel, net

Potential shelter and transportation for invasive species. Credit: Lindsey Hoshaw

And while natural modes of transportation – such as driftwood or even marine mammals like whales – also get unwanted species from point A to B, they tend to be less buoyant, less numerous and more constant in number throughout time than debris. Barnes also estimated that marine debris about doubles the opportunities for marine organisms to propagate at tropical latitudes and more than triples it at high latitudes.

Invasions of non-native species can be bad news for biodiversity – especially if the native species being pushed out are scarce in other parts of the world or are entirely unique to their ecosystems.  Since much of the marine debris doesn’t break down quickly, and we keep putting more garbage into the ocean, these numbers are just going to keep increasing – unless we change our behavior.

The long-distance transport of exotic and unwanted colonizers is yet another reason to keep the oceans free of garbage. When you’re at the beach or river, take away everything you came with to ensure that garbage doesn’t reach our waterways in the first place. There’s no knowing how far garbage will travel once it takes to the sea – or who’s hitching a ride.