POWRE: Hydrogeology and Geochemistry of Streambeds in Karst Aquifers

基于对河流下面的河床物质的研究，已经确定了不同的水文地质、地球化学和生态活动区(Rouch，1988)。动物在间隙空间的生态聚集是沉积物的水力传导性和间隙水的溶解氧浓度的函数。在洞穴溪流中，河床沉积物中存在间隙孔隙，但很少有研究人员调查这些间隙空间中可能存在水生轮虫物种的可能性。关于水生轮虫物种的栖息地偏好的信息缺乏。通常认为这些物种喜欢开阔水域条件、池塘和冲浪(Barr，1968；Brown和Willis，1984)。进行洞穴内有机体计数的科学家假设，在视觉流检查中发现的个体数量与存在的有机体数量相等。Schubert(1993)已经表明，南部洞穴鱼更喜欢生活在河床(砾石大小的底物，鱼可以进入的间隙空间)的间隙孔隙空间内，而不是本身的水柱中。如果首选栖息地是在河床的间隙空间，那么目测期间计算的生物体数量可能会明显低估存在的生物体的真实数量。栖息在间隙中似乎提供了躲避捕食和获取食物的场所，因为许多水生轮虫物种都在觅食。本次勘查项目要求：1.不同生境的水文地质背景是什么？水文地质背景将通过确定河床物质的水力传导性、孔隙度和粒度分布以及沿河流的水力坡度来表征。间隙孔隙中水的地球化学特征是什么？将通过测定溶解氧和碳酸氢盐的浓度以及测定间隙水的温度、pH和Eh作为深度的函数来表征地球化学环境。流水和间隙水之间的交换率是多少？流动水和间隙水之间的交换速率将通过分析同一地点流动水和间隙水的温度波动来确定。了解水生轮虫物种的栖息地，以及这些地点的地球化学和水文地质状况，将有助于需要清点种群、确定栖息地要求和保护生物群的科学家。对次航道的地球化学和水文过程进行量化和建模的能力对于增进我们对水生轮虫物种栖息地要求的了解至关重要。这项探索性提案为描述三条喀斯特溪流的化学和水文生境的研究募集资金，这三条溪流是四种水生轮虫物种的栖息地。这项研究代表了首席调查员的一条新的调查路线，也是确定水生轮虫物种的地球化学和水动力环境的第一步。这一探索性研究项目是首次努力将地球化学和水动力条件与水生轮虫物种的栖息地要求联系起来。

9870423WicksBased on research in streambed materials underlying rivers, distinct zones of hydrogeologic, geochemical, and ecological activities have been defined (Rouch, 1988). The ecotonal assemblage of animals in the interstitial space is a function of the hydraulic conductivity of the sediment and the dissolved oxygen concentration of the interstitial water. In cave streams, interstitial pores exist within the streambed deposits, yet few researchers have investigated the possibility that aquatic troglodytic species might reside in these interstitial spaces.Information is lacking regarding the habitat preferences of aquatic troglodytic species. It is generally assumed such species prefer open-water conditions, pools and riffles (Barr, 1968; Brown and Willis, 1984). Scientists conducting in-cave organism counts have assumed that the number of individuals found during visual stream inspections is equal to the number of organisms present. Schubert (1993) have shown that southern cavefish prefer to reside within the interstitial pore spaces of streambeds (gravel-sized substrate with interstitial spaces that the fish can enter) and not in the water column proper. If the preferred habitat is in interstitial spaces of the streambed, then the number of organisms that are counted during visual inspections may markedly underestimate the true number of organisms present. Residing in the interstitial spaces would appear to provide shelter from predation, and access to food, as many of the aquatic troglodytic species forage. This exploratory project asks:1. What is the hydrogeologic setting of the various habitats? The hydrogeologic setting will be characterized by determining the hydraulic conductivity, porosity, and grain size distribution of the streambed material and the hydraulic gradient along the stream reach.2. What is the geochemistry of the water in interstitial pore space? The geochemical setting will be characterized by determining the concentrations of dissolved oxygen and bicarbonate and by determining the temperature, pH, and Eh of the interstitial water as a function of depth.3. What is the exchange rate between the flowing water and the interstitial water? The exchange rate between the flowing water and the interstitial water will be determined by analyzing the fluctuations in the temperature of the flowing water and the interstitial water at one site. Understanding where the aquatic troglodytic species reside, and the geochemical and hydrogeological regimes of those locations, will aid scientists who need to enumerate populations, determine habitat requirements, and conserve the biota. The ability to quantify and model sub-channel geochemical and hydrological processes is critical to improving our understanding of the habitat requirements of aquatic troglodytic species. This exploratory proposal solicits funding for research that will describe the geochemical and hydrological habitat of three karst streams, which are the habitats for four aquatic troglodytic species. This research represents a new line of inquiry for the Principal Investigator and a first step in determining the geochemical and hydrodynamic environment of aquatic troglodytic species. This exploratory research project is the first effort to link the geochemical and hydrodynamic conditions to the habitat requirements of aquatic troglodytic species.