Bottom-Up Effects on Coastal Marine Ecosystems Due to Nitrogen Input from Seabird Feces
Kentaro Kazama
Abstract
Breeding seabirds, often nest at high densities and supply large amounts of marine-derived nutrients, such as nitrogen, in their feces into the ecosystems surrounding their breeding colonies. It has been well demonstrated that the nitrogen supplied by seabirds (seabird-N) into terrestrial ecosystems has a strong bottom-up effect on both producers and consumers. The seabird-N can reach into the surrounding marine ecosystems near the colony through multiple pathways including the surface run-off of rainwater or leaching by ground water. However, in marine ecosystems the bottom-up effects of seabird-N have been rarely documented. A few studies using stable isotope analyses have reported that seabird-N enhances the productivity of both phytoplankton and macro algae. There have been more limited studies documenting similar positive effects of seabird-N on marine consumers. Very little is known about spatio-temporal variations in the effects of the seabird-N on marine ecosystems. To understand the ecosystem functions of seabirds in marine nutrient cycling and the bottom-up effects of seabird-N in marine ecosystems, further research is necessary.