Direct interaction of dissolved organic matter with aquatic organisms

Dissolved organic matter is widely present in aquatic environment with great ecological and environmental significance.In freshwater ecosystems,dissolved organic matter exceeds all living organisms by more than one order of magnitude.The ability of dissolved organic matter to affect aquatic biota indirectly by exerting strong control on the surrounding biogeochemical conditions is well established due to their ability to complex inorganic cations,including metals and a variety of organic compounds.In contrast,the potential direct interaction of these amphiphilic compounds with aquatic organisms themselves has been largely overlooked until recently.However,in the past decade,there has been growing recognition that dissolved organic matter can directly affect the physiology of organisms.Because of the chemical building blocks and physicochemical behavior of dissolved organic matter,researchers have postulated that these substances have a xenobiotic character,with effects such as sorption of dissolved organic matter on living membranes,alterations in membrane electrophysiological characteristics and permeability,induction of chemical stress defense reactions,induction and modulation of biotransformation enzymes and displaying hormone-like effects and so on.These interactions will impact the bioconcentration and toxic effects of environmental contaminants.Making these mechanisms clear is of critical importance in ecological understanding and risk assessment of contaminants.From the view of ecology,these interactions are thought to be a means of lifespan expansion;however,given the existence of multi-contaminants,these interactions will impact the bioconcentration and toxic effects of environmental contaminants.However,the complexity of dissolved organic matter and the variety of the methods by which the dissolved organic matter is obtained have made the explanation and the comparison between labs rather difficult.The gap between the lab and the field research also needs to be filled.In this review,the research progress on direct interaction of dissolved organic matter with organisms was introduced in detail and the bottleneck of this research aspect was discussed as well.