Operation and Maintenance phase
MZI installations can increase the amount of drift litter in the sea.
Most MZI installations are constructed from plastics. Due to wave action part of the MZI installation (e.g. jerry cans, ropes) can become loose and start drifting. This is called macro-plastic pollution. The macro-plastic pollution can be reduced by a robust construction which is able to withstand destructive forces, such as waves.
Another type of contamination by the MZI installation is micro-plastic pollution. The mussel seed attaches onto ravelled parts of the ropes. Very small ravelled parts can become loose, e.g. during harvest. Hereby micro elements of the used materials may disappear into the environment. In case of synthetic materials (plastics, polymers) this may have a negative effect on the ecology. The micro plastics may be taken in by filter organisms. These organisms are mostly on the base of the marine food chain. The micro plastics itself are toxic and in addition to this organic pollution in the water (DDT derivates, PCB’s and modern relatives) may attach to the micro plastics. When the micro plastics go through the digestive system these contaminations can be absorbed by the organism. Because the effects of micro plastics are not completely known, more research should be conducted to investigate the effects of these micro plastics. More research needs to be conducted into base material which in case of fragmentizing in the seawater are fast degradable. And materials which are their total lifespan harmless.
Currently the mussel sector is improving the different MZI techniques.