The Effects of Microplastics on Dolioletta gegenbauri (Tunicata, Thaliacea)

Oceanographic studies revealed the abundance of minute plastic particles in coastal regions. Such particles, called microplastics, are abundant in sizes smaller than 100 µm ESD (Equivalent Spherical Diameter) and can be collected and ingested by planktonic copepods. Those animals are the most abundant metazoans on our planet. Abundantly co-occurring with planktonic copepods in subtropical and temperate neritic waters are doliolids (Tunicata, Thaliacea), which can dominate subtropical shelves because of their high asexual reproductive performance. Our studies were designed to examine the effects of polystyrene beads at low abundance, compared with phytoplankton, on abundantly occurring gonozooids of Dolioletta gegenbauri. Our findings reveal that such abundance of microplastic particles, in the presence of environmental concentrations of phytoplankton, reduces rates of feeding, growth, and oxygen consumption of this tunicate. Feeding rates on phytoplankton in the presence of beads were reduced by up to 58%, growth rates by up to 85%, and oxygen consumption rates by up to 33%. We conclude that such microplastic particles could limit the often in situ encountered pronounced proliferation of this tunicate species (Deibel in: Bone (ed) The biology of pelagic tunicates, Oxford University Press, Oxford, 1998).