Carbon Uptake in Surface Water Food Webs Fed by Palaeogroundwater. Issue 5 (6th May 2019)

• Record Type: Journal Article
• Authors: Mazumder, Debashish; Saintilan, Neil; Hollins, Suzanne; Meredith, Karina; Jacobsen, Geraldine; Kobayashi, Tsuyoshi; Wen, Li
• Is Part Of: Journal of geophysical research. Volume 124:Issue 5(2019)
• Page Start: 1171
• Page End: 1180
• Publication Date: 2019-05-06
• Subjects: old carbon -- food web -- groundwater -- surface water -- Great Artesian Basin; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2018JG004925
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: The use of 14 C to elucidate sources of carbon within freshwater aquatic ecosystems is challenging the assumption that modern autochthonous carbon dominates energy flows. We measured the uptake of old carbon through several trophic levels of a wetland fed by groundwater of the Great Artesian Basin, Australia, the largest artesian basin in the world. Stable isotopes (δ 13 C and δ 15 N) and radiocarbon ( 14 C) were used to quantify food chain links and connection between groundwater and surface water food webs. Our results suggest that old groundwater was the dominant carbon source even at the highest trophic levels, with predatory fish returning apparent carbon ages of up to 11 ka. Stable isotope analysis (δ 13 C and δ 15 N) identified trophic links between fish, aquatic insects, and algae with smaller contributions from particulate organic matter to the food webs. As natural mound springs and associated wetlands are the only source of reliable water during dry periods over vast areas of the western Great Artesian Basin, the result has potential implications for the interpretation of archaeological artifacts associated with indigenous passage within the interior. Plain Language Summary: The Great Artesian Basin, the largest and deepest artesian basin in the world, contains water up to millions of years old, and this water discharges to create small wetlands in the dry interior of Australia. We examined the source and transfer of carbon within an ecosystem fed by groundwater from the Great Artesian Basin, using stable and radioactive isotopes. In the first demonstration of groundwater contribution to ecosystem carbon in semiarid or arid regions, we found very old carbon to be the dominant carbon source to all levels of the food chain, including fish, which returned ages of up to 11, 000 years old. Our results have implications for the dating of artifacts from interior Australia, where these wetlands were utilized by aboriginal peoples for millennia. Key Points: We report the uptake of old carbon in the surface water food webs of a semiarid zone wetland fed by groundwater of the Great Artesian Basin (GAB), Australia Stable carbon and nitrogen isotopes were used in conjunction with 14 C to determine connection between groundwater and surface water food webs We found 14 C‐depleted carbon from old groundwater contributed to aquatic food webs with very little dilution by modern atmospheric carbon; fish were up to 11 ka and algae 23 ka