A diatom‐inferred record of lake variability during the last 900 years in Lützow–Holm Bay, East Antarctica

Abstract

Decadal-centennial-scale climate variability in coastal Antarctica remains poorly understood due to the limited number of highly resolved, well-dated records. We present a 900-year, decadal-scale reconstruction based on sedimentary diatoms from Lake Abi in L€ utzow-Holm Bay, East Antarctica. Hydrological change is inferred from diatom ecological preferences in conjunction with an existing regional training set and implies that lake water specific conductivity, depth and nitrogen availability are the key drivers of diatom assemblage change. Lake Abi underwent a series of subtle environmental changes related to these environmental variables, possibly driven by changes in catchment snow melt and the duration of seasonal ice cover. Ordination is used to trace the major patterns of change in the diatom community, with notable shifts identified between 470 and 400 and at $350 cal a BP (where present ¼ CE 1950). The frequency of environmental variability at Lake Abi is broadly consistent with a record of the Interdecadal Pacific Oscillation during the last millennium, but contrasts with the apparent climate stability elsewhere in eastern Antarctica. Further research is required to constrain the limnological and ecological responses of lakes in coastal Antarctica to obtain more rigorous palaeoclimate reconstructions from these sites of immense potential.

Ecological and habitat preferences of diatoms in lakes of Lützow‐Holm Bay, East Antarctica

“…Ideally, an even gradient of lake chemical and physical characteristics would be studied, but this is limited by the types of lakes present in the landscape, and by field logistics. This means that for some species this study is unable to shed much light on chemical or habitat preferences, including C. antarctica , which is a common diatom taxon in lake sediment diatom records in the region (e.g., Rudd et al, 2016; Tavernier et al, 2014). Craticula antarctica was most abundant in the benthic lake‐floor samples from Lakes Kuwai and Hotoke in this study and was not observed at Lake Nurume.…”

“…The intensity of light in the shallow littoral zone of Antarctic lakes can be a physical stressor influencing assemblage differences (Hughes et al, 2006; Tanabe et al, 2008), which may, in combination with the low nutrient availability on rock surfaces in the shallow littoral zone, result in the lower proportional representation of littoral diatoms in deeper sediments. The clear distinction between littoral and lake‐floor diatom assemblages across the nine lakes studied, and the presence of diatom species commonly associated with littoral habitats within lake core samples (Rudd et al, 2016) consequently suggests that there is potential to qualitatively infer changes in lake ice cover from the ratio of littoral to lake‐floor of sedimentary diatoms in Lützow‐Holm Bay lakes.…”

“…Diatoms are a valuable paleoclimate indicator in the sediments of Antarctic lakes (Hodgson et al, 2016;Jones et al, 2000;Roberts et al, 2004;Rudd et al, 2016), but in order to effectively employ diatoms preserved at these sites for palaeoclimate research, detailed ecological information is required. Salinity, as inferred from specific conductivity, is a key control on diatom composition of surface sediments in the Sub-Antarctic Islands (Saunders et al, 2015), Antarctic Peninsula (Kopalová et al, 2013(Kopalová et al, , 2019 and East Antarctica (Roberts et al, 2004;Sabbe et al, 2004;Tavernier et al, 2014;Verleyen et al, 2003), and has allowed for the development of conductivity transfer functions for these regions.…”

“…This suggests that salinity alone is not driving the observed changes in the diatom records, or that the transfer functions are not sufficiently sensitive to explain the variability observed. Fossil diatoms from the past 900 years at Lake Hamagiku, formerly known as Lake Abi, also in the Skarvsnes region, show large fluctuations in relative abundance of a limited number of species which are tentatively associated with subtle fluctuations in salinity, depth and nutrient input, although confident interpretations are hindered by a limited knowledge of diatom ecology in the Lützow-Holm Bay region (Rudd et al, 2016). The relative simplicity of lake systems in Antarctica provides an opportunity to untangle the influence of substrate and chemistry on lake ecology, excluding some of the habitat complexity and landscape effects found in more temperate systems, as has been done for Arctic lakes (Griffiths et al, 2017).…”