Midge- and diatom-based palaeosalinity reconstructions for Mahoney Lake, Okanagan Valley, British Columbia, Canada |
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Authors: | Mark L Heinrichs Susan E Wilson Ian R Walker John P Smol Rolf W Mathewes Kenneth J Hall |
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Institution: | (1) Department of Biology, North Kelowna Campus, Okanagan University College, 3333 College Way, V1V 1V7 Kelowna, British Columbia, Canada;(2) Department of Biological Sciences, Simon Fraser University, V5A 1S6 Burnaby, British Columbia, Canada;(3) Paleoecological Environmental Assessment and Research Laboratory (PEARL) Department of Biology, Queen's University, K7L 3N6 Kingston, Ontario, Canada;(4) Westwater Research Centre, University of British Columbia, 1933 West Mall Annex, V6T 1Z2 Vancouver, British Columbia, Canada |
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Abstract: | Salinity fluctuations in lakes of semi-arid regions have long been recognised as indicators of palaeoclimatic change, and
have provided a valuable line of evidence in palaeo-climatic reconstruction. In the present study, fossil remains of diatoms
and midges were used to reconstruct salinity changes at Mahoney Lake from the early postglacial, through the early, mid and
late Holocene. A transition from midges typical of a freshwater community (Protanypus, Sergentia, Heterotrissocladius, Cladopelma, Dicrotendipes) during the early postglacial, to those indicative of saline environments (Cricotopus/Orthocladius, Tanypus) occurred in the early Holocene. The midge-inferred salinity values reflected the shift from freshwater (0.031 g/L) immediately
after deglaciation, to saline water (2.4 to 55.2 g/L) in subsequent periods. A less saline period was found to have occurred
after 1000 yr BP, suggesting a cooler or wetter period. The diatom record indicates similar trends, with freshwater taxa (e.g.,Cyclotella bodanica var. aff.lemanica) dominating near the bottom of the core. Diatom-inferred salinities indicate that saline conditions (about 30 g/L) prevailed
throughout subsequent Holocene time, although relatively fresh conditions are indicated following deposition of the Mazama
Ash, and from about 1500 yr BP until the present day. Midge and diatom-inferred salinity reconstructions for Mahoney Lake
compare favorably with each other, and with climate trends inferred from earlier palynological evidence. The palaeosalinity
record thus contributes new data relevant to past climatic conditions, in a region where little data have previously been
collected. |
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Keywords: | Chironanidae diatoms palaeoclimate palaeolimnology palaeoecology palaeosalinity salinity postglacial climate change |
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