DOES MUSSEL FARMING INFLUENCE CARBON DIOXIDE, METHANE AND NITROUS OXIDE INVENTORIES? A case study on the Swedish west coast.

Abstract

Both climate change, caused by anthropogenic emissions of greenhouse gases (GHGs), and food security remain substantial challenges for the global community. Against this backdrop, aquaculture is seen to present some remedies. Of particular interest is the farming of marine bivalves, such as blue mussel (Mytilus edulis), since they can be a source of nutrition and have the potential to provide other ecosystem services. However, the effect of blue mussel farming on GHG emissions is not widely studied. This study aims to investigate if mussel farming directly leads to higher emissions of the three major GHGs, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Concentrations of these gases were measured around two active and commercially used mussel farms on the Swedish west coast that produce blue mussels for human consumption, to investigate if mussel farming influences greenhouse gas dynamics. A control site, not impacted by aquaculture, was chosen for each of the mussel farms. For data collection and sampling three different measuring campaigns were undertaken in September 2023, October 2023 and in February 2024 to account for variations in temperature, water column conditions, and the status of the mussel farms. Discrete water samples were collected from a research vessel at each studied area, at three different depths for later analysis of dissolved inorganic carbon (DIC), dissolved CH4 and N2O in the water column via single-phase gas chromatography and solid-state infrared detection. Additionally, in situ measurements of the surface water concentrations for the three GHGs were conducted at both farms and both control areas using optical feedback-cavity enhanced absorption spectroscopy (OF-CEAS). The mussel farms were found to not have an environmentally significant impact on the local marine GHG dynamics, suggesting that the aquaculture of bivalves, and blue mussels in particular, can be a sustainable source of protein.