On the Antarctic peninsula, nitrogen-rich poop from seal and penguin colonies create biodiversity hotspots by enriching the soil, according to a new study published on 9 May in Cell Press (1).
The team of researchers, Dr Stef Bokhurst and Prof Rien Aerts from the Vrije Universiteit Amsterdam and Dr Pete Convery from the British Antarctic Survey, endured the desolate Antarctic landscape to examine the biological diversity of the region. And they discovered that, while scarce, life becomes increasingly more abundant close to penguin and seal colonies.
According to the authors, elephant seals and penguins transfer nitrogen from the sea to land via their poop, which partially evaporates as ammonia and is absorbed into the surrounding soil. Moreover, since ammonia is picked up by the wind, the enriched soil regions extend thousands of meters beyond the borders of the marine vertebrate colonies.
Species in the region include the elephant seals (Mirounga angustirostris) and Antarctic penguins, including gentoo (Pygoscelis papua), chinstrap (P. antarcticus), and Adélie penguins (P. adeliae).
The so-called nitrogen enrichment footprints ― circular areas of nutrient enrichment surrounding colonies ― promote biodiversity. Even more interesting, the size of this footprint depends on the size of the seal and penguin population. Therefore, knowing the location and size of penguin and elephant seal populations can now predict biogeographical patterns of Antarctic terrestrial biodiversity.
Surprisingly, the size of the enrichment footprint depends on the size of the colony and not on how cold or dry a region is. Bokhurst and his colleagues used this information to create maps of the biodiversity hotspots that can be updated in the future with data from satellite images showing the size of marine vertebrate communities – thus, avoiding the need for more gruelling fieldwork.
Increased soil nitrogen in the Antarctic region is linked to improved plant growth and soil respiration. The researchers discovered a flourishing community of mosses and lichens that support smaller animals living within the moss and lichen, such as springtails (Collembola), mites (Acari), and roundworms (Nematoda) – which are 2 to 8 times more abundant than elsewhere.
Whereas grasslands in the US or Europe support about 50,000 to 100,000 per square meter of these species, in Antarctic hotspots, there are millions per square meter.
While the region remains relatively isolated, climate change and human activity pose potential threats. One risk is that these Antarctic biodiversity hotspots could provide a welcoming environment for invading species, including predatory insects like spiders and beetles carried into the system by seabirds or humans, or even invasive plant species, as seeds can blow over from South Africa and South America.
The next step for the authors will be to determine whether invading species really do pose a threat in such a cold, desolate, and isolated part of the world. And how to protect these currently untouched regions in both the Antarctic and Arctic.
(1) Bokhorst, S., Convey, P., and Aerts, R. Nitrogen Inputs by Marine Vertebrates Drive Abundance and Richness in Antarctic Terrestrial Ecosystems. Current Biology (2019). DOI: 10.1016/j.cub.2019.04.038