Significance and impact of the study: In the integrated multi-trophic aquaculture system in this study, planktonic and sediment bacterial communities in the aquaculture system were monitored over a year. In this study, obvious seasonal variations were found in planktonic bacteria but not in sediment bacteria. In each season, there were no obvious variations in planktonic and sediment bacteria between fish cages, shellfish rafts and some control sites. The results indicate that no apparent impact of feeding operations in the fish culture cage system on bacterial communities in the IMTA system was observed in the current study.

In this study, we conducted a comparative analysis of the abundance and diversity of bacteria on the surface of the submerged macrophyte Myriophyllum spicatum, as well as in the surrounding water column and sediment in the low-salinity area of Hangzhou Bay, China. Bacterial clones from three clone libraries were classified into 2089 operational taxonomic units (OTUs), most of which affiliated with bacterial divisions commonly found in marine ecosystems. Alphaproteobacteria, Cyanobacteria and Gammaproteobacteria were the most abundant groups of bacteria on the surface of plants, in the water column and sediment, respectively. Epiphytic bacterial communities were more closely related to those in the sediment than bacterioplankton, and some species of epiphytic bacteria were found only on the surface of M. spicatum. The relative abundance of epiphytic bacterial genera associated with breakdown of organic compounds and with cellulose digestion was higher in October than that in July. These results suggested that bacterial communities on the surface of M. spicatum may originate from sediment bacterial communities and their specific structure was gradually formed on the surface of M. spicatum after being cultivated in low-salinity seawater.

Sulfate attack is one of the most important problems affecting concrete structures, especially magnesium sulfate attack. This paper presents an investigation on the mechanical properties and damage evolution of high performance concrete (HPC) with different contents of fly ash exposure to magnesium sulfate environment. The microstructure, porosity, mass loss, dimensional variation, compressive strength, and splitting tensile strength of HPC were investigated at various erosion times up to 392 days. The ultrasonic pulse velocity (UPV) propagation in HPC at different erosion time was determined by using ultrasonic testing technique. A relationship between damage and UPV of HPC was derived according to damage mechanics, and a correlation between the damage of HPC and erosion time was obtained eventually. The results indicated that (1) the average increasing amplitude of porosity for HPCs was 34.01% before and after exposure to magnesium sulfate solution; (2) the damage evolution of HPCs under sulfate attack could be described by an exponential fitting; (3) HPC containing 20% fly ash had the strongest resistance to magnesium sulfate attack.

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