Variability in δ15N, δ13C and Kjeldahl nitrogen of soils from islands with and without seabirds in the Marlborough Sounds, New Zealand

Nutrients brought to land by seabirds may provide important subsidies to terrestrial ecosystems. We measured the total Kjeldahl nitrogen (TKN) and carbon and nitrogen isotope ratios of soils from islands with and without seabirds in the Marlborough Sounds, New Zealand to investigate one means by which seabirds may influence island ecosystem function. Isotope analysis revealed a seabird influence in island soils on the seabird-inhabited islands. However, significant differences in TKN were not related to seabird presence or absence. Pre-existing differences between the islands and high productivity even in the absence of seabirds were concluded to be the reasons for the lack of measurable seabird influence on nitrogen levels.