Marine litter in local environments from mussel aquiculture activities: modelling and validation

The initial conditions of marine litter transport models continue to be one of the big handicaps to produce accurate results to obtain useful information for stakeholders. The amount and the type of marine debris emitted by the different sources introduces a huge uncertainty.

In marine local environments under industrial activity, the sources are confined in space and time and some industrial activities introduce particular debris objects. This allows us to reduce the uncertainties mentioned above in the marine litter modelling problem. 

One of these activities is the mussel aquiculture. In Galicia (NW Spain), the mussel farms (Fig.(1)) are based in floating rafts inside the rias(estuaries), with vertical ropes submerged where the mussels are attached to grow up. To avoid the mussel detachment, plastic sticks called mussel pegs or stoppers with a length of 22 cm and a width of 2 cm on average are used (Fig. (2)). These mussel pegs can be lost when the mussel extracting activity takes place. There are estimations of lost around 3 million units per year due to this activity.

The CleanAtlantic project (http://www.cleanatlantic.eu/) aims to protect biodiversity and ecosystem services in the Atlantic Area by improving knowledge and capabilities to monitor, prevent and remove (macro) marine litter. In the scope of this project, we will focus on the modelling of floating mussel pegs lost by mussel farm activity in Ría de Arousa, in the region of Galicia (northwest of Spain).

To that end, we use the met-ocean operational model data from Meteogalicia to perform Lagrangian simulations with MOHID-Lagrangian transport model to obtain concentrations of mussel pegs and the probability maps on surrounding areas inside the Ría de Arousa for the years 2018-2019. Also, we analyze the impact of the different met-ocean conditions in the beaching and coastal accumulation.

Finally, we validate the results with real data obtained from clean beaches surveys from beaches inside the ría during 2018 and 2019.