全球变化下的国际水文学研究进展:特点与启示——2011年欧洲地球科学联合会会员大会述评

欧洲地球科学联合会2011年会员大会于4月3-8日在奥地利首都维也纳举行。其中,水文学专场重点讨论了全球变化对陆地表层水文过程的影响。主要包括气候变化下的洪涝灾害与干旱胁迫、冰川融雪、降雨特性、区域水平衡、土壤侵蚀与泥沙搬运、景观进化与水文过程、地下水与溶质迁移、植被动态与水文格局、气候-水-健康、气候和土地利用综合影响下的区域水行为、耦合水与人类经济社会的关键要素、基于公众和利益相关者参与的水资源优化管理等重要科学进展。众多议题凸现了多学科交叉、多区域、跨尺度、系统性以及先进技术设备的广泛应用等几大特点,对于今后应对气候变化和环境变迁所带来的种种挑战具有重要启示。当前和今后的工作中应瞄准与把握以下几个基本原则。(1)进一步加强基础研究、促进学科交融与渗透,以实现方法和理念互补、共同解决复杂生态学问题。(2)重视区域分异、以凸现具体科学问题,实现研究目标、对象、内容和方法的有机统一。(3)重视系统性研究,加强国际合作、共同研发,促进先进技术和研究手段的创新与应用。     

Climate change impact on Balearic shearwater through a trophic cascade

A recent study showed that a critically endangered migratory predator species, the Balearic shearwater Puffinus mauretanicus, rapidly expanded northwards in northeast Atlantic waters after the mid-1990s. As a significant positive correlation was found between the long-term changes in the abundance of this seabird and sea temperature around the British Isles, it was hypothesized that the link between the biogeographic shift and temperature occurred through the food web. Here, we test this conjecture and reveal concomitant changes in a regional index of sea temperature, plankton (total calanoid copepod), fish prey (anchovy and sardine) and the Balearic shearwater for the period 1980-2003. All three trophic levels exhibit a significant shift detected between 1994 and 1996. Our findings therefore support the assertion of both a direct and an indirect effect of climate change on the spatial distribution of post-breeding Balearic shearwater through a trophic cascade.     

Parsimony Analysis of Endemicity (PAE) of Mexican hydrological basins based on helminth parasites of freshwater fishes

Aim The distributional patterns of helminthological fauna of freshwater fishes were analysed to postulate a general hypothesis on the relationships of some Mexican hydrological systems. Location Eight hydrological systems of central and eastern Mexico were studied and compared with records from Nicaragua. Methods A Parsimony Analysis of Endemicity (PAE) was applied to the presence/absence of ninety‐two helminth parasite taxa (Monogeneans, Digeneans, Cestodes, Acanthocephalans and Nematodes) of freshwater fishes, from eight Mexican hydrological systems, using the Hennig86 program. Results The results represent the first attempt for a biogeographical analysis through application of the PAE method to the distributional patterns of helminth parasites of freshwater fishes in Mexico. A single most parsimonious cladogram was obtained, which grouped all the Neotropical systems in accordance with previous proposals based on other plant and animal taxa. Main conclusions The most basal systems were Santiago and Lerma basins, which exhibited Nearctic affinities. The remaining areas of the cladogram showed Neotropical affinities. All the southeastern systems were grouped in a clade with the Nicaragua system, providing support for a ‘Mesoamerican province’ based on helminth parasites of cichlids. The cladogram also suggests that the treatment of the Lerma‐Santiago basin as a single biogeographical unit is inaccurate and that they should be treated as separate systems.     

Comparison Between Tidally Driven Groundwater Flow and Flushing of Animal Burrows in Tropical Mangrove Swamps

Tidal groundwater in a mangrove swamp can return to the mangrove creek by one of two mechanisms: (a) it can either flow through the swamp soil due to the water table difference between the creek and the groundwater in the swamp; or (b) it can flow via tidal flushing of animal burrows. This paper compares the magnitude of these two mechanisms for different regions of a mangrove swamp. Direct groundwater flow rates resulting from water stored in the sediment as a consequence of infiltration, especially during and after tidal inundation, were calculated for every square meter in the surface of a mangrove forest from piezometer data. Flow rates of water due to burrow flushing were determined based on published surveys, by estimating the burrow volume and the percentage of the burrow water that is flushed at each tidal inundation. Although direct groundwater flux was found to decrease further away from the creek compared to close to the creek, it was also found to have a similar range as burrow flushing flow. Specifically, direct groundwater flow ranged from 0.004 to 0.04 m³/m²/day, whilst burrow flushing flux ranged from 0.01 to 0.04 m³/m²/day.Considering the errors involved in the experiments and calculations, these ranges can be considered as being the same and neither of the two processes can be considered as negligible compared to the other. As a consequence, surveys of groundwater processes in mangrove areas, and more generally in swamp and tidal areas where animal burrows are present, will need to consider both mechanisms. Investigations of the influence over flushing mechanisms of different residence times of the water in burrows and in the sediment body would also be recommended in order to establish salt and nutrient budget in mangrove swamps.     

Hydrodynamics and mass transfer coefficient in activated sludge aerated stirred column reactor: experimental analysis and modeling

The aerated stirred reactor (ASR) has been widely used in biochemical and wastewater treatment processes. The information describing how the activated sludge properties and operation conditions affect the hydrodynamics and mass transfer coefficient is missing in the literature. The aim of this study was to investigate the influence of flow regime, superficial gas velocity (U(G)), power consumption unit (P/V(L)), sludge loading, and apparent viscosity (mu(ap)) of activated sludge fluid on the mixing time (t(m)), gas hold-up (epsilon), and volumetric mass transfer coefficient (k(L)a) in an activated sludge aerated stirred column reactor (ASCR). The activated sludge fluid performed a non-Newtonian rheological behavior. The sludge loading significantly affected the fluid hydrodynamics and mass transfer. With an increase in the U(G) and P/V(L), the epsilon and k(L)a increased, and the t(m), decreased. The epsilon, k(L)a, and t(m), were influenced dramatically as the flow regime changed from homogeneous to heterogeneous patterns. The proposed mathematical models predicted the experimental results well under experimental conditions, indicating that the U(G), P/V(L), and mu(ap) had significant impact on the t(m), epsilon, and k(L)a. These models were able to give the t(m), epsilon, and k(L)a values with an error around +/-8%, and always less than +/-10%.     

北京市红门川流域森林植被/土地覆被变化的水文响应

根据北京市红门川流域原有1∶1万土地利用图,结合流域1990年、1995年、2000年和2005年4期遥感影像,在GIS支持下,得到4期土地利用图,采用ArcView分析获得空间数据和属性数据。并利用研究区逐日降水量和径流量数据,从年径流量、汛期(6-9月份)径流量和单次径流量3个层次,分析不同土地利用时期的水文响应。结果表明:不同土地利用变化对流域径流具有显著影响。2001-2005年植被条件较好的土地利用较1990-1995年和1996-2000年产流有所减少,多年平均径流系数下降了70%以上。不同土地利用在相同降水条件下的产流仅在生长季节具有明显差异,也就是说土地利用变化对产流的影响具有季节性,在枯水季节无显著影响。2001-2006年的单次产流均小于1990-1995和1996-2000年的单次产流,仅为前期的1/3,降水利用率提高,发生洪涝灾害的可能性减小。     

Translocation and Spread of Piscivorous Fishes in the Burdekin River, North-eastern Australia

The distribution of the biogeographically distinctive fish fauna of the Burdekin River, north-eastern Australia, is largely determined by the presence of a large waterfall located at the lower quarter of the river’s length. Downstream of the falls, assemblages are characterised by the presence of piscivorous fishes whereas such species are largely absent from upstream reaches. Sleepy cod (Oxyeleotris lineolatus), a large piscivorous gudgeon, was first introduced into the upper reaches of the Burdekin River in 1980 and other releases, both official and unofficial, have occurred subsequently. The population remained small and restricted to the site of introduction for a decade, but expanded in size and distribution after the occurrence of a large flood and entry into a prolonged period of drought. This gudgeon is now present in every tributary system of the Burdekin Basin. Despite the occurrence of substantial temporal variation in fish abundance due to a highly variable flow regime, negative impacts on one species, a small gudgeon (Mogurnda adspersa), are evident. Both deliberate and accidental releases of other species into the upper Burdekin River have also occurred, often to satisfy recreational fishing demand. Such species are typified by large size and piscivorous habit, characteristics alien and inimical to the native fish fauna. It is hypothesised that these piscivorous species may have even greater impact than O. lineolatus in some tributary systems of the upper Burdekin River.     

Alternation of Factors Affecting Bacterioplankton Abundance in the Danube River Floodplain (Kopački Rit, Croatia)

The purpose of this investigation was to determine the influence of different phases of the hydrological cycle on the abundance of colony-forming units (CFU) of bacteria in the Kopački Rit floodplain and to assess temporal and spatial variations in the proportion of eutrophic and oligotrophic bacteria (r- and K-strategists) as a biological indicator of dissolved organic carbon (DOC) availability. Determination of bacterial abundance was performed with abiotic variables (water temperature, depth, Secchi disc transparency, dissolved oxygen, pH, electrical conductivity, ammonia, nitrates+nitrites, total nitrogen and total phosphorus) and one biotic (chl-a) variable, and dimensionality reduced with principal component analysis (PCA). The component scores were used as independent variables in a multiple regression and the relationship between scores (indirect variables) and bacterial abundance was examined. An elevated bacterial abundance was observed during the limnophase (floodplain isolated from the river) and potamophase (flood). During the limnophase also the highest chl-a concentrations were found and in Sakadaš Lake during September 2003 significantly higher numbers of eutrophic than oligotrophic bacteria emerged (p = 0.026). During potamophase the opposite state was established. Elevated bacterial abundance occurred in parallel with minimal chl-a concentrations and during July 2004 in the Čonakut Channel a significantly higher number of oligotrophic than eutrophic bacteria emerged (p < 0.001). Differentiation in the number of eutrophic and oligotrophic bacteria suggests the existence of a higher concentration of labile DOC during September 2003 than during July 2004. Multiple regression analysis explains 13.6% of the variation in abundance of eutrophic bacteria. The regression model for oligotrophic bacteria is not significant. The results suggest two different mechanisms control bacterioplankton numbers to some extent in the Kopački Rit floodplain. In addition, two sources of DOC differentiating the quality of organic matter predominate under totally different hydrological regimes. Under these conditions, eutrophic bacteria may be partially bottom-up controlled, whereas it is not clear how the abundance of oligotrophs is controlled.