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Wintering chironomids mine oxygen

Murray K. Gingras, Stefan V. Lalonde, Larry Amskold and Kurt O. Konhauser
Wintering chironomids mine oxygen
Palaios (July 2007) 22 (4): 433-438

Abstract

Seasonally sampled cores of burrowed sediment containing chironomid larvae were collected from Cooking Lake, Alberta, and analyzed to (1) assess and establish the typical burrowing behavior and burrow architecture of chironomid larvae; (2) record micrometer-scale geochemical profiles of O (sub 2) , H (sub 2) S, and pH in the uppermost sedimentary layers throughout a seasonal cycle; and (3) link changing geochemical conditions to changing burrowing behaviors. We observed that the larvae lived in soft, water-saturated sediment, maintained by open burrows accreted by the animal's mucous. Chironomid-larvae burrows were small and Y-shaped (e.g., Polykladichnus-like) or Y-shaped with basal branches (Thalassinoides-like) and were 20 cm deep. The larvae moved up and down from the oxygenated zone ("sounding" behavior) to exploit food in suboxic and anoxic sediment. Geochemical analyses showed that H (sub 2) S was present in the pore waters to within 1.5 mm of the sediment-water interface during the summer, when lake-bottom algae and cyanobacteria generated sufficient O (sub 2) to drive the oxic-anoxic redoxcline into the sediment. In the winter, the H (sub 2) S front extended upward into the water column owing to the cessation of algal and cyanobacterial activity. The prevalence of H (sub 2) S results from a combination of high-dissolved-sulfate concentrations in the lake and the abundance of microbial biomass that fuels an active subsurface population of sulfate-reducing bacteria. Interestingly, burrowing behavior was not linked to seasonal changes in the sediment chemistry. This is in part due to the ability of chironomid larvae to exploit oxygen islands in the sediment: in the winter, the chironomid larvae harvest their oxygen from the uppermost photosynthetic layer in otherwise O (sub 2) -impoverished sediments.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 22
Serial Issue: 4
Title: Wintering chironomids mine oxygen
Affiliation: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Pages: 433-438
Published: 20070701
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 34
Accession Number: 2007-087618
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
N53°23'60" - N53°23'60", W113°01'60" - W113°01'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200739
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