西南山区河流阶梯-深潭系统的生态学作用

山区河流发育的阶梯—深潭系统具有显著的生态学作用。阶梯—深潭系统增大水流阻力和河床抗冲刷力,稳定了河床和岸坡。大卵石堆积成阶梯,细颗粒泥沙在深潭河段的缓流滞流区沉积下来形成淤泥层,形成适宜多种生物的栖息地。选择小江支流——深沟、蒋家沟和小白泥沟,以及四川九寨沟和金沙江进行野外实验、取样分析。结果发现阶梯—深潭系统较发育的深沟和九寨沟底栖动物密度高达552个/m2,生物量高达5.96 g/m2。而邻近的小白泥沟和蒋家沟底栖动物密度仅0.75个/m2,生物量不到0.006 g/m2。考虑河流不同部位底质、水深、流速等特性,提出了生物栖息地多样性及其计算方法,研究发现大型无脊椎动物的生物多样性随栖息地多样性增加而增加。利用阶梯—深潭系统治理山区河流,既能保持河道稳定,又能维持较高的生物多样性,保持健康的河流生态系统。     

湖滨带开发利用对大型底栖动物群落结构的影响:以洪泽湖为例

湖滨带是湖泊与陆地生态系统间非常重要的生态过渡带,能够保障周围生态系统结构的完整以及功能的正常发挥.随着湖滨带被持续开发与利用,人为干扰对湖滨带的影响逐渐增强.大型底栖动物是淡水生态系统的重要生物类群之一,也是物质循环和能量流动的主要环节,起着承上启下的关键作用.为了解湖滨带开发利用对大型底栖动物群落结构的影响,2020年8月对洪泽湖湖滨带49个样点的大型底栖动物进行调查.共采集到大型底栖动物49种,隶属3门7纲17目26科44属,各样点大型底栖动物的密度差别较大,介于6.67~1386.67 ind./m²之间,整体上呈现西北高,东南低的趋势.相似性分析结果表明,河口型湖滨带和大堤型湖滨带与其他类型湖滨带差异显著,而围网型、圈圩型和光滩型3种湖滨带类型之间的大型底栖动物群落差异均不显著.相似性百分比分析结果表明,腹足纲的环棱螺属是造成不同湖滨带类型差异的主要物种.典范对应分析结果表明,悬浮物（SS）、溶解态总氮、pH、透明度（SD）、浊度、水生植物盖度和扰动指数对大型底栖动物群落有显著影响.考虑不同湖滨带宽度的开发利用情况,发现湖滨带开发利用200 m范围内,物种-环境解释率最高,说明200 m湖滨带范围内的开发利用情况对大型底栖动物的影响最大,对湖滨带200 m范围内的开发利用应该加强管控.结构方程模型表明湖滨带开发利用主要通过影响水生植物盖度、总氮、硝态氮、叶绿素a、SS、SD等进而影响大型底栖动物,且围网也会直接影响大型底栖动物群落结构.     

应用底栖动物完整性指数评价滇池流域入湖河流生态系统健康

采用底栖动物完整性指数(B-IBI)评价滇池流域入湖河流健康状况.根据滇池流域38个样点(9个参照点,29个干扰点)于2009年丰水期和2010年平水期采得的大型底栖动物数据,对19个生物参数进行分布范围、Spearman相关性和判别能力分析,确定构成滇池流域底栖动物生物完整性的指数为甲壳动物+软体动物分类单元数、集食者%、捕食者%和耐污类群%.用比值法统一量纲,计算各个生物参数的值,并将所得的值相加即得到B-IBI指数值.根据B-IBI指数值的25%分位数确定健康等级标准,并对小于25%分位数的值进行四等分,即得到滇池流域底栖动物完整性的评价标准,B-IBI>1.62为健康,1.03～1.62为亚健康,0.31～1.03为一般,0.10～0.31为较差,<0.10为极差.评价结果表明,滇池流域的38个样点中,16个为健康,5个为亚健康,6个为一般,6个为较差,5个为极差.B-IBI值与硝态氮和水温有较大的负相关关系,与其他理化因子相关性不明显.     

应用底栖动物完整性指数评价上海市河流健康

据2011-2013年对上海市31条河流底栖动物的调查结果,对31个生物参数进行分布范围、判别能力以及相关性等进行分析,确定构建上海市河流底栖动物完整性指数(B-IBI)的4个参数:(寡毛类动物+蛭纲)数量百分比、耐污类群分类单元数、双翅目数量百分比和集食者分类单元数百分比.采用比值法统一量纲,将各个生物参数分值加和得到上海市河流B-IBI值.利用构建的B-IBI对上海市31条河流健康状况进行评价,结果表明:31条河流中,有4条河流处于健康状态,8条河流处于亚健康状态,9条河流处于一般状态,8条河流处于较差状态,2条河流处于极差状态;远郊河流健康状态最好,近郊次之,市区最差.     

The zoogeomorphology of case-building caddisfly: Quantifying sediment use

Caddisfly (Trichoptera) larvae are an abundant and widespread aquatic insect group characterized by the construction of silk structures, including nets and cases. Case-building caddisfly have the potential to modify the sorting and mobility of sand and fine gravel via: (1) case construction, resulting in altered sediment properties; (2) transporting sediment incorporated into cases over the river bed; and (3) changing the structure of river beds via burrowing activity. To investigate these mechanisms, it is necessary to understand the mass, size distribution and spatial variability of sediment use by case-building caddisfly larvae. We quantified the mineral sediment used by individuals and communities of case-building caddisfly in 27 samples, from three sites on a gravel-bed stream. The mass and size distribution of sediment in individual cases varied between taxa (mass = 0.001–0.83 g, D₅₀ = 0.17–4 mm). The mean mass of sediment used by the caddisfly community was 38 g m⁻² and varied locally. Sediment use was predominantly coarse sand (D₅₀ = 1 mm). 64% of sediment use was attributable to Agapetus fuscipes (Glossosomatidae). Due to within-species variability in case mass, the abundance of most taxa, including A. fuscipes, was only weakly associated with the mass of sediment used by this species, at the river scale. Whilst the caddisfly community used a small percentage of the total sediment available (average 2.99% of the 1–1.4 mm size fraction), A. fuscipes used more fine sediment in their cases at sites where it was more available. Despite variability in local habitat, all sites supported diverse case-building caddisfly communities utilizing mineral sediment. Consequently, geomorphological effects of case-building caddisfly are potentially widespread. The results provide novel insights into the specific grain sizes and quantities of fine sediment used by caddisfly larvae, which represents an important step towards understanding their zoogeomorphic activities. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.     

枯季长江口南汇东滩潮间带盐沼湿地冲淤变化对大型底栖动物功能群的影响

盐沼湿地的冲淤变化是影响大型底栖动物功能群组成及其分布特征的一个重要因素。本文选择长江口南汇东滩作为研究区域,设置固定样地,分别于2015年11月和2016年2月,进行了大型底栖动物和沉积物理化因子的季节性取样分析,并在期间内每月进行滩面冲淤变化的观测,分析了枯季长江口南汇东滩潮间带盐沼湿地冲淤变化对大型底栖动物功能群的影响及作用机理。调研期间共采集到大型底栖动物37种,从功能群组成来看,以杂食者居多,共25种;植食者次之,共7种;肉食者最少,仅为5种。3种食性功能群的物种数、密度和生物量的时空变化特征有所不同。调研期间,3个功能群物种数都略有下降;植食者密度显著增加（P<0.01）,而肉食者、杂食者密度变化不显著（P>0.05）;3个功能群的生物量变化均不显著（P>0.05）。植食者密度和生物量在样地间都存在极显著差异（P<0.01）;肉食者和杂食者仅密度在2016年2月的调研中存在样地间的显著差异（P<0.05）。不同样地月际冲淤变化特征有所不同,但总体均呈淤涨态势。多数环境因子存在显著的空间差异（P<0.05）,仅不同深度的沉积物中值粒径在样地间无显著差异（P>0.05）。滩面冲淤变化对沉积物理化指标的变化具有主导作用。通过非线性回归分析筛选出的与各功能群物种数、密度、生物量变化具有显著相关性（P<0.05）的环境因子组合存在差异。其中,对植食者密度、生物量的变化和肉食者物种数的变化有显著影响的环境因子组合中都包含绝对冲淤变化量。滩面冲淤变化除对大型底栖动物产生直接影响外,还会通过改变沉积物理化因子特征,间接对大型底栖动物产生影响。对于3种食性功能群来说,产生影响作用的主要生境因子存在明显差异。虽然各食性功能群的物种数均有下降,但相对另外两种功能群而言,沉积物中的营养环境还是更利于杂食者的生存,因此杂食者在竞争过程中更具优势。未来相关研究需要在多因子系统监测的基础上,结合洪季的观测结果,进行综合分析。     

Influence of a breakwater on nearby rocky intertidal community structure

It is widely recognised that coastal-defence structures generally affect the structure of the assemblages they support, yet their impact on adjacent systems has been largely ignored. Breakwaters modify the nearby physical environment (e.g. wave action) suggesting a local impact on biological parameters. In the present study, an ACI (After-Control-Impact) design was used to test the general hypothesis that the artificial sheltering of an exposed coast has a strong effect on the structure and functioning of adjacent systems. The effects of a reduction in hydrodynamics were clear for a number of taxa and included the replacement of barnacles, limpets and frondose algae by an increasing cover of ephemeral algae. These effects were evident both at early and late successional stages. Results suggest that the artificial sheltering of naturally exposed coasts can have a strong impact promoting a shift from consumer- to producer-dominated communities, which has important ecological and energetic consequences for the ecosystem.     

Strategic priorities for assessing ecological impacts of marine renewable energy devices in the Pentland Firth (Scotland,UK)

The Pentland Firth, located between the north coast of mainland Scotland (UK) and the Orkney Islands, is recognised as an excellent location for the utilisation of tidal stream technology. Potential ecological impacts associated with tidal stream technology may ultimately depend on device design, array size and deployment location. Available ecological data for the Pentland Firth is summarised and strategic priorities for assessing ecological impacts are provided. Baseline data on marine species and habitats in the Pentland Firth is severely lacking and consequently the integrity of any environmental impact assessment could be compromised by this lack of data.     

Diversity patterns along and across the Chilean margin: a continental slope encompassing oxygen gradients and methane seep benthic habitats

In the present study we review datasets available for the Chilean margin to assess the relationship between environmental (or habitat) heterogeneity and benthic diversity. Several factors, such as the presence of different water masses, including the oxygen-deficient Equatorial Sub-surface Waters (ESSW) at the continental shelf and upper slope, and the Antarctic Intermediate Waters (AIW) at mid slope depths appear to control the bathymetric distribution of benthic communities. The presence of methane seeps and an extended oxygen minimum zone (OMZ) add complexity to the benthic distribution patterns observed. All these factors generate environmental heterogeneity, which is predicted to affect the diversity patterns both along and across the Chilean continental margin. The response to these factors differs among different faunal size groups: meio-, macro-, and megafauna. Physiological adaptations to oxygen deficiency and constraints related to body size of each group seem to explain the larger-scale patterns observed, while sediment/habitat heterogeneity ( e.g. at water mass boundaries, hardgrounds, biogeochemical patchiness, sediment organic content, grain size) may influence the local fauna diversity patterns.     

Mapping Seabed Geology by Ground-Truthed Textural Image/Neural Network Classification of Acoustic Backscatter Mosaics

We present a novel, automated method for seabed classification based on shallow water backscatter mosaics from Sydney Harbour. Our approach compares the results between two different methods of image feature extraction when combined with artificial neural networks. The association of image textures with seabed geology is used to train the artificial neural networks to recognise the variability of textural attributes for three seabed classes comprising mud, sand and gravel. After network training, we classify unknown portions of the backscatter mosaic with a success rate ranging from 77% to 92%. Our results suggest that the computationally fast grey-level co-occurrence iteration algorithm holds promise for benthic habitat mapping in space and time, leading to real-time data analysis at sea.