Tracking Holocene Climatic Change with Aquatic Biota from Lake Sediments: Case Studies of Commonly used Numerical Techniques

Abstract

It is now widely recognized that reliable long-term climatic data are required to evaluate the impact of human activities on climate. Lake-sediment records are an important source of such paleoclimatic information, on timescales from years to millennia. However, unequivocal interpretation of biological climate-proxy data preserved in lake sediments can be very challenging. Here we review the different numerical approaches that are used to evaluate the sensitivity and reliability of species assemblages of aquatic biota (algae and invertebrates) extracted from lake-sediment records as proxies of past climatic conditions. The most common techniques used to assess this relationship between these proxies and climate include calibration functions that model the relationship across modern lake environments between species composition in the indicator group and particular climate-influenced aspects of their aquatic habitat, and assessments of the main directions of variation in species composition in relation to independent climatic data. Other statistical techniques, such as variation partitioning analysis, are used to assess the relative importance of climate versus other factors in influencing limnological changes seen in the sedimentary record. These techniques show that in climate-sensitive lake systems, the sedimentary remains of aquatic biota can be sensitive and trustworthy proxies, permitting quantitative reconstructions of past climatic conditions with high temporal resolution.

Mid-Holocene palaeolimnological record of a Southern Hemisphere subtropical lake spanning the last ~6000 years: Lake Jennings, Fraser Island, Australia

“…Data were analysed and displayed using RStudio version 0.99.902 (R Studio Team, 2015), and the statistical packages rioja v 0.9-7 (Juggins, 2015), and vegan v 2.3-5 (Oksanen et al, 2016). All relative abundance data were square root transformed prior to statistical analysis, and species representing < 2% of the assemblage removed to reduce noise in the visual display (Cumming et al, 2012). A Bray-Curtis distance matrix was created, and a stratigraphically constrained hierarchical cluster analysis performed using the incremental sum of squares algorithm (CONISS), to identify significant groupings between samples (Juggins, 2015; Legendre and Birks, 2012).…”

POLLEN METHODS AND STUDIES | Numerical Analysis Methods

“…Recent palynological examples include Willis et al (1999) and paleolimnological examples are reviewed by Dutilleul et al (2012) and Cumming et al (2012). It estimates the proportion of the variance that can be attributed to each of a continuous range of frequencies.…”

Meteorological validation of chironomids as a paleotemperature proxy using varved lake sediments

“…Hence, understanding past, present, and future climate changes requires spatially distributed proxy data (PAGES 2k Consortium, 2013). In the absence of meteorological data that predate the most recent centuries, paleoclimatic records, such as those stored in lake sediment archives, can be used to reconstruct past climates (Cumming et al, 2012). Of the available paleolimnological proxies, chironomids (Insecta: Diptera), which are sensitive to even small temperature changes, have been found particularly useful to quantitatively infer past climate changes (Brooks, 2006; Eggermont and Heiri, 2012; Luoto et al, 2014a).…”