Ecological perspective on water quality goals

The central assumption of nonpoint source pollution control efforts in agricultural watersheds is that traditional erosion control programs are sufficient to insure high quality water resources. We outline the inadequacies of that assumption, especially as they relate to the goal of attaining ecological integrity. The declining biotic integrity of our water resources over the past two decades is not exclusively due to water quality (physical/chemical) degradation. Improvement in many aspects of the quality of our water resources must be approached with a much broader perspective than improvement of physical/chemical conditions. Other deficiencies in nonpoint pollution control programs are discussed and a new approach to the problem is outlined.     

永定河底栖动物生物完整性指数构建与健康评价

构建大型底栖动物生物完整性指数是河流健康评价与河流修复的重要步骤.根据2017年4月永定河流域23个采样点的大型底栖动物生物监测数据,基于监测点水质状况与栖息地质量综合评估指数得分,选择潮白河水系大型底栖动物类群相似且人为干扰较小的5个监测点作为参照区域,构建永定河B-IBI（大型底栖动物生物完整性指数）.通过对大型底栖动物33个生物参数的分布范围检验、判别能力分析和Spearman相关性检验,最终确定永定河B-IBI由总分类单元数、蜉蝣目（E）-襀翅目（P）-毛翅目（T）个体相对丰度、优势分类单元个体相对丰度、摇蚊科个体相对丰度、敏感类群分类单元数、科级耐污指数（family biotic index,FBI值）等6个核心参数构成.采用生物完整性研究中常用的比值法和三分法构建的B-IBI评价得分体系.结果表明,两种方法计算出的B-IBI均具有较高的判别能力,均能较好地判别参照水体和受损水体的健康状况,二者具有较高的相关性和一致性（R>0.90）.永定河河流健康评价结果表明,洋河、桑干河和永定河干流监测点B-IBI平均得分分别为1.97、1.86和1.78,妫水河B-IBI平均值为2.48,23个采样点中有16个处于较差状态,7个处于一般状态.相关性分析表明,B-IBI指数与栖息地质量综合评估指数得分、ρ（DO）呈显著正相关,与ρ（NH₄+）、浊度、电导率呈显著负相关,表明B-IBI指数对于栖息地人为干扰和水质污染均具有较强的指示作用.研究显示,永定河大型底栖动物生物完整性基本丧失,全流域底栖动物群落呈现全面退化趋势,识别影响大型底栖动物群落的关键要素、恢复永定河河流生态系统结构和功能研究亟待开展.      

Predation and aggressiveness in host plant protection: a generalization using ants from the genus Azteca

In studying the ant genus Azteca, a Neotropical group of arboreal species, we aimed to determine the extent to which the ants use predation and/or aggressiveness to protect their host plants from defoliating insects. We compared a territorially dominant, carton-nester, Azteca chartifex, and three plant-ant species. Azteca alfari and Azteca ovaticeps are associated with the myrmecophyte Cecropia (Cecropiaceae) and their colonies shelter in its hollow branches; whereas Azteca bequaerti is associated with Tococa guianensis (Melastomataceae) and its colonies shelter in leaf pouches situated at the base of the laminas. Whereas A. bequaerti workers react to the vibrations transmitted by the lamina when an alien insect lands on a leaf making it unnecessary for them to patrol their plant, the workers of the three other species rather discover prey by contact. The workers of all four species use a predatory behaviour involving spread-eagling alien insects after recruiting nestmates at short range, and, in some cases, at long range. Because A. alfari and A. ovaticeps discard part of the insects they kill, we deduced that the workers' predatory behaviour and territorial aggressiveness combine in the biotic defence of their host tree.     

HCH residues in point-source contaminated samples of the Teltow Canal in Berlin,Germany

Contaminated groundwater and a riverine sediment core heavily affected by the same industrial point source were analysed for hexachlorocyclohexanes (HCH) and its degradation products. A detailed quantification by GC/MS revealed contamination levels up to 730 μg/L and 396 ng/g in sum for the water and sediment samples, respectively. The isomer pattern differed significantly in both compartments. The ground water samples were depleted in γ-HCH, whereas a significant loss of α-HCH was evident in the sediments as compared to the technical composition. The data obtained revealed interesting insights into the transformation behaviour and fate of HCH mixtures in anaerobic environmental compartments. In the affected groundwater system an ongoing microbial degradation was pointed out by the identification of indicative anaerobic metabolites. On the contrary in the sedimentary system a high environmental stability or rather a hindered degradation was observed as indicated by unaltered concentration levels as compared to production rates as well as by the absence of metabolites. Interestingly, the environmental fate of HCH in subaquatic sediments as well as in anaerobic ground water differs highly in contrast to the behaviour in anaerobic soil or surface water systems. Further on, it has to be stated, that the knowledge about the long-term behaviour of HCH residues in sedimentary material under anaerobic conditions is rather limited so far.     

Community Structure and Quality After 10 Years in Two Central Ohio Mitigation Bank Wetlands

We evaluate two 10-year-old mitigation bank wetlands in central Ohio, one created and one with restored and enhanced components, by analysis of vegetation characteristics and by comparison of the year-10 vegetation and macroinvertebrate communities with reference wetlands. To assess different measures of wetland development, we compare the prevalence of native hydrophytes with an index of floristic quality and we evaluate the predictability of these parameters in year 10, given 5 years of data. Results show that the mitigation wetlands in this study meet vegetation performance criteria of native hydrophyte establishment by year 5 and maintain these characteristics through year 10. Species richness and floristic quality, as well as vegetative similarity with reference wetlands, differ among mitigation wetlands in year 1 and also in their rate of change during the first 10 years. The prevalence of native hydrophytes is reasonably predictable by year 10, but 5 years of monitoring is not sufficient to predict future trends of floristic quality in either the created or restored wetland. By year 10, macroinvertebrate taxa richness does not statistically differ among these wetlands, but mitigation wetlands differ from reference sites by tolerance index and by trophic guild dominance. The created wetland herbivore biomass is significantly smaller than its reference, whereas detritivore biomass is significantly greater in the created wetland and smaller in the restored wetland as compared with respective reference wetlands. These analyses illustrate differences in measures of wetland performance and contrast the monitoring duration necessary for legal compliance with the duration required for development of more complex indicators of ecosystem integrity.     

The missing pieces for better future predictions in subarctic ecosystems: A Torneträsk case study

Arctic and subarctic ecosystems are experiencing substantial changes in hydrology, vegetation, permafrost conditions, and carbon cycling, in response to climatic change and other anthropogenic drivers, and these changes are likely to continue over this century. The total magnitude of these changes results from multiple interactions among these drivers. Field measurements can address the overall responses to different changing drivers, but are less capable of quantifying the interactions among them. Currently, a comprehensive assessment of the drivers of ecosystem changes, and the magnitude of their direct and indirect impacts on subarctic ecosystems, is missing. The Torneträsk area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years, and is one of the most studied sites in the Arctic. In this study, we summarize and rank the drivers of ecosystem change in the Torneträsk area, and propose research priorities identified, by expert assessment, to improve predictions of ecosystem changes. The research priorities identified include understanding impacts on ecosystems brought on by altered frequency and intensity of winter warming events, evapotranspiration rates, rainfall, duration of snow cover and lake-ice, changed soil moisture, and droughts. This case study can help us understand the ongoing ecosystem changes occurring in the Torneträsk area, and contribute to improve predictions of future ecosystem changes at a larger scale. This understanding will provide the basis for the future mitigation and adaptation plans needed in a changing climate.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01381-1) contains supplementary material, which is available to authorized users.     

不同土地利用对溪流大型底栖无脊椎动物群落的影响

2010年4月调查了钱塘江中游区域29个样点的水环境特征和底栖动物。聚类排序将样点分为参照、农业和城镇3组,相似性分析表明不同组间底栖动物群落有显著差异(r=0.863,P=0.001)。环境因子的主成分分析表明,研究区域主要的环境胁迫是农业和城镇用地及其引起的水质变化,并能较好解释组间物种差异的关键环境胁迫因子为农业用地比例、城镇用地比例、溶解氧、总氮和平均底质得分(Rho=0.568,P=0.001)。底栖动物参数(总分类单元数、Shannon-Weaver多样性指数、BI指数和丰富度指数)和k-优势度曲线显示农业和城镇组的生物完整性遭到很大程度的破坏,且农业组较城镇组严重。     

The origin of speciation: trace metal kinetics over natural water/sediment interfaces and the consequences for bioaccumulation

The speciation of heavy metals was measured over a variety of natural and undisturbed water/sediment interfaces. Simultaneously, two benthic species (oligochaete Limnodrilus spp. and the midge Chironomus riparius) were exposed to these sediments. Under occurring redox conditions, free ion activities of trace metals Cd, Cu, Ni, Pb, and Zn were measured with a chelating exchange technique, while geochemical conditions (i.e., redox) remained in tact. Free ion activities were compared with total dissolved concentrations in pore waters and surface waters in order to relate speciation to bioaccumulation. Limnodrilus spp. and C. riparius have accumulation patterns that could be linked to time-dependent exposure concentrations, expressed as chemical speciation, in the surface water and the sediment's pore water. Concentrations of free metal ions in the overlying surface water, rather than in sediment pore water, proved to be the best predictor for uptake. For the first time, measurements are obtained from sediments without disturbing physical-chemical conditions and thus bioavailability, a major restriction of other studies so far.     

Identifying Biotic Integrity and Water Chemistry Relations in Nonwadeable Rivers of Wisconsin: Toward the Development of Nutrient Criteria

We sampled 41 sites on 34 nonwadeable rivers that represent the types of rivers in Wisconsin, and the kinds and intensities of nutrient and other anthropogenic stressors upon each river type. Sites covered much of United States Environmental Protection Agency national nutrient ecoregions VII—Mostly Glaciated Dairy Region, and VIII—Nutrient Poor, Largely Glaciated upper Midwest. Fish, macroinvertebrates, and three categories of environmental variables including nutrients, other water chemistry, and watershed features were collected using standard protocols. We summarized fish assemblages by index of biotic integrity (IBI) and its 10 component measures, and macroinvertebrates by 2 organic pollution tolerance and 12 proportional richness measures. All biotic and environmental variables represented a wide range of conditions, with biotic measures ranging from poor to excellent status, despite nutrient concentrations being consistently higher than reference concentrations reported for the regions. Regression tree analyses of nutrients on a suite of biotic measures identified breakpoints in total phosphorus (~0.06 mg/l) and total nitrogen (~0.64 mg/l) concentrations at which biotic assemblages were consistently impaired. Redundancy analyses (RDA) were used to identify the most important variables within each of the three environmental variable categories, which were then used to determine the relative influence of each variable category on the biota. Nutrient measures, suspended chlorophyll a, water clarity, and watershed land cover type (forest or row-crop agriculture) were the most important variables and they explained significant amounts of variation within the macroinvertebrate (R ² = 60.6%) and fish (R ² = 43.6%) assemblages. The environmental variables selected in the macroinvertebrate model were correlated to such an extent that partial RDA analyses could not attribute variation explained to individual environmental categories, assigning 89% of the explained variation to interactions among the categories. In contrast, partial RDA attributed much of the explained variation to the nutrient (25%) and other water chemistry (38%) categories for the fish model. Our analyses suggest that it would be beneficial to develop criteria based upon a suite of biotic and nutrient variables simultaneously to deem waters as not meeting their designated uses.     

IMPROVED ESTIMATION OF ECOLOGICAL EFFECTS USING AN EMPIRICAL BAYES METHOD1

ABSTRACT: The US Environmental Protection Agency is currently developing guidance for assessing environmental impact using biocriteria within a regulatory framework. Of particular interest are statistical methods of design and analysis to test for impairment of biological assemblages in stream ecosystems associated with water pollution. Current recommendations emphasize frequentist statistical methods with the problem expressed as one of classical hypothesis testing. An empirical Bayes approach is proposed here as an alternative and applied for multi-site inference. The advantages of an empirical Bayes approach, in particular the substantive contribution of collateral information from nearby sites, are discussed in contrast to traditional methods that employ site-specific information only. The approach is illustrated in an application concerning trends in the Index of Biotic Integrity (IHI) for the Scioto River in Ohio.