Multidecadal characterization of biogenic compounds and nutrients in Antarctic ice-free coastal lake sediments

Although about 98% of the Antarctic continent is covered by an ice sheet, seasonal lakes and small streams resulting from ice and snow melting are formed during the Austral summer. These ice-free areas, mainly located in coastal sites, provide a fertile environment for the development of microbial life. Isolation and extreme conditions in terms of light, temperature and nutrient availability generate peculiar ecosystems in the lake waters, characterized mainly by the presence of planktonic and/or benthonic microorganisms, especially cyanobacteria and microalgae. The water budget of coastal lakes is regulated only by melting and evaporation/sublimation, so that the organic matter from the catchment and the lake biomass is buried in sediments, which therefore represent a precious archive for the study of seasonal and interannual changes in the hydrology and primary productivity of the lakes. The high sensitivity of these environments to local climatic shifts is key to understanding how deglaciated areas may respond to larger scale changes. The lakes considered in this proposal are all located close to Terra Nova Bay, in the vicinity of the Italian research station Mario Zucchelli. Sediment samples from the same lakes were collected repeatedly in the period from 1990 to 2014 in the framework of the Italian National Antarctic Research Program (PNRA). So far, no study was ever performed on the temporal evolution of the lakes. The sediment samples analyzed here make up a 25-year long series that would encompass medium-term changes in the ecologic conditions of such sensitive environments. Samples were made available by the Antarctic Environmental Specimen Bank (BCAA, University of Genoa), associated to the Italian Antarctic National Museum.

Macroscopic changes were observed in coastal lakes in Northern Victoria Land over the last few years, regarding their extension that exhibited an overall decreasing trend that found no explanation yet. Organic markers buried in sediments could help identifying the factors that are driving the observed transformations and evaluating the sensitivity of these ecosystems to future change. Here, we investigate changes in the lipid composition through untargeted and targeted analysis of apolar and polar lipids using GC-MS and UHPLC-HR-MS/MS.

In order to complete the information gathered through the characterization of lipids, the study of nutrient availability, here performed through the detection of e.g. zinc ions in the range of 0.1-2 ppm using a paper-based printed electrochemical sensor and a miniaturized 3D printed extraction system for soil analysis, to understand if a correlation exists between the variation of nutrient content and lipid biomarkers and small to large-scale changes.