The rise and fall of an ancient Adélie penguin ‘supercolony’ at Cape Adare, Antarctica

Abstract

We report new discoveries and radiocarbon dates on active and abandoned Adélie penguin (Pygoscelis adeliae) colonies at Cape Adare, Antarctica. This colony, first established at approximately 2000 BP (calendar years before present, i.e. 1950), is currently the largest for this species with approximately 338 000 breeding pairs, most located on low-lying Ridley Beach. We hypothesize that this colony first formed after fast ice began blocking open-water access by breeding penguins to the Scott Coast in the southern Ross Sea during a cooling period also at approximately 2000 BP. Our results suggest that the new colony at Cape Adare continued to grow, expanding to a large upper terrace above Ridley Beach, until it exceeded approximately 500 000 breeding pairs (a ‘supercolony’) by approximately 1200 BP. The high marine productivity associated with the Ross Sea polynya and continental shelf break supported this growth, but the colony collapsed to its present size for unknown reasons after approximately 1200 BP. Ridley Beach will probably be abandoned in the near future due to rising sea level in this region. We predict that penguins will retreat to higher elevations at Cape Adare and that the Scott Coast will be reoccupied by breeding penguins as fast ice continues to dissipate earlier each summer, restoring open-water access to beaches there.

Receding ice drove parallel expansions in Southern Ocean penguins

“…Although estimates of precise LGM breeding ranges for penguins remain elusive (but see ref. 36), our findings are consistent with the hypothesis of (6) that during the LGM, many Southern Ocean species retreated to ice-free refugia (e.g., Gough, Amsterdam, and Falklands islands; southern South America; and New Zealand's southern islands) ( Fig. 2B; see refs.…”

Genomic insights into the secondary aquatic transition of penguins

“…Interestingly, taxa that increased in population size towards the end of the LGP (e.g., A. forsteri, P. adeliae, S. magellanicus, E. filholi, E. moseleyi, E. sclateri, and E. schlegeli are typically migratory, and tend to forage offshore (>50 km; see Supplementary Data 1 17 ), while taxa that decreased towards the end of the LGP (e.g., S. humboldti, S. demersus, M. a. antipodes and likely M. a. richdalei ) tend to be residential, and forage inshore; see Supplementary Data 1 . Taxa that disperse farther may have overcome local impacts of global climate cooling during the LGP (e.g., changes in sea-ice extent, prey abundance and terrestrial glaciation, however see 18 ) largely by relocating to lower latitudes (e.g., 14 ), whereas locally-restricted taxa may have been more prone to sudden population collapses.…”

6,000‐Year Reconstruction of Modified Circumpolar Deep Water Intrusion and Its Effects on Sea Ice and Penguin in the Ross Sea

“…Organic remains are well preserved in the cold and dry Antarctic environment (Koch et al., 2019). We produced a synthesis of the frequency of penguin remains and relevant radiocarbon dates from previous research, in order to reconstruct a history of penguin occupation of the Ross Sea spanning the last 7 kyr (Baroni & Hall, 2004; Baroni & Orombelli, 1991, 1994a; Emslie, 2020; Emslie et al., 2003, 2007, 2014, 2018; Gardner et al., 2006; Hall et al., 2006; Hall & Denton, 2017; Harrington & Mckellar, 2017; Hofstee et al., 2006; Lambert et al., 2002; Lorenzini et al., 2009, 2010, 2011; Nie et al., 2015; Stuiver et al., 1986). Since the radiocarbon age calibration methods varied between different publications, we recalibrated the conventional ages using a uniform methodology (see Section 2.2).…”