Effects of Microplastic Fibers on American Lobster Larvae (Homarus americanus)

Due to anthropogenic activity, plastic has become a prevalent pollutant in the world’s marine ecosystems, found even in Arctic and deep sea waters. Plastics make their way into the ocean from terrestrial and river sources at a rate of ~6-15 MT yr^-1. The majority of ocean plastic exists as microplastics, particles less than 5 mm in length. Among these particles, microplastic fibers (MPF) are the most common, making up 91% of the microplastics in the ocean. In zooplankton and invertebrate larvae, microplastics have been observed to cause developmental and behavioral issues. MPFs pose a potential threat to larval stages of the ecologically and economically significant American lobster (Homarus americanus), which is already threatened by climate change. Such planktonic larvae float and coexist in the same ocean surface layer where buoyant MPFs accumulate. Laboratory experiments were conducted to determine the effects of MPFs on the survival and development of H. americanus larvae under different MPF concentrations. Larval survival (stage I and stage II) was higher at lower MPF concentrations. Larval molting (stage I to II) appeared faster at higher MPF concentrations. Further experiments quantified the accumulation of fibers in the carapace as a function of food availability, fiber color, and larval stage. Fibers accumulated preferentially under the carapace in the presence of food for stage II larvae. MPF color had a slight effect on fiber accumulation under the carapace for stage II. MPF accumulated more in stage III than stage I larvae, indicating stage specificity. Food availability and larval stage contributed more strongly to carapace fiber accumulation than fiber color. It should be noted that for all treatments, there was no significant difference on the effect of ambient MPF concentrations (≤ 1 MPF ml^-1) with respect to no fibers (control = 0 MPF ml^-1).