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

Abstract

This study presents a diatom-based analysis of the post-glacial Holocene environmental history at Lake RS29 on Somerset Island in the Canadian High Arctic. Earliest post-glacial diatom assemblages (10 200-10 000 cal yr BP) consisted mainly of small, benthic fragilarioid taxa. Poor diatom preservation in the early Holocene (~10 000-6200 cal yr BP) is associated with warm conditions, as determined by pollen data from the same core and other paleoclimate estimates from the region. Analysis of this and other sites from across the Canadian Arctic suggest that zones of poor diatom preservation or diatom absence in lake sediment records may be associated with warm conditions. After 6200 cal yr BP, acidophilic assemblages consisting of Aulacoseira spp. and a suite of periphytic taxa indicate acidification since the mid-Holocene. During this time period, cooling causing changes in lake ice phenology was likely a major driver of the reconstructed mid-Holocene pH decline. Watershed processes, including reduced fluxes of base cations as the rate of sediment accumulation slowed, may also be contributors to long-term shifts in lake water pH and associated changes in diatom assemblages. The uppermost sediments in the Lake RS29 record were characterized by abrupt declines in Aulacoseira alpigena and increases in benthic diatom taxa Cyclotella sensu lato, suggesting an increase in lake water pH and longer ice-free seasons.Key words: paleoclimate, Holocene, Canadian Arctic Archipelago, lake sediments, diatoms, paleolimnology, pollen, diatom dissolution.Résumé : Cette étude présente une analyse basée sur les diatomées afin d'examiner l'histoire environnementale de l'Holocène postglaciaire au lac RS29 sur l'île Somerset dans le Haut-Arctique canadien. Les tout premiers assemblages de diatomées postglaciaires (10 200 -10 000 ans BP) étaient constitués principalement de petits taxons benthiques fragilarioid. La pauvre conservation des diatomées au cours de l'Holocène précoce (~10 000-6 200 ans BP) est associée aux conditions chaudes, comme déterminées par les données de pollen provenant de la même carotte et d'autres évaluations paléoclimatiques de la région. L'analyse de ce site et d'autres sites à travers l'Arctique canadien suggère que les zones de pauvre conservation de diatomées ou d'absence de diatomées dans les données de sédiments lacustres enregistrées pourraient être associées aux conditions chaudes. Après 6 200 ans BP, les assemblages d'acidiphiles constitués d'Aulacoseira spp. et d'une gamme de taxons periphytiques indiquent l'acidification depuis l'Holocène moyen. Pendant cette période, le refroidissement causant des changements phénologiques de la glace lacustre était probablement un facteur du milieu important causant la baisse du pH reconstruit de l'Holocène moyen. Les processus des bassins hydrographiques, y compris les flux réduits de cations basiques alors que le taux d'accumulation de sédiments a ralenti, peuvent aussi être des facteurs

Postglacial flooding and vegetation history on the Ob River terrace, central Western Siberia based on the palaeoecological record from Lake Svetlenkoye

“…yr BP are characterized by poor diatom preservation, few taxa and low diatom concentration. Paull et al (2017) suggest that poor diatom preservation in lake sediments records from Canadian Arctic may be associated with warmer climate conditions. Around 3700 cal.…”

Long-term ecological changes in Mediterranean mountain lakes linked to recent climate change and Saharan dust deposition revealed by diatom analyses

“…(Table S2, Michelutti et al, 2006;Vinocur & Maidana, 2010), Pinnularia spp. (Table S2, Michelutti et al, 2006;Paull et al, 2017;Vinocur & Maidana, 2010), Eunotia spp. (Table S2; Falasco and Bona, 2011;Küttim et al, 2017) and A. minutissimum (Table 1, Keatley et al, 2006;Lotter et al, 2010) were observed during this period in lakes.…”

Multiple drivers of ecological change in Arctic lakes and ponds

“…Diatoms were apparently being deposited in the sediments, but no Chla accumulated. Large changes in diatom concentrations have been recorded in Holocene diatom studies from the Canadian Arctic, and these may be associated either with climate changes, with lake history, or with diagenesis [27]. Low diatom concentrations in sediments seem to be associated with warm temperatures at many sites, perhaps due to dissolution of the diatoms [27].…”