Auks transform Arctic ecosystems.

By JW. Dowey - 15 Feb 2017 10:20:0 GMT
Auks transform Arctic ecosystems.

Little auks are the supreme ecosystem engineers of the High Arctic. Many other seabird colonies have the same effect, but these extreme climates are highly likely to be affected by global warming. The more northerly ecosystems such as these have no alternative site left because you cannot get any further north!

Svalbad little auks; Credit: © Michael Haferkamp (CC)

The High Arctic is little understood by most of us, with marine-derived nutrients increasing productivity in some areas, just as they do in several less extreme environments. For example, the salmon of the Pacific provide massive MDN for both Asian and North American ecosystems. With the loss of several of its relatives, the little auk stands out as an abundant animal that modifies the freshwater and terrestrial Arctic environments around it with these MDN. The auk lives in huge colonies that make these effects highly significant within the ecosystem.

The authors of this paper were Ivan Gonzalez-Bergonzoni, Kasper L. Johansen, Anders Mosbech,Frank Landkildehus, Erik Jeppesen and Thomas A. Davidson, from Universidad de la Republica and Instituto de Investigaciones Biologicas Clemente Estable, Uruguay, the Greenland Institute of Natural Resources in Nuuk, NCAS, China and the University of Aarhus in Denmark. They title their paper, Small birds, big effects: the little auk (Alle alle) transforms high Arctic ecosystems, publishing in the Proceedings of the Royal Society B.

When you migrate, you move energy and nutrients between ecosystems. With a relatively unproductive Arctic, productivity and biomass are vastly increased by the actions of many seabirds. Measurements included the stable isotope ratios of 15nitrogen and 13carbon of freshwater and terrestrial biota, assessment of terrestrial vegetation, physico-chemical properties, productivity and community structures. The differences that were observed when little auks were present were profound. 85% of biomass was fuelled by the MDN from this species alone.

The little auk has a mass of only 160g (5.6oz) with most of its huge population of 33 million pairs near the NOW (North water Polyna) of NW Greenland. Our photograph shows a pair from Svalbad. They consume about 24% of the copepod (shrimp) stock in that area of the Atlantic. The resultant faeces are the main source of nutrients, which are placed 10km inland because the colonies are located there.

Aquatic mosses and Chironomid (midge) larvae were enriched with carbon in freshwater systems while nitrogen is relayed to both freshwater and terrestrial ecosystems. The hair from Arctic hares and many lake and zooplankton samples were some of the significantly enriched nitrogen samples at the auk sites. Algal biomass in all freshwater could be attributed to the elevated nutrient levels, especially in total nitrogen and total phosphorus. We are interested in particular in the greater taxonomic richness, given this sparse set of habitats. The greening of the environment, and the increased numbers of fox, hare, geese species and musk ox speak for themselves. In freshwater, the algae, as always, decreased richness of species, while the decreased pH (increased acidity) of down to pH 3.4 caused loss of biodiversity too. All fish and macroinvertebrates could be lost in some sites.

Production however was increased in general, to much higher levels than in the famed Pacific salmon example, which relies on them being eaten by carnivores such as bears. Much of the coastal foreland of NW Greenland has been engineered by the little auk. Arctic fox introduction elsewhere has reverse engineered this natural process. The result on some islands has been reversion of grassland to tundra, with vast effects on many species. If the warming of the Arctic continues to accelerate, the same effect seems likely, as the fat-rich copepods reduce, and the auks decline.