Effects of environmentally relevant concentrations of micro(nano)plastics on aquatic microorganisms:Changes in potential function but not in overall composition

Micro(nano)plastics(MNPs)are a growing problem as persistent environmental pollutants.Here,we investigated the impact of MNPs on microorganisms in aquatic microbial floc exposed to NPs(80 nm)and MPs(8μm)for 35 days.Water quality indicators were tested weekly and microbiological analyses were conducted on Day 7 and 28 after exposure.The results showed that there were significant differences in the levels of total ammonia nitrogen or nitrite between the MNPs groups and the control group,spanning from Day 7 to Day 28.For the microbial response,microbial community richness in the NPs and MPs groups were significantly increased at Day 7.Functional prediction showed that the relative abundances of bacteria associated with the“Forms Biofilms”,“Potentially Pathogenic”,“Plastic Degradation”and nitrogen cycle processes were significantly different after MNPs exposure.The results suggest that MNPs had no significant effect on the microbial diversity of mature microbial flocs.Findings suggest MPs could cause an increase in the relative abundance of potentially pathogenic bacteria,while NPs do not.In addition,stress associated with MNPs affected the nitrogen cycle of microorganisms,and NPs exerted greater impacts than MPs.Findings from this study further our understanding of the impact of MNPs at environmentally relevant concentrations on microorganisms in aquatic ecosystems.

Study on Biogenic Amines in Various Dry Salted Fish Consumed in China

This study was carried out to investigate the biogenic amines(BAs), physicochemical property and microorganisms in dry salted fish, a traditional aquatic food consumed in China. Forty three samples of dry salted fish were gathered from retail and wholesale markets and manufacturers, which had been produced in various regions in China. Cadaverine(CAD) and putrescine(PUT) were quantitatively the most common biogenic amines. About 14% of the samples exceeded the histamine content standards established by the FDA and/or EU. The highest histamine content was found in Silver pomfret(Pampus argenteus)(347.79 mg kg^(-1)). Five of forty three samples exceeded the acceptable content of TYR(100 mg kg^(-1)), and 23.26% of dried-salted fish contained high contents of biogenic amines(above 600 mg kg^(-1)). In addition, species, regions, pickling processes and drying methods made the physicochemical property, microorganisms and biogenic amines in dry salted fish to be different to some extents. The total plate count(TPC) was much higher than that of total halophilic bacteria in all samples. The biogenic amines, physicochemical property and microbiological counts exhibited large variations among samples. Furthermore, no significant correlation between biogenic amines and physicochemical property and TPC was observed. This study indicated that dry salted fish may still present healthy risk for BAs, depending on the processing methods, storage conditions among others.