Marine Ecosystems in Garbage Patches

The Great Pacific Garbage Patch seems like the last place where marine life would thrive. Covering an area of the Pacific Ocean about three times the size of France, the Patch accumulates large quantities of man-made plastic waste. The garbage patch is known for its inhospitality, poisoning and entangling many small organisms. Recently, however, researchers have discovered that a variety of life forms are surviving in the garbage patch, forming an ecosystem that we know very little about.

In a paper published in Nature in April 2023, a group of researchers observed many life forms near the surface of the garbage patch. Among them were animals native to the open ocean, such as sea snails. However, coastal animals such as sea anemones and mollusks were also found thriving in the patch—a surprising development, as coastal organisms usually cannot survive and reproduce in the open ocean.

Gyres are permanent systems made up of smaller rotating ocean currents, driven by changes in temperature, wind, tides, and salinity. In the Pacific, gyres sweep plastic waste out to the garbage patch, where reduced current activity allows the plastic waste to accumulate over time. Small coastal animals can travel with the plastic through a process known as rafting. Common forms of small plastic waste, such as toothbrushes and old bottles, serve as vessels for the organisms to reach the garbage patch. 

Rafting is not a new phenomenon. Since the 19th century, rafting has been thought to be a mechanism by which coastal organisms reach open seas. Natural materials, such as pumice rocks created by volcanic eruptions, and organic materials, such as logs, have carried coastal animals to open seas. However, such rafts are either rapidly degraded or denatured by ocean water, and do not serve as long-term habitats for the species. Most organisms swept to the open sea on natural rafts die due to the inhospitable environment. 

Unlike natural rafts, plastic does not quickly degrade in the open ocean and can provide permanent habitats for coastal organisms. Based on an analysis of 105 plastic samples from the Great Pacific Garbage Patch, scientists found coastal organisms on more than 70% of the debris. Not only were coastal organisms very prominent in the garbage patch, but a wide variety of organisms were discovered. Of the 46 species found in the garbage patch sample, nearly 80% were of coastal origin. In each taxonomic group studied (Bryozoa, Anthropoda, Cnidaria, Annelida, Porifera, and Mollusca), there were more species of coastal origin than pelagic (open ocean) origin, with only coastal species being observed in the Porifera phylum (sponges). These species have become successful in the garbage patch; Researchers have observed coastal crustaceans laying eggs and anemones cloning themselves. 

Scientists previously assumed that coastal species, even if transported to the open ocean, would be unfit to survive and reproduce due to the low-nutrient nature of the environment. However, this new finding illustrates that coastal species have not only adapted to this plastic environment but have become a thriving community in the garbage patch. While it is encouraging to learn that the garbage patch is acting as a habitat, the growth of manmade garbage patches may disrupt the balance of the existing ecosystem that they ultimately conquer, leading to serious consequences for native oceanic species like sea snails.

Most of the coastal organisms were found living side by side with the pelagic organisms, implying that they have adapted to cohabit the environment with pelagic species. As these coastal animals survive and reproduce in the garbage patch, they become more prominent in the open ocean, potentially outcompeting native open ocean organisms. For instance, coastal sea anemones have been found to consume native sea snails inhabiting the garbage patch. The open ocean also has limited nutrients, and the growth in coastal marine life presents risks to native species.

Our view of plastic marine pollution has predominantly been centered around the direct negative impact of plastics on marine life. Marine animals, especially sea turtles, birds, and mammals, often become entangled in plastic nets and other debris, limiting their mobility and hunting capacity. Furthermore, marine animals ingest microplastics or mistake large human plastic waste for food, leading to many marine animals’ untimely deaths. However, small marine organisms are neither susceptible to becoming entangled or ingesting large plastics, meaning they are less affected by plastic pollution. As these organisms survive and even thrive, the way that marine pollution allows for invasive species and can inadvertently destroy an ecosystem is often overlooked. Little is known about the ecosystem of small organisms in the open ocean and their interactions with coastal species, but the potential for these interactions to dramatically change the ecosystem makes it important that more research is focused on better understanding these effects.

The discovery of large numbers of coastal species thriving in the open ocean and potentially outcompeting native species makes tackling marine pollution a more urgent issue than ever. When creating strategies to tackle marine pollution, scientists need to take into account ways to preserve the native ecosystems of the Pacific Ocean and eliminate invading coastal species. Cleaning the entire garbage patch is difficult, but mechanisms can be developed to eliminate the floating parts of the garbage patch so coastal organisms don’t have a habitat in the open ocean to survive and reproduce. Oceans play a major role in the global ecosystem, and addressing the growing garbage patch crisis is important to marine life all over the world.