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 (C-14) have led to increased use of natural C-14 as both a source and age tracer in aquatic ecosystem and food web studies. Here, we review (1) Delta C-14 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 C-14 data on aquatic consumers across a range of inland water ecosystem types. Using Delta C-14 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.