Can Zooplankton Be Entangled by Microfibers in the Marine Environment?: Laboratory Studies

We investigated the probability of copepod entanglement in microfibers in a laboratory experiment. This experiment was inspired by an accidental observation of entangled copepods with microfibers during isolating copepods for grazing experiments. The exposure of microfibers to copepods was designed by applying conditions similar to environmentally relevant concentrations of microfibers to zooplankton in the Yellow Sea as well as highly elevated concentrations of microfibers compared to the previously reported maximum natural concentration. Copepod entanglement in microfibers was reproduced in laboratory. The entanglement was not observed in the condition which simulated the environmental scenario of copepods outnumbering microfibers observed in the Yellow Sea, while it occurred inconsistently in the conditions of the maximum and 10-fold maximum natural concentrations of microfibers. However, consistent entanglement of copepods by microfibers was found in the 100-fold maximum environmental concentration of microfibers. These results suggest that copepod entanglement by microfibers can happen accidentally under the maximum natural concentration of microfibers occurring in the marine environment; however, copepods are likely to be entangled in microfibers consistently if copepods encounter highly enhanced concentration of microfibers.