Microplastics in the Water Column: The Role of Lanternfish (Myctophidae) in Microplastic Trophic Transfer to Striped Dolphins (Stenella Coeruleoalba) and Their Cycling in the Western Mediterranean
In spite of knowing that microplastics are already ubiquitous in the marine environment, their distribution along the water column and their circulation in the marine food webs is yet to be fully understood. Here, we analyze microplastic content in the digestive tract of three pelagic lanternfish species, which occupy an intermediate position in the marine food web. Also, we also explore their role as a vector of microplastics for one of their predators, the striped dolphin ( Stenella coeruleoalba) . Almost half of the analyzed lanternfish contained microplastics, mostly blue and black fibers (40.9% and 34.66%, respectively). The median of microplastics found per fish, in fishes with at least one microplastic, was 3 (CI 95% = 3.46 – 6.8); similar to other studies performed in other fish species in the area. Biometric parameters of fish, such as total length and body condition, were not correlated with number of microplastics. However, microplastics’ frequency of occurrence in our samples (40.21%) were significantly different from the occurrence in the digestive tracts of striped dolphins from the same area (90.5%). The amount of microplastics per individual among these species was also significantly different, with a median of 1.907 items/fish (CI 95% = 3.46 – 6.8) and a median of 7 items/dolphin (CI 95% = 3 - 13), suggesting the possible biomagnification role of lanternfish in the food web in the study area. Data presented here contributes to quantify the severity of microplastic pollution in the understudied pelagic environment and in wild, non-commercial and protected species. It will also help to build modelling scenarios together with studies that target microplastic retention and egestion rate in these species.