扬州宝应湖底栖大型无脊椎动物的生物多样性及其变化

底栖大型无脊椎动物作为水环境监测的重要指示生物, 其群落结构和多样性能够有效地反映水环境的健康状况。为了更好地了解扬州宝应湖大型底栖动物的群落多样性, 本文于2015-2019年对扬州宝应湖底栖大型无脊椎动物进行野外调查和采样, 联合经典形态学和高通量测定DNA条形码方法进行物种鉴定, 进一步分析了这些大型无脊椎动物群落结构和多样性的年度变化, 并应用Shannon-Wiener指数(H′)和污染生物指数(biotic index, BI)对水质状况进行生物评价。结果显示: 共记录大型底栖动物3门5纲57种, 其中软体动物门23种, 隶属2纲9科(腹足纲7科15种, 双壳纲2科8种); 环节动物门寡毛纲12种, 隶属2科; 节肢动物门22种, 隶属2纲6科(软甲纲4科5种, 昆虫纲2科17种)。腹足纲是优势类群, 5年间的密度占比均在65%以上。优势种是赤豆螺(Bithynia fuchsiana)、槲豆螺(B. misella)和长角涵螺(Alocinma longicornis)。Margalef丰富度指数(2.27 ± 0.28)、Simpson优势度指数(0.82 ± 0.02)和Pielou均匀度指数(0.78 ± 0.08)在5年间呈现明显的波动变化。对水质状况的生物评价结果表明, 湖区水体环境在5年间均呈现不同程度的污染状态, 这与过度围湖水产养殖等经济活动引起水体富营养化有一定关系。     

长江口东滩湿地芦苇生境大型底栖无脊椎动物群落结构的月动态

2015年5月至2016年4月对长江口东滩湿地芦苇生境的大型底栖无脊椎动物群落结构进行监测,分析了该生境下底栖动物群落物种组成和多样性的月变化.结果表明: 芦苇株高和盖度均在3—8月逐渐增大,9月后逐渐降低;芦苇密度和地上生物量(干质量)均在7月达到最大值.调查期间,共发现大型无脊椎底栖动物20种(包括2种鉴定到属,2种鉴定到科).其中,腹足纲种类最多,有11种(包括1种鉴定到属);软甲纲有5种;昆虫纲和多毛纲均只有2种.以緋拟沼螺、堇拟沼螺和尖锥似蟹守螺等为主要优势种.从生活型来看,底上附着型种类数最多(11种),其次为穴居型(5种)和底内型(4种).大型底栖动物密度和生物量存在明显的季节或月变化,夏季(8月)出现全年最高值.Margalef物种丰富度指数(D)和Shannon指数(H)月份间差异显著,Pielou均匀度指数(J)月份间差异不显著(除11月).大型底栖动物群落在42%相似性水平上划分为3个群聚.从非度量多维标序(nMDS)排序图可知,5月、10—11月与其他月份差异较大.水温、芦苇地下生物量和盐度等环境因子对于底栖动物密度变化具有一定影响,但未达到显著水平(P>0.05).受人类活动的持续影响,长江口东滩湿地芦苇生境底栖动物群落物种多样性有所下降,芦苇生境价值急需重视.     

福建省主要海湾潮下带大型底栖无脊椎动物组成与分布特征

根据2010年8月对福建省12个主要海湾潮下带大型底栖无脊椎动物的调查资料,分析了大型底栖无脊椎动物的种类组成、生物多样性和群落结构分布特征及其与环境因子的关系.结果表明: 12个海湾共采集到大型底栖动物382种,包括环节动物170种、甲壳动物75种、软体动物78种、棘皮动物19种,以及其他类群40种.物种数、丰度、生物量和生物多样性指数空间差异较大: 罗源湾物种数最高,为92种,旧镇湾最低,为25种,所有海湾平均(55±21)种;所有海湾在物种组成上均为多毛类占优势,其平均物种数百分比为(51.8±5.5)%;诏安湾平均丰度最高,为(1330±1094) ind·m^-2,其次为福清湾、厦门湾、湄洲湾,泉州湾最低;兴化湾平均生物量最高,为(821.2±2387.7) g·m^-2,其次为福清湾、厦门湾,深沪湾最低;丰富度指数和Shannon多样性指数在罗源湾、湄洲湾、深沪湾、厦门湾和东山湾呈现较高值,而在福清湾和旧镇湾呈现较低值,两者的全域均值分别为(0.80±0.09)和(2.73±0.64).以相似度20%为界,可将研究区域的大型底栖无脊椎动物划分为14个群组,其中罗源湾内各站位间群落相似度最高,湾内差异最小,其次为三沙湾、福清湾、深沪湾和诏安湾,而其他海湾不同站位的群落组成差异较大.物种数、多样性指数和环境因子间的相关性分析和主成分分析显示,造成研究区大型底栖动物群落结构组成和分布差异的主要环境因子依次为沉积物铜、水深和底层水体活性磷酸盐.     

杭州西溪湿地大型底栖动物群落特征及与环境因子的关系

为揭示现阶段西溪湿地大型底栖动物群落现状及其对湿地生态保护工程的响应,于2009年8月至2010年5月对西溪湿地在3个不同时期建设的区域(Ⅰ区、Ⅱ区和Ⅲ区)中的大型底栖动物进行季度调查.共记录大型底栖动物3门8纲15科45种.霍甫水丝蚓(Limnodrilus hoffmeisteri)、多毛管水蚓(Aulodrilus pluriseta)和梨形环棱螺(Bellamya purificata)是现阶段西溪湿地大型底栖动物的优势种.最早建设的Ⅰ区的环节动物密度在各季节均低于建设较晚的Ⅱ区和Ⅲ区,而软体动物的密度和生物量的变化趋势则相反;Ⅰ区大型底栖动物的总密度虽然与Ⅱ区和Ⅲ区没有明显差异,但总生物量、物种数、Margalef物种丰富度指数和Shannon-Wiener多样性指数均显著上升.上述结果表明,西溪湿地生态保护工程早期建设区域的底栖动物多样性趋于增加,水生生态系统环境质量得以改善.ANOSIM分析显示,西溪湿地不同区域或季节间大型底栖动物群落结构均存在显著差异,且这些差异的主要贡献物种为多毛管水蚓(Aulodrilus pluriseta)和梨形环棱螺(Bellamya purificata),表明这两个优势物种对西溪湿地底栖环境变化反应敏感,可作为湿地环境评价的指示物种.BIO-ENV分析表明,水温是影响春季和夏季大型底栖动物群落结构的主要环境因子,水深是影响秋季和冬季大型底栖动物群落的主要因子,同时底泥总磷含量对解释大型底栖动物生物量和群落结构具有一定作用.     

雅鲁藏布江中下游底栖动物物种多样性及其影响因素

雅鲁藏布江流域维系着丰富而独特的生物资源, 是全球生物多样性研究的热点区域。然而, 该流域底栖动物多样性的调查却极不充分。本文于2015年10月和2016年3月对雅鲁藏布江干流(朗县至墨脱段)和主要支流的底栖动物进行了调查, 并采用单因素方差分析(one-way ANOVA)和典范对应分析(canonical correspondence analysis)等对群落多样性格局进行解析。共采集到底栖动物270种, 隶属于5门8纲20目92科, 包括昆虫纲246种, 寡毛纲14种, 腹足纲4种, 其他动物6种。春季和秋季分别采集到底栖动物184种和214种, 优势种均以喜清洁和冷水的水生昆虫为主, 包括四节蜉属一种(Baetis sp.)、花翅蜉属一种(Baetiella sp.)、蚋属一种(Simulium sp.)、小突摇蚊属一种(Micropsetra sp.)和短石蛾属一种(Brachycentrus sp.)等。全流域平均密度为939.1 ind./m²,sp.)等。平均生物量为5.44 g/m²。底栖动物的物种组成、密度和多样性在季节和区域之间存在一定差异, 支流的多样性显著高于干流。典范对应分析显示, 海拔、流速、河宽和底质类型等环境因子是影响雅鲁藏布江流域底栖动物群落结构的关键环境因素, 而大峡谷地区多变的气候类型和地理阻隔是造成群落变化的根本原因。本研究可为雅鲁藏布江流域底栖动物多样性评估和环境监测提供重要的基础和参考。     

黄河三角洲石油生产对东营湿地底栖动物群落结构和水质生物评价的影响

为了解石油开采对湿地生态系统的影响,2009年10月调查了黄河三角洲东营湿地34个样点的水体物理化学属性和大型底栖无脊椎动物群落结构。共获得3门6纲12目41科70属84个大型底栖无脊椎动物分类单元。Shannon-Wiener多样性指数(r=-0.446,P=0.02)和TN显著负相关,BI指数与理化指标无显著相关性;软体动物分类单元数与盐度(r=-0.422,P=0.028)显著负相关,与pH值(r=0.435,P=0.023)显著正相关;软体动物个体百分数同样与盐度(r=-0.395,P=0.041)呈显著负相关,与pH值(r=0.565,P=0.002)呈极显著正相关;寡毛类分类单元数与TN(r=0.524,P=0.005)极显著正相关。水体石油含量与生物指数无显著相关性。典范对应分析(CCA)显示,TN、pH、盐度是影响东营湿地底栖动物群落结构的主要环境变量,水体石油污染并不是主要的胁迫因子。寡毛类和软体动物是该地区对环境变化的主要指示生物类群。Shannon-Wiener多样性指数水质生物评价结果显示,溢洪河支流、广利河上游、挑河上游、东张水库属于清洁;轻污点位有9个,其余点位为中污或重污。     

金沙江上中段大型底栖无脊椎动物群落结构特征和多样性分析

研究将2010—2019年的大型底栖无脊椎动物观测资料进行了系统整理分析,旨在为金沙江上中段大型底栖无脊椎动物的多样性评估以及高海拔地区河流的生物多样性研究和保护提供较为全面的基础资料。研究结果显示,金沙江上中段大型底栖无脊椎动物种类组成上水生昆虫占据绝对优势地位,主要由双翅目、蜉蝣目、毛翅目和襀翅目组成,软体动物占比较低,且以基眼目为主。就科级水平而言,四节蜉科、摇蚊科、扁蜉科和石蝇科为整个研究区域的常见分类单元,其中摇蚊科和四节蜉科在干支流和丰枯期均较为常见。干流和支流大型底栖无脊椎动物的群落结构显著不同,不受丰水期和枯水期的影响。丰水期和枯水期大型底栖无脊椎动物的群落结构差异显著,不受干流和支流的局限。四节蜉(四节蜉属Baetis、二翼蜉Cloeon dipterum、花翅蜉属Baetiella和四节蜉科Baetidae)和石蝇(纯石蝇属Paragnetina和石蝇科Perlidae)以及纹石蛾(纹石蛾属Hydropsyche)是造成不同群组群落结构差异的关键分类单元。整个研究区域大型底栖无脊椎动物呈现较高的嵌套度,且嵌套度枯水期高于丰水期,支流高于干流。底栖物种丰富度和现存量枯...     

环境因子对河流底栖无脊椎动物群落结构的影响

底栖无脊椎动物是河流生态系统的重要组成部分,在物质循环和能量流动中是不可或缺的重要环节。其群落结构特点与河流环境因子密切相关,能较好地反映河流生态系统健康状况。综述了物理因子(底质、温度、水深、水流、洪水干扰等)、化学因子(溶氧量、p H值、磷、氮等)、生物因子(水生植物、竞争和捕食)、人为干扰(电站建设、城镇化等)和综合因子对河流底栖无脊椎动物群落结构的影响,并根据国内外研究现状指出水流、海拔和洪水干扰等环境因子对河流底栖无脊椎动物群落结构影响的研究较少或不足,对这些环境因子的研究应是今后河流生态学领域需要着力推进重要内容。深入研究和完善环境因子与底栖无脊椎动物群落结构的关系可为保护底栖无脊椎动物群落、流域水生态系统管理和受损河流生态系统修复提供更为全面的科学依据。     

滇西北高山微水体与溪流生境底栖动物多样性和环境特征

高山微水体由于面积微小且通过地表径流形成串联结构常常被认为与高山溪流具有类似的生境, 然而由于这两类生境中环境因子与底栖动物多样性存在差异, 它们在生态系统中的作用可能完全不同。滇西北地区是全球生物多样性热点区域之一, 境内高山微水体和高山溪流分布密集, 在区域底栖生物多样性维持方面具有重要的功能, 然而目前对这两类高山淡水生态系统的研究较少。为了比较这两类生境环境因子的异同及其对底栖动物多样性的维持作用, 2015年6月, 作者在云南省怒江州贡山县的高山峡谷内, 对27个高山微水体和同区域分布的1条高山溪流(海拔高差500 m范围)的底栖动物多样性和水环境因子进行了实地调查。结果表明: (1)高山微水体和高山溪流底栖动物群落中优势分类单元种群数量均比较庞大, 而稀有分类单元数量较多且种群较小; (2)两种生境在环境因子、物种多样性、功能多样性和群落结构方面的差异明显, 高山溪流有较高的物种丰富度、物种多样性和功能多样性; (3)高山微水体底栖动物多样性的分布与水环境因子无关, 而高山溪流底栖动物多样性与群落结构的形成受到与流速关联的水环境因子和海拔的影响。因此, 高山微水体与高山溪流不能简单地视为类似的生境类型, 它们对区域底栖动物多样性和生态功能维持可能具有不同的作用。     

广东车八岭国家级自然保护区大型底栖动物多样性

大型底栖动物在当地生物多样性、食物链构成、水质指示和物质循环中有重要的作用, 但目前国内对森林内陆水体(湖泊、水库、溪流)中的大型底栖动物综合调查较少。作者于2019、2020年对广东车八岭国家级自然保护区的9个采样点开展了大型底栖动物的定性调查, 采样点涵盖保护区不同功能区、海拔、水体环境和水体底质。共鉴定出大型底栖动物4门6纲18目38科57种, 水生昆虫稚虫占大多数, 且多喜好清洁流动水体。在低海拔实验区即可采集到种类与数量可观的清洁水体指示物种。当地的大型底栖动物以亚热带森林典型物种为主, 多偏好栖息于流动水体, 反映了保护区的物种区系及其水体环境。本研究可为保护区的物种编目、环境评估和长期监测提供基础资料。     

空间和环境因子对黄河口自然和淡水恢复湿地底栖动物群落的差异影响

生物多样性的形成和维持机制是生态学研究的核心问题,其中环境和空间因子在群落构建中的相对重要性是生态学家面临的重要挑战。为探究黄河口湿地底栖动物群落的关键影响因子,及环境和空间因子对底栖动物群落结构的相对调控作用。于2017年10月与2018年5月对黄河口湿地32个样点（淡水恢复湿地19个和自然湿地13个）的底栖动物和水体理化指标进行采集分析。非度量多维标度排序（NMDS）结果显示,黄河口淡水恢复湿地和自然湿地的底栖动物群落结构显著不同。典范对应分析（CCA）表明,影响淡水恢复湿地底栖动物群落结构的环境因子主要为电导率、盐度和氧化还原电位;而自然湿地底栖动物群落结构主要受pH和无机碳的影响;盐度是两类湿地底栖动物群落组成差异的关键因子。变差分解（VPA）结果显示,环境过滤对淡水恢复湿地底栖动物群落起主导作用;在自然湿地中,空间因子对底栖动物群落具有主要的调控作用,同时环境和空间因子的相互作用也至关重要。本研究明确了黄河口的自然和恢复湿地中环境和空间因素对底栖动物群落特征的相对作用,对黄河三角洲河口湿地中生物多样性的保护和生态系统管理提供参考。     

Spatial and seasonal variation in nutrient excretion by benthic invertebrates in a eutrophic reservoir

1. Nitrogen (N) and phosphorus (P) fluxes via excretion by benthic invertebrates were quantified in a eutrophic reservoir (Acton Lake, Ohio, U.S.A.). We quantified variation in nutrient fluxes seasonally (June until November 1997), spatially (three sites) and among taxa (chironomids, tubificid oligochaetes and Chaoborus). 2. The three taxa differed in spatial distribution and contribution to nutrient fluxes. Tubificids were the most abundant taxon at two oxic sites (1.5 and 4 m depth), and were exceedingly rare at an anoxic, hypolimnetic site (8 m). Chironomids were abundant only at the shallowest oxic site. Chaoborus was the only abundant taxon at the anoxic site. Total benthic invertebrate biomass was greatest at the shallowest site and lowest at the anoxic, hypolimnetic site. 3. Mass‐specific excretion rate [μmol NH₄–N or soluble reactive P (SRP) excreted mg dry mass^–1 h^–1] varied among experiments and was influenced by temperature. Differences among taxa were not significant. Thus, nutrient flux through benthic invertebrates was affected more by total invertebrate biomass and temperature than by species composition. 4. Fluxes of N and P via benthic invertebrate excretion (μmol NH₄–N or SRP m^–2 day^–1) were greatest at the oxic sites, where fluxes were dominated by the excretion of tubificids and chironomids. The N and P fluxes at the anoxic site were much lower, and were dominated by excretion by Chaoborus. The ratio of N and P excreted by the benthic invertebrate assemblage varied seasonally and was lowest at the anoxic site. 5. Comparison with other measured inputs shows that excretion by benthic invertebrates could be an important source of nutrients, especially of P. However, the relative importance of nutrient excretion by the benthos varies greatly spatially and temporally.     

Benthic macroinvertebrate assemblages of coastal and continental streams and large rivers of southwestern British Columbia, Canada

In southwestern British Columbia (BC, Canada) and within a relatively small geographic area, lotic environments range from streams in coastal rainforests, to streams in arid continental grasslands, to very large rivers. Little is known about the invertebrate communities in large rivers in general, or in the streams of continental BC. The purpose of this study was to determine whether the benthic invertebrate community structure changes spatially between small coastal and small interior streams; between small streams versus large rivers; and whether changes in the benthic community are related to the environmental conditions. Kicknet samples and environmental data were collected from three coastal streams, three continental streams and two large rivers (discharge of 781 and 3620 m³/s, respectively). The large river sites had low invertebrate abundance, species richness and diversity, relative to the small streams. The coastal streams had the highest species richness and the continental streams had the highest invertebrate abundance. A number of taxa were specific to each class of stream. Invertebrate abundance decreased with river size, and increased with elevation, pH, conductivity, alkalinity, NO₂NO₃-N, total Kejldahl nitrogen and percent carbon in suspended solids.     

Context-dependent effects of freshwater mussels on stream benthic communities

1. We asked whether unionid mussels influence the distribution and abundance of co‐occurring benthic algae and invertebrates. In a yearlong field enclosure experiment in a south‐central U.S. river, we examined the effects of living mussels versus sham mussels (shells filled with sand) on periphyton and invertebrates in both the surrounding sediment and on mussel shells. We also examined differences between two common unionid species, Actinonaias ligamentina (Lamarck 1819) and Amblema plicata (Say 1817). 2. Organic matter concentrations and invertebrate densities in the sediment surrounding mussels were significantly higher in treatments with live mussels than treatments with sham mussels or sediment alone. Organic matter was significantly higher in the sediment surrounding Actinonaias than that surrounding Amblema. Actinonaias was more active than Amblema and may have increased benthic organic matter through bioturbation. 3. Living mussels increased the abundance of periphyton on shells and the abundance and richness of invertebrates on shells, whereas effects of sham mussels were similar to sediment alone. Differences in the amount of periphyton growing on the shells of the two mussel species reflected differences in mussel activity and shell morphology. 4. Differences between living and sham mussel treatments indicate that biological activities of mussels provide ecosystem services to the benthic community beyond the physical habitat provided by shells alone. In treatments containing live mussels we found significant correlations between organic matter and chlorophyll a concentrations in the sediment, organic matter concentrations and invertebrate abundance in the sediment and the amount of chlorophyll a on the sediment and invertebrate abundance. There were no significant correlations among these response variables in control treatments. Thus, in addition to providing biogenic structure as habitat, mussels likely facilitate benthic invertebrates by altering the availability of resources (algae and organic matter) through nutrient excretion and biodeposition. 5. Effects of mussels on sediment and shell periphyton concentrations, organic matter concentrations and invertebrate abundance, varied seasonally, and were strongest in late summer during periods of low water volume, low flow, and high water temperature. 6. Our study demonstrates that freshwater mussels can strongly influence the co‐occurring benthic community, but that effects of mussels are context‐dependent and may vary among species.     

The impact of harbour sludge disposal on benthic macrofauna communities in the Weser estuary

During an open-water disposal of about 710,000 m³ of harbour sludge in the polyhaline zone of the Weser estuary, Germany, a monitoring programme was carried out to investigate the impact on benthic invertebrates. The macrofaunal communities of four sites within the disposal area and five sites in a reference area were compared after discharge. The location and extent of the potentially affected area were inferred from a morphodynamic computer model (TIMOR 3; Zanke 1998). Disposal effects were analysed by comparing species numbers, densities, diversity and faunal similarity using multivariate methods. A loss of diversity and a decline in the abundance of several species in the disposal area were measured. The species number was reduced up to 50% and important habitat structures were absent from the disposal area. Several benthic species were affected by the disposal. The importance of species such as Mytilus edulis (Mollusca) and Lanice conchilega (Polychaeta) for the diversity of the community, and the sensitivity of these species to sediment discharge are analysed. The difficulties of separating dumping effects from natural variation in a dynamic estuarine channel system are discussed.Communicated by H.-D. Franke     

缺锌和HCO_3~-处理对诸葛菜和油菜有机酸特征的影响

以诸葛菜和油菜为材料,水培环境下设置4个不同的缺锌和碳酸氢根离子胁迫处理,分别为+Zn0(含Zn且不加HCO3-的处理组),+Zn10(含Zn且加10 mmol·L-1HCO3-的处理组),-Zn0(缺Zn且不加HCO3-的处理组)和-Zn10(缺Zn且加10 mmol·L-1HCO3-的处理组),利用离子色谱法分析了4个处理的两种植物幼苗器官(根、茎、叶)及根系分泌物中的有机酸特征。结果表明:(1)高浓度碳酸氢根离子处理显著增加了两种植物器官及根系分泌的有机酸总量,尤其是在缺锌和高浓度碳酸氢根离子双重胁迫下(-Zn10处理),诸葛菜器官和根系分泌的有机酸比油菜更敏感,草酸、柠檬酸和苹果酸是诸葛菜器官和根系分泌物中的优势酸,这三种有机酸的含量分别占其有机酸总量的75%及以上;(2)叶片是两种植物有机酸产生的主要器官,有机酸的含量和分配比例从地上部分(叶和茎)到地下部分(根)减少;(3)两种植物器官和根系分泌物中的有机酸变化趋势一致,叶片中有机酸主要来源于暗呼吸过程和光呼吸过程,其他器官和根系分泌物中的有机酸主要来源于暗呼吸过程;(4)诸葛菜对缺锌和高浓度碳酸氢根离子的适应能力强于油菜,为诸葛菜的喀斯特适生性和低锌和高浓度碳酸氢根离子环境(如喀斯特环境)的生态修复提供了理论依据。     

Abundance and diversity of littoral invertebrates in the Socorro Island,Revillagigedo Archipelago,Mexico

Composition, abundance, diversity and distribution of the littoral benthic invertebrates of Socorro Island with transects (parallel to the coast and with 1 m2 quadrats) were analyzed. During the spring of 1991 and 1992 samples were taken from the upper and middle levels of the intertidal zone in Vargas Lozano, Braithwaite, Blanca SW, Blanca NE, Binners, Grayson, Academia and Norte bays. The 161 species found belong to Porifera, Cnidaria, Platyhelmintha, Nemertina, Sipunculida, Annelida, Mollusca, Anthropoda and Echinodermata. Crustaceans and mollusks were the richest groups in both years, as in other rocky shores. Highest total density was found in Blanca NE bay in both samplings, with 281 orgs./m2 in the first and 172 orgs./m2 in the second. Most frequently found species were Isognomon janus (Mollusca, Pelecypoda), Littorina pullata (Mollusca, Gastropoda), Hipponix panamensis (Mollusca, Gastropoda), Pachygrapsus transversus (Crustacea, Grapsoidea) and Turbo funiculosus (Mollusca, Gastropoda). Because of the complexity of the habitat structure, Vargas Lozano was the bay with the highest specific richness (83 species), greatest diversity (4.7 bits/individual) and lowest dominance (0.065). Most species were classified as accidentals with the Dajoz's frequency classification, while the dominant species were accessories and only I. janus, in the spring 1991, was a constant species. Two kinds of bays were distinguished: those with some dominant species (density) and those in which there was no evident dominance by a particular species. Consequently, the diversity and evenness values were set apart: homogeneous communities (Vargas Lozano and Binners) and heterogeneous communities (Grayson bay and others), characterized by intermediate evenness values. The Jaccard similarity index identified two regions: one formed by bays found mainly in the southwest part of the island (Binners, Vargas Lozano, Braithwaite, Grayson and Blanca SW) and the other found in the northern region that included Blanca NE, Academia and Norte; however, Blanca NE had the most diverse species composition because of its physiographic particularities and because the sediment retained by the filamentous algae on the flat stones allow many species to settle down. Isognomon janus, Mitrella baccata (Mollusca, Gastropoda), P. transversus and Xanthodius cooksoni (Crustacea, Xanthoidea) were the most common species in all bays in both expeditions. The dominance-diversity relationship, the high specific richness and the low dominance of coastal invertebrates from the different bays, are indicative that the communities in Socorro Island are little disturbed; their specific richness are similar to those of coral reefs.     

Environmental correlates of plant and invertebrate species richness in ponds

Ponds (lentic water bodies <2 ha) constitute a considerable biodiversity resource. Understanding the environmental factors that underlie this diversity is important in protecting and managing the habitat. We surveyed 425 ponds for biological and physical characteristics with 78 of those also surveyed for chemical characteristics. A total of 277 invertebrate species and 265 plant species were found. Species richness varied between 2 and 99 (mean 27.2 ± 0.6 SE) for invertebrates and 1 and 58 (mean 20.8 ± 0.4 SE) for plants. Generalised additive models were used to investigate variables that correlate with the species richness of plants and invertebrates, with additional models to investigate insect, Coleoptera, Odonata, Hemiptera, Trichoptera and Mollusca species richness. Models performed reasonably well for invertebrates in general (R ² = 30.3%) but varied between lower-order invertebrate taxa (12.7–34.7%). Ponds with lower levels of shading and no history of drying contained higher numbers of species of plants and all invertebrate groups. Aquatic plant coverage positively correlated with species richness in all invertebrate groups apart from Trichoptera and the presence of fish was associated with high invertebrate species richness in all groups apart from Coleoptera. The addition of chemistry variables suggested non-linear relationships between oxygen demand and phosphate concentration and higher-order richness. We demonstrate that the composition of biological communities varies along with their species richness and that less diverse ponds are more variable compared to more diverse ponds. Variables positively correlated with richness of one taxon may be negatively correlated with that of another, making comprehensive management recommendations difficult. Promoting a high landscape-level pond biodiversity will involve the management of a high diversity of pond types within that landscape.     

Effects of macrophyte growth forms on invertebrate communities in saline lakes of the Wyoming High Plains

In saline lakes, areal cover and both species and structural diversity of macrophytes often decline as salinity increases. To assess effects of the loss of certain macrophyte growth forms, we characterized benthic and epiphytic invertebrates in three growth forms (thin-stemmed emergents, erect aquatics, and low macroalgae) in oligosaline lakes (0.8–4.2 mS cm⁻¹) of the Wyoming High Plains, USA. We also measured the biomass and taxonomic composition of epiphytic and benthic invertebrates in two erect aquatics with very similar structure that are found in both oligosaline (Potamogeton pectinatus) and mesosaline (9.3–23.5 mS cm⁻¹) (Ruppia maritima) lakes. Although total biomass of epiphytic invertebrates varied among oligosaline lakes, the relative distribution of biomass among growth forms was similar. For epiphytic invertebrates, biomass per unit area of lake was lowest in emergents and equivalent in erect aquatics and low macroalgae; biomass per unit volume of macrophyte habitat was greatest in low macroalgae. For benthic invertebrates, biomass was less beneath low macroalgae than other growth forms. Taxonomic composition did not differ appreciably between growth forms for either benthic or epiphytic invertebrates, except that epiphytic gastropods were more abundant in erect aquatics. Total biomass of epiphytic and benthic invertebrates for the same growth form (erect aquatic) did not differ between oligosaline (Potamogeton pectinatus) and mesosaline (Ruppia maritima) lakes, but taxonomic composition did change. In the oligosaline to mesosaline range, direct toxic effects of salinity appeared important for some major taxa such as gastropods and amphipods. However, indirect effects of salinity, such as loss of macrophyte cover and typically higher nutrient levels at greater salinities, probably have larger impacts on total invertebrate biomass lake-wide.     

Regulation of nitrous oxide emission associated with benthic invertebrates

1. A number of freshwater invertebrate species emit N₂O, a greenhouse gas that is produced in their gut by denitrifying bacteria (direct N₂O emission). Additionally, benthic invertebrate species may contribute to N₂O emission from sediments by stimulating denitrification because of their bioirrigation behaviour (indirect N₂O emission). 2. Two benthic invertebrate species were studied to determine (i) the dependence of direct N₂O emission on the preferred diet of the animals, (ii) the regulation of direct N₂O emission by seasonally changing factors, such as body size, temperature and availability and (iii) the quantitative relationship between direct and indirect N₂O emission. 3. Larvae of the mayfly Ephemera danica, which prefer a bacteria‐rich detritus diet, emitted N₂O at rates of up to 90 pmol Ind.^?1 h^?1 under in situ conditions and 550 pmol Ind.^?1 h^?1 under laboratory conditions. In contrast, larvae of the alderfly Sialis lutaria, which prefer a bacteria‐poor carnivorous diet, emitted N₂O at invariably low rates of 0–20 pmol Ind.^?1 h^?1. The N₂O emission rate of E. danica larvae was positively correlated with seasonally changing factors (body size, temperature and availability). Direct N₂O emission by E. danica larvae was limited by low temperature in winter, larval development in spring and low availability in summer. 4. Both E. danica and the non‐emitting S. lutaria increased the total N₂O and N₂ emission from sediment in a density‐dependent manner. While N₂O directly emitted by benthic invertebrates can be partially consumed in the sediment (E. danica), non‐emitting species can still indirectly contribute to total N₂O emission from sediment (S. lutaria).