1.3.1 Seabirds and nearshore ecosystems

The circular seabird economy – whereby seabirds feed in the ocean, transport marine-derived nutrients onshore to their breeding colonies, and then seabird-derived nutrients runoff into the ocean, enriching nearshore ecosystems – is a critical driver of biodiversity and functioning on islands and in nearshore marine ecosystems including coral reefs and sea grass beds.

Traces of the marine-derived nutrients deposited by seabirds can be found at every trophic level on these islands, from invertebrates through to plants. The nutrients can be tracked using a peculiarity of nitrogen, which naturally forms stable isotopes (variants). One isotope can be used to track the marine origins of this nutrient. It is now clear that the vegetation cover of islands is not able to use all this material and, therefore, much of it runs off into the coastal environment. Much more is bonded into the soil, some of which washes off during heavy rain.4