A novel approach to determining dynamic nitrogen thresholds for seagrass conservation

1. Seagrass decline is often related to eutrophication, with sudden and drastic losses attributed to tipping points in nutrient loads. The identification of these threshold loads is an important step in the sustainable management of nutrient discharges.
2. In this study, a novel methodological approach is presented to simulate the spatial and temporal dynamics of coastal nitrogen loads, and its relationship to seagrass loss. The analysis allows the identification of nitrogen thresholds associated with the loss of Posidonia and Amphibolis spp. in Adelaide, South Australia.
3. The identified thresholds varied between 0.8 and 1.1 t N km-2 over 6 months, and explained up to 95% of all seagrass losses in the region.
4. Posidonia spp. was predominantly lost nearshore, indicating a threshold for this species in the higher end of the values reported here. In contrast, Amphibolis spp. was selectively lost further offshore, suggesting a lower threshold for the onset of fragmentation and decli...