[A-HW22] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW22-P09] Carbon accumulation rates and stocks in a semi-enclosed bay under the influence of anthropogenic activities

*Muhammad Shahinur Rahman^1,2, Shin-ichi Onodera¹, Mitsuyo Saito¹, Yu Umezawa³, Kunyang Wang¹, Takahiro Hosono⁴, Takuya Ishida¹ (1.Graduate School of Advanced Science and Engineering, Hiroshima University, 2.Physical and Space Oceanography Division, Bangladesh Oceanographic Research Institute, 3.Department of Environmental Science on Biosphere, Tokyo University of Agriculture and Technology, 4.Faculty of Advanced Science and Technology, Kumamoto University)

Keywords:Organic Carbon, Stable Isotopes, Organic matter source, Marine sediment

The sequestration of atmospheric carbon dioxide accumulated in sediment for the long term emerges as a potential nature-based solution for mitigating and adapting to climate change. This study focuses on the organic carbon accumulation rates and stocks in Osaka Bay, one of the most eutrophicated semi-enclosed bays in Japan. Human-induced activities, including urbanization, industrialization, land reclamation, and land-use changes, have significantly altered the Osaka Bay ecosystem and its productivity.
We aimed to examine the impact of terrestrial nutrient loading on carbon accumulation and storage in Osaka Bay using 3 sediment cores for the last 100 years. TOC, TN, and Carbon and Nitrogen ratio (C/N) range from 0.86%-1.83%, 0.12%-0.25%, and 7.55-10.24 respectively. We also evaluated the source of TOC using stable isotopes of δ¹³C and δ¹⁵N. Our finding reveals that TOC sources and accumulation rate can be altered by various anthropogenic activities. Our study can be used to understand the carbon stock of human-dominated semi-enclosed bays worldwide.
Acknowledgement: This study is supported by Asia-Pacific Network for Global Change Research Project (CRRP2019-09MY-Onodera) and Grant for Environmental Rehabilitation and Creation of the Osaka Bay Area (PI: Mitsuyo Saito, Grant Number: 040006, 2022).