Extent, properties, and landscape setting of geographically isolated wetlands in urban southern New England watersheds

We assessed the extent and characteristics of geographically isolated wetlands (i.e., wetlands completely surrounded by upland) in a series of watersheds in the urban northeast US. We applied a previously developed index of urbanization to a sample of 10 watersheds selected at random from a set of 30 watersheds whose boundaries lay within the borders of Rhode Island, USA. The index of urbanization in our sample watersheds ranged over more than an order of magnitude and increased with increasing amount of urban land use in the watersheds (r ² = 0.51, F = 8.22, P = 0.02). The density of isolated wetlands in the watersheds averaged 1.93 ± 0.21 wetlands km⁻² and comprised 38.2 ± 1.77% of all wetlands. Isolated wetlands were smaller than those connected to other waters (non-isolated), and accounted for 6.01–16.5% of the total wetland area in the watersheds. The area of isolated wetlands as a percent of all wetland area significantly increased with increasing watershed urbanization (r ² = 0.62, F = 12.9, P = 0.007). Isolated wetlands were predominantly deciduous forested wetlands, and urban land cover in the 50 m buffer surrounding isolated wetlands was significantly higher than in the 50 m surrounding non-isolated wetlands. The proportion of urban land cover was greater in a 150 than a 50 m buffer surrounding the wetlands. Our results suggest that an increase in the index of urbanization of 50 will result in 7% of the watershed’s wetlands being lost from federal protection. These findings indicate that the process of urbanization, along with accompanying habitat fragmentation, may result in an increase in the vulnerability of wetlands to loss and degradation and therefore has implications for the management and conservation of geographically isolated wetlands.     

Changes in the impact of anthropogenic effects on river water quality during the last 50 years in Japan

Japan’s rapid urbanisation over the last 50 years has resulted in land use and lifestyle changes, all of which are likely to have changed the quality of river water, and consequently the wetland and coastal environment. We examined changes in river water quality over this period by means of a review of previous studies. Around the 1950s, the weighted average of chloride using discharge of Japan’s 30 major rivers was 6.1 mg/l while in the 2000s it was 11.3 mg/l. Because there were no significant changes in the natural conditions, we have attributed the increase to the urbanisation of the last 50 years. Nitrate levels in the mountain streams of southern Japan have increased, particularly in the western part of the Kanto region. As this area is located on the leeward side of the Tokyo Metropolitan Area, depositions from aerosols are thought to be the main cause of the increased nitrate concentration. These two findings suggest that certain uses of land may affect river water quality differently over time, and that changes in land use may also affect river water quality in remote areas.     

河流生态学研究中的几个热点问题

近年来河流生态系统成为湖沼学研究的重点,很多新理论、新方法被应用到研究中．文章综述了国内外的相关研究,并着重从河流连续、河流的生态需水量、河流生态系统的服务价值与健康评价、河流的生态系统管理以及流域生态学等几个热点方向作了详细论述．作者认为,今后河流生态学的研究应在流域尺度上展开,结合河流健康及生态系统服务评价进行河流生态系统可持续管理研究将是近期河流生态学的重点问题之一．鉴于我国的实际情况,作者建议应该尽快开展相关领域的研究．     

Using simplified watershed hydrology to define spatially explicit ‘zones of influence’

Riparian areas represent dynamic spatial gradients characterized by a varying degree of terrestrial–aquatic interaction. Many studies have considered riparian zones to be discrete watershed sub-portions (e.g., 100-m riparian buffers), whereas I introduce ‘zones of influence’ that are subsets of the riparian zone. The purpose of this study is to introduce the concept of hydrologically defined influence zones using a simple hydrologic model to delimit land-cover. I describe a method for identifying zones of influence using watershed hydrologic patterns to delimit zones along a near-stream continuum between a downstream point (e.g., sample reach) and the watershed boundary. Using hydrologic modeling equations and GIS, travel time was calculated for every 30 × 30-m cell in 10 watersheds providing spatially explicit estimates of watershed hydrology and enabling us to calculate the travel time required for rainfall in any watershed cell to reach the watershed terminus. Shorter-duration travel times (i.e., 30–60 min) described smaller areas than longer-duration travel times (i.e., 210–300 min). This method is an alternative method to delimit near stream areas when quantifying watershed influence. Handling editor: K. Martens     

Potential of constructed wetland in reducing total nitrogen loading into the Truckee River

A pilot-scale wetland was constructed along Steamboat Creek (SBC) at the Truckee Meadows Water Reclamation Facility (TMWRF), Sparks, Nevada. SBC is a major non-point source of total nitrogen (TN) for the Truckee River. In this study, four (16.2 m²) parallel wetland trains with two different experimental designs were utilized to assess seasonal variations in TN. The experimental designs included: (1) SBC water and SBC sediments (Configuration-1) and (2) TMWRF effluent and SBC sediments (Configuration-2). Over a period of 2 years, the TN in both designs was routinely monitored. TN was reduced by an average of 47% (0.60 mg/l) in Configuration-1 and an average of 24% (0.39 mg/l) in Configuration-2. Nitrogen speciation was an important factor influencing the effectiveness of nitrogen removal within the wetland system. Ammonia-N (NH₃-N) and nitrate plus nitrite nitrogen ((NO₃ + NO₂)-N) were removed more effectively than organic nitrogen. The results obtained from this pilot-scale wetland system suggest that a proposed large-scale constructed wetlands system along SBC would be expected to overall reduce TN loading into the Truckee River from 19 to 30% on an annual basis. This research was jointly funded by the Environmental Protection Agency (EPA) Region 9 and the Nevada Division of Environmental Protection.     

Strategies for Protecting and Restoring Rhode Island's Watersheds on Multiple Scales

The Clean Water Act has traditionally preserved the quality and quantity of a region's water by focusing resources on areas with known or anticipated problems. USEPA Region 1 is taking the supplemental, longer-range approach of protecting areas of New England where natural resources are still healthy. As part of Region 1 's “New England Resource Protection” approach, stakeholders participate in an open process that identifies healthy ecosystems and characterizes how well they support aquatic life and human health. Since the concerns of stakeholders are usually local, the process also displays areas of nonattainment within individual watersheds and determines their likely causes. One of the most powerful ways to display these types of information on multiple scales is to use a geographic information system (GIS). The case of phosphorus in southern Rhode Island's Tucker Pond illustrates how a GIS can help integrate concerns from the public, data from Clean Water Act monitoring, and information from the New England Resource Protection Project to identify types of environmental assessment questions on scales ranging from states to subwatersheds. By involving the public at all stages of the process and better informing them about their watersheds, this new approach makes them better stewards of their environment.     

Morphological characterisation of yeast colony growth on solid media using image processing

To rapidly determine the effect of environmental factors on yeast growth, a cell counting and colony sizing image analysis method was developed to characterise colony growth on solid media. A digitised microscopic image of the yeast was analysed using the Watershed algorithm for cell number determination and a morphological edge detection for colony size determination. The influence of temperature and physiological stress on yeast growth was then investigated over 12.5 h and data extracted by the image analysis method. © Rapid Science Ltd. 1998