What is the relation between phytoplankton biomass and delta 13 carbon?

Phytoplankton biomass can influence δ¹³C values because the carbon isotopic signature of phytoplankton varies with factors such as nutrient availability and light conditions during photosynthesis. Higher biomass often indicates more significant primary production, which can lead to more fractionation of carbon isotopes, resulting in lower δ¹³C values. Conversely, changes in δ¹³C can also reflect shifts in phytoplankton community composition or environmental conditions affecting their growth, linking the isotopic signature to the ecological dynamics of phytoplankton.