## 5 Discussion
Moreover, the biofouling model employed in the present study indicates that the biomass growth and, consequently, the depth of immersion of the particle are both dependent on the temperature of the surrounding water. This is the reason why the Oc05 particle, once in the region of warm Atlantic waters, sank to a depth of 400 m. Furthermore, despite a subsequent trajectory passing considerably further south in the Greenland Sea, the maximum depth reached during the immersion did not exceed 100 m (Figure 3). In summary, the most significant distinction between the present and previous findings is the oscillatory behavior of particles in the vertical plane due to the growth and degradation of the biofilm. The simulation results demonstrate that the incorporation of biofilm degradation into the biofouling model prevents particles from sinking to significant depths, as was previously determined by [PERSON] et al., 2024 [45]. Most particles do not sink below 75 m in polar latitudes, unless they have entered a region of relatively warm Atlantic waters, where the particle immersion could reach a depth of 400 m.  
Figure 7: Sinking velocity (\(w_{s}\)) as a function of biofilm thickness (\(BT\)) for particles of various sizes. A positive velocity corresponds to the sinking of the particles, while a negative velocity corresponds to their rising in the ocean waters. The intersection of two points on the plot indicates the thickness of the biofilm when a larger particle begins to sink at a faster rate than a smaller particle. The exception is the direct output of particles to detritus, which this study is specified based on the findings of [PERSON] et al., 2020 [60]. This paper presents a preliminary assessment of the potential role of aggregates in the sequestration of microplastics in ocean sediments. The study was based on the results of climate system modeling, including several categories of phytoplankton and a single type of zooplankton as well as previously published data on microplastic concentrations in the surface ocean. The authors indicated that their methods for detritus formation from phytoplankton mortality, as well as zooplankton mortality, sloppy feeding, and excretion, resulted in the export of microplastics to the seafloor at a rate of approximately 0.06-8.8% of the total annual ocean plastic pollution. In the absence of a biological model in our research, and consistent with the estimates above [60], we have proposed that 5% of the total mass of plastic present in our model ocean is forcibly removed each year. The current study is based on a number of assumptions that require further examination and more precise observational data. Firstly, it is not considered that biofilms may already be present on microplastic particles when they enter the Arctic Ocean with river discharge. We suggest that the presence of biofilms formed in fresh river water may result in either rapid sedimentation near the estuary or loss of biofilms due to the inability of freshwater organisms to survive in the oceanic environment. In general, it is a common practice to release riverine microplastic particles into the ocean without algae attached. An example of this approach is illustrated in a recent similar study modeling microplastic transport using the Kooi biofouling model. The simulation was conducted in warmer latitudes, namely in the Tyrrhenian Sea [74]. This approach guarantees that all particles are subjected to identical initial conditions. The next group of assumptions relates to the particle biofouling model. The biofouling on the particles in sea ice was estimated to be dependent on the latitude of the particle location and independent of the climatic situation. The satellite data on chlorophyll-a concentration that were used to construct the biofouling model are only available at the ocean surface. The vertical distribution was reconstructed approximately using observational data that are not fully representative for the considered region.