Round goby (Neogobius melanostomus) and native fishes as potential nest predators of centrarchid species in the upper St. Lawrence River

Widespread invasion of Round Goby (Neogobius melanostomus) throughout the Great Lakes has raised concerns regarding increased egg predation on fish species. To better understand nest predation, we examined nesting habitat selected by three upper St. Lawrence River Centrarchid species and the predator assemblage at nests during the 2011 and 2012 egg incubation and larval periods. Following removal of guarding males by angling, 5-min observations were used to identify and enumerate predators at rock bass (Ambloplites rupestris; n = 81), pumpkinseed (Lepomis gibbosus; n = 80), and smallmouth bass (Micropterus dolomieu; n = 40) nests. Differences in nesting habitat among centrarchids corresponded with differences in nest predator assemblages along a gradient defined primarily by depth and substrate. Pumpkinseed nests in shallow depths with soft substrate were visited principally by minnow spp., but few round goby. Smallmouth bass nests at greater depth with hard substrates were frequented nearly exclusively by round goby, while rock bass nests at intermediate depth with a mix of hard and soft substrates were visited by round goby and yellow perch (Perca flavescens). Rock bass nests had a higher predator burden than pumpkinseed nests in 2011, but no differences were observed among centrarchid species in 2012. Round goby were a major component of the predators at rock bass and smallmouth bass nests. However, predation burden imposed by yellow perch was higher than round goby at rock bass nests. We conclude nesting habitat selection influences native and non-native egg predator assemblages, but whether round goby predation is additive or compensatory remains unclear.     

Farmers' responses to climate change impact on water availability: insights from the Indrawati Basin in Nepal

There is a need to assess the potential impacts of climate change on agriculture in order to plan appropriate adaptation measures. Farmers are already adapting to these changes to a certain degree. This article presents a case study of rainfed and farmer-managed irrigated agriculture in the Indrawati Basin, Nepal. It describes farmers' perceptions of climate change, an analysis of historical water availability, and future projections of temperature and precipitation. Adaptation strategies already being used by farmers are identified and new ones are recommended based on primary information collected from farmers and an in-depth analysis of the climate data.     

精河流域径流变化特征及其对降水变化的响应

利用精河水文站1964年-2012年径流、降雨数据,采用M-K检验、累积曲线模型及交叉小波分析等方法,对艾比湖流域精河的径流、降水的变化特征及多时间尺度相关进行分析,并定量分析了降水变化对径流变化的贡献率。精河年径流量总体上径流呈增长趋势,但趋势不明显;降雨总体上呈增加趋势,且增加趋势明显。精河年径流量与降水量在多时间尺度上存在显著相关关系,且以正相关关系为主,显著相关区域集中在1986年-1991年在2~4a的周期带、1985年-1990年的7a周期带、2002年-2011年的4~5a周期带。分析认为,近50年来该流域降水变化对径流增加的贡献率平均为68.4%。     

Water productivity responses and adaptation to climate change in the lower Mekong basin

A crop growth simulation model was used to study the impact of climate change for the period 2010–2050 on water productivity of rainfed rice. In general, the results suggest that water productivity of rainfed rice may increase significantly in the upper basin in Laos and Thailand and may decrease in the lower basin in Cambodia and Vietnam. Significant net increases in water productivity can be achieved by applying simple adaptation options such as shifting the planting dates, applying supplementary irrigation, and increasing fertilizer inputs.     

气候变化与人类活动影响下大清河流域上游河流径流响应研究

河北雄安新区的设立,引起了各界对雄安新区所在的大清河流域的广泛关注,特别是其水资源的变化特征与影响因素是了解雄安新区水资源情势的重要参考。研究解析了人类活动和气候变化对大清河流域上游径流过程的相对影响,采用SWAT模型模拟了大清河流域上游径流过程,并结合弹性系数法验证比对,分离了人类活动与气候变化对大清河流域上游径流过程的贡献率。结果表明,1981-2015年,大清河流域上游山区倒马关站及紫荆关站径流量均呈减少趋势,倒马关站及紫荆关站年径流量递减速率分别为0.10m3/s及0.07m3/s。人类活动为影响径流的主导因子,其贡献率为53.4%～60.8%;气候变化较人类活动影响径流稍小,其贡献率为39.2%～46.6%。研究结果可为支撑未来雄安新区建设区域水资源规划和管理提供依据。     

海流兔河基流特征及其对气候变化和人类活动的响应分析

基流是海流兔河流域地表径流的主要组成部分,是流域河流枯水期流量的重要来源,更是维护流域生态环境健康的基本保证。本文采用不同方法对海流兔河流域1957-2011年基流数据进行分析。基于流域水文及气象数据,应用双累积曲线法和SWAT模型分析流域基流对气候变化和人类活动的响应关系。结果表明:流域基流年内分配不均匀,夏季基流分配量普遍较少;基流年际变化整体呈现下降趋势,并分别于1968、1989和2001年发生突变。流域基流对人类活动的响应强于气候变化,人类活动是流域基流变化的主要因素,降雨是次要因素,气温是第3因素。     

Contemporary abundance patterns of Cyclotella sensu lato diatom taxa in Lake Superior: Assessing responses to physical and chemical gradients and potential links to climate change

Many studies attribute shifts in relative abundances of Cyclotella sensu lato diatom taxa in freshwater lakes over the past 150?years to climate change. Although abundances of several of these taxa have also changed in Lake Superior over the last century, the specific drivers are currently unclear. This study used multiple linear regression to analyze long-term planktonic monitoring data to identify drivers of changing cell densities of six Cyclotella sensu lato species, four shown to be responsive to climate-driven change in smaller lakes and two species with similar morphology to two previously assessed taxa: Discostella stelligera and the morphologically similar D. pseudostelligera, Lindavia comensis and the morphologically similar L. delicatula, Lindavia ocellata, and Lindavia bodanica. Assessed variables associated with climate-driven physical change included surface water temperature and light availability, with turbidity and thermocline depth as indicators of the light environment. One to three variables explained 8–61% variation for each of 5 taxa from 2001 to 2011, significant predictive variables were not identified for D. stelligera. Multiple linear regression identified nutrients, including nitrate, phosphorus, and silica, as essential in explaining distributions of all the other assessed taxa. A physical variable associated with climate explained changes of one taxon: L. ocellata, which increased with lower water temperatures. Climate-driven species responses were not as apparent as in other systems; specifically, changes in the light environment of this clear lake did not explain abundance changes in any of the taxa. Multiple and complex environmental variables drive Cyclotella sensu lato abundance patterns in Lake Superior, possibly suggesting ecotype formation.