Influence of different diets on protein composition and microplastic retention capacity of the mucus of the jellyfish Aurelia aurita

There is increasing evidence that globally occurring jellyfish blooms are caused by anthropogenic impacts or as response to climate change. These blooms often result in damages for fisheries by clogging fish nets, for the industry by blocking cooling water intake screens or for tourism by stinging swimmers. Furthermore, many people are repelled by the slimy surface or excretions of jellyfishes. However, the mucus of marine organisms is generally important for marine ecosystems. First of all, it is a defence mechanism for the excreting organism. Secondly, it serves as a food source for other animals and, lastly, it can bind chemicals and pollutants in the marine environment. Microplastic is one of these pollutants. The number of plastic particles in the water column is increasing and with it its accessibility for many animals, which mistake the plastic for food. Therefore, there is the need to deal with this problem. Besides the transport through the food web, further consequences of ingestion are inflammations, suffocation or starvation of marine animals. The idea of this study was to make use of jellyfish and the accompanied copious amounts of mucus by investigating the microplastic retention capacity of the mucus of the jellyfish Aurelia aurita. Furthermore, potential effects of different diets on properties of the mucus were tested by exposing individuals of the jellyfish to different feedings regimes for one week (n=4). Feeding regimes were the following: high quality food in high concentrations, high quality food in low concentrations, low quality food in high concentrations and low quality food in low concentrations. The results showed that jellyfish mucus can retain microplastic particles, while neither the protein composition nor the retention capacity for microplastic particles of the mucus were influenced by the different diets. However, the microplastic retention capacity of the mucus was linked to the carbon content of the jellyfish medusae and mucus of individuals kept under the poorest feeding regime showed the lowest retention capacity.