Is CO2 in the Pacific Ocean depleted or enriched in Carbon-13 compared to the Atlantic, and why?
"The decrease in &delta;13C as water flows from the Atlantic to the North Pacific is due mainly to the addition of organically produced material and its subsequent oxidation as it falls through the water column. Marine organic carbon has a &delta;13C of near -250/00, hence the addition of this material decreases the &delta;13C of the &Sigma;CO2." (from conclusion)

P. M. Kroopnick, Deep-Sea Research Part a-Oceanographic Research Papers, 1985, 32, 57-84.
https://www.sciencedirect.com/science/article/pii/0198014985900172