Emerging biological archives can reveal ecological and climatic change in Antarctica

Abstract

Anthropogenic climate change is causing observable changes in Antarctica and the Southern Ocean including increased air and ocean temperatures, glacial melt leading to sea-level rise and a reduction in salinity, and changes to freshwater water availability on land. These changes impact local Antarctic ecosystems and the Earth's climate system. The Antarctic has experienced significant past environmental change, including cycles of glaciation over the Quaternary Period (the past ~2.6 million years). Understanding Antarctica's paleoecosystems, and the corresponding paleoenvironments and climates that have shaped them, provides insight into present day ecosystem change, and importantly, helps constrain model projections of future change. Biological archives such as extant moss beds and peat profiles, biological proxies in lake and marine sediments, vertebrate animal colonies, and extant terrestrial and benthic marine invertebrates, complement other Antarctic paleoclimate archives by recording the nature and rate of past ecological change, the paleoenvironmental drivers of that change, and constrain current ecosystem and climate models. These archives provide invaluable information about terrestrial ice-free areas, a key location for Antarctic biodiversity, and the continental margin which is important for understanding ice sheet dynamics. Recent significant advances in analytical techniques (e.g., genomics, biogeochemical analyses) have led to new applications and greater power in elucidating the environmental records contained within biological archives. Paleoecological and paleoclimate discoveries derived from biological archives, and integration with existing data from other paleoclimate data sources, will significantly expand our understanding of past, present, and future ecological change, alongside climate change, in a unique, globally significant region.

Keywords: Southern Ocean; benthos; coalescent inference; lake sediments; mosses; paleoecology; peat; sclerochronology; stable isotopes; terrestrial invertebrate.

FIGURE 1

Map of Antarctica and the Southern Ocean showing the locations of studies investigating biological archives with a Quaternary focus. Ice‐free areas (brown areas on the Antarctic continent) indicate the Antarctic Conservation Biogeographic Regions (ACBRs) in (Terauds & Lee, 2016) and are important locations for moss beds, terrestrial invertebrates, and many animal colonies. Currents: PF, Polar Front; SBACC, Southern Boundary of the Antarctic Circumpolar Current. Ice Sheet: EAIS, East Antarctic Ice Sheet; WAIS, West Antarctic Ice Sheet. Localities: AL, Adélie Land; AP, Antarctic Peninsula; AS, Amundsen Sea; AUK, Auckland Is.; BAL, Balleny Is.; BH, Bunger Hills; BOU, Bouvet Is.; CAM, Campbell Is.; CZ, Crozet Is.; EI, Elephant Is.; FI, Falkland Is.; KI, Kerguelen Is.; LH, Larsemann Hills; MAR, Marion Is.; MQ, Macquarie Is.; RS, Ross Sea; SG, South Georgia; SHE, South Shetland Is.; SI, Scott Is.; SOI, South Orkney Is.; SR, Shag Rocks; SSI, South Sandwich Is.; VH, Vestfold Hills; WL, Wilkes Land; WS, Weddell Sea. For references of each datapoint, see Figure S1 and Tables S1–S6.

FIGURE 2

Landscape location and timespan of the Antarctic and Southern Ocean biological archives. (A) Antarctic and Southern Ocean biological archives in situ. (a) snow petrel breeding colony; (b) extant seal and penguin colonies; (c) extant marine benthos, such as brittle stars, octopus, and corals; (d) moss beds, which with time, become peat, and their associated invertebrate communities, here the Antarctic midge, Belgica antarctica; (e) historic preserved colonies of seals and penguins, which can contain bones, guano, feathers, hairs, eggs shells; and (f) lake sediments that contain preserved traces of copepods (e.g., Boeckella poppei generally mandibles and spermatophores), cladocerans (e.g., Daphniopsos studeri) and diatoms; and, (g) marine shelf sediments (e.g., pelagic Archaea), here shown beneath an ice shelf. (B) Indicative time span of the utility of biological archives compared to direct instrumental observations (red), which commenced in the 1950s. Live moss (light green) can be frozen under ice for 1,530 years, be revived and continue to grow (Roads et al., 2014). Partially decayed moss and organic matter and their transformation to peat over time (dark green). Live terrestrial invertebrates (yellow) (tardigrades can reproduce after being frozen for 30.5 years) (Tsujimoto et al., 2016). Lake sediment core (aqua) records date back to 300,000 years (Hendy, 2000). Live colonial animals (dark orange) (snow petrels, seals and penguins live for ~25 years or less), historic preserved animal colonies (light orange) are known from ~100,000 years ago. Benthic marine species (dark purple), (some Southern Ocean scleractinian coral species likely live for ~100 years (Roman Gonzalez, 2021)). Fossilised benthic marine species (light purple), (fossil coral can be used for sclerochronological studies over 10,000s of years (Wilson et al., 2020)). Marine shelf sediment core (blue) records have received greater attention over deep time scales. Erosion of shelf sediments during ice advance limits their utility in obtaining continuous records back past the last glaciation. DNA symbol indicates the use of genetic data from modern moss, terrestrial invertebrates, animal colonies, and benthic marine species to investigate past population size using coalescent methods over a timeframe from ~100 – 1,000,000 years. Illustrator: Daniel A. Becker.

FIGURE 3

Images of Antarctic and Southern Ocean biological archives. (a) Moss samples from a moss bed on Byers Peninsula, Livingston Island (photo credit—Melinda Waterman), (b) sub‐Antarctic weevil, Ectemnorhinus viridis, a terrestrial invertebrate from Kerguelen Island (photo credit—Bernard Chaubert), (c) Sub‐Antarctic lakes on Macquarie Island (photo credit—Krystyna Saunders), (d) Adélie penguin colony, Paulet Island (photo credit—Steven Chown), (e) Limatula sp., a benthic marine invertebrate, (photo credit—Nerida Wilson/Greg Rouse), (f) R/V JOIDES Resolution on an ocean drilling expedition as part of the IODP (International Ocean Discovery Program) in Amundsen Sea (photo credit—Gohl et al., 2017).