The impacts of climate change in Antarctica and the Southern Ocean are not uniform and ice‐obligate species with dissimilar life‐history characteristics will likely respond differently to their changing ecosystems. We use a unique data set of Weddell
Predators impact preyscapes (3-D distribution of forage species) by consuming prey according to their abilities or by altering prey behavior as they avoid being consumed. We elucidate prey (Antarctic silverfish[
- NSF-PAR ID:
- 10224118
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Leptonychotes weddellii and crabeater seals' (CESs)Lobodon carcinophaga breeding season distribution in the Weddell Sea, determined from satellite imagery. We contrast the theoretical climate impacts on both ice‐obligate predators who differ in life‐history characteristics: CESs are highly specialized Antarctic krillEuphausia superba predators and breed in the seasonal pack ice; Weddell seals (WESs) are generalist predators and breed on comparatively stable fast ice. We used presence–absence data and a suite of remotely sensed environmental variables to build habitat models. Each of the environmental predictors is multiplied by a ‘climate change score’ based on known responses to climate change to create a ‘change importance product’. Results show CESs are more sensitive to climate change than WESs. Crabeater seals prefer to breed close to krill, and the compounding effects of changing sea ice concentrations and sea surface temperatures, the proximity to krill and abundance of stable breeding ice, can influence their post‐breeding foraging success and ultimately their future breeding success. But in contrast to the Ross Sea, here WESs prefer to breed closer to larger colonies of emperor penguins (Aptenodytes forsteri ). This suggests that the Weddell Sea may currently be prey‐abundant, allowing the only two air‐breathing Antarctic silverfish predators (Pleuragramma antarctica ) (WESs and emperor penguins) to breed closer to each other. This is the first basin‐scale, region‐specific comparison of breeding season habitat in these two key Antarctic predators based on real‐world data to compare climate change responses. This work shows that broad‐brush, basin‐scale approaches to understanding species‐specific responses to climate change are not always appropriate, and regional models are needed—especially when designing marine protected areas. -
null (Ed.)One of the most fundamental changes predicted to occur under warming scenarios for Antarctica is the invasion of durophagous (shell-breaking or peeling) predators—like decapod crustaceans—which were last common in Antarctic waters during the warmer Eocene Period, over 30 million years ago. Since then, Antarctica’s shallow-water benthos developed Paleo- zoic (or deep-sea-like) ecosystems dominated by epi- benthic echinoderms. Despite the looming predatory carnage, little is known about how predators structure shallow subtidal communities in Antarctica, especially in regard to predation on shelled prey. We therefore need to have a baseline of shell repair—if it occurs— prior to the initial invasion of crabs. Here, we assess whether the shell of the Antarctic Scallop, Adamussium colbecki, living in the shallow subtidal under sea ice, records an ontogenetic history of shell repair. Shells of A. colbecki(n=623 valves; ~ 0.50 mm thick) were collected from shallow depths (6–24 m) within western McMurdo Sound, Ross Sea, from the coldest waters on Earth (-1.97 °C): Four sites in Explorers Cove (EC) with semi-permanent (decadal or more) sea ice and a Ferrar Glacier site (located ~30 km south of EC) with annual sea ice and icebergs. All sites were composed of fine sediments interspersed with glacial erratics that were more common at Ferrar than EC. Ju- venile (≤ 50 mm) and adult portions of the shells were examined under a dissecting scope for shell repair. Results indicate that repair did occur and was consistent with predatory damage: 1) valves had ste- reotypic damage patterns, both in style and spatial distribution; 2) there were five styles of repair rang- ing from typical crab-like (jagged) repair to elongate repair; 3) scallops living under ice scour regimes (Ferrar) did not have significantly different repair frequencies than those living under semi-permanent sea ice (EC sites); and 4) none of the shells had shell repair consistent with ice scour as described previ- ously for Laternula elliptica, an Antarctic burrowing bivalve. Frequency of repair varied between 0.04 and 0.26 for the five sites and depths (mean 0.10) and adults had the highest frequency of repair. The mean repair frequency is similar to infaunal Laternulafrom other semi-permanent sea ice sites in McMurdo Sound, but higher than those reported for epifaunal brachio- pods from the Antarctic Peninsula where ice scour does occur. We posit that shell repair can be used as an indicator of durophagy in Antarctica: The forensic agents are unexpectedly sea stars and possibly fish. In a warming world, this scallop may not survive long withboth an increase in ice scour and the putative ar- rival of shell-breaking crabs at ~1 °C.more » « less
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null (Ed.)Abstract Group-size variation is common in colonially breeding species, including seabirds, whose breeding colonies can vary in size by several orders of magnitude. Seabirds are some of the most threatened marine taxa and understanding the drivers of colony size variation is more important than ever. Reproductive success is an important demographic parameter that can impact colony size, and it varies in association with a number of factors, including nesting habitat quality. Within colonies, seabirds often aggregate into distinct groups or subcolonies that may vary in quality. We used data from two colonies of Adélie penguins 73 km apart on Ross Island, Antarctica, one large and one small to investigate (1) How subcolony habitat characteristics influence reproductive success and (2) How these relationships differ at a small (Cape Royds) and large (Cape Crozier) colony with different terrain characteristics. Subcolonies were characterized using terrain attributes (elevation, slope aspect, slope steepness, wind shelter, flow accumulation), as well group characteristics (area/size, perimeter-to-area ratio, and proximity to nest predators). Reproductive success was higher and less variable at the larger colony while subcolony characteristics explained more of the variance in reproductive success at the small colony. The most important variable influencing subcolony quality at both colonies was perimeter-to-area ratio, likely reflecting the importance of nest predation by south polar skuas along subcolony edges. The small colony contained a higher proportion of edge nests thus higher potential impact from skua nest predation. Stochastic environmental events may facilitate smaller colonies becoming “trapped” by nest predation: a rapid decline in the number of breeding individuals may increase the proportion of edge nests, leading to higher relative nest predation and hindering population recovery. Several terrain covariates were retained in the final models but which variables, the shapes of the relationships, and importance varied between colonies.more » « less
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Abstract Seasonal migration, driven by shifts in annual climate cycles and resources, is a key part of the life history and ecology of species across taxonomic groups. By influencing the amount of energy needed to move, external forces such as wind and ocean currents are often key drivers of migratory pathways exposing individuals to varying resources, environmental conditions, and competition pressures impacting individual fitness and population dynamics. Although wildlife movements in connection with wind and ocean currents are relatively well understood, movements within sea‐ice fields have been much less studied, despite sea ice being an integral part of polar ecology. Adélie penguins (
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We evaluated annual and regional variation in the dietary niche of Pygoscelis penguins including the sea ice-obligate Adélie penguin ( Pygoscelis adeliae ), and sea ice-intolerant chinstrap ( Pygoscelis antarcticus ) and gentoo ( Pygoscelis papua ) penguins, three species that nest throughout the western Antarctic Peninsula (AP) to test the sea ice trophic interaction hypothesis , which posits that penguin breeding populations with divergent trends, i.e., declining or increasing, are reliant on differing food webs. Our study relies on values of naturally occurring carbon ( 13 C/ 12 C, δ 13 C) and nitrogen ( 15 N/ 14 N, δ 15 N) stable isotopes as integrated proxies of penguin food webs measured over three years at three different breeding colonies. At Anvers Island in the north, where reductions in sea ice and changes in breeding population trends among sympatric sea ice-obligate (Adélie) and sea ice-intolerant (chinstrap and gentoo) penguins have been most notable, our analyses show that all three species of Pygoscelis penguins became more similar isotopically over the reproductive period. By late chick-rearing at Anvers Island, crèched chicks at 5-weeks-old for all species occupied similar trophic positions. Isotopic mixing models indicated that the proportions of prey provisioned by adult penguins to 5-week-old chicks at Anvers Island were generally similar across species within years, consisting primarily of Antarctic krill ( Euphausia superba ). Crèched Adélie chicks had higher δ 13 C and δ 15 N values at Avian and Charcot Islands, southern breeding colonies where sea ice is more prominent and populations of Adélie penguins have increased or remain stable. Trophic position increased with latitude, while the proportions of prey provisioned by Adélie penguin adults to chicks at southern breeding colonies included species typical of high Antarctic marine food webs, especially crystal krill ( Euphausia crystallorophias ). A Bayesian metric for dietary niche width, standard ellipse area (SEA-B), indicated that Pygoscelis penguins with greater population changes in the north had more variability in dietary niche width than stable populations further south. Our results lend insight on marine food web drivers of Pygoscelis penguin reproduction at the regional scale and question the long-standing paradigm that Antarctic krill are the only food web component critical to penguin reproductive survival in this region of the Southern Ocean.more » « less
