白山市江源区特种野猪养殖现状及发展前景

分析了白山市江源区发展特种野猪养殖的优势,介绍了该区特种野猪发展历史及现状,并就其未来发展前景进行展望,以为特种野猪的养殖提供参考。

Transformation and source of nutrients in the Changjiang Estuary

The concentrations of phosphate （PO43 ）, ammonium, nitrite, nitrate, silicate, dissolved organic nitrogen （DON）, dissolved or- ganic phosphorus （DOP）, particulate phosphorus （PP） and particulate nitrogen （PN） along the salinity gradient were measured in the Changjiang Estuary in April 2007. The behavior of nutrient species along the continuum from the freshwater to the coastal zone is discussed. In the mixing zone between the riverine and marine waters, nitrate and phosphate behave non-conservatively, while silicate behaves conservatively. Nutrient import was quantified from the fiver load. Nutrient export to the sea was quantified from fiver discharge and from the salinity-nutrient gradient in the outer estuary. Using these data, a nitrogen and phosphorus budget was made. The internal estuarine fluxes played an important role in the nutrient estuarine fluxes, which accounted for approximately 41% of the nitrogen flux and 45% of the phosphorus flux. The mixing experiments in the laboratory generally reproduced well the inorganic process affecting nutrient dynamics in the Changjiang Estuary, indi- cating that the primary P and N transformation processes were phosphate and nitrate desorption along the salinity gradient.

Seasonal changes of organic matter origins and anammox activity in the Changjiang Estuary deduced from multi-biomarkers in suspended particulates

Human activity-induced eutrophication and harmful algal blooms are main causes of the expansion of the hypoxic zone in the Changjiang Estuary. Among the many changes in biogeochemical processes, anaerobic ammonium oxidation(anammox) is proposed to play an important role in the nitrogen cycle in hypoxic areas. Ladderane lipids have been used as biomarkers to indicate anammox activity in ecosystems, but the origins of anammox bacteria and ladderanes in suspended particulates are still unclear. In this study, we report the results of a suite of biomarker analyses of suspended particulates across a salinity gradient of the Changjiang Estuary in both the spring and summer to evaluate the origins of the ladderanes and their potential as proxies for anammox activity and hypoxia. The spatio-temporal variations in terrestrial biomarkers(n-alkanes and n-alkanols), marine biomarkers(brassicasterol and dinosterol), and the Terrestrial and Marine Biomarker Ratio and Branched and Isoprenoid Tetraether indices reveal that marine organic matter was dominant in the particulates in both the spring(55%) and summer(86%) seasons. Correlations with both marine and terrestrial biomarkers suggest that ladderanes were mainly produced in the water column, and therefore that ladderane concentrations in suspended particulates in the Changjiang Estuary mainly reflect anammox activity in the water column, although changes in anammox bacterial assemblages may also have played a role in ladderane concentrations. Overall, ladderane results suggest that anammox activity was widespread in the Changjiang Estuary; but higher ladderane concentrations in the summer(especially in the upwelling zone) were correlated with lower dissolved oxygen concentrations, which suggest that they are useful proxies for hypoxia.

Quantifying the sources of dissolved inorganic carbon within the sulfate-methane transition zone in nearshore sediments of Qi'ao Island, Pearl River Estuary, Southern China

The significance of the various biogeochemical pathways that drive carbon cycling and the relative fractions of dissolved inorganic carbon(DIC) produced by these reactions within the sulfate-methane transition zone(SMTZ) are still being debated. Unraveling these processes is important to our understanding of the benthic DIC sources and their contributions to the global carbon cycle. Here, we measure pore water geochemistry(chlorine, sulfate, methane, Ca^(2+), Mg^(2+), DIC and δ^(13)C-DIC) as well as solid geochemistry(sedimentary organic carbon(SOC) and δ^(13)C of SOC) in nearshore sediments from Qi'ao Island in the Pearl River Estuary of the Southern China Sea. Our analysis indicates that SOC originates from the mixing of carbon from terrestrial and marine sources, and that terrestrial materials dominate the net loss of SOC during the degradation of organic matter, especially at sites located near the river outlets. Sulfate reduction via SOC degradation is not appreciable in the upper sediment layer due to conservative mixing-dilution by freshwater. However, below this layer, the anaerobic oxidation of methane(AOM) and methanogenesis occur. Within the SMTZ, the δ^(13)C mass balance shows that the proportions of DIC derived from organoclastic SO_4^(2-) reduction(OSR) and AOM are 50.3% to 66.7% and 0.1% to 17.9%, respectively, whereas methanogenesis contributes 17.0% to 43.9%. This study reveals that the upward diffusion of DIC from ongoing methanogenesis significantly influences carbon cycling within the SMTZ in these estuarine sediments. As a result, we suggest that the plots of the ratio of change in sulfate to change in DIC in pore water should be used with caution when discriminating between sulfate reduction pathways in methane-rich sediments.