Macroinvertebrate Richness Research Articles

Testing Predictions from an Environmental Stress Model on Macroinvertebrate Diversity Across Rocky Intertidal Elevation Gradients in Mumbai, India

Intertidal organisms distributed in different zones experience strong environmental stress due to various biotic and abiotic factors. Environmental stress model (ESM) predicted that overall species richness and diversity should follow a unimodal trend along the vertical elevation gradient. In the present study, species richness and diversity of macroinvertebrates (molluscs and crustaceans) were measured on a rocky shore of Mumbai, the west coast of India. Data on species abundance were collected for two years (January 2005 to December 2006) after fixing three transects from high-to-low-shore zones based on the tidal heights. Quadratic regression analysis was applied to examine the pattern of variation in overall species richness and diversity across the stress gradient. The analysis revealed that both the variables followed unimodal trends across elevations and suggested that ESM predictions can also be applied to taxonomic groups besides different functional groups of intertidal organisms. It was also found that ESM can be useful in predicting local species richness and diversity as a function of environmental stress and helpful in providing a better understanding of distribution and dynamics of communities at local scale.

Short-Term Responses of Aquatic and Terrestrial Biodiversity to Riparian Restoration Measures Designed to Control the Invasive Arundo donax L.

Invasive species are among the top five causes of biodiversity loss worldwide. Arundo donax has progressively colonized the riparian zones of Mediterranean rivers with detrimental effects on terrestrial and aquatic biodiversity, being catalogued as one of the 100 worst invasive species. In order to control this invasive species and restore native riparian vegetation, different methods have been traditionally used, depending on the environmental, economic and social context. Here, the effect of repeated above-ground removal of A. donax on aquatic and terrestrial communities was assessed by testing two different frequencies of mowing (monthly-intensive and quarterly-extensive), combined with the plantation of native species. Specifically, it was evaluated if riparian vegetation, birds and aquatic macroinvertebrates showed significant responses throughout time and between restoration treatments based on 4-year annual biomonitoring data (2015–2018). Changes in taxonomic diversity and ecological quality indices for the different biological communities were tested using mixed-effect models (LMEs). Similarly, comparisons between restored and reference sites were also performed. LMEs were also applied to assess how riparian variables were related to bird and aquatic macroinvertebrate indices. NMDS and MGLM-Mvabund analyses were performed to detect significant post-treatment differences in taxa composition compared to the initial state and reference sites. During this short-term assessment, increases in riparian and aquatic macroinvertebrate richness and quality indices were found, as well as significant decreases in A. donax height, density and cover, without significant differences between restoration treatments. However, differential effects between extensive (positive-neutral effect) and intensive treatments (neutral-negative effect) were detected for bird richness, density and abundance. After three years of restoration actions, restored sites are still far from reference values in terms of taxa composition, species richness and ecological quality, especially for riparian vegetation and birds. Given the high cost and the great efforts required for restoration, extensive repeated mowing, together with native species plantation, are only recommended on river reaches not fully invaded by A. donax and with a high ecological interest.

The effects of road crossings on stream macro-invertebrate diversity

Although it is well known that the increasing size of the human population has a negative effect on freshwater biodiversity, the subject of whether or how the intersection of roads and streams (hereafter road crossings) influence the diversity of stream macro-invertebrates is under-researched. To fill this gap in our knowledge, we collected stream macro-invertebrates from road crossings (bridges and culverts) and compared their diversity with upstream and downstream sections. We found that road crossings had negative effects on the richness and abundance of native macro-invertebrates, as well as on the number of protected taxa. Our results showed also that alien individuals were more abundant at road crossings. These findings support the assumption that road crossings contribute to the spread of alien species. The assessment of environmental variables indicated that road crossings caused habitat modifications, and based on these it can be assumed that habitat modifications and associated phenomena (e.g. pollutants and storm events) were the major drivers of the observed patterns in biodiversity. Our results fill a knowledge gap and contribute to the deeper understanding of the effect of road crossings on freshwater biodiversity.

Recovery of an Acid Mine Drainage-Impacted Stream Treated by Steel Slag Leach Beds

The East Branch of Raccoon Creek, Ohio is highly impacted by pre-regulation coal mining and contains 10 steel slag leach beds that passively treat the low pH, and the Fe and Al-rich waters. Water chemistry, sediment chemistry, aquatic macroinvertebrate richness and diversity, habitat quality, and stream gradient were examined along the mainstem and a headwater tributary where multiple treatment systems are located. The stream gradient showed no significant relationship with sediment quality. Higher flows increased instream concentrations of Fe and the portion of suspended Fe in the water column. Macroinvertebrate richness and diversity varied from good to very poor and were negatively correlated with sediment Cu, Fe, Mn, and other water quality parameters such as specific conductivity and total dissolved solids, but were positively correlated with pH.

Does catchment geodiversity foster stream biodiversity?

ContextOne approach to maintain the resilience of biotic communities is to protect the variability of abiotic characteristics of Earth’s surface, i.e. geodiversity. In terrestrial environments, the relationship between geodiversity and biodiversity is well recognized. In streams, the abiotic properties of upstream catchments influence stream communities, but the relationships between catchment geodiversity and aquatic biodiversity have not been previously tested.ObjectivesThe aim was to compare the effects of local environmental and catchment variables on stream biodiversity. We specifically explored the usefulness of catchment geodiversity in explaining the species richness on stream macroinvertebrate, diatom and bacterial communities.MethodsWe used 3 geodiversity variables, 2 land use variables and 4 local habitat variables to examine species richness variation across 88 stream sites in western Finland. We used boosted regression trees to explore the effects of geodiversity and other variables on biodiversity.ResultsWe detected a clear effect of catchment geodiversity on species richness, although the traditional local habitat and land use variables were the strongest predictors. Especially soil-type richness appeared as an important factor for species richness. While variables related to stream size were the most important for macroinvertebrate richness and partly for bacterial richness, the importance of water chemistry and land use for diatom richness was notable.ConclusionsIn addition to traditional environmental variables, geodiversity may affect species richness variation in streams, for example through changes in water chemistry. Geodiversity information could be used as a proxy for predicting stream species richness and offers a supplementary tool for conservation efforts.

Elevation, aspect, and local environment jointly determine diatom and macroinvertebrate diversity in the Cangshan Mountain, Southwest China

Abstract Freshwater ecosystems in high-mountain regions are subject to emerging threats such as global warming and expanding human activities. Stream diatoms and macroinvertebrates form an essential component of freshwater ecosystems in high-mountain regions. Although these organisms are sensitive to environmental changes, knowledge regarding their elevational diversity patterns remains limited. Opposite aspects (e.g., north vs south; west vs east) usually receive different amounts of solar radiation and precipitation, leading to distinct in-stream characteristics such as discharge, flow regime, and water temperature. Despite the suggested strong influence of aspect on biodiversity patterns in mountains, its effect on stream diatoms and macroinvertebrates has been largely overlooked. The aims of our study were to 1) investigate whether macroinvertebrate and diatom taxon richness follows the same pattern along an elevational gradient; 2) test the effect of aspect on the elevational diversity (i.e., taxon richness and assemblage dissimilarity) patterns of macroinvertebrate and diatom assemblages; and 3) examine the relative importance of elevation, aspect, and the local environment (e.g., in-stream physicochemical variables) in shaping macroinvertebrate and diatom assemblages. We investigated macroinvertebrate and diatom assemblages in six nearly parallel streams (three streams on the east aspect and three on the west) in the Hengduan Mountains region. We found that the taxon richness of both macroinvertebrates and diatoms showed a monotonic increase with elevation (1623–2905 m a.s.l.) when aspect was not accounted for. When aspect was taken into consideration, macroinvertebrate taxon richness still showed a monotonically increasing elevational pattern on both the east and west aspects, but with significantly different model slopes, while a monotonical pattern for diatoms only remained on the west aspect. In addition, taxon richness of macroinvertebrates may also follow a potential unimodal pattern. The distance-decay relationships followed the same patterns as taxon richness, suggesting that the influence of aspect on diatom and macroinvertebrate assemblages was not negligible. Our results suggested that the diversity of both diatoms and macroinvertebrates was jointly determined by elevation, aspect and local environment. Compared to macroinvertebrates, the diatom assemblages were more strongly influenced by the local environment. To gain a better understanding of the underlying mechanisms driving elevational patterns of stream biodiversity in high-mountain regions, comparative studies that involve multiple organisms, streams, and mountains across a large elevational range are needed.

Aquatic macroinvertebrate assemblages associated with two floating macrophyte species of contrasting root systems in a tropical wetland

Aquatic macrophytes play an important role in structuring biotic communities. A comparative study of macroinvertebrate community structures associated with Salvinia auriculata Aublet and Eichhornia crassipes (Mart.) Solms was conducted in a Brazilian wetland (Sao Paulo State) during two periods. Our working hypothesis is that the aquatic macrophyte with the highest root system biomass and volume (E. crassipes) will result in the highest abundance and richness of associated macroinvertebrates. There were significant differences in the taxa richness and density of macroinvertebrates between macrophytes and sampling periods. The density of macroinvertebrates was higher in S. auriculata than in E. crassipes during both sampling periods, but there was little difference in mean taxa richness. Negative correlations between the macrophyte root biomass and volume and macroinvertebrate density were found. Insecta, Crustacea and Annelida were the most numerous groups of invertebrates sampled during the study, and Diptera (Insecta) dominated in the root systems of both macrophytes. Macroinvertebrates associated with E. crassipes roots may have undergone a vertical gradient of decreased oxygen concentration in the water, as well as of the available periphyton biomass, because of the low penetration of light in the region of the root system, which resulted in a lower density of macroinvertebrates.

The Relative Importance of Spatial Scale Variables for Explaning Macroinvertebrate Richness in Different Aquatic Ecological Function Regions

Identifying the key drivers of aquatic fauna structuring at multiple spatial scales is critical in reducing biodiversity loss. Macroinvertebrates are the most sensitive indicators of disturbance and they are used as a cost-effective tool for bioassessment at catchment and site scales. The focus of our study was to identify the key drivers from three classes of environmental variables (geophysical landscape, land use, and site habitat) that influence macroinvertebrate richness in different aquatic ecological function regions (AEFRs) of the Liaohe River Basin. We sampled macroinvertebrate assemblages, extracted geophysical and climate variables from geospatial data, and quantified physical and chemical habitats from 407 randomly distributed sites that belong to the three level-I AEFRs. We analyzed our data through multiple linear regression models by using the three classes of predicted variables alone and in combination. The models that were constructed in the first level-I AEFR explained similar amounts of macroinvertebrate richness and had the maximum ability to explain how macroinvertebrate richness distributed (denoted “explaining ability”; geophysical landscape: RGL2 ≈ 60%, land use and site habitat: RLU2 and RSH2 ≈ 50%, and combined: RCB2 ≈ 75%). The explaining abilities for the third level-I AEFR were as follows: RGL2 ≈ 11%, RLU2 ≈ 14%, RSH2 ≈ 25%, and RCB2 ≈ 38%. The explaining abilities for the 4th level-I AEFR were as follows: RGL2 ≈ 30%, RLU2 ≈ 7%, RSH2 ≈ 40%, and RCB2 ≈ 55%. We conclude that: (1) all of the combined models explained more interaction as compared with the single models; (2) the environmental variables differed among different level-I AEFRs; and, (3) variables in the site habitat scale were the most robust explainers when analyzing the relationship between environmental variables and macroinvertebrate richness and they can be recommended as the optimal candidate explainer. These results may provide cost-effective tools for distinguishing and identifying the drivers of sensitive aquatic organisms at regional scales.

The effectiveness of aquatic plants as surrogates for wider biodiversity in standing fresh waters

Abstract Freshwaters are among the most globally threatened habitats and their biodiversity is declining at an unparalleled rate. In an attempt to slow this decline, multiple approaches have been used to conserve, restore or enhance waterbodies. However, evaluating their effectiveness is time‐consuming and expensive. Identifying species or assemblages across a range of ecological conditions that can provide a surrogate for wider freshwater biodiversity is therefore of significant value for conservation management and planning. For lakes and ponds in three contrasting landscapes of Britain (lowland agricultural, eastern England; upland, north‐west England; urban, central Scotland) we examined the link between macrophyte species, macrophyte morpho‐group diversity (an indicator of structural diversity) and the richness of three widespread aquatic macroinvertebrate groups (molluscs, beetles, and odonates) using structural equation modelling. We hypothesised that increased macrophyte richness and, hence, increased vegetation structural complexity, would increase macroinvertebrate richness after accounting for local and landscape conditions. We found that macrophyte richness, via macrophyte morpho‐group diversity, was an effective surrogate for mollusc, beetle, and odonate richness in ponds after accounting for variation caused by physical variables, water chemistry, and surrounding land use. However, only mollusc richness could be predicted by macrophyte morpho‐group diversity in lakes, with no significant predicted effect on beetles or odonates. Our results indicate that macrophyte morpho‐group diversity can be viewed as a suitable surrogate of macroinvertebrate biodiversity across diverse landscapes, particularly in ponds and to a lesser extent in lakes. This has important implications for the restoration, conservation, and creation of standing water habitats and for assessing their effectiveness in addressing the decline of global freshwater biodiversity. Management actions prioritising the development of species‐rich and structurally diverse macrophyte assemblages will be likely to benefit wider freshwater biodiversity.

Effects of agricultural landscapes and land uses in highly biodiverse tropical streams of the Ecuadorian Choco

ABSTRACTThe ecosystem-level consequences of agricultural land use in Neotropical forests have not been fully studied. In areas like the Choco-Darien, conflict exists between the conservation of highly diverse ecosystems and the use of economically important production areas. Current agricultural practices involve complete deforestation, with consequent multiple effects on stream ecosystems. To address the issue of land use change in tropical rivers of Ecuador, we studied streams draining 3 different land use types in the Mashpi River drainage (Ecuadorian Choco): (1) pristine montane cloud forest, (2) organic farms that included forest patches, and (3) palmito (Bactris gasipaes) production land with extensive use of the insecticide endosulfan and the herbicide glyphosate. We sampled macroinvertebrates (quantitative and qualitative samples) and periphyton, and measured environmental variables during dry and wet seasons, and found a direct relationship between the decline of certain macroinvertebrate groups (e.g., Anacroneuria, Hyallela) and the type of land use. Furthermore, we found that species loss in streams draining organic farms was negligible. Species richness of macroinvertebrates was considerably lower in palmito monoculture farmlands than in the other 2 types of land use. Stream communities of the Mashpi drainage area have been transformed by human agricultural disturbances, and urgent changes to land management practices are necessary.

Aquatic macroinvertebrate community responses to wetland mitigation in the Greater Yellowstone Ecosystem

Abstract Wetlands are critical components of freshwater biodiversity and provide ecosystem services, but human activities have resulted in large‐scale loss of these habitats across the globe. To offset this loss, mitigation wetlands are frequently constructed, but their ability to replicate the functions of natural wetlands remains uncertain. Further, monitoring of mitigation wetlands is limited and often focuses exclusively on vegetation and physical characteristics. Wetland fauna are assumed to be present if suitable habitat restoration is achieved, but this assumption is rarely tested. We used the macroinvertebrate community as a proxy for wetland function to compare recently created mitigation wetlands, natural wetlands impacted but not destroyed by road construction activity, and unimpacted reference wetlands along a highway corridor in the Greater Yellowstone Ecosystem. Unlike most other studies of invertebrate communities in created wetlands which have occurred in warm climates, our study area has a cold temperate climate with short growing seasons. We estimated macroinvertebrate taxonomic richness and used linear models to test for effects of wetland design features (wetland age, isolation, depth, vegetation, size, and pH) on invertebrate richness. We also used non‐metric multidimensional scaling to visualise differences in community composition among wetland types and used indicator species analysis to determine which taxa were causing observed differences. Taxonomic richness of macroinvertebrates was lower in created wetlands than impacted or reference wetlands, whereas richness was similar in impacted and reference wetlands. Wetland age was positively correlated with taxonomic richness. The amount of aquatic vegetation in wetlands had the greatest influence on taxonomic richness, so that recently created wetlands with little vegetation had the simplest invertebrate communities. Community composition of invertebrates in created wetlands also differed from community composition in reference and impacted wetlands. Most notably, created wetlands lacked some passive dispersers that were common in other wetland types, although we found no relationship between taxonomic richness and wetland isolation. Overall, constructed wetlands had diminished and altered macroinvertebrate communities relative to reference and impacted wetlands, suggesting that periods in excess of 5 years may be required for wetland mitigation projects in cold temperate climates to attain full functionality.

Microbial and macroinvertebrate communities, but not leaf decomposition, change along a mining‐induced salinity gradient

Abstract Natural levels of salinity in aquatic ecosystems drive biodiversity patterns across broad spatial scales; however, less is known about changes in biotic communities and the ecosystem functions they support along anthropogenic salinisation gradients. Resource extraction often causes salinisation of freshwater ecosystems which may extirpate salinity‐sensitive macroinvertebrates and microbes and thus reduce rates of organic matter decomposition. We quantified bacterial (16S), fungal (ITS) and macroinvertebrate taxonomic richness, composition, and β‐diversity across the resulting gradient of specific conductance (annual mean: 25–1,383 μS/cm) in 24 headwater streams in the eastern U.S.A. variously influenced by surface coal mining but selected to minimise habitat and water‐quality differences other than salinity. Furthermore, we measured rates of organic matter decomposition in submersed leaf packs (Quercus alba) across these same sites. Bacterial and reach‐wide macroinvertebrate richness was reduced along the mining‐induced salinity gradient whereas fungal or leaf‐pack macroinvertebrate richness remained similar. Community composition of microbes and macroinvertebrates changed along the salinity gradient, with mining‐influenced sites becoming increasingly dissimilar to reference sites as salinity increased. Beta‐diversity was driven by taxonomic replacement rather than nestedness for microbial and macroinvertebrate communities. Organic matter decomposition rates in mining‐influenced streams were not reduced even at mean specific conductance levels 10× higher than reference sites. We attribute maintenance of decomposition rates to salinity tolerance of both fungi and macroinvertebrate shredders found in leaf packs. Our study informs theory linking anthropogenic alteration of biotic communities to rates of ecosystem functions by providing evidence that taxonomic replacement and stressor‐tolerance of specific functional groups along a mining‐induced salinity gradient can maintain certain ecosystem functions, at least within the studied salinity range. We therefore advise against generalising biodiversity–ecosystem function relationships in other salinised systems, but caution that organic matter decomposition may be altered at salinity levels above those observed in our study and that other ecosystem functions may be affected by loss of salinity‐sensitive taxa.

Does stream current modify crayfish impacts on a benthic community?

Non-native crayfish can have impacts on stream communities that are highly variable. A possible explanation for this variability is that crayfish are responding in a context-dependent manner to variation in environmental factors. Among the most critical environmental factors in streams is current velocity. Moving water defines lotic ecosystems and many benthic organisms, including crayfish, respond to its influence. To examine how current velocity affected the impacts of non-native Orconectes rusticus crayfish on benthic communities, we conducted a cage-enclosure experiment in a Wisconsin stream. We hypothesized that current velocities > 50 cm s−1 would decrease the effects that O. rusticus had on community composition (macroinvertebrate richness and numbers) and physical structure (sediment accumulation). Three cage enclosure treatments (open, closed crayfish and closed control) were grouped into eight replicate blocks divided equally among streambed regions of slow (< 50 cm s−1) and fast (> 50 cm s−1) current. Open cages allowed resident crayfish access, closed crayfish cages contained one O. rusticus, and closed controls had no crayfish. After three weeks, crayfish cages had lower macroinvertebrate abundance and richness and less sediment accumulation. Current velocity showed a positive relationship to macroinvertebrates in general, and a negative relationship to sediment build-up. The most common macroinvertebrates were hydropsychid caddisflies that responded to O. rusticus in a context-dependent manner such that cages containing crayfish had decreased hydropsychid numbers in fast current, but not in slow. Open cage treatments showed a similar pattern, suggesting that natural crayfish densities in the stream were also sufficient for lowering hydropsychid numbers in fast current. Our study demonstrates that current velocity may provide an important context for understanding the effects that O. rusticus have on benthic communities, not just in terms of what these crayfish do, but how the benthic communities respond to their presence.

Response of aquatic organism richness to physiochemical factors at different regions in Jinan City

水生生物与水环境因子是水生态系统中重要的组成部分，研究水生生物与水环境因子的响应关系对制定水生态系统修复方案具有重要意义.于2014年5、8和10月，对济南市水生态系统进行野外采样调查.共设36个采样点，采集鱼类、底栖动物、浮游动物和浮游植物四种生物，并测定了26个水环境因子.采用Spearman相关分析法、小提琴图法和冗余分析法，筛选主要的水环境因子，分析济南市水生生物丰富度和主要水环境因子的分布特征，以及两者间的相互关系.结果表明，共筛选出6个主要的水环境因子，分别为流量（Flow）、溶解氧（DO）、栖息地质量指数（QHEI）、电导率（Cond）、化学需氧量（COD）和总氮（TN）.黄河区Flow、DO、QHEI和水生生物丰富度均较高，小清河区COD、TN、Cond和水生生物丰富度最低.黄河区Cond与鱼类丰富度呈显著相关，城区TN与底栖动物丰富度呈显著相关，小清河区COD、DO和QHEI对水生生物丰富度有显著影响，徒骇马颊河区TN对水生生物丰富度有显著影响.该研究为济南市水生态修复方案的制定提供参考，也为其他城市水生态文明建设提供一种思路.;Aquatic organisms and physiochemical factors were important components in the aquatic ecosystem. It will be benefited for understanding the health condition of aquatic ecosystem and planning restoration project by investigating the relationships between aquatic organisms and physiochemical factors. In this study, 36 sampling stations were set to investigated fish, macroinvertebrate, zooplankton and phytoplankton assemblages during May, August and October in 2014 in Jinan City, whilst, 26 physiochemical variables were tested as well. Methods of Spearman analysis, violin-plots and redundancy analysis were used to select the main physiochemical factors, exhibit the distribution of biological richness and main factors at each regions, and analyze the relationship between biological richness and main factors at each region. The results showed that six physiochemical factors including Flow, dissolved oxygen (DO), qualitative habitat evaluation index (QHEI), COD, electrical conductivity (Cond) and total nitrogen (TN) were selected as the main environmental factors based on the Spearman analysis. The distribution of Flow, DO, QHEI and biological richness were higher in Yellow River regions than those in other regions, and COD, TN, Cond and biological richness were the lowest in the Xiaoqing River region. Based on the Spearman analysis, Cond had a significant correlation with fish richness in Yellow River region, and TN were significant correlated with macroinvertebrate richness in urban region. The redundancy analysis showed that TN had a significant impact on the biological richness in Tuhaimajia River region, and COD, DO and QHEI significantly affected the biological richness in Xiaoqing River region. This study could be used as reference for the management or government to design a restoration project of aquatic ecosystem in Jinan City, and provided a new way for other cities to develop the aquatic ecosystem as well.

STATUS, DISTRIBUTION AND HABITAT SPECIFICITY OF BENTHIC MACRO-INVERTEBRATES: A CASE STUDY IN FIVE TRIBUTARIES OF BUDDHIGANGA RIVER IN WESTERN NEPAL

Benthic macro-invertebrates are organisms that inhabit the bottom of substrates such as sediments, debris, logs, macrophytes and filamentous algae of streams, rivers and lakes for some span of their lifecycle. They are important part of food chain since they are source of food for different species of fishes and process organic matters. These organisms are considered vital tools to assess any environmental change caused by anthropogenic interference in the river ecosystems. In this study, we sampled macro-invertebrates from 5 different rivers across altitudinal ranges of 600- 800 m and 1500-1700 m above sea level. We observed that the macro-invertebrate diversity varied substantially across altitudinal ranges. The diversity of macro-invertebrates was higher in lower altitudinal range, where 11 families were found, more than the higher altitudinal range. Some rare and dominant families were also identified in our study. We also examined the substrate specificity of macro-invertebrates. Results revealed that Ephemeroptera,Tricoptera, Coleoptera, Diptera and Odonata were found in all seven substrates namely bedrock, boulder, cobble, stone, pebble, gravel and sand. The richness and abundance of macro-invertebrates were documented in cobble, stone and pebble substrates. Similarly we also investigated the ecological river quality class of rivers using Ganga River System Biotic Score-Average Score per Taxon (GRS-BioS/ASPT) system which indicated good status. The outcomes of this study serve as a baseline data since no prior research has been done in these rivers.

Macroinvertebrate communities characteristics and their responses to fluvial geomorphological feature of typical debris flow gullies in the Xiaojiang River Basin, Yunnan Province

云南小江流域为典型干热河谷区，该区域干热少雨，流域内泥石流沟众多，生态环境十分脆弱.2017年4月和9月对小江流域的吊嘎河、蒋家沟、蓝泥坪沟、清水沟、陶家小河5条泥石流沟及小江干流开展了系统调查，旨在摸清5条泥石流沟及小江干流河流地貌、水环境及底栖动物群落现状，分析不同河床结构发育程度的泥石流沟间的底栖动物群落差异，揭示底栖动物对反映河床结构发育程度的河流地貌特征参数凹凸度的响应关系.调查期间于5条泥石流沟及小江干流中共采集到底栖动物70种，隶属于4门6纲38科69属，其中环节动物6种，软体动物2种，节肢动物61种，扁形动物1种.从种类类群来看，5条泥石流沟及小江干流的底栖动物物种数、密度、生物量上均以节肢动物占绝对优势，分别占总量的78.0%~92.5%、98.7%~100%、65.0%~100%.从功能摄食类群上来看，5条泥石流沟及小江干流底栖动物密度上均以直接收集者为主，占总量的74.3%~96.3%.回归分析表明，5条泥石流沟中底栖动物物种数、密度及生物量均与河流地貌特征参数凹凸度呈正相关关系，由此可见，发育良好的河床结构在维持河流地貌稳定和改善河流生态方面起着举足轻重的作用.本研究结果可为小江流域山区河流泥石流沟河床结构重建及生态修复提供科学依据.;The Xiaojiang River Basin is a typical dry-hot valley area, characterized by high temperatures, little rain and many debris flow gullies, where ecological environment is very fragile. In April and September of 2017, field surveys were conducted in the five debris flow gullies (i.e., the Diaoga Creek, the Jiangjia Creek, the Lanniping Creek, the Qingshui Creek, and the Taojiaxiaohe Creek) and the Xiaojiang River. The purpose of this study is to understand fluvial geomorphological feature, water environment, and macroinvertebrate communities in the five debris flow gullies and the Xiaojiang River, to analyze the differences in macroinvertebrate communities among debris flow gullies with different riverbed structures, and to reveal the responses of macroinvertebrates to the fluvial geomorphological parameter (degree of concavity-convexity) reflecting the development degree of riverbed structure. A total of 70 taxa of macroinvertebrates were identified, belonging to 4 phyla, 6 classes, 38 families and 69 genera. With regard to the taxonomic groups, arthropods were dominant in the species richness, density, and biomass of macroinvertebrates in the five debris flow gullies and the Xiaojiang River, accounting for 78.0%-92.5%, 98.7%-100.0% and 65.0%-100.0% of the total richness, densities, and biomass, respectively. With regard to the functional feeding groups, collector-gatherers were all dominated in the five debris flow gullies and the Xiaojiang River, accounting for 74.3%-96.3% of the total densities. Regression analyses showed that the species number, density, and biomass of macroinvertebrates were all positively correlated with the fluvial geomorphological parameter (degree of concavity-convexity) of the five debris flow gullies. The present study indicated that the well-developed riverbed structure plays an important role in maintaining the stability of the fluvial geomorphology and ecological quality. The results of this study can provide scientific basis for riverbed structure reconstruction and ecological restoration of debris flow gullies in mountain regions of the Xiaojiang River Basin.

Diversity Assessment of Benthic Marine Macroinvertebrates Using Artificial Substrates

Diversity Assessment of Benthic Marine Macroinvertebrates Using Artificial Substrates

Responses of macroinvertebrate assemblages to environmental variations in the river-oxbow lake system of the Zoige wetland (Bai River, Qinghai-Tibet Plateau)

The biodiversity value of river-oxbow lake systems in high plateau peatland has been little recognized, and there are many gaps in our understanding of their ecology. In this study, we investigated the river-oxbow lake system of the Bai River basin, the main tributary of the Yellow River Source in the Zoige wetland from 2015 to 2016, in attempt to show how the environmental variations, especially hydrological connectivity and macrophyte biomass in the river-oxbow lake system influenced macroinvertebrates. Habitat patches were investigated in 11 river cross-sections and 18 oxbow lakes in the Bai River basin. Through hierarchical clustering and non-metric multidimensional scaling, four main types of habitats were identified in the river-oxbow lake system in the plateau: sand-bed river, cobble-bed river, sparse-macrophyte oxbow lake, and luxuriant-macrophyte oxbow lake. The luxuriant-macrophyte oxbows were characterized by high dissolved oxygen concentrations, alkalinity, and higher macroinvertebrate richness, density, biomass, and the Improved Shannon-Wiener Index in comparison to the other habitat types. Additionally, influential patterns of environmental variables on macroinvertebrates were analyzed using redundancy analysis. Lasso regression models were established to describe how macroinvertebrate density responded to macrophyte biomass and other variables, and how macrophyte biomass responded to hydrological connectivity and oxbow size. It was revealed that reduced hydrological connectivity and reduced oxbow size played important roles in increasing the biomass of submerged macrophyte, and dense macrophyte was directly responsible for the high biodiversity of macroinvertebrates. Different from the commonly believed unimodal influential pattern that medium hydrological connectivity supports the highest biodiversity in oxbow lakes reported in previous studies, macroinvertebrates in the high plateau river-oxbow lake systems benefited from low connectivity and reduced size. Oxbow lakes, especially those covered with luxuriant macrophytes, diversified the macroinvertebrate assemblages and enhanced primary consumer biomass at the regional scale.

Testing the relative importance of intertidal seaweeds as ecosystem engineers across tidal heights

The persistence of seaweeds as community-structuring organisms is critical for the maintenance of many ecosystem functions on rocky intertidal shores. We measured the relative importance of seaweeds in structuring the abundance, richness, and distribution of macroinvertebrates at three tidal levels on a rocky shore. Through manipulative experiments, we characterized temperature, irradiance, and desiccation underneath seaweed canopy plots made up of either Silvetia compressa or Stephanocystis dioica, assembled at three biomasses. We assessed differences in the abundance, richness, and the distribution of macroinvertebrates underneath the canopy as a function of seaweed species and biomass and evaluated differences due to the tidal height of the installed experimental seaweeds. We found that manipulated seaweed biomass significantly affected the community structure of associated macroinvertebrates at all tidal levels, especially at higher biomass treatments. Although contrary to other studies, we found no effect on richness underneath the canopies at any tidal height. Our results show that intertidal seaweeds provide protection from water loss, heat, and irradiance when compared to manipulative controls with no canopy cover. We also found that the relative importance of the experimental seaweed canopies in their ability to mitigate stressful abiotic conditions increased with prolonged emersion periods, such as at higher levels in the intertidal zone. At the higher tidal level tested, a greater abundance of macroinvertebrates was associated with the experimental canopies in comparison to the manipulation-control plots and the natural substrate. These results emphasize the role of intertidal seaweeds as bioengineers and highlight the importance of preserving and restoring high densities of leathery seaweeds on degraded shores in order to preserve the dynamics of the intertidal ecosystem overall.

Life in the slow drain: Landscape structure affects farm ditch water quality

Agrichemical contamination is a major threat to aquatic ecosystems in farmland. There is a need to better understand the influence of the surrounding landscape on farm wetlands to recommend land management options that minimize water quality impacts from agricultural practices. We tested hypothesized relationships between landscape structure and multiple water quality measures in farm drainage ditches in a multi-landscape study in Eastern Ontario, Canada. We measured physicochemical water quality (levels of atrazine, glyphosate, neonicotinoid insecticides, inorganic nitrogen, and dissolved oxygen), and biological water quality indicators (aquatic macroinvertebrate richness, leaf litter decomposition, and Ceriodaphnia dubia population responses) in 27 farm ditches, and measured the amounts of forest cover and high-intensity crop cover (landscape composition), and field edge cover (landscape configuration) in 1-km radius landscapes surrounding each ditch sampling site. We used confirmatory path analysis to simultaneously model the direct and indirect relationships between the landscape predictors and water quality variables. Landscape composition measures were the strongest predictors of water quality: pesticides decreased as surrounding forest cover increased, and nitrogen increased with increasing amounts of high-intensity crop cover. Crop cover was also indirectly negatively related to macroinvertebrate richness via its effects on nitrogen and dissolved oxygen. We found no effects of landscape configuration on agrichemical levels, but there was some support for a positive relationship between macroinvertebrate richness and field edge cover. Our results indicate that aquatic macroinvertebrate richness is strongly impacted by fertilizer use in our region, and that macroinvertebrate richness is a more sensitive biotic indicator of farmland water quality than leaf litter decomposition or C. dubia responses. We conclude that, in our region, landscape management to improve farmland water quality should focus primarily on landscape composition. Such management should aim to increase amounts of non-crop cover such as forest, and reduce amounts of crop cover with high agrichemical inputs.