Extreme ecological response of a seabird community to unprecedented sea ice cover

Abstract

Climate change has been predicted to reduce Antarctic sea ice but, instead, sea ice surrounding Antarctica has expanded over the past 30 years, albeit with contrasted regional changes. Here we report a recent extreme event in sea ice conditions in East Antarctica and investigate its consequences on a seabird community. In early 2014, the Dumont d'Urville Sea experienced the highest magnitude sea ice cover (76.8%) event on record (1982-2013: range 11.3-65.3%; mean±95% confidence interval: 27.7% (23.1-32.2%)). Catastrophic effects were detected in the breeding output of all sympatric seabird species, with a total failure for two species. These results provide a new view crucial to predictive models of species abundance and distribution as to how extreme sea ice events might impact an entire community of top predators in polar marine ecosystems in a context of expanding sea ice in eastern Antarctica.

Keywords: Antarctic; breeding; penguins; petrels; sea ice; skuas.

Figure 1.

Monthly sea ice concentration in the Dumont d'Urville Sea colour coded by season (summer: December–March; winter: April–November). The rate of increase in monthly sea ice concentration increased significantly in summer beginning in 2011 (red dashed line) and the sea ice concentration in winter started to decrease in 1992 (blue dashed line). Dotted lines indicate ±s.d. calculated on the variation between months.

Figure 2.

Box plots of breeding success of emperor penguins (EP), Adélie penguins (AP), southern fulmars (SF), snow petrels (SP), cape petrels (CP), Wilson storm petrels (WP), south polar skuas (SK) and all species combined (all). The band inside the box is the median, the bottom and top of the box are the 25% and 75% quartiles, respectively, the lower and upper whiskers are the 10% and 90% quartiles, respectively, the lower and upper crosses are the 5% and 95% quartiles, respectively. Dots indicate breeding success data for the 2013–2014 breeding season. Colours indicate penguins (orange), petrels (black), skuas (brown) and all (red). Numbers indicate the number of years breeding success was recorded. Breeding success was defined as the proportion of eggs laid producing a fledging for species that lay a single egg and as the number of fledged chicks per breeding pair for two egg laying species (AP and SK).

Figure 3.

Fitted GAM results showing the relationship between the seabird breeding success data and the summer sea ice concentration (SIC) in the Dumont d'Urville Sea for the period 1982–2013. Dotted lines indicate 95% CIs. Red dots indicate the observed breeding success in 2014. Breeding success was defined as the proportion of eggs laid producing a fledging for species that lay a single egg and as the number of fledged chicks per breeding pair for two egg laying species (Adélie penguin and south polar skua.).