Plastic debris accumulation in the seabed derived from coastal fish farming

Area of Science:

• Marine Biology
• Environmental Science
• Ecotoxicology

Background:

• Finfish aquaculture, particularly using floating net-pens, is a growing industry.
• Plastic debris poses a significant threat to marine ecosystems.
• Understanding plastic sources and accumulation in aquaculture environments is crucial.

Purpose of the Study:

• To assess macroplastic and microplastic accumulation in marine sediments near finfish farms.
• To identify the types and sources of plastic pollution associated with aquaculture.
• To compare plastic concentrations with other anthropogenic pressures in the region.

Main Methods:

• Video monitoring for macroplastic identification and quantification.
• Sediment sampling for microplastic analysis (<5 mm).
• Infrared spectroscopy for polymer identification and thermal analysis (enthalpy of melting, degree of crystallinity) to assess degradation.

Main Results:

• Macroplastic debris (ropes, nets, fibres) was prevalent near facilities, with contributions from both aquaculture and fishing activities.
• Microplastic concentrations ranged from 0 to 213 particles/kg dry weight, with higher levels directly under fish farms.
• Polyethylene (PE) and polypropylene (PP) were the dominant polymers, showing signs of degradation.
• Microplastic levels were one order of magnitude lower than in other anthropogenically impacted regions.

Conclusions:

• Finfish aquaculture contributes to plastic pollution in marine sediments, though levels may be lower than other regional sources.
• Plastic debris near farms originates from both aquaculture operations and associated fishing activities.
• Further research is necessary to fully understand the long-term impacts and establish definitive conclusions.