Moving iron around the Southern Ocean: what can Northern Giant Petrels contribute?

Steve Wing (Department of Marine Science, University of Otago, Dunedin, New Zealand) and colleagues have published open access in the journal Marine Ecology Progress Series on levels of iron in the guano of sub-Antarctic seabirds on New Zealand's Auckland Islands, including the ACAP-listed Northern Giant Petrel Macronectes halli.

The paper’s abstract follows:

"Biological vectors are important for redistribution of nutrients in many ecological systems.  While availability of iron (Fe) to phytoplankton limits pelagic productivity in the Southern Ocean, biomagnification within marine food webs can lead to high concentrations of Fe in the diet of seabirds and marine mammals.  We investigated patterns in concentrations of the micronutrients Fe, Co, Zn and Mn, and the toxins Cd and As, in the guano of oceanic, coastal and predatory seabirds and in faeces of 2 species of marine mammals that congregate to breed in the sub-Antarctic Auckland Islands. We found that much of the variability in concentrations of Fe, Co, Zn and Mn among species could be explained by foraging behaviour and by trophic position. We observed concentrations of Fe to be 8 orders of magnitude higher in the guano of predators and coastal foragers than in the sub-Antarctic mixed layer. High concentrations of As and Cd were associated with organic matter sources from macroalgae.  Analyses of the molar ratio Fe:Al indicated that Fe within food webs supporting seabirds has likely been extensively recycled from its lithogenic source.  Patterns in Fe:N among species indicated that Fe is concentrated 2 to 4 orders of magnitude in the guano of seabirds compared to limiting conditions for phytoplankton growth in sub-Antarctic waters.  These data highlight the potential role of seabirds and marine mammals in the redistribution of micronutrients in the Southern Ocean and their likely role as key nutrient vectors in the ecosystem, particularly around the sub-Antarctic islands during the breeding season.”

Northern Giant Petrel, photograph by Marienne de Villiers

Reference:

Wing, S.R., Jack, L., Shatova, O., Leichter, J.J., Barr, D., Frew, R.D. & Gault-Ringold, M. 2014.  Seabirds and marine mammals redistribute bioavailable iron in the Southern Ocean.  Marine Ecology Progress Series 510: 1-13.

John Cooper, ACAP Information Officer, 29 September 2014.