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Evidence for the assimilation of ancient glacier organic carbon in a proglacial stream food web
Author(s) -
Fellman Jason B.,
Hood Eran,
Raymond Peter A.,
Hudson John,
Bozeman Maura,
Arimitsu Mayumi
Publication year - 2015
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10088
Subject(s) - trophic level , food web , environmental science , ecosystem , total organic carbon , dissolved organic carbon , glacial period , microbial food web , ecology , organic matter , carbon fibers , biology , paleontology , materials science , composite number , composite material
We used natural abundance δ 13 C, δ 15 N, and Δ 14 C to compare trophic linkages between potential carbon sources (leaf litter, epilithic biofilm, and particulate organic matter) and consumers (aquatic macroinvertebrates and fish) in a nonglacial stream and two reaches of the heavily glaciated Herbert River. We tested the hypothesis that proglacial stream food webs are sustained by organic carbon released from glacial ecosystems. Carbon sources and consumers in the nonglacial stream had carbon isotope values that ranged from −30‰ to −25‰ for δ 13 C and from −14‰ to 53‰ for Δ 14 C reflecting a food web sustained mainly on contemporary primary production. In contrast, biofilm in the two glacial stream sites was highly Δ 14 C‐depleted (−215‰ to 175‰) relative to the nonglacial stream consistent with the assimilation of ancient glacier organic carbon. IsoSource modeling showed that in upper Herbert River, macroinvertebrates (Δ 14 C = −171‰ to 22‰) and juvenile salmonids (Δ 14 C = −102‰ to 17‰) reflected a feeding history of both biofilm (∼ 56%) and leaf litter (∼ 40%). We estimate that in upper Herbert River on average 36% of the carbon incorporated into consumer biomass is derived from the glacier ecosystem. Thus, 14 C‐depleted glacial organic carbon was likely transferred to higher trophic levels through a feeding history of bacterial uptake of dissolved organic carbon and subsequent consumption of 14 C‐depleted biofilm by invertebrates and ultimately fish. Our findings show that the metazoan food web is sustained in part by glacial organic carbon such that future changes in glacial runoff could influence the stability and trophic structure of proglacial aquatic ecosystems.