低径流量条件下海平面上升对长江口淡水资源的影响

基于长江口水动力及盐水入侵三维数值模式ECOM-si,统筹考虑气候变化导致流域极端低径流量的前提下,研究在未来（2030、2050和2100年）海平面上升过程中,长江口淡水资源分布及总量变化过程,探讨河口三大重要水库取水活动对海平面上升的响应,对防范未来可能出现的盐水入侵危害具有重要作用,也为长江口水源地建设与水库取水调度提供理论依据和技术支持。1999年冬季、2006年秋季和2011年春季期间长江径流量均为自1980年以来的同期最低,且长江口均发生了极为严重、影响巨大的盐水入侵,考虑到径流量的季节变化特点,选取上述3个时期的径流量作为上游边界条件。结果表明,长江口淡水资源在1999年冬季径流量条件下随海平面上升而减少,至2100年大、小潮期间淡水总量相比于2012年分别减少42%和41%,水库最长不宜取水天数增加70%以上;在2006年秋季径流量条件下,淡水资源随海平面上升而减少,但在海平面上升至2050年情况下,河道水位抬升使进入北支的径流量增加,削弱盐水倒灌,水库最长不宜取水天数减少40%~50%;在2011年春季径流量条件下,淡水资源在海平面上升至2100年后大、小潮期间分别减少43%和20%,水库最长不宜取水天数增加1~3 d。     

Similarities in the behaviour of Chernobyl derived Ru-103, Ru-106 and Cs-137 in two freshwater lakes

Measurements of the concentrations of Ru-103 and Ru-106 in the water column and sediments of two productive temperate lakes were made during an eight month period following the Chernobyl accident. Ru-103 accumulation in the sediments began simultaneously with that of Cs-134 and a constant ratio (approx. 2.0 on a decay corrected basis) of Ru-103/Cs-137 was observed in surface waters and sediments throughout the measurement period. The ratio is not statistically different from that reported for atmospheric input and for epilimnetic water. The results suggest that the processes of removal of radioactive ruthenium and caesium from the mixed water column to the sediments are the same.Enhancement of Cs, compared with Ru, in the isolated bottom waters of one of the lakes in the summer months provided evidence for Cs release from the sediments during a period of hypolimnetic anoxia.     

The flank margin model for dissolution cave development in carbonate platforms

The Bahama Islands contain many abandoned dissolution caves at elevations between two and seven metres above current sea level. The development of dissolution caves in tropical carbonate islands is dependent on the position and nature of the freshwater lens. Lens position is controlled by sea level, which in stable carbonate platforms like the Bahamas is a function of glacioeustatic sea level still stands. Caves in the Bahamas that are currently subaerial must have developed during past higher sea levels. During the Late Quaternary, sea levels higher than present have been relatively short-lived, and that limits the amount of time that a freshwater lens could be situated at the elevation required for the cave formation. The Bahama Islands are low-lying landforms where only aeolian ridges extend to elevations higher than six metres above current sea level. Past high sea level events greatly reduced the exposed land area of the Bahama Islands, thus also limiting both the catchment for and size of freshwater lenses. Caves must be younger than the rock in which they are developed; most subaerial Bahamian caves are found in limestones that are less than 150000 years old. Development of large dissolution caves under these limitations of time and lens size requires a powerful dissolutional mechanism. The mixing of discharging freshwater with tide-pulsed incoming marine water under the flanks of emergent dune ridges may have produced the conditions necessary. Bahamian caves formed by this process are phreatic chambers with complex interconnections and blind tubes. Their presence demonstrates that significant dissolution can occur rapidly as a result of the mixing of fresh and marine waters beneath small carbonate islands.     

关于淡水浮游动物和原生动物分开研究的建议

正《湖泊科学》编辑部:国内关于淡水浮游动物的文章中,一般浮游动物包含四大类,即原生动物、轮虫、枝角类和桡足类,其中枝角类和桡足类又合称为浮游甲壳动物.除了这四大类外,浮游动物还包括软甲类甲壳动物(如糠虾、钩虾等)、水生昆虫(如幽蚊等)、水蜘蛛、丰年虫、淡水水母、浮游贝类幼虫等,由于这些类群在淡水水体中分布有限,尤其在敞水区,一般的浮游动物研究并不包括这些类群.从分类阶元来看,淡水原生动物的主要种类属于原生动物亚界的肉鞭门和纤毛门,肉鞭门包括鞭毛亚门(植鞭毛纲-自养鞭毛虫和动鞭毛纲一异养鞭毛虫)、肉足亚门根足总纲(变形虫和有壳肉足虫),一般将淡     

钙质砂水理性质及对岛礁淡水透镜体形成的影响

钙质砂的水理性质对岛礁地下淡水透镜体的形成至关重要。通过室内试验的方法从透水性、容水性和给水性3个方面对南海钙质砂的水理性质进行了研究,并在此基础上进一步结合数值模拟手段,探讨了上述相关性质对岛礁淡水透镜体形成的影响。结果表明：南海钙质砂多具有级配不良且不均匀的特征;其渗透系数通常在0.023~110 m/d之间,区域间差异较大,而孔隙度和给水度则主要集中在0.40~0.55和0.012~0.310之间,与同粒径范围的陆源砂相比,呈现出容水性好但给水性偏低的特征。钙质砂的水理性质对岛礁地下淡水透镜体形成的影响主要体现在流速、厚度、资源储量以及形成时间等方面,其中钙质砂的透水性越好,地下水中的流速越快,咸淡水间的混合作用越强,导致淡水透镜体的厚度越薄,储量越少;给水性则主要影响钙质砂中淡水透镜体的资源储量,对淡水透镜体的厚度及形状影响较小。     

Propagation of tides in the Mandovi-Zuari estuarine network

Located in Goa on the west coast of India and joining the Arabian Sea, the Mandovi and the Zuari are two estuaries, each about 50 km long, connected by a narrow canal. A number of small rivers join the two estuaries, forming a network of channels, whose cross-sectional area decreases rapidly in the upstream direction. They receive large freshwater influx during the southwest monsoon and little during the rest of the year. During April (dry season) and August (wet season) 1993, the water level and salinity at 15 locations in the network were monitored for 3 days to determine characteristics of tidal propagation in the network. Analysis of the data shows that the speed of propagation of both the diurnal and the semi-diurnal tide through the main channels of the network is approximately 6 m/s. Amplitudes of these tides in the channels remain unchanged over a distance of about 40 km from the mouth and then decay rapidly upstream over the next 10 km. The undamped propagation is a consequence of the balance between geometric amplification, due to decrease in the cross-sectional area in the upstream direction, and frictional dissipation. The rapid decay near the upstream end of the channels appears to result primarily from freshwater influx.     

Structure and dynamics of fisheries in Nigeria

The changes that have taken place in Nigerian fisheries are reviewed. Artisanal fishery has continued to dominate the fisheries,contributing over 85% of total fish production. The inland water and coastal seas are fully exploited and the increase in fishery production is not likely. Aquaculture potentials remain untapped as much as deep-sea fisheries. The combined potential of the fisheries resources-freshwater,marine and aquaculture can meet over 90% of the nation's demand for fish. Opportunities for invest-ments,therefore,exist in the various subsectors,especially in the areas of storage,processing and preservation for the capture fishery and fish seed multiplication for aquaculture.     

中国球状绿藻新纪录属-索囊藻属(Choricystis)

在西藏那曲的错鄂和湖北武汉的紫阳湖采集到两株淡水绿色海绵。形态观察显示,两株海绵呈现绿色是由于其内共生有球状绿藻。基于形态观察和分子系统发育分析确定为该球状绿藻为索囊藻属的寄生索囊藻(Choricystis parasitica(K.Brandt)Pr?scholdDarienko)。结果表明:(1)两株藻均为纺锤形或倒卵形,长1.2—2.8μm,宽0.8—1.5μm;具一个侧位片状色素体;(2)依据18S r DNA和rbc L cp DNA的进化分析显示这两株藻均位于胶球藻科(Coccomyxaceae),索囊藻属(Choricystis);(3)基于ITS2的二级结构分析显示这两株藻与寄生索囊藻具有相同的二级结构,表明这两株内共生的球状绿藻均为寄生索囊藻。寄生索囊藻为中国新纪录种,所在属索囊藻属为中国新纪录属。本研究以形态性状和分子性状描述了采自中国的寄生索囊藻标本,为今后研究提供依据和参考。     

理想化南极融冰方案的海洋边界条件初探

基于气候态的SODA(simple Ocean Data Assimilation)数据,比较了气候态意义下南极附近和南极绕极流区域的海洋层结,对南极融冰问题的合理海洋边界条件进行了初步探讨.结果表明:南极融冰所注入的淡水通量在大西洋东部和印度洋海区将沿着表层路径到达南极绕极流区,在大西洋西部和太平洋的经向运动路径视淡...     

The hydrological response of surface water to recent climate variability: A remote sensing case study from the central tropical Pacific

For small tropical islands with limited freshwater resources, understanding how island hydrology is influenced by regional climate is important, considering projected hydroclimate and sea level changes as well as growing populations dependent on limited groundwater resources. However, the relationship between climate variability and hydrologic variability for many tropical islands remains uncertain due to local hydroclimatic data scarcity. Here, we present a case study from Kiritimati, Republic of Kiribati (2°N, 157°W), utilizing the normalized difference vegetation index to investigate variability in island surface water area, an important link between climate variability and groundwater storage. Kiritimati surface water area varies seasonally, following wet and dry seasons, and interannually, due to hydroclimate variability associated with the El Niño/Southern Oscillation. The NIÑO3.4 sea surface temperature index, satellite‐derived precipitation, precipitation minus evaporation, and local sea level all had significant positive correlations with surface water area. Lagged correlations show sea level changes and precipitation influence surface water area up to 6 months later. Differences in the timing of surface water area changes and variable climate‐surface water area correlations in island subregions indicate that surface hydrology on Kiritimati is not uniform in response to climate variations. Rather, the magnitude of the ocean–atmosphere anomalies and island–ocean connectivity determine the extent to which sea level and precipitation control surface water area. The very strong 2015–2016 El Niño event led to the largest surface water area measured in the 18‐year data set. Surface water area decreased to pre‐event values in a similarly rapid manner (<6 months) after both the very strong 2015–2016 event and the 2009–2010 moderate El Niño event. Future changes in the frequency and amplitude of interannual hydroclimate variability as well as seasonal duration will thus alter surface water coverage on Kiritimati, with implications for freshwater resources, flooding, and drought.