This is super interesting: "We observed a general increase in sterol δ13C signatures with depth, which is likely related to a combination of particle size effec

This is super interesting: "We observed a general increase in sterol δ13C signatures with depth, which is likely related to a combination of particle size effects, selective feeding on larger cells by zooplankton, and growth rate related effects" https://www.biogeosciences.net/10/2787/2013/bg-10-2787-2013.pdf https://www.biogeosciences.net/10/2787/2013/bg-10-2787-2013.... Carbon-14 is created in the atmosphere where it is C02 and photosynthetic organisms convert it to more complicated organic compounds. The rate of diffusion of the Carbon-14 through the water column is measurable.