| Eutrophication problem has attracted more attention, for its bad effect on the environment andit becomes a threat to people health. Cycle of matter occurred in the sediment-water interface playsan important role in the eutrophication process. On the first hand, nutrient accumulated in thesediment, and on the other hand, sediment acts as the nutrient source for the overlying water. Eventhe external pollution is under control, nutrient can release from the sediment to the overlyingwater through nutrient exchange across the sediment-water interface and eutrophic status lasts for along time. There are many microbes and infaunal animals on the sediments, and then physical andchemical properties of the sediment are changed through their metabolic activities (excretion,mineralization and burrowing). As a result, through exploration on the nutrient cycle, changes ofmicrobial community and P fraction in the sediment disturbed by the infaunal animals, we canbetter understand the complicated cycle process in the sediment and support the eutrophicationcontrol.1. In August,2010, sediments from ponds with and without algal blooms were sampled fora comparison study, and the vertical distribution of NH4+-N、NO3--N and PO43--P within theinterstitial water were analyzed, as well as the microbial activity (FDA) and alkaline phosphatase(APA) in surface sediments. The results showed the concentration of NH4+-N increased fromsuperficial waters to interstitial waters in both types of sediments, indicating a risk of NH4+-Nreleasing from interstitial waters. However, the concentrations of NO3--N and PO43--P decreased.The decreasing trend was observed for organic matter content (reflected by Loss-on-Ignition, LOI),FDA activity, and APA in the top10cm sediments. Correlation analyses showed that theconcentration of NH4+-N in interstitial waters was positively correlated with the activities of FDAand APA in surface sediments (0-10cm), suggesting that the effect of microbe on N decompositionand mineralization was mainly influenced by the activities of APA and FDA in an anaerobicenvironment.2. Model ecosystem was constructed in June,2010and phospholipid fatty acids (PLFAs)were applied to determine changes in microbial community structures affected by the bioturbation of B.aeruginosa. The results showed that the total biomass of PLFA had a distinguished increase intreatments contained snails comparing with the control group. Furthermore, it was highly related tothe content of TOC, r=0.541(p<0.05). The value of bacteria/fungus changed remarkably during theexperiment, the value of bacteria/fungus in mid-density treatment is significantly higher than theother treatments (p<0.05), indicating that bacteria grew more quickly than fungus and the bacteriabiomass increased significantly in Mid-density condition. Principle components analysis(PCA) ofPLFA profiles demonstrated that the microbial community structures were similar in low and highdensity treatments and the control, and no obvious changes were observed; while in Mid-densitytreatments(196ind/m2), microbial community structures had varied apparently.3. Phosphorus is widely regarded as a limiting nutrient for primary production of the watersystem, and the excessive P concentrations were mainly responsible for eutrophication.Disturbation of sediment can promote the release of internal phosphorus and result in highconcentration of P in the overlying water. Model ecosystem was constructed in September,2010and method of SMT was applied to determine influences of two kinds of infauna (Bellamyaaeruginosa and Corbicula fluminea) on vertical distribution of the sediment P fraction. Resultsshow that: decomposing and transformation of OP were observed, the OP content was decreaseddramatically during the experiment period. NAIP, as an important composition of bio-available Paccumulated over the experimental period. Bioturbation of C. fluminea was significantly strongerthan B. aeruginosa, for example, the NAIP content in the2-3cm sediment of the C. flumineatreatments was1.44g/kg in the end of the experiment, which is significantly higher than those inother two treatments. The contents of AP were more stable and no significant differences wereobserved. TP content in the0-1cm sediment disturbed by the benthic animals increased in themiddle and end of the experiment, TP content in the1-2cm sediment disturbed only by C. flumineaincreased in the end of the experiment, and no significances were observed among treatments inthe2-3cm sediment. |
PDF Full Text Request