Invertebrates colonize dump in the middle of the Pacific Ocean – 04/26/2023 – Science

Large areas of the Pacific Ocean that are now littered with floating litter (almost always made up of pieces of plastic of all sizes) are still home to small communities of marine invertebrates, reveals a new study.

Many of the animals belong to coastal species, which normally would never be found on the high seas. The animals hitched a ride on the debris and ended up at points that are thousands of kilometers from the coast. Even so, they are reproducing and colonizing the ocean dump.

The surprising results have just been published in an article in the specialized journal Nature Ecology & Evolution. For the research authors, the debris released by humanity has become so ubiquitous that it has given rise to what they call the neopelagic community — a new set of species that has settled in the middle of the ocean.

In the work, whose first author is Linsey Haram, from the Smithsonian Environmental Research Center (USA), the scientists studied debris that was floating in the so-called NPSG (North Pacific Subtropical Gyre). This region of the ocean is home to the Great Pacific Garbage Patch, where ocean currents have concentrated debris of all kinds over the last few decades.

Contrary to popular belief, the NPSG floating dump is mostly made up of very small plastic fragments, although of course larger pieces are also present. It is already known that coastal species of invertebrates are capable of crossing great distances clinging to this type of garbage or to debris of natural origin, such as tree branches. That’s what happened after the tsunami that hit Japan in 2011, for example — marine animals of Japanese origin ended up on the American west coast.

Haram and his colleagues decided to see if a similar process could lead to the biological colonization of the Great Garbage Patch. They collected a total of 105 fragments from the eastern portion of the NPSG—in general, they were pieces of things like boxes and plastic baskets that had already been greatly degraded by their time at sea, becoming thin and friable (easy to break). . There were also pieces of nylon netting, rope and crates.

Analysis of the wrecks revealed that 95% of them contained pelagic species —that is, naturally typical of the high seas—, but 70% also harbored invertebrates that are normally coastal. Each piece of litter contained an average of five different species, most of which are coastal in origin. In total, around 50 species were identified —the count could be higher because researchers have not always been able to determine the exact species of invertebrate.

Among the floating animals were anemones, several types of crustaceans, such as isopods (the same group as woodlice, which are terrestrial) and amphipods (which resemble shrimp), and also lesser known groups, such as hydroids and bryozoans, which can form colonies, similar to corals.

Furthermore, the researchers noted that at least some of the critters appear to be breeding there. There are females with eggs and animals of different sizes, indicating growth processes.

Incidentally, reproductive success may be explained by the characteristics of the species themselves. Most coastal animals have direct development (no passage through complicated larval stages with specific habitat requirements) or reproduce asexually. This may have facilitated NPSG colonization aboard the debris.