Eran Hood Peter A. Raymond J.H. Hudson Maura Bozeman Mayumi L. Arimitsu Jason Fellman 2015 <p>We used natural abundance &delta;¹³C, &delta;¹⁵N, and &Delta;¹⁴C 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&permil; to -25&permil; for &delta;¹³C and from -14&permil; to 53&permil; for &Delta;¹⁴C reflecting a food web sustained mainly on contemporary primary production. In contrast, biofilm in the two glacial stream sites was highly &Delta;¹⁴C-depleted (-215&permil; to 175&permil;) relative to the nonglacial stream consistent with the assimilation of ancient glacier organic carbon. IsoSource modeling showed that in upper Herbert River, macroinvertebrates (&Delta;¹⁴C = -171&permil; to 22&permil;) and juvenile salmonids (&Delta;¹⁴C = &minus;102&permil; to 17&permil;) 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, ¹⁴C-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 ¹⁴C-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.</p> application/pdf 10.1002/lno.10088 en American Society of Limnology and Oceanography Evidence for the assimilation of ancient glacier organic carbon in a proglacial stream food web article