Adélie penguins north and east of the ‘Adélie gap’ continue to thrive in the face of dramatic declines elsewhere in the Antarctic Peninsula region

Abstract

While population declines among Adélie penguins and population increases among gentoo penguins on the Western Antarctic Peninsula are well established, the logistical challenges of operating in the sea ice-heavy northern tip of the Antarctic Peninsula have prohibited reliable monitoring of seabirds in this region. Here we describe the findings of an expedition to the northern and eastern sides of the Antarctic Peninsula—a region at the nexus of two proposed Marine Protected Areas—to investigate the distribution and abundance of penguins in this region. We discovered several previously undocumented penguin colonies, completed direct surveys of three colonies initially discovered in satellite imagery, and re-surveyed several colonies last surveyed more than a decade ago. Whereas our expectation had been that the Peninsula itself would divide the areas undergoing ecological transition and the apparently more stable Weddell Sea region, our findings suggest that the actual transition zone lies in the so-called "Adélie gap," a 400-km stretch of coastline in which Adélies are notably absent. Our findings suggest that the region north and east of this gap represents a distinct ecoregion whose dynamics stand in sharp contrast to surrounding areas and is likely to be impacted by future conservation measures.

Quantifying Antarctic krill connectivity across the West Antarctic Peninsula and its role in large-scale Pygoscelis penguin population dynamics

“…Here, only a handful of small chinstrap and gentoo colonies are present and no Adélie penguin colonies are found (Fig. 1 ) 77 – 80 .…”

Examining the Connectivity of Antarctic Krill on the West Antarctic Peninsula: Implications for Pygoscelis Penguin Biogeography and Population Dynamics

“…Our results illustrate that adult krill populations in the Bellingshausen and Weddell Seas are only weakly connected to the rest of the Antarctic Peninsula waters. Penguin populations north of the Adélie gap have been doing well in recent years 42,43 . The NWLC supports a number of Adélie penguins an order of magnitude greater than anywhere else in our study region (Table 3) 43 .…”

“…Therefore, we hypothesize that the volume of resources available within each of these current features is likely highly heterogeneous and may be differentially impacted by changes to the environment observed over the last several decades. The Weddell Sea may serve as a krill sanctuary due to the extent and persistence of sea ice in the region, whereas sea ice -a critical overwintering habitat for krill [9][10][11][12] -is declining in the Bellingshausen 42,92,93 . Signi cantly higher resource availability north of the Adélie gap from the Weddell Sea may be the cause of the signi cantly larger colonies there.…”

“…We hypothesize that krill connectivity in this region of the WAP plays a signi cant role in Pygoscelis penguin population dynamics north and south of the Adélie gap. Adélie penguin populations are growing or stable north of the gap but are performing poorly elsewhere 42,43 .…”

Sea ice concentration decline in an important Adélie penguin molt area

“…The Adélie penguin is well known as a sea ice obligate, it is found only in areas with sea ice and is declining in areas where sea ice is declining ( 6 , 7 , 32 , 33 ). While the mechanisms that drive this dependence on sea ice are complex, previous studies have offered numerous hypotheses linking Adélie penguin population size and growth rates to SIC and sea ice extent at various geographic and temporal scales ( 5 , 8 , 34 – 37 ).…”