Growing interest in mitigating climate change has increased global attention toward seaweed aquaculture as a potential nature-based solution. As seaweed gains attention as a potential blue carbon resource, understanding how the expansion of seaweed aquaculture may influence organic matter concentrations and characteristics in surrounding coastal waters has become increasingly important. In this study, the concentrations and characteristics of organic matter were investigated at 11 stations, including control sites, located within and around seaweed aquaculture farms in the Jindo coastal area, Korea, during two sampling campaigns conducted in August and October 2025, to evaluate the influence of seaweed farming on the distribution and composition of organic matter. Particulate and dissolved organic carbon concentrations exhibited clear seasonal and vertical variations, whereas no significant differences were observed between stations inside and outside the aquaculture farms. The carbon stable isotope ratios (δ¹³C) and C/N ratios of particulate organic matter were clearly distinguishable from those of seaweed during both sampling periods, with no consistent differences between the aquaculture and reference stations. Likewise, sedimentary organic matter showed a similar range of δ¹³C values across all stations. Fluorescent dissolved organic matter (FDOM) analysis revealed limited spatial differences between stations inside and outside the aquaculture farms. Significant differences were observed only for HIX in both surface and bottom waters during October and for BIX in October bottom waters. PARAFAC analysis indicated that the tryptophan-like component (C1) exhibited the highest Fmax values in both surface and bottom waters during August, while the contribution of the tyrosine-like component (C4) increased at several surface stations in October. Nevertheless, the spatial distributions of fluorescent components showed no consistent differences between stations inside and outside the aquaculture farms. These findings indicate that organic matter dynamics in the study area are primarily driven by seasonal and vertical variations in hydrographic conditions rather than by seaweed aquaculture. This suggests that seaweed-derived organic matter did not exert a dominant influence on organic matter dynamics in the surrounding coastal waters during the sampling periods. However, the influence of seaweed-derived organic matter may vary with the scale of seaweed aquaculture, the extent of its long-term accumulation, and environmental conditions. Therefore, further studies are needed to better understand its effects under different spatial and temporal conditions.