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Migratory animals such as seabirds, salmon and whales can transport large quantities of nutrients across ecosystem boundaries, greatly enriching recipient food webs. As many of these animals biomagnify contaminants, they can also focus pollutants at toxic levels. Seabirds arguably represent the most significant biovectors of nutrients and contaminants from the ocean to the land, given their sheer numbers and global distribution. However, long-term census data on seabirds are rare. Using palaeolimnological proxies, we show that a colony of Arctic seabirds has experienced climate-induced population increases in recent decades. We then document increasing concentrations of contaminants, including polychlorinated biphenyls and cadmium, in pond sediments that are linked to biotransport by seabirds. Our findings suggest that climate-related shifts in global seabird populations will have the unexpected consequence of restructuring coastal ecosystems.

The role of northern fulmars (Fulmarus glacialis) was investigated for the transport of nutrients and trace elements to a series of 10 ponds located along a gradient of seabird influence below a fulmar colony in the high Arctic (Cape Vera, Devon Island, Canada). Phosphorus, Cd, K, Zn, and As were identified as seabird-derived elements, having both a high concentration in fulmar guano and a low concentration in background pond sediments (i.e., a high biogenic enrichment factor). Fluxes of these elements were highest in the pond closest to the colony and declined exponentially with distance. Sediments in several of the ponds exceeded Canadian Sediment Quality Guidelines for the Protection of Aquatic Life set for As (5.9 mg/kg) and Cd (0.6 mg/kg), and in the pond closest to the colony, which receives the most seabird subsidies, sediments contained 343 mg/kg Zn, exceeding the threshold for probable adverse biological effects. Although nutrient subsidies from fulmars create an Arctic oasis at Cape Vera, which supports a variety of flora and fauna, the same biological transport pathway puts at risk some of these species by creating sedimentary As, Cd, and Zn concentrations at this remote site similar to those usually observed only near industrialized locations.

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