DEVELOPING A ‘UNIVERSAL’ CALCULATION OF BIOMASS (G ORGANIC CARBON) FOR FOSSILS

Ecologists often use biomass (grams of Carbon per-individual) to measure change and variation in populations, communities, and entire ecosystems, but this parameter has remained elusive to paleontologists, who tend to rely instead on body size or biovolume. Fossil size can be a reliable proxy for biomass, as shown in calculations using shell length of marine bivalves, even if rarely converted to grams of organic Carbon (Corg). However, when original shell material is available, as in many sievable Mesozoic and Cenozoic records, shell or skeleton weight can calculate biomass in Corg more accurately than traditional length-based methods and creates a calculation with biologically meaningful coeficients. Here, I adapt weight-based methods developed by ecologists, calculating biomass using shell or skeletal weight and three biologically meaningful parameters: Corg = α/β*(Shellwt/ε). Corg is biomass in g Carbon per individual, α is the percent carbon in the individual total wet weights, β is the percent shell weight in the individual total wet weight both estimated from living analogs, ε is the percent of original shell present surviving taphonomic processes, and Shellwt is the measured weight of the fossil material in the sample. This equation both improves estimates of biomass and increases the number of individuals that can be reliably used for calculations of biomass, and is best used in tandem with length based calculations. It also mirrors methods used by ecologists, thus permitting direct comparisons of living and ancient systems. Finally, because α and β are biologically meaningful coefficients rather than empirically fitted coefficients, the equation is ‘universal’, that is can be derived for any taxon leaving shelly or other biominerlized remains.