Nutrients and seabird biogeography: Feather elements differ among oceanic basins in the Southern Hemisphere, reflecting bird size, foraging range and nutrient availability in seawater

Abstract

AbstractAimBiodiversity hotspots in wide‐ranging marine species typically overlap with regions of high productivity, which are often associated with nutrient‐rich waters. Here we investigate how element concentrations in feathers vary among highly mobile seabirds in global seabird biodiversity hotspots.LocationSouthern Hemisphere.Time periodContemporary.Major taxa studiedFifteen species in the order Procellariiformes.MethodsWe collected data on the concentration of 15 elements in feathers for 253 seabirds sampled across Australia and New Zealand and compared the “fingerprint” of micronutrient element profiles to feathers of related seabirds from global hotspots using principal component analysis (PCA), cluster analysis and permutational analysis of variance (PERMANOVA).ResultsBreast feather concentrations of some elements, including aluminium, iron, cobalt, chromium, manganese, nickel, arsenic and cadmium, were tens‐to‐hundred‐fold higher in smaller (<400 g) than larger species (≥400 g). We suggest these results reflect the dominance of pelagic crustaceans in the diet of smaller seabirds, blooms of which are influenced by input of limiting ocean nutrients. Cluster analysis revealed three broad groups of feather elements: large seabirds, and small seabirds in each of the South Pacific and South Atlantic Ocean basins. High concentrations of some elements in feathers match seawater availability and are detectable in lower‐trophic feeding seabirds with local movements. Conversely, the element fingerprints of longer‐distance, higher‐trophic foragers, including albatrosses, do not match availability in seawater at the collection site.Main conclusionsThe feather element concentrations of shorter‐range foraging, lower‐trophic feeding seabirds vary significantly among ocean basins, reflecting availability in seawater, while longer‐range, higher‐trophic species do not. We propose that geographically diverse availability of micronutrients, in addition to primary productivity, may play an underrecognized role in seabird biogeography and intra‐hemispheric migration, though more research is needed. This study has important implications, considering the role of element availability in supporting biodiversity hotspots for dispersive marine predators and for the designation of protected areas.