Characterizing Small Subbasins: A Case Study from Coastal Oregon

A fine-grained statisticaly robust probability sample of stream segments is used to compare two small (20,000 hectare) subbasins of the Tillamook watershed, north coastal Oregon. The two subbasins are matched with respect to several variables [size coastal climates], but vary in terms of geology and consequently land use. A total of 67 wadeable + non-wadeable sizes were identified for sampling in the two subbasins (combined) over two field seasons from a sampling universe consisting of the River Reach File 3 (blue lines on 1:100,000 maps). Target variables include an extensive array of physical habitat endpoints, selected water chemistry endpoints, species composition, and relative abundance of both benthic macroinvertebrates and fish. Field protocols generally followed those of the U.S. EPA's Environmental Monitoring and Assessment Program (EMAP).Eleven fish species were encountered, a typically low number for coastal Oregon streams. Exploratory analysis using nonmetric multidimensional scaling revealed that 92.4% of the variation in the fish assemblages could be explained with two ordination axes. Environmental factors related to stream size and substate were the most correlated to these axes. Further, stream segments for the two subbasins tended to map in different areas of species space. Therefore, we also give unweighted probability distributions for several of the factors that heavily on these two axes by subbasins, as well as probability distributions for chemical endpoints. Results from the subset of sites sampled during the first year (21 wadeable sites) reveal: 1) differences between samples from the two subbasins relates to dream size and substrate composition that are consistent with known differences in geology and land use, 2) unexpectedly minor differences between samples from the two subbasins for stream temperature, canopy cover, and dissolved oxygen, 3) differences between samples from the two subbasins for total P, and total N, possibly related to land use, and 4) unexpected differences in samples from the two subbasins for conductivity, probably related to geological factors. Sample size for each subbasin is low and therefore our samples cannot be taken to necessarily characterize either subbasin. However, our findings are consistent with a comprehensive assessment that had been previously produced for one of the two subbasins.All field work was completed in 8 weeks 3-person field crew. We conclude that rapid assessment protocols, based on probability samples at this level of resolution, can be a cost-effective approach to watershed analysis. This approach should be seen as a complement to, rather than a replacement for, systematic surveys that produced finer scale, reach specific information on factors such as channel complexity and cover relevant to in-stream restoration planning.     

Using Multiple Taxonomic Groups to Index the Ecological Condition of Lakes

Biological indicators of communitiestypically reflect a common environmental signalreflecting the general condition of the ecosystem, as well asindividual signals by indicators differentiallysensitive to particular environmental conditions. Wedescribe here a method of integrating and interpretingsuch indicators from 19 New England lakes for fivetaxonomic groups (diatoms, benthos, zooplankton, fish,and birds). Our approach provides a systematicstandardized way to integrate multiple metrics fromdifferent taxonomic groups by addressing four elementscrucial to analyzing data from multiple indicators: covariate control, re-scaling of data, standardizing the sign of responses, and dimensional reduction. We evaluated the biologicalmetrics against individual environmental stressors andagainst multivariate physicochemical metricscharacterizing general anthropogenic stress among thelakes. The method detected a response to variationin the gross environmental condition of the lakes thatwas correlated across taxa and metrics. In addition,a differential response to near shore conditions wasdemonstrated for fish. The success of the approach inthis study lends support to its general application toecological monitoring involving complex data sets.     

海河流域河流生态系统健康评价

随着经济发展,人类活动对河流生态系统的胁迫日益强烈,生态系统健康状况受到严重威胁.本研究以海河流域2010年73个采样点的水质、营养盐和底栖动物指标为例,采用指标体系法,从化学完整性和生物完整性两方面评价了流域内河流生态系统健康.结果表明,海河流域河流生态系统健康状况整体较差,有72.6%的样点处于"极差"健康状态,同时表现出明显的地区集聚效应;河流水质与人类活动强度密切相关;海河流域水体富营养化趋势明显;流域内底栖动物多样性低,清洁物种较少.氨氮、总氮、总磷等营养盐指标是影响河流生态系统健康的关键因子,应从控制上述指标入手,遏制海河流域河流生态系统健康恶化.对于河流生态系统健康评价,多因子的综合评价法优于单因子评价法.     

青海湖硅藻组合及其季节变化——来自沉积物捕获器的初步研究

通过对青海湖捕获器中2010年7月至2011年10月份沉积物样品与青海湖湖岸7个地点表层样品的分析,获得青海湖现代硅藻组合及季节变化特征。捕获器沉积物样品中共鉴定出硅藻2纲32属56种,主要为咸水种与微咸水种。其中,优势种为Berkeleya rutilans、Cocconeis placentula var. euglypta、Cyclotella choctawhatcheeana和Nitzschia inconspicua,此四种占总数的82%以上。硅藻组合变化具显著的季节性差异,冬季主要以浮游种Cyclotella choctawhatcheeana占优势;非冰封期则以附生种Berkeleya rutilans、Nitzschia inconspicua与Cocconeis placentula var. euglypta占优势。青海湖湖水具有高碱度,硅藻的保存率不高,其保存率具有夏季高、冬季低的季节性变化,但这不是造成硅藻组合显著季节性变化的主要原因,其季节性变化主要取决于水生植物的生长与湖区冰情。     

底栖藻对水丝蚓生物扰动效应的抑制研究

霍甫水丝蚓(Limnodrilus hoffmeisteri)是富营养化湖泊中的底栖动物优势种,通过生物扰动可以提高水体营养盐浓度,并促进浮游植物生长.富营养浅水湖泊经生态修复后,水体透明度会得到改善,有利于底栖藻快速生长,从而降低水体营养盐水平.那么,底栖藻能否抑制水丝蚓对富营养水体水质的不良影响?为此,本文开展了双因素(底栖藻和水丝蚓)的室外受控实验,结果表明:在无底栖藻处理中,水丝蚓显著提高了水体总氮(TN)、总磷(TP)、总溶解磷(TDP)和叶绿素a(Chl-a)浓度,同时显著降低水体溶解氧(DO)浓度;而在有底栖藻处理中,水丝蚓对水体TP、DO及Chl-a浓度的影响不显著.研究结果表明,水丝蚓的生物扰动提高了水体营养盐和浮游植物浓度,促进水体富营养化.但底栖藻群落的发展能在一定程度上抑制水丝蚓的生物扰动效应.     

浑太河不同水生态区营养盐对底栖硅藻的影响及阈值

为全面了解浑太河不同水生态区营养盐对底栖硅藻的影响状况及进行底栖硅藻群落的保护,本研究对3个水生态区共287个采样点的营养盐因子(NH_4~+-N、TP)及底栖硅藻群落进行调查分析,并通过局部加权回归散点修匀法(locally weighted scatterplot smoothing,LOWESS)探究了底栖硅藻群落的NH_4~+-N、TP保护阈值.结果表明:(1)浑太河3个水生态区NH_4~+-N、TP浓度差异性显著并呈现出水生态Ⅰ区水生态Ⅱ区水生态Ⅲ区的趋势.(2)底栖硅藻特征指标[运动性硅藻百分比、敏感性硅藻百分比、具柄硅藻百分比、Pielou均匀度指数、特定污染敏感指数(specific polluosensitivity index,IPS)、硅藻生物指数(biological diatom index,IBD)、硅藻属指数(generic diatom index,IDG)]均在3个水生态区间存在差异,运动性硅藻百分比呈现出水生态Ⅰ区水生态Ⅱ区水生态Ⅲ区的变化,而其余6个生物参数的变化与之相反,表明水生态Ⅲ区底栖硅藻受到的干扰最大,水生态Ⅰ区最小.(3)经LOWESS拟合和独立样本T检验,发现3个水生态区底栖硅藻的NH_4~+-N、TP保护阈值不同,水生态Ⅰ区、Ⅱ区、Ⅲ区的NH_4~+-N阈值分别为0.13、0.30、1.98 mg·L~(-1),TP阈值分别为0.04、0.06、0.20 mg·L~(-1).本研究可为浑太河3个水生态区底栖硅藻群落的保护和水生态区管理提供理论依据.     

基于干扰梯度的钦江流域底栖动物完整性指数候选参数筛选

候选参数的科学筛选是构建底栖动物完整性指数的关键步骤.在缺乏足够参照样点的情况下,生物参数与环境梯度的响应关系是重要依据.以广西钦江流域冬季枯水期22个样点的环境和底栖动物数据为例,应用主成分分析法提取研究流域的环境梯度,进而采用多重回归分析确定对环境干扰敏感且预测性强的构成参数.相关性分析表明,38个候选参数中有12个参数与其他参数间的信息冗余性很高(|r|>0.80,P<0.05);余下的26个生物参数与环境梯度主成分Ⅰ(PCⅠ)、主成分Ⅱ(PCⅡ)和栖境质量参数的多重回归分析表明,有13个参数能和环境胁迫较好地响应(P<0.05).参考各指数的代表性和实用性,提出了适于构建该区域底栖动物完整性指数的8个生物参数:科级丰度、蜉蝣目丰度、鞘翅目丰度,EPT多度、优势种百分比,捕食者百分比,属级香农多样性指数和BI指数.本研究为类似情况下底栖动物完整性指数的构建提供了一个较好的解决途径.     

汤旺河着生硅藻群落及其与环境因子的关系

2018年8月(丰水期),在松花江支流汤旺河,调查了24个点位的着生硅藻群落结构和水环境特征.使用聚类分析、 Mcnaughton优势度分析和生态型分析3种方法研究了汤旺河着生硅藻群落结构和清洁度,使用主成分分析、 Spearman相关分析和冗余分析等方法研究了汤旺河着生硅藻群落和环境因子的响应关系.结果表明,汤旺河共鉴定出着生硅藻99种(变种),物种丰富.汤旺河丰水期水生态环境质量状况较为健康,着生硅藻主要由清洁种构成,其中Achnanthidium minutissimum优势度为0.32,为绝对优势种.聚类分析结果表明,汤旺河采样点位可分为3组;其中组1和组2健康程度较高,优势种均为清洁种,组3健康程度较其余两组偏低,Nitzschia palea和Ulnaria ulna等耐污种在组3的优势度增加.与组1相比,组2中-高度腐生型和中-富营养型硅藻比例有所增加,极度需氧型硅藻比例有所下降,影响组2硅藻群落结构变化的主要水质因子为高锰酸盐指数.与其他两组相比,组3富营养型硅藻和极度富营养型硅藻比例显著上升,影响组3硅藻群落结构变化的主要水质因子为NH~+_4-N和TN.由此可见,着生硅藻群落可以有效地指示汤旺河水体腐生状况和营养状况.     

根据SSD推导PFOS沉积物质量基准及其在生态风险评估中的应用

沉积物中蓄积的PFOS（perfluorooctane sulfonate,全氟辛烷磺酸）对水体生态环境具有潜在的危害.为了合理评估沉积物中PFOS的危害,探究了沉积物中PFOS对摇蚊（Chironomus kiiensis）、钩虾（Hyalella azteca）、霍甫水丝蚓（Limnodrilus hoffmeisteri）等底栖生物的毒性效应;同时,以毒性试验结果和搜集的PFOS相关毒性数据为基础,利用SSD（species sensitivity distributions,物种敏感度分布法）推导PFOS沉积物质量基准;最后,将基准值与从文献中搜集得到的我国七大水系沉积物中w（PFOS）进行比较,以评估PFOS风险.结果表明:①沉积物中PFOS对摇蚊的毒性效应最为显著,其96 h、10 d、21 d毒性试验中LC₅₀分别为0.894、0.770和0.536 μg/g（以干质量计,下同）;10 d毒性试验中w（PFOS）最高值为156.5 μg/g时,钩虾未出现显著死亡,21 d毒性试验中LC₅₀为70.5 μg/g;在w（PFOS）最高值分别为112.4和76.4 μg/g的10和21 d毒性试验中,霍甫水丝蚓均未出现显著死亡.②沉积物中PFOS的CMC_sed（急性基准值）为28.6 μg/g,CCC_sed（慢性基准值）为0.060 μg/g.③我国七大水系96.0%的沉积物中w（PFOS）低于CCC_sed;其余的沉积物中w（PFOS）高于CCC_sed但低于CMC_sed,这些采样点主要分布在黄河中下游和长江下游.研究显示,我国七大水系沉积物中PFOS总体风险较低,但黄河中下游和长江下游沉积物中蓄积的PFOS可能具有潜在的风险,需要给予更多的关注.      

中国北方河流底栖动物群落季节性演替对水生态环境质量评价的影响

大型底栖动物是评价水生态质量最常用的生物类群,鉴于水生昆虫的生活史特点,在一年当中群落结构会发生季节性变化,如何利用底栖动物数据准确评价水生态质量状况,反映客观实际,值得探讨。将黑龙江省2012—2015年水生生物试点监测47个采样点的108组底栖动物数据进行比较,对群落结构的相似性、物种的更替率和BMWP指数评价结果进行分析,探讨群落的演替及BMWP指数的变化规律。结果表明不同时间采集的样品底栖动物群落之间存在较大差异,评价的结果也存在差异,越是水环境质量好的区域,这种差异越明显。利用底栖动物评价水生态状况,宜选择长时间段的多个采集数据,经统计整理后,利用复合样方(年均值)的特征,评价一段时间内(如以年为单位)的水生态质量状况,使评价结果更具准确性。