Microplastics are a well-known environmental pollutant throughout the environment, including the oceans. There, they can be easily ingested by marine organisms.
What happens next, however, is unclear, especially in animals that live near the bottom of the ocean.
Now, a group of Italian researchers have published a report in ACS’ Environmental Science & Technology journal in which they conclude that lobsters can eat and break down some of this microplastic material, releasing even smaller fragments into the water that other deep-sea organisms could ingest.
Microplastic pollution that makes its way into the ocean eventually sinks to the seabed, the habitat of Nephrops norvegicus, which is also known as the Norway lobster, langoustine or scampi. Earlier studies into the contents of stomachs or entire digestive tracts from these lobsters demonstrated that they can ingest microplastics.
Also, previous lab experiments had shown that a different type of crustacean that lives in the water column, rather than the seabed, can break plastic into smaller particles through digestion.
Could this also be going on with species, like the Norway lobster, that live on the seabed, wondered Alessandro Cau and his colleagues, the authors of the article.
In lobsters collected near Sardinia in the Mediterranean Sea, the researchers found that larger plastic particles became trapped in the crustaceans’ stomachs.
“Our results show that the stomach can act as a size-bottleneck for ingested MPs, enhancing the retention of larger particles within the stomach and promoting fragmentation into smaller plastic debris, which is then released in the intestine,” they reported.
How? Some of the particles were shown to pass into the “gastric mill,” a complex of small calcified plates that grind against each other to break down food in a lobster’s stomach. This process fragmented some of the plastic into smaller particles, which then moved on to the lobsters’ intestines. In live animals, these smaller fragments would presumably be expelled into the ocean.
According to the researchers, this is evidence that the langoustine is responsible for the fragmentation of MPs already accumulated in sediments through its scavenging activity and digestion. These findings highlight the existence of a new kind of “secondary” microplastic, introduced into the environment by living organisms, that could represent a significant pathway of plastic degradation in the deep sea, the authors say.
They also note that these tinier particles could then be more bioavailable to smaller creatures in the deep-sea food chain.
The authors acknowledge that funding for this research was provided by the European Commission (DG MARE and POR FSE), Italy’s Ministry of Agricultural, Food and Forestry Policies and JPI Oceans’ EPHEMARE Project.