Reproductive failure of emperor penguins in the Weddell Sea

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Adult emperor penguins. Photo: British Antarctic SurveyAdult emperor penguins. Photo: British Antarctic Survey

By Cesar Cardenas
Translation by George Chambers
Last week, the journal Antarctic Science published a study undertaken by researchers from the British Antarctic Survey titled “Emperors on thin ice: three years of breeding failure at Halley Bay.
Some years ago, there was a local extinction of an emperor penguin colony on the Dion Islands (Marguerite Bay, Antarctic Peninsula, 67° 51.9’ S, 68° 42.6’ W), at the northernmost point of the species’ geographic dispersal. Now, this time on the other side of the peninsula, west of the Weddell Sea, a drastic reduction has been reported in one of the largest known emperor colonies (which makes up 5% to 9% of the global population, close to 20 thousand pairs).
Emperor penguins reproduce on stable areas of sea ice. However, none of their offspring could survive the 2016 collapse of the ice sheet in Halley Bay (75° 33’ S, 27° 32’ W). This happened again in 2017 and 2018.
This situation coincides with years of climate change that had led to the breaking and instability of the ice.
In 2019, according to the last count (taken via high-resolution satellite images), there were hardly any adult emperor penguins left in the colony. However, the study also found a significant increase of 1,000% in a colony 55 kilometres to the south – suggesting the penguin pairs were migrating to this colony and other colonies with better conditions.
A young emperor penguin on King George Island. Photo: Cesar CardenasA young emperor penguin on King George Island. Photo: Cesar Cardenas

The warming of the Antarctic peninsula is affecting the durability and size of marine ice and the stable zones of land ice are shrinking at a rate of many kilometres per year. It is thought that the global population of emperor penguins will be reduced by 50% to 70% in the following decades solely because of Antarctic warming.
Thus, in an environment changing so quickly, it is important to guarantee that species will be protected from environmental variability and other threats – such as over-fishing, pollution and human interference in reproductive zones – so that they can be resilient to climate changes.
To this effect, the Marine Protected Area: Territory 1 (western Antarctic and south of the Scotia Arc), a proposal presented in October 2018 (fig. 1) by Chilean and Argentinian scientists, looks into the protection of large areas susceptible to melting at the south of the peninsula, where special attention will be given to controlling the impacts of human activity and to the study of the effects of climate change on biota and the ecosystem in general.
It also looks into a general protected zone in the region south of Marguerite Bay to lend extra protection to the emperor penguin colonies. For example, it described the existence of a colony of over 6,000 adults located on Smyley Island (72° 18’ S, 78° 49.8’ W), according to a 2009 estimation. The protected zone would likewise assist in other important challenges in conservation: safeguarding waters in which krill reproduce and orcas feed, and zones vital in the reproduction and early stages of fish.
Findings like the one recently published don’t just highlight the importance of the creation of protected marine areas in the Antarctic to preserve the species and ecosystems within them against climate change. They also call out the need to develop a plan of research and monitoring in the region to better understand how organisms will react to environmental changes.
Figure 1. Map of the Marine Protected Area proposed by Chilean and Argentinian scientists in 2018 (AMPD1), marking the protected areas for colonies of emperor penguins. A red triangle represents the colony studied by the scientists from the British Antarctic Survey (BAS). 
The author, Cesar Cardenas, is a researcher with the Chilean Antarctic Institute.