The number of reproductive pairs of Adélie penguins at Penguin Point increased from 1985/1986 to 2014/2015, in contrast to the reported for colonies in the west of the Antarctic Peninsula where populations are in evident decline (Forcada et al. 2006; Carlini et al. 2007, 2009; Hinke et al. 2007; Schofeld et al. 2010; Trivelpiece et al. 2011; Lynch et al. 2012a; Korzak-Abshire et al. 2013; Lynch and LaRue 2014; Juáres et al. 2015; Santos et al. 2018). Adélie colonies located to the east closer to the Antarctic Peninsula have also reported a decline, but those further away remain relatively stable (Lynch et al. 2013; Lynch and LaRue 2014; Borowicz et al. 2018) or, as in our case, seem to be experiencing growth. Although this population growth in Penguin Point has fluctuated, with this last census a recovery of the reproductive population was verified. The lowest number of breeding pairs was published by Lynch et al. (2013) for the 2009/2010 season, which could be due to the abnormally cold summer of that season (Costa & Agosta 2012), where there was also a large accumulation of snow on the island (Marinsek personal communication 2010). Accumulation and persistence of snow can lead to loss of nesting sites early in the season, as well as reduced reproductive output due to loss of nests with eggs and chicks (Lynch et al. 2009, 2010; Hinke et al. 2012; Frazer et al. 2013; Juáres et al. 2013, 2015 among others).
The Weddell Sea has lower water and air temperatures and a higher abundance of sea ice than the Bellingshausen Sea to the west of the Antarctic Peninsula (Cook and Vaughan 2010; Vernet and Cape 2019), providing a feeding area more stable for the Adélie penguin (Borowicz et al. 2018).
On the other hand, it is also worth mentioning that although commercial krill fishing takes place in the eastern Antarctic Peninsula, it is less developed than in other sectors of Antarctica (CCAMLR krill fishery report 2020).
These are perhaps some of the reasons why the Adélie penguin colony at Penguin Point has not experienced as and population changes as those reported west of the Antarctic Peninsula. Variations in Adélie penguin populations may be due to variables such as decreased sea ice extent; winter survival of adults and chicks; decreased availability of krill, high snow deposition in nesting areas or due to human activities (e.g. Stammerjhon et al. 2008; Barbosa 2011; Juáres et al.2013; 2015, 2020). In turn, these variables may or may not operate together (Carlini et al. 2009; Juáres et al. 2015).
Our work updates the estimate of the abundance of Adélie penguin populations in the eastern Antarctic Peninsula and seeks to support discussions on the need and importance of implementing the proposed MPA in the Weddell Sea (WSMPA) (Teschke et al.2020, 2021; Handley et al. 2021) as it reinforces the importance of this area for the conservation of the Adélie penguin. It is essential to continue conducting long-term studies to better understand the factors or variables that operate on their reproductive populations, determine their trends taking into account interannual fluctuations (Carlini et al. 2007) and highlight the importance of marine protected areas as a tool for the conservation of biodiversity and the normal functioning of the ecosystem.