645 / 2024-09-18 19:25:35
The indicative role of amino acids in the remineralization process of particulate organic matter in the Northwestern Pacific Ocean
Particulate organic carbon,Microbial remineralization,Amino acids,Northwestern Pacific Ocean,Carbon export
Session 45 - New Data and Technologies Driven Insights into Marine Organic Matter Cycling
Abstract Review Pending
The biological carbon pump (BCP) transfers atmospheric carbon from the surface ocean to deeper waters via particulate organic carbon (POC), playing an important role in global carbon balance and climate stability. Its strength and efficiency are primarily assessed through the downward export flux of POC, which is regulated by the production sources, particle sizes, and remineralization processes of POC. The variation in those factors across latitudes and gyres in the Northwestern Pacific Ocean (NWPO) makes it an ideal zone to study the regulation mechanisms of POC export. Size‐fractionated (1 –51 μm; >51 μm) POC and particulate hydrolysable amino acids (PHAA) were collected and analyzed from low- and mid-latitude NWPO in our study. Indexes derived from PHAA were used to trace the sources, compositions, and biodegradation of POC in both large and small particle sizes. Our findings demonstrate the joint control of POC export by particle size and microbial degradation as follows:
- The composition and sources of POC exhibit distinct differences in large and small particle sizes. Larger POC is predominantly of siliceous origin with gravitational sinking, accounting for the majority of POC export. In contrast, smaller particles exhibit greater susceptibility to physical subduction such as eddies and currents.
- The microbial remineralization is crucial for the biological carbon pump's efficiency. Greater decomposition of POC in the core of gyre leads to a significantly lower export flux of POC despite the similar storage of POC in both the gyre’s core and edge.
- A distinct latitudinal variation exists in the distribution of POC across different sizes. While biological activity within the surface layer of POC remains consistent among various sizes, deeper layers beneath the euphotic zone at mid-latitude stations exhibit a higher degradation rate for larger POC compared to their smaller counterparts. Conversely, at low-latitude stations, this pattern is reversed, which is closely associated with differences in primary production, community structure, and bacterial activity across latitudes.
This study evaluates the contributions of different-sized POC to carbon export and identifies critical factors influencing carbon export efficiency. The results provide vital insights into the mechanisms and efficiency of BCP within the oceanic carbon cycle.