微塑料和致病性弧菌联合作用对许氏平鲉幼鱼抗氧化能力及营养品质的影响OA

Microplastics(MPs),owing to their small size and strong concealment,have become a new type of pollutant that is widely present in global marine ecosystems.Owing to their complex sources and wide distribution in marine environments,they are easily ingested by aquatic organisms,migrate through food webs,and accumulate among organisms at different trophic levels,posing a potential threat to biological health.Previous studies have shown that over 400 fish species in Asia and at least 800 worldwide contain microplastics in their bodies.Microplastic pollution is characterized by widespread biological exposure.In addition to direct ingestion risks,microplastics,which have large specific surface areas,rough surface structures,and strong hydrophobicity,can provide an ideal substrate for the attachment,colonization,and biofilm formation of microorganisms(including potentially pathogenic bacteria),thus becoming important carriers for the migration and spread of pathogenic bacteria in the marine environment.The concept of"Plastisphere"was proposed in 2013,further revealing a unique microbial community structure on microplastic surfaces,with up to 24％of microorganisms belonging to the genus Vibrio in some samples.Since then,many studies have documented extensive attachment of Vibrio bacteria to microplastic surfaces across multiple global seas,including the Baltic Sea,the Mediterranean Sea,Bohai Bay,and the Maowei Sea in China.Against this background,an increasing number of studies have suggested that microplastics may significantly increase the bioavailability of pathogenic bacteria through the"Trojan horse effect,"thereby promoting the co-entry of microplastics and pathogenic bacteria into organisms,inducing oxidative stress,inhibiting metabolic functions,and weakening the body's immune defense system.However,most experimental studies have used exposure concentrations higher than those in natural marine environments,making it difficult to accurately reflect the ecological risks posed by the combined effects of microplastics and pathogenic bacteria,and the underlying biological response mechanisms remain unclear.Therefore,this study focused on juveniles of the economically important fish Sebastes schlegelii in the Yellow and Bohai Seas as the research object,examining the combined toxic effects of environmental concentrations of polyethylene microplastics and Vibrio parahaemolyticus.The experiment established a blank control group,a polyethylene microplastic exposure group at 20 μg/L,a V parahaemolyticus exposure group at 104 CFU/mL,and a combined exposure group of polyethylene microplastics and V parahaemolyticus,and conducted indoor simulated toxicological experiments.The liver tissues of the juvenile S.schlegelii were collected at 0,7,14,and 21 days of the experiment to determine the activity of superoxide dismutase(SOD),the content of malondialdehyde(MDA),and the activities of acid phosphatase(ACP)and alkaline phosphatase(AKP).At the same time,the muscle tissues were collected on the 21st day of the experiment to analyze their basic nutritional components,amino acid composition and content,and evaluate the amino acid nutritional value.The results showed that,in terms of oxidative stress,the combined exposure to polyethylene microplastics and V parahaemolyticus significantly reduced SOD activity in the liver of juvenile SS.schlegelii and significantly increased the MDA content(P＜0.05),indicating that the oxidative damage caused by the combined stress exceeded the antioxidant capacity of the body,intensifying lipid peroxidation in liver cells.In terms of the immune response,the combined stress initially induced a significant increase in the activities of ACP and AKP(P＜0.05),indicating that the non-specific immune defense system of the body was activated to assist in the clearance of foreign substances and enhance detoxification metabolism.In the later stage of the experiment,the activity of ACP decreased,whereas that of AKP remained high,suggesting that the combined effect of polyethylene microplastics and V.parahaemolyticus could cause chronic damage to the cell membrane structure and function and continuously induce detoxification metabolic processes,thereby posing a long-term potential risk to the immune system.The analysis of muscle nutrient components showed that the combined exposure led to a significant increase in the water and ash content of the body(P＜0.05)and a significant decrease in the content of five essential amino acids,including valine,isoleucine,leucine,phenylalanine,and lysine(P＜0.05).Although it did not substantially impair the nutritional quality of muscle proteins at this stage,a reduction in multiple essential amino acid levels indicated a potential risk of deterioration in the muscle's nutritional value.In summary,this study revealed the hepatotoxic mechanism and the potential impact on muscle nutritional quality resulting from the combined exposure to environmental concentrations of polyethylene microplastics and V.parahaemolyticus in juvenile S.schlegelii.It also suggests that,in future research,we should pay close attention to the chronic toxic effects and molecular mechanisms of the combined action of environmental pollutants under low-dose,long-term exposure.