In order to sustainably provide safe food, we are conducting research to protect and restore the environments in which coastal organisms live. Specifically, our activities center on two main topics.
At the Laboratory of Aquatic Plant Ecology Laboratory (Nagasaki University), we work on the restoration and protection of coastal ecosystems so that safe food resources can continue to be supplied in a sustainable manner. To that end, we focus on two primary research areas concerning vegetated marine ecosystems beds (seaweeds and seagrasses) that are affected by environmental pollution. First, we develop and refine techniques for assessing the health of these underwater forests. By quantifying ecosystem area, density, and biodiversity, we can detect early signs of stress and degradation. In particular, we investigate how marine debris, especially plastic waste, alters the structure and function of these beds.
Second, we promote fundamental research aimed at restoring and protecting these ecosystems. We are elucidating the mechanisms by which algal beds take up atmospheric carbon dioxide and store it as “blue carbon,” with the goal of improving the precision and accuracy of carbon stock estimates. Accurately assessing the carbon-sequestration capacity of algal beds and clarifying their role in climate‐change mitigation is the ultimate aim of this research.
More than half of our laboratory’s efforts are devoted to fieldwork in support of these studies. We regularly measure the extent and density of algal beds and collect samples of marine debris and sediments deposited there. However, in the laboratory, we analyze organic‐carbon content in sediments and seawater using equipment from Elementar and Shimadzu Corporation. By combining field observations, lab analyses, and data processing, we strive to achieve a comprehensive understanding of the processes of algal‐bed decline and recovery.
As one aspect of our blue‐carbon research, we are evaluating the carbon‐sequestration potential of seaweed aquaculture farms. Cultivated seaweeds absorb CO2 from the atmosphere during their growth and may sequester carbon in biomass or sediments, making them a promising climate‐change mitigation strategy.
One of our major achievements, Sato et al. (2022) in Frontiers in Marine Science (https://doi.org/10.3389/fmars.2022.861932), quantitatively evaluated carbon fixation in Japanese seaweed farms. That study demonstrated that, depending on how harvested seaweed biomass is used, aquaculture sites can function as net carbon sinks. These findings pave the way for formally incorporating seaweed aquaculture into international greenhouse‐gas accounting and policy frameworks.
Furthermore, in a press release from Nagasaki University dated September 18, 2024, it was announced that our laboratory is leading a CREST Strategic Basic Research Program project titled “High‐Precision Quantification and Assessment of Blue‐Carbon Fixation Potential in Seaweed Aquaculture Sites.” This project, the first CREST award for Nagasaki University, is being carried out jointly by Professor Gregory Nishihara of Nagasaki University, Professor Teruko Konishi of the University of the Ryukyus, and with the cooperation of RIKEN Foods Co., Ltd.
Under this project, we focus on net ecosystem production (NEP) and conduct detailed CO2 monitoring in wakame (Undaria pinnatifida) farms in Miyagi Prefecture and okinawa-mozuku (Cladosiphon okamuranus) farms in Okinawa Prefecture. By tracking the dynamics of CO2 uptake and release by seaweeds, as well as the fate of organic substances such as polysaccharides they exude, we aim to comprehensively assess their carbon‐dioxide removal (CDR) capacity. The results are expected to inform carbon‐credit scheme design and contribute to the decarbonization of the seaweed industry.