Nutritional support of inland aquatic food webs by aged carbon and organic matter

Aged (typically tens to thousands of years old) forms of non‐living carbon (C) and organic matter (OM) predominate in many inland water ecosystems. Advances in the methodologies used to measure natural abundance radiocarbon ( 14 C) have led to increased use of natural 14 C as both a source and age tracer in aquatic ecosystem and food web studies. Here, we review (1) Δ 14 C values and ages of C and OM typically found in different inland water systems, (2) the mechanisms through which these materials enter inland water ecosystems, and (3) all available 14 C data on aquatic consumers across a range of inland water ecosystem types. Using Δ 14 C values of aquatic consumers and their potential nutritional resources, we estimate contributions of aged C and OM to aquatic consumer biomass. We conclude that in nearly every case, one or more forms of aged C and/or OM contribute to aquatic consumer nutrition in inland water ecosystems.