A palaeolimnological record of diatom-community dynamics and late-Holocene climatic changes from Prescott Island, Nunavut, central Canadian Arctic

Abstract

Palaeolimnological analyses from Lake PW03, a small, dilute lake on crystalline bedrock on Prescott Island, Nunavut, Canada (73°07′ N, 96°41′ W, 243 m a.s.l.), provide a sensitive record of the impacts of Holocene climatic change on diatom communities. A high-resolution sequence from 3500 cal. BP to present indicates that a significant change in diatom assemblages takes place at 2300 cal. BP, when alkaliphilous fragilarioids and planktonic taxa are replaced by benthic, epiphytic and acidophilous diatoms. These changes coincide with the onset of neoglacial cooling and likely reflect more persistent ice-cover and associated acidification of lake water. Maximum diatom species richness occurs during this period of transition. Dense bryophyte communities in the littoral zone provide habitats to sustain diatom production even under the cooler conditions following 2300 cal. BP. The concentration of diatom valves declines at 500 cal. BP, coincident with cooling at the time of the `Little Ice Age', and minor changes in species composition take place at that time. The sediments deposited over the past 150 years show modest increases in fragilarioids and planktonic diatoms, in response to a longer ice-free season under a warmer climate. Diatom valve production increases significantly in these recent sediments but increases in diversity are relatively small. Diatom diversity, production and the species composition of diatom communities do not change simultaneously in response to climatic changes.

Interactions between climate and landscape drive Holocene ecological change in a High Arctic lake on Somerset Island, Nunavut, Canada

“…They are dominated by small, colonial fragilarioid diatom taxa (Staurosira venter, Staurosirella pinnata, and Stauroforma exiguiformis) that typically occupy benthic habitats and are generally associated with early post-glacial paleoenvironments where glacial runoff supplies some mineral nutrients to sustain diatom communities in recently established ultra-oligotrophic lakes. These taxa have been widely reported in those conditions in early post-glacial sediments of Arctic lakes for the Holocene (Smol 1983;Cremer et al 2001;Finkelstein and Gajewski 2007;Rouillard et al 2012) and for earlier interglacials (Wilson et al 2012). At Lake RS29, this early post-glacial assemblage was quickly replaced by a more unusual assemblage dominated by Eunotia praerupta, Neidium affine, Pinnularia nodosa, and Tabellaria flocculosa.…”

“…This suite of changes is often associated with the onset of anthropogenic climate warming in the late 19th or early 20th century (Douglas et al 1994;Smol et al 2005;Rühland et al 2008), although the situation may be more complex (Saros and Anderson 2015). According to the age-depth model developed for Lake RS29, these shifts are occurring considerably earlier, as has been found elsewhere (e.g., Finkelstein and Gajewski 2007;Perren et al 2009Perren et al , 2012aSaros and Anderson 2015). Given the uncertainties of radiocarbon (Gajewski et al 1995) and 210 Pb (e.g., Hadley et al 2010) chronologies in Arctic lakes, the timing of these changes should be interpreted with caution.…”

“…Changes in habitat availability and growing season length may result in increased diatom diversity and production. Although most of these responses are observed in post-19th century records, these patterns of community response are not always consistent in records that span several millennia (LeBlanc et al 2004;Finkelstein and Gajewski 2007;Michelutti et al 2007).…”

Middle and late Holocene climate change and human impact inferred from diatoms, algae and aquatic macrophyte pollen in sediments from Lake Montcortès (NE Iberian Peninsula)

“…Freshwater primary producers can be very sensitive to climate change, especially to abrupt fluctuations that alter their habitats and metabolism. Diatom response to Holocene climatic variability has been documented across many latitudes, owing to their direct (Wolfe 2003) and indirect responses to climate change (Finkelstein and Gajewski 2007;Morellón et al 2009a). Diatom community diversity and productivity respond quickly to changes in conductivity, nutrient concentration, and habitat availability that are associated with variations in the hydrologic balance (precipitation/evaporation) of lakes.…”

Reconstitution paléolimnologique des conditions environnementales récentes dans la région de Saglek, Labrador /

“…2004, Michelutti étal. 2006, Finkelstein and Gajewski 2007. Cette modification significative de la structure des communautés de diatomées, généralement associée à une réduction de la diversité spécifique et de la productivité limnologique, marque vraisemblablement la fin de la période hypsithermique de l'Holocène (HTM -Holocene Thermal Maximum) et le début du refroidissement néoglaciaire dans le Nord-Est de l'Arctique canadien.…”