Detritus, degradation, and diet: Using isotopes to trace the fate of ocean biomass

The vast majority of organic matter in the ocean is nonliving. Particulate organic detritus, in particular, comprises a critical component of the marine carbon cycle via the “biological pump” and is a food source for diverse marine biota. However, it can be difficult to connect the biological origins and detrital, or dietary fate, of organic matter due to alteration of chemical and morphological characteristics during degradation. I will discuss ways in which we are combining organic and isotope geochemistry to identify the effects of microbial degradation, higher trophic level consumption, and particle dynamics on the distribution of organic matter in the water column. I will focus on our recent studies linking size-differentiated particles to mesopelagic diets in contrasting oceanographic settings, as well as some intriguing new work from a methane seep.

Speaker: Hilary G. Close, Univ. of Miami