Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of Wilmot Creek

The effects of the lampricide, TFM, on the abundance of macroinvertebrates in the benthos of Wilmot Creek, a hardwater tributary to Lake Ontario, was examined over 1 year. Drifting macroinvertebrates were also collected before, during and after TFM treatment. Significant decreases in benthic abundance were exhibited by Dolophilodes sp., Tubificoidea, Cricotopus sp. and Macrotendipes sp. throughout the 350 days following treatment. Only the decrease in abundance of Dolophilodes sp. and Tubificoidea could be attributed to TFM treatment. Increases in drift abundance observed during treatment were generally an accurate indicator of TFM-sensitive macroinvertebrates. The most sentive taxa (Dolophilodes sp., Dugesia sp. and Tubificoidea) responded immediately following the introduction of TFM. Branchiobdellida, Diamesa sp., Dicranota sp., Lumbricidae and Nemouridae exhibited increases in drift abundance 8–10 h after the introduction of TFM, however, were considered less sensitive than the former taxa because a decline in their abundance in the benthos was not detected.The response of the benthic invertebrates found in this hardwater creek was similar to those observed during studies of softwater streams. Only the most severely affected taxa were not present in the benthos 350 days after treatment.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates within the hyporheic region of a small stream

The effect of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM), on the benthic macroinvertebrates within the hyporheic region of Dam Creek, Ontario was investigated. Organisms were regularly found to a depth of 70 cm in the substrate throughout the study period. Of the eight major taxa found at both the treated and untreated sites only Tubificoidea exhibited a decrease in abundance attributable to TFM.One day after treatment, TFM concentrations were greatest at a depth of 55 cm, the greatest depth to which water samples were taken. The movement of TFM into the hyporheic region during the present study may be due to the large convective forces created by the rapid decrease in surface water temperature. These convective forces are usually greatest in the late fall and winter when TFM is not applied. The greater part of TFM stream treatments are carried out during the summer when surface water temperatures remain fairly constant. It is suggested that the hyporheic region may act as a refuge zone for benthic macroinvertebrates against the lampricide during most of the TFM application season.     

The stabilizing effect of resting egg banks of the <Emphasis Type="Italic">Daphnia longispina</Emphasis> species complex for longitudinal taxon heterogeneity in long and narrow reservoirs

The aim of this study was to determine the effect of monsoonal spates and land uses on abundance, richness, diversity, and evenness of benthic macroinvertebrates in streams, and whether these factors interacted with each other to influence community structure. Two groups of streams with different underlying disturbance profiles were studied. One group was in a native forest (non-degraded area) and experienced only spate, and the other group drained an area degraded by agriculture and cattle grazing, and so was subject to two types of disturbances. Spates produced a strong decline in invertebrate abundance and an increase in evenness, whereas changes in land uses caused an increase in abundance of tolerant taxa and a significant decline in richness, diversity, and evenness. Differences in richness and Oligochaeta abundance between land uses were mostly evident in the pre-spate period due to low water levels magnifying some physicochemical changes caused by ecosystem degradation. Canonical correspondence analysis indicated that degraded sites had the highest conductivity, nitrate, pH, and water temperature. Upstream non-degraded streams generally exhibited higher dissolved oxygen values. Taxa such as Psychodidae and Tipulidae, Camelobaetidius penai, Austrelmis spp. (adult), Macrelmis spp. (adult), and Marilia spp. dominated in non-degraded sites, while Tricorythodes popayanicus, Caenis ludicra, Dodecabates dodecaporus, Atractides sp., and Torrenticola columbiana were abundant in downstream degraded streams. These two groups of taxa may be useful biological indicators of water quality in streams of northwestern Argentina.     

Colonization of a headwater stream during three years of seasonal insecticidal applications

We investigated recolonization by insects of a small headwater stream in the southern Appalachian Mountains that was treated along its entire length with an insecticide (methoxychlor). Initial treatment (December 1985) resulted in massive insect drift. Applications continued seasonally for three years, and drift was measured during each treatment. Taxonomic composition of the drift indicated several responses: (1) Some taxa were eliminated. (2) A number of taxa occurred only sporadically following initial treatment. (3) Early instars for some taxa showed seasonal occurrences which closely paralleled known life cycles and flight periods of adults. Groups which provided strong evidence for aerial recolonization included several Ephemeroptera, Plecoptera (Peltoperlidae and Isoperla spp.), and Trichoptera (Parapsyche cardis, Diplectrona modesta, Pycnopsyche spp., and Lepidostoma spp.). (4) Some long-lived taxa survived and exhibited distinct growth through several treatment periods. These include Odonata (Lanthus and Cordulegaster), some Ephemeroptera, and some Diptera (Tipulidae, Ceratopogonidae, and Tanypodinae). (5) Some taxa which were not present at the time of initial treatment appeared during the experiment. Chironomidae dominated the drift in all samples, and the number of genera did not decrease during the three-year treatment period. Of the 27 chironomid genera identified, only Micropsectra decreased in proportional abundance during treatment. In contrast, several genera (Corynoneura, Meropelopia, Parametriocnemus, and Tvetnia) showed little change in relative abundance. Larsia (Tanypodinae) increased in proportional abundance during the treatment period.     

山地河流浅滩生境潜流层大型无脊椎动物群落拓殖

通过包埋人工基质法研究大型无脊椎动物在山地河流潜流层中的拓殖过程。结果表明:群落个体密度在7—29 d呈"J"型增长,在29 d后骤然降低,55 d后呈波动趋势;物种丰富度在1—29 d呈增加趋势,29 d后呈波动状态;群落的生物量总体呈增加趋势。群落的物种丰富度、密度和生物量在第29、71和83天时没有显著性差异(P0.05),Shannon-Wiener多样性指数和Pielou均匀度指数在第55、71、83天没有显著性差异(P0.05),综合不同拓殖时间段物种的主成分分析,表明潜流层大型无脊椎动物群落在55 d后趋于稳定。群落优势种为摇蚊(Camptochironomus sp.)、河蚬(Corbicula fluminea)、四节蜉(Baetis sp.)、动蜉(Cinygmina sp.)、纹石蛾(Hydropsyche sp.)和扁泥甲科的一种(Psephenidae)。滤食者和收集者在整个拓殖过程中均是优势功能摄食群。群落拓殖过程是一个群落自身恢复能力和外部环境影响相互作用的过程,拓殖初期潜流层的结构是影响着无脊椎动物迁入的主要因素,中期动物的生活史特征起主要作用,稳定期之后群落可能受到各因素的综合影响。     

Effects of electroshocking on macroinvertebrate drift in three cold water streams

The effect of electroshocking and walking on the substrate on macroinvertebrate drift was evaluated in three streams located in southwestern Oregon, USA. A randomized block experimental design was used to determine treatment (electroshocking and walking, electroshocking-only, walking-only) and drift distance effects on the number, biomass, and length of macroinvertebrates drifting up to 30 m downstream. In all streams, electroshocking caused significantly (p < 0.05) greater number of macroinvertebrates to drift compared to merely walking on the substrate. The differences among treatments decreased the farther downstream the macroinvertebrates drifted. No significant difference (p > 0.05) was observed in mean biomass between electroshocking and walking on the substrate among the drift distances. The longest macroinvertebrates were collected from the electroshocking treatment at the shortest drift distance (2.5 m) in all of the streams. The length of macroinvertebrates collected between electroshocking and walking on the substrate were similar at drift distances of 10 m and greater and represented predominately the smaller, poor swimming taxa.     

Drift and benthic invertebrate responses to stepwise and abrupt increases in non-scouring flow

We conducted two experiments to assess drift and benthic invertebrate responses to stepwise and abrupt changes in non-scouring flow in gravel-bed experimental streams. Intuitively, a stepwise flow increase should allow aquatic invertebrates more time to seek refuges than would an abrupt increase. We hypothesized that abrupt flow increases would result in larger increases in taxon richness and in the number of invertebrates in the drift, and a larger decrease in benthic density than would stepwise flow increases. Two kinds of drift response to flow increases were observed in the stepwise experiment: (1) no response (e.g. Caenissp. [Ephemeroptera] and Sphaeriidae [Pelecypoda]); (2) threshold response of some aquatic (e.g. Crangonyx pseudogracilis[Amphipoda]) and semiaquatic (e.g. Ormosiasp. [Diptera]) taxa. Drift richness and drift density in both experiments declined after reaching a peak. The peak was reached almost immediately in the abrupt treatment and later in the stepwise treatment. Maximum richness of taxa and taxon composition in the drift were similar in both experiments. Despite significant increases in drift, stepwise and abrupt increases in flow did not have a significant effect on benthic density. However, relative to reference streams, the percentage of total benthic invertebrates in the drift increased 10× in the stepwise experiment and 33× in the abrupt experiment. These non-scouring increases in flow were non-trivial. Our results suggest that several high flow events of the same magnitude (i.e. 2.5–3.0 fold increases) may cause considerable losses of benthic populations to the drift. The rate of increases in flow appears to be important: abrupt increases in flow had a stronger effect on invertebrate drift than did stepwise increases.     

新薛河溪流生境底栖动物群落结构季节动态

明确底栖动物在时空尺度上的自然变化规律对有效评估和保护水生态系统十分重要。基于2012年季节调查数据,对新薛河典型生境底栖动物群落季节动态进行了研究。共鉴定底栖动物108种,隶属5门10纲74属。短脉纹石蛾、长钝直突摇蚊、拟长跗摇蚊、Neozarelia sp.为研究区域优势分类单元,相对丰度分别为25.1%、9.8%、9.0%、8.6%;各季节间优势分类单元组成差异较大,3个季度共同优势物种仅短脉纹石蛾1种。密度、物种丰度、香农指数表现为4月和12月显著高于10月;均匀度指数10月份最高。非度量多维标度排序表明,不同季节底栖动物群落结构差异显著;对照河段(D河段)群落结构季节间差异相对较小。指示物种法分离出了新薛河及各河段代表性物种41种,但B河段未分离出指示物种;双向聚类分析进一步明确了指示物种的指示属性(特有或者相对丰度最高)。     

Colonizing macroinvertebrates in the Upper Mississippi River with a comparison of basket and multiplate samplers *

SUMMARY. Colonizing aquatic macroinvertebrates were collected from two kinds of artificial substrate placed on wing dams in Pool 13 of the Upper Mississippi River in September 1978. Thirty-one taxa were collected from basket samplers containing cement spheres and twenty-one taxa from multiplate samplers constructed from tempered hardboard. Hydro-psychidae (Trichoptera), especially Cheumatopsyche sp., Potamyla flava and Hydropsyche sp., were the dominant macroinvertebrates which colonized both samplers. Basket samplers had a significantly greater macroinvertebrate density, biomass and number of taxa compared with multiplate samplers. Precision of the arithmetic mean for density, biomass and number of taxa was 19.9, 18.3 and 8.1% for basket samplers and 18.8, 18.7 and 8.5% for multiplate samplers. The number of sampling units required for a precision of 20% for macroinvertebrate density, biomass and number of taxa was 13, 11 and 2 for basket samplers and 11, 11 and 2 for multiplate samplers. Basket samplers with 7.5-cm cement spheres are recommended for use instead of multiplate samplers.     

Colonization,variability, and the use of substratum-filled trays for biomonitoring benthic communities

Sampling variability and colonization rate of introduced substrates (plastic trays filled with pebble and cobble) in two southwestern Virginia streams are described. Substrates were rapidly colonized by aquatic macroinvertebrates, but colonization rates differed between years, possibly due to annual variability in macroinvertebrate abundance. To examine the applicability of using these substrates for biomonitoring benthic communities, trays were placed at several locations in a river receiving power plant discharges. Only six samples were necessary to detect a 15%reduction in macroinvertebrate density and a 12% reduction in number of taxa at effluent sites. Benthic communities established on rock-filled trays and multiplate samplers collected from the same stations during the same period were compared. Although multiplate samplers were more variable than rock trays and were selective for different taxa, both substrate types showed significant differences in community parameters among locations. Rock trays at all sites were dominated by Cheumatopsyche sp., whereas chironomids were more abundant on multiplate samplers. The relative abundance of mayflies was reduced at the effluent site on both substrate types.     

广东横石水河流域溪流大型底栖动物漂流的昼夜节律

比较了广东横石水河流域二条相邻的3级溪流大型底栖动物的漂流种类组成及昼夜节律,其中一条溪流受广东大宝山矿外排的酸性矿山废水严重污染,水体pH值仅为3.45且重金属严重超标,而另一条为相邻的清洁溪流.结果表明：清洁溪流中大型底栖动物的数量和种类远比受酸性矿山废水污染的溪流丰富.在清洁溪流中共采获漂流底栖动物6 871头,隶属10目52类群,其中水生昆虫的数量和种类占绝对优势 (99.5%).但总漂流密度占优势的类群（相对多度超过5%）不多,主要集中在以下几种水生昆虫：七鳃假二翅蜉 (28.5%)、宜兴似动蜉 (13.8%)、短脉纹石蛾(13.2%)、白背锯形蜉（7.5%)、摇蚊科(6.5%) 和肖扁泥甲(5.0%).蜉蝣目种类和数量最多,占全部漂流底栖动物总个体数的65%,其中又以四节蜉科居多,占蜉蝣目总个体数的63%.毛翅目昆虫的数量（18%）仅次于蜉蝣目.大型底栖动物的漂流表现出明显的昼夜节律,漂流主要在夜间进行,未发现有日漂者.漂流密度高峰出现在21:00和2:00,漂流密度分别为（70.3±10.8）和（289.0±124.6） 头·100 m^-3.大多数优势种类漂流高峰出现的时段略有不同,但有些优势种类（如摇蚊科和肖扁泥甲）并未表现出明显的漂流昼夜差异.在受酸性矿山废水污染的溪流中,漂流动物只有1种嗜酸性的多足摇蚊,其漂流活动也在夜间进行,并有3个明显的漂流高峰,分别出现在19:00、0:00和4:00,最高漂流密度仅为（6.7±5.2)头·100m^-3.说明酸性矿山废水不仅降低了溪流中漂流底栖动物的物种多样性和数量,也改变了其漂流模式.     

Macroinvertebrate communities as bioindicators of water quality in conventional and organic irrigated rice fields in Guanacaste,Costa Rica

The purpose of this study was to compare how aquatic macroinvertebrates are affected by certain management practices and agrochemicals in organic and conventional rice cultivations (treatments) in northwestern of Costa Rica. We sampled macroinvertebrates in both treatments, at the water entrances (irrigation) and exits (drainage) during two cycles (8 months total) of rice field cultivation. We employed a water quality index using macroinvertebrates (BMWP/CR) as bioindicators in both management treatments. Insect family mean (P = 0.0019) and species mean richness (P = 0.0340) were greater in the organic vs. the conventional treatments as well as at the entrances rather than their exits. Both macroinvertebrates mean abundance (P = 0.0281) and insects mean abundances (P = 0.0065) were greater at the organic vs. the conventional treatments. The water quality index (BMWP/CR) was greater in the organic treatment at the entrance (124) comparing with the exit (72), and also at the conventional entrance (92) vs. the exit (66), thus showing that the management practices affected the macroinvertebrate community. The organic treatment showed the settlement of a greater number of families and species of macroinvertebrates both in general and in those considered sensitive to pollution than in the conventional treatment. This sensitive group of macroinvertebrates (Baetis sp., Fallceon sp., Leptohyphes sp., Tricorythodes sp., Farrodes sp., Phyllogomphoides sp., Hydroptila sp., Mayatrichia sp., Neotrichia sp., Oxyethira sp., Nectopsyche sp.1, Nectopsyche sp.2, Oecetis sp.) can be used as a bioindicators of water quality in these agroecosystems. On the contrary, more macroinvertebrates resistant to pollution were found in the conventional compared to the organic treatment, showing that aquatic macroinvertebrates respond to the type of management/products that are applied to the rice field.     

Composition and seasonality of benthic invertebrates,and drift in the Naro Moru River,Kenya

A survey was carried out to establish the nature and composition of the benthos along the Naro Moru, a tropical river in central Kenya using artificial substrate baskets, from November 1986 to October 1987. A clear longitudinal zonation existed for Diptera and Ephemeroptera which were the major benthic taxa. Maximum colonization took place after ten days of exposure. Seasonal variations in abundance were also observed. All taxa collected from the bottom samples were also collected in the drift samples, but the percentage composition of the benthos showed variations with that of the drift. Simulium sp. dominated the benthos whilst Baetis spp. dominated the drift. There was a positive correlation between drift rate and benthic fauna density.     

Invertebrate colonization of woody debris in coastal plain streams

We studied colonization dynamics and habitat preferences of macroinvertebrates associated with submerged woody debris in Louisiana coastal plain streams. In an in situ experiment, Branches of magnolia Magnolia grandiflora and water oak Quercus nigra were anchored over sand and gravel substrate at two sites in the Bogue Falaya River, St. Tammany Parish, Louisiana, U.S.A. Branches were removed from the units weekly for 4 weeks and biweekly for 1 month to assess colonization. Invertebrate numbers were highest at weeks three and six on magnolia over gravel habitat, although numbers of the most dominant taxa (Baetidae, Hydropsyche sp., Cernotina sp., Oecetis sp. and Hydroptilia sp.) peaked at different times during the study. Abundances of Hydropsyche sp. and Cernotina sp. were greatest on magnolia branches secured over gravel substrate, whereas Oecetis sp. abundances were greatest on oak branches secured over sand substrate.We also surveyed six streams in southeast Louisiana to examine the relative importance of wood, gravel and sand as substrate for lotic macroinvertebrates. In fall 1997 and spring 1998, we took water samples and measured in situ water quality characteristics at one site on each stream, and then collected submerged wood (surface area about 3051 cm²) and sand and gravel substrate (Surber samples totaling 2800 cm² for each substrate) to determine the density and taxonomic composition of resident macroinvertebrates. Highest numbers of invertebrates were collected in fall and spring from gravel substrate (P=0.0001). Macronychus sp. were more abundant on wood than gravel or sand (P<0.0003) and Hydropsyche sp. was more abundant on fall wood samples (P=0.0001). Analyses of water quality parameters revealed associations between Hydropsyche sp. abundance and potassium (P=0.0070) and specific conductance (P=0.0080), although both parameters exhibited interactions with substrate type (P<0.0144).     

Benthic macroinvertebrates associated with four species of macrophytes

Benthic macroinvertebrates associated with four species of macrophytes (Nymphoides peltata, Ceratophyllum demersum, Polygonum amphibium and Carex sp.) were investigated during two growing seasons (2001 and 2002) in the slow-flowing Čonakut Channel in the Kopački rit Nature Park in Croatia. A total of 31 macroinvertebrate taxa were found. C. demersum, a submerged plant with dissected leaves, supported the highest macroinvertebrate abundance, almost seven times more than N. peltata, a floating plant with undissected leaves, which harboured the lowest abundance during the research period. Chironomidae larvae (50–83%) and Oligochaeta (14–46%) were the most abundant groups recorded on all macrophyte species. Water-level fluctuation, because of its influence on the appearance and growth of aquatic vegetation, and the trophic state of water within the macrophyte stands seemed to be the main factors which affected the taxonomic composition and abundance of macroinvertebrates.     

Colonization and succession of benthic macroinvertebrates in Arcadia Lake,a South-Central USA reservoir

Colonization and succession of benthic macroinvertebrates in Arcadia Lake, an urban reservoir, were studied for four years. Physicochemical conditions including water temperature, dissolved oxygen concentrations, pH, specific conductance, and Secchi disc depth were also recorded. Colonization of the reservoir occured fairly rapidly through a sequence of three invasions. The first, and most significant, colonists were primarily facultative species already present in streams and ponds that were inundated by the impoundment. Later arrivals tended to be limnophilic species that probably came from other bodies of water. Of 30 species encountered in a pre-impoundment collection, only six were still present three years following impoundment. Thirty-three additional benthic macroinvertebrates species invaded the area following impoundment. Dominant taxa in the reservoir included Dero nivea, Limnodrilus sp., Chaoborus punctipennis, Chironomus sp., and Procladius sp. Pollutants accumulating in this urban reservoir, including metals and pesticides, and siltation probably have kept benthic populations relatively low and possibly reduced potential species diversity.     

Benthic, Drifting and Marginal Macroinvertebrate Assemblages in a Lowland River: Temporal and Spatial Variations and Size Structure

Aquatic macroinvertebrates living in anastomosing lowland rivers use different habitats and respond differently to the hydrological regime. In this paper, the structure and composition of benthic, drifting and marginal macroinvertebrate assemblages are analyzed in the lowland river Ctalamochita (Córdoba, Argentina). The assemblages were studied in an annual cycle; a comparison among the composition of benthos, drift and marginal fauna was carried out; and size structure of the assemblages was characterized. Samples were obtained from two sites: a rural and an urban site. In total 73 taxa of aquatic macroinvertebrates were collected. Benthos was characterized by Chironomidae and Oligochaeta; marginal fauna was mainly constituted by Coleoptera, Heteroptera, Decapoda, the Trichoptera Nectopsyche sp., Ephemeroptera and Odonata. Drifting assemblage was composed by macroinvertebrates from local and remote upstream benthos, and from the marginal zone. Marginal fauna diversity was higher than benthos and drift. Total biomass of the assemblages pooled together was relatively equitably among size classes. Larger size classes consisted of organisms from the marginal zone whereas the smallest ones were composed by benthic and drifting organisms. In the study area there is habitat partitioning in the lateral dimension of the river. Marginal fauna was more diverse due to the asymmetry of transport and deposit processes, which generate a heterogeneous habitat in the bankside. The relation between fine substrate and high current velocity determines an unstable habitat in the central channel, which makes colonization by benthic macroinvertebrates difficult.     

Factors affecting the distribution of stream macroinvertebrates in geothermal areas: Taupo Volcanic Zone,New Zealand

The distribution of macroinvertebrates was investigated among sites within five geothermally influenced and two non- or minimally-influenced streams in the Taupo Volcanic Zone, New Zealand, to examine the responses of communities to broad environmental gradients within and among habitats. To date, examination of geothermal stream macroinvertebrates has typically been from single habitats, and has not been examined over a regional scale. Sites within and among streams represented a range of sizes, depths, water velocities and substrate types. Sites with little or no geothermal influence typically had temperatures less than 15°C and pH between 5 and 8. Four of the geothermally influenced streams had temperatures greater than 25°C, and ranged from alkaline (pH 9.1) to highly acidic (pH 3.0). Most taxa recorded were typical inhabitants of non-geothermal streams that are tolerant to elevated temperatures, extreme pH conditions and/or high toxicant levels. Diptera, Coleoptera and Mollusca dominated geothermal sites, and Ephemeroptera, Plecoptera and Trichoptera were absent. In addition, an obligate dweller of geothermal habitats, Ephydrella thermarum, and a nonindigenous tropical gastropod, Melanoides tuberculata, were recorded. Canonical correspondence analysis implicated multiple factors in determining the distribution of invertebrates over the region. Overall, distribution was most strongly associated with temperature gradients, particularly longitudinally within streams. This distribution was likely directly related to species temperature tolerances, but also temperature effects on algal abundance and composition, its differential effects on species’ potential competitors and predators, and its effects on toxicant availability. Differences in invertebrate composition among streams were associated with major differences in pH and substrate. Increased acidity was associated with a significant decrease in invertebrate taxa richness, with acidic sites having a limited fauna dominated by dipterans (e.g., Naonella sp., Polypedilum sp.). Stability of flow and environmental conditions may enhance competitive interactions among taxa, enhancing the importance of substrate type in these systems. The presence of non-indigenous species (e.g., M. tuberculata, Poecilia reticulata), currently limited in distribution, also affected species composition. Overall, communities become less speciose, although more unusual in composition, with increased geothermal influence. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: K. Martens     

Freshwater diatom and macroinvertebrate diversity of coastal permanent ponds along a gradient of human impact in a Mediterranean eco-region

Mediterranean coastal areas are characterised by heavily transformed landscapes and an ever-increasing number of ponds are subjected to strong alterations. Although benthic diatoms and macroinvertebrates are widely used as indicators in freshwater ecosystems, little is still known about the diatom communities of lowland freshwater ponds in the Mediterranean region, and, furthermore, there are few macroinvertebrate-based methods to assess their ecological quality, especially in Italy. This article undertakes an analysis of benthic diatom and macroinvertebrate communities of permanent freshwater ponds, selected along a gradient of anthropogenic pressures, to identify community indicators (taxa and/or metrics) useful to evaluate the effect of human impacts. A series of 21 ponds were sampled along Tyrrhenian coast in central Italy. Five of these ponds, in a good conservations status and surrounded by woodland were selected as ‘reference sites’ for macroinvertebrates and epipelic diatoms. The remaining sixteen ponds were located in an agricultural landscape subject to different levels of human impact. The total number of macroinvertebrate taxa found in each pond was significantly higher in reference sites than in both the intermediate and heavily degraded ones, whereas the diatom species richness did not result in a good community variable to evaluate the pond ecological quality. The analysis revealed a substantial difference among the compositions of diatom communities between reference ponds and degraded ponds. The former were characterised by the presence of several species belonging to genera, such as Pinnularia sp., Eunotia sp., Stauroneis sp., Neidium sp., all of which were mostly absent from degraded ponds. Furthermore, the taxonomic richnesses of some macroinvetebrate groups (Odonata, Ephemeroptera, Trichoptera, Coleoptera), and taxa composition attributes of macroinvertebrate communities (total abundance, percentages of top three dominant taxa, percentages of Pleidae, Ancylidae, Hirudinea, Hydracarina) significantly correlated with variables linked with anthropogenic pressures. The results of the investigation suggested that diatoms tended more to reflect water chemistry through changes in community structure, whereas invertebrates responded to physical habitat changes primarily through changes in taxonomic richness. The methodologies developed for the analysis of freshwater benthic diatom and macroinvertebrate communities may have a considerable potential as a tool for assessing the ecological status of this type of water body, complying with the European Union Water Framework Directive 2000/60/EC. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

Environmental gradients determining the distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan

Effects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake’s status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom-layer pH. Five species of Chironomidae [Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae (Tubifex tubifex, Aulodrilus limnobius and Aulodrilus sp.) and two of Chironomidae (Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic-rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low-OMC sites, whereas Tanypus sp. (Chironomidae) preferred high-OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.