Biochemical properties and vertical distribution of particulate organic carbon in the northern Chukchi Sea.

The vertical dynamics of biopolymeric carbon (BPC) components are essential for understanding their role in the biological pump and carbon cycling. However, little research has addressed their distribution and transformation across the epipelagic, mesopelagic, and bathypelagic zones, particularly in the northern Chukchi Sea. This study investigated the contributions to particulate organic carbon (POC), reduction rates, and vertical distribution of BPC components, including carbohydrate carbon (CHO-C), protein carbon (PRT-C), and lipid carbon (LIP-C), across the Mendeleev Ridge (MR), Chukchi Basin (CB), and Northwind Basin (NB), along with analyzing potential factors influencing the distribution patterns of BPC components and POC. In all three regions (MR, CB, and NB), LIP-C was the dominant BPC component, exhibiting the highest contribution to POC and the lowest reduction rate as depth increased, highlighting its significant role in carbon cycling and export. In the MR and CB regions, elevated POC concentrations were observed at specific depths, corresponding to high LIP-C levels. These findings indicate that BPC components, particularly LIP-C, play a substantial role in influencing POC distribution in these regions. In contrast, the NB displayed distinct POC distribution, with consistently high concentrations extending from the epipelagic to bathypelagic zones. Unlike the MR and CB, POC distributions in the NB appeared less influenced by autochthonous BPC sources, suggesting additional contributions from external factors such as lateral transport. These findings highlight the pivotal role of BPC components in driving POC dynamics and carbon cycling in the northern Chukchi Sea.