长江口北支湿地自然保护区生态评价

选取多样性、代表性、稀有性、自然性、面积适宜性、脆弱性和人类威胁等7个指标,采用专家咨询法,对长江口北支湿地自然保护区进行了生态评价,结果表明:该保护区生态质量一般,不足以有效保护湿地生物多样性,亟需采取科学、有效、严格的保护和管理措施。     

长江口冲积岛浅滩演变的可视化分析

为了解剧烈开发背景下长江口浅滩的演变特征,运用GIS技术建立1879年以来长江口地区水下数字高程模型(DEM),再现百余年来长江口长兴岛—横沙岛和九段沙浅滩的演变过程,并计算浅滩的面积、体积、冲淤量和冲淤厚度。结果表明:百余年来长兴岛—横沙岛和九段沙浅滩总体上呈淤涨趋势,并沿东南方向向海推进;长江流域中上游的开发和保护以及河口地区重大工程对浅滩演变的影响越来越大。     

Similarities between Yangshan Harbor area and the Yangtze estuary

By analysis of published papers on the Yangtze estuary and hydrological and sediments data in Yangshan Harbor area, many similarities are found between Yangshan Harbor area and the Yangtze estuary. These similarities include the phenomenon of stagnating flow areas, the distributive characteristics of the highest suspended sediment concentration areas, superficial sediments and shoal bars. The stagnating flow area is the major similarity which causes other similarities. These similarities indicate that: 1) Turbidity Maximum and mouth bars in estuaries are mainly caused by the hydraulic balance of stagnating flow areas of estuaries; 2) The stagnating sand area of sands caused by stagnating flow area often locates on the narrower side of the stagnating flow area; 3) The location (or shape) of fine sediments area caused by stagnating flow area reflects the location (or shape) of the stagnating flow area. Both Yangshan Harbor area and the Yangtze estuary are the important developmental areas in the future (man-made similarity). In-depth studies on these similarities between Yangshan Harbor area and the Yangtze estuary will have momentous theoretical and practical significance.     

Reproductive cycle and minimal length at sexual maturity of Engraulis encrasicolus (L.) in the Zrmanja River estuary (Adriatic Sea, Croatia)

The reproductive cycle of anchovy, Engraulis encrasicolus (L.), was studied from monthly random samples of purse seine catches. A total of 1477 anchovy specimens were collected from January to December 2003 in the Zrmanja River estuary (Novigrad Sea). The analysis was based on the temporal evolution of gonadosomatic index, mass and stage of gonads. The total length of anchovy ranged from 4.5 to 14.5 cm and mass from 0.56 to 19.80 g. Sex ratio was slightly different from 1:1; the females were insignificantly predominated (♂/♀ = 0.99). The period of reproductive activity was from April to September coinciding with the most developed stages of gonads as well as with the highest gonad weights, and gonadosomatic indices. To estimate the length at maturity, a sub sample of 454 anchovy was taken from May to July (peak of anchovy spawning period). The length at which 50% of anchovy were mature (L₅₀) was calculated to be 8.2 cm. The length–weight relationship of anchovy was described by the expression: W = 3.51 × 10⁻³ L_T^3.211 (r² = 0.998). The relationships between total length–standard length and total length–fork length are L_T = 1.1405L_S + 0.2420 and L_T = 1.0425 L_F + 0.3944, respectively.     

Long-term changes in the production by estuarine macrobenthos affected by multiple stressors

The macrobenthic production of an estuarine system was evaluated over a 14-year study period in a seagrass bed and in a sandflat. Over this period, the estuary suffered severe eutrophication and extreme weather events with important impacts on the community, impairing system functioning and ultimately the goods and services provided by the estuary (decline in the seagrass bed, decreased community production and/or a boost in the production by opportunist species, such as Hydrobia ulvae). Following the anthropogenic impacts, management measures were introduced which allowed a gradual recovery of the seagrass bed and a new macrobenthic community structure manifested by production increases of slow-growing species, such as Scrobicularia plana and Hediste diversicolor. There was a gradual re-orientation of energy into population biomass instead of population density but this was not translated into higher community production, mainly due to the decreased production of opportunist species (H. ulvae and several polychaetes). Several weather extreme events occurred during this post-mitigation phase - floods, heatwaves and droughts, all of which had negative impacts on macrobenthic dynamics and production. The heatwaves led to the greatest decreases in macrobenthic production, mainly due to S. plana perhaps associated with its physiological intolerance of higher temperatures. The prolonged drought that followed the heatwaves maintained low levels of production by S. plana and H. ulvae. With climate change, the frequency and intensity of extreme weather events are likely to increase worldwide so that the recovery of impacted/disturbed systems from impacts such as eutrophication may be seriously affected by these additional stressors, compromising attempts to improve the ecological quality of estuarine ecosystems.     

GEOCHEMICAL CHARACTERISTICS OF SEDIMENTS AND ANALYSIS OF THE CHANGJIANG ESTUARY ENVIRONMENT

Analysis of material from three 55- cm long cores collected with box corer m summer of 1988 in the Changjiang Estuary region yielded data on the sedimentation rate, granulometric composition and contents of carbonates, organic matter, Al, Fe, Mn, Zn, Cu and Pb there. Subsequent study of the data led to the conclusion that there is no obvious pollution in the region based on the absolute value of the content of heavy metals, but the region is in potential danger of being polluted as seen by the obvious increase of sedimentation flux of heavy metals to and the enrichment of them on the surface sediment during the last several years, e.g. Pb increased by 10-20μg/g, Zn by about 30μg/g, Cu by 5-10μg/g and Mn by 150μg/g.A ferromanganese redox interface was found at about 40 cm depth of sediments where Fe and Mn and associated trace metals are enriched. The trace metals such as Zn, Cu have (but Pb does not) the same source, forms, displacement mechanism and geochemical behaviours as those of Fe and Mn in t     

The short-term impact of managed realignment on soil environmental variables and hydrology

In July 2000 a flood defence embankment protecting abandoned agricultural land in the estuary of the River Torridge, Devon, UK, was breached as part of a managed realignment (MR) project. The objective was to restore the agricultural land, reclaimed from saltmarsh some 200 years previously, to its former habitat. Changes to the soil hydrological regime and alteration of the soil environment at the site were studied. The most significant observed impact at the MR site was the change in flooding regime, with regular tidal inundation occurring to a maximum depth of 52 cm during spring tides. Prior to the realignment, soil water table fluctuations were linked to patterns of spring and neap tides. Post-realignment, a change in mean water table height of more than 50 cm was observed at the MR site, and soil redox potential at 5 cm depth was reduced by over 700 mV immediately following reflooding, changing the soil environment from an oxidised to a reduced environment. Topsoil water (collected from 10 cm depth) demonstrated large, short-term reductions in pH. Prior to realignment topsoil water pH ranged from 6.6 to 8.7, but following realignment remained below 5 for approximately nine weeks, reaching a minimum of 3.3. Short-term changes in conductivity and NH₄⁺ concentrations in topsoil water also occurred, conductivity rising from <2000 μS to >40,000 μS following realignment, while NH₄-N concentrations rose from 0.10 mg l⁻¹ to 10.05 mg l⁻¹. Cotton tensile strength loss (CTSL) reflected these changes, exhibiting large decreases in decomposition rates at 5–10 cm depth immediately following the realignment. These results have implications for the management of MR projects, and for the health and quality of the estuary in general.     

Riverine Composition and Estuarine Geochemistry of Particulate Metals in China—Weathering Features, Anthropogenic Impact and Chemical Fluxes

Suspended sediments from large and middle size Chinese estuaries, including the Yalujiang, Shuangtaizihe, Luanhe, Jiaojiang and Zhujiang, were analysed to understand trace metal transport in the coastal zone. The determinations of 13 major and trace elements plus organic carbon were made of total concentrations and were fully validated by certified reference materials (CRMs). The combination of the data sets with other Chinese estuaries, such as Changjiang and Huanghe, provides an overview of particulate trace metal geochemistry in this region. Trace metal levels in Chinese rivers are relatively low compared with those draining industrialized regions of Europe and North America. In the estuaries, most particulate elements illustrate stable distribution in the mixing zone until a salinity of 30, especially when absolute concentrations are normalized to aluminium, although the total suspended matter (TSM) is quite different in time and space. Using Al as a reference, it was estimated that 25–40% for Cu, and 5–20% for Pb could remain in labile part in the Jiaojiang, Shuangtaizihe and Zhujiang, whereas different features of labile elements were found in the Changjiang and Luanhe. The mean enrichment factor (EF_m) increases with higher sewage to river runoff ratio (S/R) over the drainage basin and EF_m for suspended matter is higher than that for bottom sediments. Finally, inputs of particulate trace metals to the coast are estimated based on the riverine sediment load and chemical compositions.     

‘ Global Change ’ Impact of Inter-Annual Variation in Water Discharge as a Driving Factor to Dredging and Spoil Disposal in the River Rhine System and of Turbidity in the Wadden Sea

Between 1970 to 2000, the annual mean suspended matter (SPM) concentrations in the Vlie and Marsdiep tidal inlets of the Wadden Sea varied over five times. The present paper examines the possible relationship between SPM in the Wadden Sea and changing river Rhine discharges and dredging operations. The major short-term variations in annual mean SPM in part of the Wadden Sea appears to be a non-linear, exponential, function of river Rhine discharge and dredge spoil disposal (110 km to over 200 km from the area in front of the Dutch coast near the river Rhine outlet). Correlation coefficients (with SPM as the fixed and dredge disposal as the independent variable) ranged from R=0·8 (deep tidal inlet of Marsdiep) to R=0·2 (shallow inner area of Vlie) and weakened mainly as a function of distance to the disposal site. The best correlation with river discharge was for Marsdiep tidal inlet (r=0·45), indicating the superior effect of dredge disposal over river discharge-related processes. Taking the estimated regression equation as an explorative model, indicates that, without any disposal of dredge spoil, the expected SPM concentration levels in the tidal inlets of the Wadden Sea will be <15 g m⁻³ (comparable to the 1950s). The overall mean (and the highest mean) annual concentrations for the investigation period reached 42 (90) g m⁻³ at Marsdiep and 35 (75) g m⁻³ at Vlie. Assuming a 10% (220 m⁻³ s⁻¹) increase in river Rhine discharge over the next 50 years, and unchanged dredging policy and other circumstances, SPM concentrations would increase 5–15% for Marsdiep and Vlie. Compared with the calculated (12·4 g m⁻³ SPM in Marsdiep and 14·8 g m⁻³ SPM in Vlie) and measured (15 g m⁻³ SPM in Marsdiep) background SPM concentrations, the expected overall mean increase since 1950 is at least 250% of background. The natural variation in river Rhine discharge will cause further inter-annual variation. Changes in SPM concentrations, due to expected changes in wind climate, combined with river discharge are estimated to increase SPM concentrations 20% above the present situation. The possible implications of changes in land use in combination with further increasing river discharge, changed wind fields and increased temperature are discussed. An important management conclusion is that increasing mean river discharge will significantly increase the need for dredging and spoil disposal, and result in further elevated SPM concentrations in the Dutch coastal zone and the Wadden Sea. The presented relationships offer possibilities for developing new management strategies in relation to dredging and its effects.