Exploring the variations in molecular characteristics of dissolved organic matter driven by aquaculture types

In recent decades, global aquaculture has expanded rapidly, raising concerns about coastal environmental degradation due to unregulated or poorly regulated discharge of aquaculture tailwater. Despite the crucial role of dissolved organic matter (DOM) in biogeochemical processes and aquatic biodiversity, the influence of aquaculture type on the molecular characteristics of DOM remains largely unexplored. Herein, this study investigated the variations in chemical and spectroscopic properties as well as molecular characteristics and composition of DOM across different aquaculture types including crustacean, fish and shellfish. Our findings revealed notable differences in DOM quantities among different aquaculture types, with crustacean and fish aquaculture water containing higher DOM amount compared to shellfish aquaculture water. This disparity can be attributed to the more frequent formulated feeds of crustacean and fish in contrast to shellfish aquaculture. Furthermore, distinct differences were also observed in the characteristics and composition of DOM among the different aquaculture waters. Specifically, DOM in shellfish aquaculture water exhibited a higher abundance of unsaturated and reduced molecules as well as increased aromaticity compared to the other two aquaculture waters. Conversely, DOM from fish aquaculture water showed a greater contribution from terrestrial origin characterized by elevated levels of plant-based components such as lignin-like and tannin-like compounds. Interestingly, DOM from shellfish aquaculture water contained lower levels of microbial-derived components such as lipid-like and protein-like compounds, likely due to reduced microorganism populations resulting from lower nutrients availability and higher salinity. Overall, these significant variations in characteristics and composition of DOM underscore the potential impacts of aquaculture type on the DOM biogeochemical cycle and the environmental quality in aquatic ecosystems.