Radiocarbon Dating: Development of a Nobel Method

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

“…Natural 14 C as a source and age tracer of C and OM in aquatic systems Natural abundance radiocarbon ( 14 C), the radioactive isotope of carbon (t 1/2 5 5568 yr; Stuiver and Polach 1977), has at least a one to two order-of-magnitude greater dynamic range than d 13 C, d 15 N, and d 2 H. Natural ("pre-bomb") D 14 C values range over $ 950& (i.e., from 21000& to $ 250&; McNichol and Aluwihare 2007;Taylor 2016) and are even greater (up to $ 1900& range) when anthropogenic 14 C inputs such as thermonuclear weapons testing and nuclear reactors are considered (McNichol and Aluwihare 2007;Taylor 2016). In addition to being a highly sensitive source tracer, 14 C uniquely allows for determination of C and OM ages in both non-living and living aquatic C-containing components.…”

“…To our knowledge, no such studies have yet been carried out in desert (e.g., hypersaline), tropical, or arctic aquatic systems. While the use of natural 14 C for estimating ages of C and OM utilized in aquatic food webs is in principal relatively straightforward, the influence of 1950s–1960s nuclear weapons testing (i.e., the so‐called “bomb” 14 C) must also be considered, especially for the mid‐20 th to early 21 st century period (McNichol and Aluwihare ; Taylor ). In addition to the apparent ages of consumer organisms resulting from their utilization of non‐living aged OM, live aquatic autotrophs consumed for nutrition may also possess apparent “age” due to fixation of aged DIC (as CO 2 (aq)) commonly observed in inland waters (Ishikawa et al 2013, 2014) and must be accounted for.…”

“…However, the advent of accelerator mass spectrometry (AMS) has resulted in increased use of natural 14 C measurements in ecosystem studies. Prior to the development and widespread use of AMS, 14 C analyses were conducted using β‐decay methods such as gas proportional and liquid scintillation counting (McNichol and Aluwihare ; Taylor ). Decay counting requires grams of C and up to days of counting time per sample for an accurate assessment of 14 C content, whereas AMS methods require only tens to hundreds of micrograms of C and minutes or less analysis times (McNichol and Aluwihare ; Taylor ).…”