Primary producers are the foundation of marine food webs and require reliable nutrient sources to maintain their
important role with ecosystems. While marine mammals and seabirds can play critical roles in marine nutrient
cycling, their contributions are often overlooked. The fjord systems of Southeast Alaska support a high diversity of
marine mammals and seabirds in addition to some of the most valuable fisheries in the US. Nonetheless, there is
still relatively little known about nutrient sources and fluxes in this region which is a critical component of fisheries
management. The goal of our study was to advance knowledge of the role of mammals and seabirds in marine
nutrient cycling and to understand how changing marine mammal and seabird populations may alter ecosystem
dynamics. We analyzed nutrient levels in marine mammal scat, seabird guano, and seawater samples collected in
Berners Bay, Southeast Alaska, to determine the influence of marine mammals and seabirds on nearshore nutrient
concentrations. Utilizing qualitative network models (QNMs), we then examined how a simulated Berners Bay
ecosystem would respond to an increase in marine mammals, seabirds, and nutrients. Researchers are
increasingly utilizing QNMs as a first step in the development of ecosystem-based fisheries management plans as
their adaptable nature is well suited to address rapidly changing climatic conditions. Our direct nutrient
measurements and QNM results indicate that marine mammals and seabirds have the potential to provide
substantial contributions to marine nutrient concentrations in the region and that these valuable ecosystem
services should not be overlooked.We sincerely thank the reviewers for their suggestions and feedbackYe
