Abstract
The crucial role of seabirds in the enrichment of nutrient-poor polar terrestrial ecosystem is well-known. However, no studies have examined the potentially different impacts associated with piscivorous and planktivorous bird colonies on the surrounding tundra soils. Therefore, we compared guano deposition and physical and chemical parameters of soil near two large seabird colonies, one of planktivorous little auks (Alle alle) and the other comprising piscivorous Brunnich’s guillemots (Uria lomvia) and kittiwakes (Rissa tridactyla). The two colonies generated similar levels of guano deposition, with the intensity of deposition decreasing away from the colony. Guano deposition adjacent to both colonies was considerably higher than that in control areas. The increased guano supply around colonies significantly enhanced soil conductivity, nitrogen (NO3 −, NH4 +), potassium (K+), and phosphate (PO4 3−) ion concentrations and led to reduced pH values. Guano deposition explained 84 % (piscivorous colony) and 67 % (planktivorous colony) of the total variation in the tested soil parameters. Planktivore and piscivore colonies affected adjacent tundra in different ways. The phosphate content and pH value of soil influenced by piscivores were significantly higher than values measured in planktivore-influenced soil. The gradient of guano deposition and associated ion content in the soil decreased more rapidly with distance from the piscivore colony. Climate-induced changes in populations of planktivorous and piscivorous seabirds are expected in the study region and may therefore have substantial consequential effects on Arctic terrestrial ecosystems.
Highlights
Birds that forage at sea and breed on land deposit large amounts of guano, eggshells, feathers, and carcasses near their colonies, initiating the formation of ornithogenic soils and thereby facilitating the development of associated tundra communities, with increased primary and secondary production and biodiversity (Mulder et al 2011; Ellis et al 2011). This large-scale transport of organic and inorganic matter from sea to land is crucial for many Arctic and Antarctic terrestrial ecosystems, which otherwise are characterized by chronic deficiency of certain nutrients such as nitrogen, phosphorus, potassium, and calcium (Ryan and Watkins 1989; Cocks et al 1998; Stempniewicz 2005; Bokhorst et al 2007; Smith and Froneman 2008)
The research took place in July 2005 and 2006, on the northern coast of Hornsund fjord, in areas influenced by two large seabird breeding colonies (Fig. 1): 1. A colony of planktivorous little auks situated on Ariekammen mountain (77°000N 15°310E) (Fig. 1a)
The little auk colony covered a large area of the relatively shallow slope and had a less clear-cut boundary than was the case for the cliffnesting species. This transect commenced from the colony center, while that for the guillemot and kittiwake colony commenced just beneath the nesting cliff; in both cases, we considered these points as being the most influenced by seabirds
Summary
Birds that forage at sea and breed on land deposit large amounts of guano, eggshells, feathers, and carcasses near their colonies, initiating the formation of ornithogenic soils and thereby facilitating the development of associated tundra communities, with increased primary and secondary production and biodiversity (Mulder et al 2011; Ellis et al 2011) This large-scale transport of organic and inorganic matter from sea to land is crucial for many Arctic and Antarctic terrestrial ecosystems, which otherwise are characterized by chronic deficiency of certain nutrients such as nitrogen, phosphorus, potassium, and calcium (Ryan and Watkins 1989; Cocks et al 1998; Stempniewicz 2005; Bokhorst et al 2007; Smith and Froneman 2008). Guano itself is typically alkaline, the process of its decomposition in the soil often results in increased soil acidity being found near seabird colonies (Gilham 1956; Garcıa et al 2002; Ellis 2005; Wait et al 2005)
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