title: Black Sea nitrogen cycling and the preservation of phytoplankton <i>δ</i><sup>15</sup>N signals during the Holocene
abstract: The stable isotopic compositions of bulk, clay‐bound, organic, and compound‐specific nitrogen were determined for mid to late Holocene Black Sea sediments from a set of box and gravity cores. The data demonstrate that cyanobacterial N 2 fixation provided ∼55% of phytoplankton‐derived N preserved in the top 1–2 cm of the sediments. Prior to widespread agricultural and industrial development in the catchment, N 2 fixation was more prominent, providing 70–80% of phytoplankton N. Organic and clay‐bo
journal: Global Biogeochemical Cycles