The Changing Antarctic Environment & Effect on its Keystone Species

Contributor(s): 
February 11, 2014

Antarctic krill are the keystone species in the Antarctic ecosystem, directly transferring energy in the form of carbon from algae to top predators. Ocean circulation is an important contributor in structuring and maintaining the circumpolar and the regional distribution of Antarctic krill.  Sea ice duration and extent — both of which might be strongly impacted by climate change — represent important factors for krill reproduction and recruitment (defined as the mean abundance of one-year old relative to total mean abundance of post-larval krill).  Our study identified regions of the western Antarctic Peninsula continental shelf that support successful completion of the early life cycle of krill and determined how they might be affected by climate-induced environmental changes.

Krill’s life cycle involves a vertical migration.  Their eggs are released near the surface, then sink to a depth of 800 meters where they develop into larvae before re-surfacing.  A one-dimensional temperature-dependent model was used to simulate the early-life cycle of embryos and larvae and determine which regions of the shelf support a successful life cycle. Lagrangian particle tracking experiments were used to simulate the transport of krill larvae along the western Antarctic Peninsula. Krill life cycles and ocean circulation were simulated using both present day and modified environmental conditions including increased wind speed and increased transport of the Antarctic Circumpolar Current, both of which affect the volume of Circumpolar Deep Water (CDW) transported onto the shelf.

The increased Antarctic Circumpolar Current transport resulted in more CDW intrusions on the shelf.  Advection of warm water to the upper-shelf reduced sea ice by 20%.  The changes in environmental conditions increased krill development on the shelf as well as transport of krill from remote inputs.  More CDW on the shelf potentially enhance larval survival, however, a 20% reduction in sea-ice distribution can act against larval recruitment, impeding larval survival of krill that overwinter on the shelf.   A moderate decrease in sea-ice extent thus affect krill differently at different stages of their life-cycle, leaving the ultimate impact on krill, and the multiple trophic levels they support, worthy of further investigation. 

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Piñones A, Hofmann EE, Daly KL, Dinniman MS, Klinck JM (2013) Modeling environmental controls on the transport and fate of early life stages of Antarctic krill (Euphausia superba) on the western Antarctic Peninsula continental shelf. Deep-Sea Research I 82: 17-31