Towards understanding how UV exposure influences "Zostera marina" seagrass habitat suitability in coastal New England.

Seagrass meadows provide many ecosystem services (e.g., carbon sequestration, organic carbon production and export, nutrient cycling, sediment stabilization) but they have been experiencing declining biomass and shifting distributions due to their proximity to the land-ocean interface and their vulnerability to anthropogenic and natural stressors. Research has shown that UV exposure can influence seagrass growth and health. However, there is still a lack of information on how natural UV exposure in shallow coastal waters actually impacts seagrass habitat suitability, and on whether it should be considered as an important factor in seagrass habitat suitability models. Here, we used field measurements (optical properties, water-constituents concentrations) and data from an in-water UV-monitoring station collected at two successful seagrass-restoration sites in New England in order to evaluate how variability in water constituents and their optical properties influences UV exposure of seagrasses. Despite both being successful, the two restoration sites are contrasting in terms of their optical properties, with one being strongly influenced by estuarine processes. The data facilitated the calculation of time-integrated values of spectral UV exposure at the two contrasting sites, thereby improving our understanding of what suitable ranges are for UV radiation at seagrass restoration sites. The data also facilitated the development of optical algorithms applicable to high-spatial-resolution sensors (e.g., Landsat-8 OLI) that can be used to map the UV optical properties in nearshore waters. This study represents a step towards a better understanding of how UV exposure influences seagrass habitat suitability in New England.