Use of subfossil <Emphasis Type="Italic">Chaoborus</Emphasis> mandibles in models for inferring past hypolimnetic oxygen |
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Authors: | Roberto Quinlan John P Smol |
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Institution: | (1) Department of Biology, York University, Toronto, ON, M3J 1P3, Canada;(2) Paleoecological Environmental Assessment and Research Laboratory (PEARL), Department of Biology, Queen’s University, Kingston, ON, K7L 3N6, Canada |
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Abstract: | Assemblages of subfossil Chaoboridae mandibles from 80 thermally-stratified shield lakes in southern central Canada were examined
to explore the influence of subfossil Chaoborus on subfossil Chironomidae-based paleolimnological inference models of deepwater oxygen, as volume-weighted hypolimnetic oxygen
(VWHO). Inclusion of subfossil Chaoborus in subfossil Chironomidae-based VWHO models only improved model performance modestly, however it produced substantively better
inferences of hypolimnetic oxygen in anoxic lakes, because Chaoborus had a much stronger positive relationship with low VWHO compared to chironomid taxa indicative of anoxic conditions, such
as Chironomus. A Chaoborus mandible:Chironomidae head capsule ratio (chaob:chir) may be a useful index in paleolimnological studies, as chaob:chir in
a surface sediment training set was significantly related to VWHO, and displayed little co-variation with other limnological
variables such as trophic status (e.g. TP, TN) or lake depth (e.g. Z
max). Chaob:chir values in a stratigraphic analysis tracked chironomid-inferred VWHO, however the use of chaob:chir in regional
‘top–bottom’ paleolimnological studies must be used with caution. |
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