Environmental DNA as a complementary tool for biodiversity monitoring: A multi-technique and multi-trophic approach to investigate cetacean distribution and feeding ecology

records, eDNA molecular detection): D. delphis, P. phocoena, T. truncatus and G. griseus. In addition to these, positive molecular detections of B. physalus were obtained through eDNA analysis. Regarding the spatial distribution of these records, it is clear that D. delphis was sighted not only in greater abundance but also with a dispersed distribution throughout the region studied, which is also in line with the data obtained by molecular detection. For the other identified species, their DNA abundance was lower and there were fewer visual records obtained as well. Overall, no pattern of spatial or temporal correlation between molecular detections and visual records is clear. An inter-seasonal comparison of the spatial distribution of the records obtained by the visual surveys with the eDNA detections reveals contrasting results (Fig 4). In Fig 4. Seasonality of cetacean records obtained by visual monitoring (A) and molecular analysis of environmental DNA (B), for summer (left) and winter (right) campaigns carried out in the North coast of Mainland Portugal, between 2021 and 2023. https://doi.org/10.1371/journal.pone.0300992.g004 PLOS ONE Environmental DNA as a complementary tool for biodiversity monitoring PLOS ONE | https://doi.org/10.1371/journal.pone.0300992 October 16, 2024 9 / 20