Dr. Ana Gonzalez-Nayeck
Baruch College - CUNY

Topic: Where does all the photosynthetic sugar go?  Exploring the consequences of sugar exudation on the carbon isotopic composition of microbial biomass 

Academic host: Elliott Mueller

Abstract: Marine phytoplankton exude between 2 and 50% of initially fixed carbon, primarily as mono-and poly- saccharides. Carbohydrate exudation varies with environmental conditions including light, oxygen and nutrient availability; however, it remains unknown whether carbohydrate exudation affects the carbon isotopic composition (δ13C) of cellular organic carbon. In this talk, I will share our attempts to culture cyanobacteria under conditions promoting variable carbohydrate exudation, and what we know thus far about the relationship between exudation and the δ13C of different carbon pools. By the end, I hope to convince the audience that stable isotope geochemists should explicitly consider these processes when interpreting the δ13C compositions of individual organisms and of both dissolved and particulate organic matter in modern ecosystems.