Abstract
Heard Island in the Southern Ocean is a biological hotspot that is suffering the effects of climate change. Significant glacier retreat has generated proglacial lagoons, some of which are open to the ocean. We used pyrotag sequencing of SSU rRNA genes and environmental data to characterize microorganisms from two pools adjacent to animal breeding areas, two glacial lagoons and Atlas Cove (marine site). The more abundant taxa included Actinobacteria, Bacteroidetes and Proteobacteria, ciliates and picoflagellates (e.g. Micromonas), and relatively few Archaea. Seal Pool, which is rich in organic matter, was characterized by a heterotrophic degradative community, while the less eutrophic Atlas Pool had more eucaryotic primary producers. Brown Lagoon, with the lowest nutrient levels, had Eucarya and Bacteria predicted to be oligotrophs, possess small cell sizes, and have the ability to metabolize organic matter. The marine influence on Winston Lagoon was evident by its salinity and the abundance of marine-like Gammaproteobacteria, while also lacking typical marine eucaryotes indicating the system was still functioning as a distinct niche. This is the first microbiology study of Heard Island and revealed that communities are distinct at each location and heavily influenced by local environmental factors.
Highlights
Heard Island (53°05′S, 73°30′E) is a 367 km[2] volcanic island located ~4350 km southwest of Western Australia on the Kerguelen Plateau[1]
Brown Lagoon had the lowest levels of ammonia, nitrate, nitrite and total nitrogen, even though it had a moderate level of dissolved organic carbon (DOC) (27 mg L−1)
This study presents the first assessment of microbial diversity in Heard Island’s aquatic systems
Summary
Heard Island (53°05′S, 73°30′E) is a 367 km[2] volcanic island located ~4350 km southwest of Western Australia on the Kerguelen Plateau[1]. Together with higher ambient temperatures and increased availability of liquid water (more precipitation as rain rather than snow), animal, plant and microbial communities will be able to expand into new niches. The effect of these changes on terrestrial and lacustrine food webs will be important to establish and monitor. Climate-related changes have implications for the marine environment surrounding Heard Island, as increased freshwater from melting glaciers will carry iron and nitrogen rich minerals, as well as microbial populations with as yet uncharacterized roles in C, N and P cycling, out into the sea and eastward along the flow of the Antarctic Circumpolar Current
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