Abundance Of Benthic Macroinvertebrates Research Articles

Impacts of wastewater treatment plants on benthic macroinvertebrate communities in summer and winter

Treated effluent from municipal wastewater treatment plants (WWTPs) is a major source of contamination that can impact population size, community structure, and biodiversity of aquatic organisms. However, because the majority of field research occurs during warmer periods of the year, the impacts of wastewater effluent on aquatic communities during winter has largely been neglected. In this study, we assessed the impacts of wastewater effluent on aquatic benthic macroinvertebrate (benthos) communities along the effluent gradients of two WWTPs discharging into Hamilton Harbour, Canada, during summer and winter using artificial substrates incubated for 8 weeks. At the larger of the two plants, benthic macroinvertebrate abundance was higher and diversity was lower at sites downstream of the outfall compared to upstream sites in both seasons. Whereas at the smaller plant, the opposite was observed, abundance increased and diversity decreased with distance from the outfall in both seasons. While the impacts of wastewater on benthic communities were largely similar between seasons, we did detect several general seasonal trends – family diversity of macroinvertebrates was lower during winter at both WWTPs and total abundance was also lower during winter, but only significantly so at the smaller WWTP. Further, benthic macroinvertebrate community composition differed significantly along the effluent gradients, with sites closest and farthest from the outfall being the most dissimilar. Our contrasting results between the WWTPs demonstrate that plants, with different treatment capabilities and effluent-receiving environments (industrial/urban versus wetland), can dictate how wastewater effluent impacts benthic macroinvertebrate communities.

Effects of littoral zone utilization on benthic macroinvertebrate community structure: A case study of Lake Hongze

湖滨带是湖泊与陆地生态系统间非常重要的生态过渡带，能够保障周围生态系统结构的完整以及功能的正常发挥.随着湖滨带被持续开发与利用，人为干扰对湖滨带的影响逐渐增强.大型底栖动物是淡水生态系统的重要生物类群之一，也是物质循环和能量流动的主要环节，起着承上启下的关键作用.为了解湖滨带开发利用对大型底栖动物群落结构的影响，2020年8月对洪泽湖湖滨带49个样点的大型底栖动物进行调查.共采集到大型底栖动物49种，隶属3门7纲17目26科44属，各样点大型底栖动物的密度差别较大，介于6.67~1386.67 ind./m²之间，整体上呈现西北高，东南低的趋势.相似性分析结果表明，河口型湖滨带和大堤型湖滨带与其他类型湖滨带差异显著，而围网型、圈圩型和光滩型3种湖滨带类型之间的大型底栖动物群落差异均不显著.相似性百分比分析结果表明，腹足纲的环棱螺属是造成不同湖滨带类型差异的主要物种.典范对应分析结果表明，悬浮物（SS）、溶解态总氮、pH、透明度（SD）、浊度、水生植物盖度和扰动指数对大型底栖动物群落有显著影响.考虑不同湖滨带宽度的开发利用情况，发现湖滨带开发利用200 m范围内，物种-环境解释率最高，说明200 m湖滨带范围内的开发利用情况对大型底栖动物的影响最大，对湖滨带200 m范围内的开发利用应该加强管控.结构方程模型表明湖滨带开发利用主要通过影响水生植物盖度、总氮、硝态氮、叶绿素a、SS、SD等进而影响大型底栖动物，且围网也会直接影响大型底栖动物群落结构.;Littoral zone is of great importance for lake and terrestrial ecosystems, which can ensure the surrounding ecosystem structure integrity and normal functional performance. With the continuous development and utilization, the impact of human disturbance on the littoral zone is gradually increasing. Benthic macroinvertebrates are important components of freshwater ecosystems. It is the main link between nutrient cycling, and energy flow and plays a key role in connecting the food web. In order to understand the impact of the littoral zone utilization on benthic macroinvertebrate community structure, a field survey was conducted at 49 sample sites in the littoral zone of Lake Hongze in August 2020. A total of 49 species were collected, belonging to 3 phyla, 7 classes, 17 orders, 26 families and 44 genera. The abundance of benthic macroinvertebrates at each site varied greatly, ranging from 6.67 to 1386.67 ind./m². Generally speaking, the abundances was higher along the northwestern coastline, but lower along the southeastern shoreline. The results of similarity analysis showed that there were significant differences among estuarine littoral zone, levee littoral zone and other types of the littoral zone, but there were no significant differences in benthic macroinvertebrate communities among purse seine type, circle polder type and light beach type. The results of similarity percentage analysis showed that Bellamya spp. is the main species causing the discrepancy among different littoral zone types. Canonical correspondence analysis showed that suspended solid (SS), total dissolved nitrogen (TDN), pH, transparency (SD), turbidity, aquatic plant coverage and Em-5year had significant impacts on the benthic macroinvertebrate communities. When the width of the littoral zone was 200 m, the variation in the species-environment relationships was the highest, indicating that the benthic macroinvertebrates within the 200 m littoral zone of Lake Hongze were the most affected. The utilization within 200 m littoral zones should be controlled and monitored. The structural equation model shows that the littoral zone utilization mainly indirectly affects benthic macroinvertebrates by affecting aquatic plant coverage, total nitrogen, nitrate nitrogen, chlorophyll-a, SS and SD, and the purse seine will also directly affect the community structure of benthic macroinvertebrates.

Disease Outbreak in a Keystone Grazer Population Brings Hope to the Recovery of Macroalgal Forests in a Barren Dominated Island

Macroalgal forests play a key role in shallow temperate rocky reefs worldwide, supporting communities with high productivity and providing several ecosystem services. Sea urchin grazing has been increasingly influencing spatial and temporal variation in algae distributions and it has become the main cause for the loss of these habitats in many coastal areas, causing a phase shift from macroalgae habitats to barren grounds. The low productive barrens often establish as alternative stable states and only a major reduction in sea urchin density can trigger the recovery of macroalgal forests. The present study aims to assess if the 2018 disease outbreak, responsible for a strong reduction in the sea urchinDiadema africanumdensities in Madeira Island, was able to trigger a reverse shift from barren grounds into macroalgae-dominated state. By assessing the diversity and abundance of benthic sessile organisms, macroinvertebrates and fishes before, during and after that particular mass mortality event, we evaluate changes in benthic assemblages and relate them to variations in grazer and herbivore densities. Our results revealed a clear shift from barren state to a macroalgae habitat, with barrens characterized by bare substrate, sessile invertebrate and Crustose Coralline Algae (CCA) disappearing after the mortality event. Overall variations in benthic assemblages was best explained by four taxa (among grazers and herbivores species). However, it was the 2018 demise ofD. africanumand its density reduction that most contributed to the reverse shift from a long stable barren state to a richer benthic assemblage with higher abundance of macroalgae. Despite this recent increase in macroalgae dominated habitats, their stability and persistence in Madeira Island is fragile, since it was triggered by an unpredictable disease outbreak and depends on howD. africanumpopulations will recover. With no control mechanisms, local urchin populations can easily reach the tipping point needed to promote a new shift into barren states. New conservation measures and active restoration are likely required to maintain and promote the local stability of macroalgal forests.

Rice paddy irrigation seasonally impacts stream benthic macroinvertebrate diversity at the catchment level

AbstractAgriculture is one of the most critical anthropogenic disturbances to freshwater ecosystems globally. In monsoon Asia, rice paddies provide habitats for aquatic species, but how their associated irrigation systems can affect downstream ecosystems is poorly understood. Here, we used structural equation modeling (SEM) to estimate seasonal variations in benthic macroinvertebrate diversity and environments and quantified indirect effects of land use, especially of rice paddy areas, on benthic macroinvertebrate diversity through local environmental alteration. Our study site was the Yasu River tributary of Lake Biwa, Japan, and we performed our investigation during both irrigation and nonirrigation periods, representing different seasons. Seasonal variations in physical and chemical variables and diversity were observed. Seasonal particulate phosphorus concentrations to a large extent determined the abundance and community composition of benthic macroinvertebrates. SEM revealed that the proportions of forest, urban, and rice paddy areas in the catchment had significant indirect effects on biodiversity indices of local benthic macroinvertebrate communities. The proportion of forest area had robust negative effects on water temperature, but the overall indirect effects on the macroinvertebrate diversity contrasted between the two seasonal periods. The proportion of rice paddy area had a strongly negative indirect effect on the diversity through increased particulate phosphorous loading during the irrigation period, while the proportion of urban area had a significantly negative indirect effect during the nonirrigation period only. The seasonal negative impacts of rice paddy irrigation on benthic macroinvertebrate communities were possibly due to siltation arising from rice paddy soils. Our results have implications for environmental restoration and biodiversity conservation in catchment management.

An Overview of DNA-Based Applications for the Assessment of Benthic Macroinvertebrates Biodiversity in Mediterranean Aquatic Ecosystems

The loss of aquatic biodiversity is increasing at a rapid rate globally. There is a worldwide effort to protect, preserve and restore aquatic ecosystems. For efficient biodiversity monitoring and reliable management tools, comprehensive biodiversity data are required. The abundance and species diversity of benthic macroinvertebrates are commonly used as indicators of the aquatic ecosystem condition. Currently, macroinvertebrate species biodiversity assessment is based on morpho-taxonomy, which could be enhanced by recent advances in DNA-based tools for species identification. In particular, DNA metabarcoding has the potential to identify simultaneously many different taxa in a pool of species and to improve aquatic biomonitoring significantly, especially for indicator species. This review is focused on the current state of DNA-based aquatic biomonitoring using benthic macroinvertebrates in the Mediterranean region.

Macroinvertebrate Recovery to Varying Hydropeaking Frequency: A Small Hydropower Plant Experiment

As the demand for hydroelectricity progresses worldwide, small hydropower operators are increasingly examining the feasibility of using existing infrastructure (e.g., settling basins) in run-of-the-river schemes for intermittent power production. Such flexible production causes short-term discharge fluctuations (hydropeaking) in downstream reaches with potential adverse effects for the sensitive fauna and flora in alpine streams. In an experimental field study on a previously unregulated section of the upper Rhone River (Switzerland), we measured density and composition of macroinvertebrate drift in two habitats (riffle, pool) following a 15-minute hydropeaking wave. The experimental hydropeaking was replicated five times over 14 days with decreasing recovery times between peaks (8, 3, 2 days, and 24 h), and drift measurements were compared with kick samples for the benthic community. Results from the kick sampling showed that benthic macroinvertebrate abundance and composition did not significantly change between the experimental peaks. There were habitat specific reactions in macroinvertebrate drift to hydropeaking, with the pool experiencing more pronounced drift abundances than the riffle. Overall, drift abundance was not significantly correlated with recovery time, but results indicate taxa-specific differences. This research advocates for the importance of completing more in-situ field experiments in order to better understand the ecological impact of flexible power production in small hydropower plants.

Revealing the influence of hyporheic water exchange on the composition and abundance of bottom-dwelling macroinvertebrates in a temperate lowland river

We studied distributions and abundances of macroinvertebrates in relation to hyporheic water exchange (HWE) patterns of the upper Biebrza − a small, lowland, low dynamic European river located in Northeast Poland. On a 6-km stretch of the river; we determined the variability of water exchange in the hyporheic zone by using direct field measurements of the pressure gradient to determine groundwater–surface water interactions. We identified locations with upwelling and downwelling fluxes of HWE as well as ambiguous hydraulic contact between groundwater and surface water along the river. In these locations, we sampled bottom-dwelling macroinvertebrates. In total, 627 individuals of benthic macroinvertebrates of 34 taxa were identified. We revealed that bottom-dwelling macroinvertebrate fauna is more abundant and diverse in river stretches where water from the river infiltrates the hyporheic zone. Results also show higher taxonomic richness and abundances of benthic macroinvertebrates in stretches with diagnosed infiltrating conditions (downwelling flux in a hyporheic zone) compared to in stretches where the river drained groundwater (upwelling flux in a hyporheic zone), but the recorded differences were not statistically significant.

Interactive effects of bitterling fish and mussel on the community structures of plankton and benthic macroinvertebrates

放养河蚌，提高水体透明度以促进沉水植物生长，是湖泊生态修复中的常用手段之一.而小型杂食性鱼类鳑鲏依赖河蚌繁殖，河蚌放养可能会促进鳑鲏种群的发展；而鳑鲏与河蚌交互作用对水生态系统的影响仍研究较少.于2018年11—12月通过原位受控实验，设置对照组、河蚌组、鳑鲏组和河蚌+鳑鲏组，研究了鳑鲏（大鳍鱊Acheilognathus macropterus）与河蚌（背角无齿蚌Sinanodonta woodiana）对水质、浮游生物和底栖生物的影响.结果表明：鳑鲏显著增加了上覆水总氮、总磷、悬浮质和叶绿素a（Chl.a）浓度；但并未显著影响无机悬浮质的浓度，说明鳑鲏对沉积物的扰动作用较弱.此外，鳑鲏显著增加了浮游植物生物量和蓝藻的比例.浮游动物总生物量并未受鳑鲏的影响，但显著增加了浮游动物的丰度，其中以轮虫为主.鳑鲏组的底栖动物总丰度（主要为水丝蚓）显著高于对照组，说明鳑鲏对水丝蚓的摄食压力较低.鳑鲏与河蚌交互作用对总磷、Chl.a、浮游植物和浮游动物丰度具有显著影响：具体表现为河蚌虽然抵消了部分鳑鲏对水质（如氮、磷和悬浮质浓度，以及Chl.a浓度和浮游植物生物量等）的负面影响，但其对浮游动物和水丝蚓生物量的影响不显著.在湖泊生态修复和管理中，需要关注和重视鳑鲏等此类小型杂食性鱼类对水生态系统可能产生的负面影响，通过物理（网簖等）或生物（放养肉食性鱼类）等方式将其控制在较低密度水平，从而降低这些鱼类对水质、浮游生物和底栖生物群落可能产生的负面影响，维持生态修复效果的长效与稳定运行.;In restoration of shallow eutrophic lakes based on recovery of submerged macrophytes, stocking of the filter-feeding mussels has been commonly used for improving water clarity, thereby enhancing the growth of submerged macrophytes. However, the small omnivorous bitterling fish has to rely on mussels for breeding. Thus, the increased abundance of mussels may enhance the population development of bitterling. Nevertheless, the effects of bitterling (Acheilognathus macropterus) and their host mussels (Sinanodonta woodiana) on the aquatic ecosystems are, so far, not well-studied. We conducted a mesocosm experiment to study the effects of bitterling, mussels, and their interactions on water quality and the community structures of phytoplankton, zooplankton and benthic macroinvertebrates, respectively. Our results showed that bitterling did not substantially affect the concentration of inorganic suspended solids (ISS) indicating weak effects on sediment resuspension. However, the concentrations of total nitrogen and total phosphorus were significantly enhanced by bitterling. Consequently, both the abundance and biomass of phytoplankton were enhanced in the bitterling-only mesocosms, and cyanobacteria dominated the phytoplankton community at the end of the experiment. However, rotifers dominated the zooplankton community leading to a higher abundance of zooplankton in the bitterling-only treatment, while the total biomass of zooplankton did not differ significantly between the control and bitterling-only treatments. Moreover, bitterling significantly increased the total abundance of benthic macroinvertebrates compared with the controls, while the biomass of macroinvertebrates was not pronouncedly affected. The presence of mussels significantly eliminated the negative effects induced by bitterling, such as reducing the concentrations of nutrients, suspended solids and chlorophyll-a and phytoplankton biomass. However, the biomass of zooplankton and benthic macroinvertebrates were not substantially affected by the presence of mussels. Our results suggest that bitterling alone can induce significantly negative effects on water quality though mussels can eliminate part of these impacts under our experimental bitterling-to-mussel biomass ratio. Therefore, in the restoration and management of shallow lakes, more attention should be paid on the effects of small omnivorous fish, like bitterling, on aquatic ecosystems. The biomass of these small omnivores should be controlled at a relatively low level by physical (e.g., trap net) or biological (e.g., stocking of effective piscivorous fish) methods to minimize the negative effects of the fish on lake ecosystems.

Application of Ecological Indices using Macroinvertebrate Assemblages in Relation to Aquaculture Activities in Rawang Sub-basin, Selangor River, Malaysia

This study aimed to evaluate benthic macroinvertebrates assemblages using the application of ecological indices in the Rawang sub-basin of the Selangor River with reference to determining the impacts of aquaculture practices on benthic macroinvertebrates. In total, seven sampling sites were selected, namely Guntong (SR1), Guntong’s tributaries (SR2, control site), Kuang (SR3 and SR7), Gong (SR4), Buaya (SR5) and Serendah (SR6) Rivers. Sites were selected using a random sampling technique and the accessibility and proximity to aquaculture farms. Macroinvertebrates were sampled from April 2019 to March 2020 using an aquatic kick net, a hand spade, and a D-frame dip net. Water samples were also taken. Twenty-seven families belonging to the Annelida, Mollusca and Athropoda phyla were identified using taxonomic keys. Tubificidae was found to be the most dominant family (36.79%) followed by Chironomidae (28.84%). The highest number of individuals from family Tubificidae was recorded in Gong River, where effluent was discharged from an aquaculture farm. The total abundance of benthic macroinvertebrates increased with increased proximity to the aquaculture farm. Based on Biological Monitoring Working Party score value, the water quality of sampling sites in close proximity to the aquaculture farm was polluted as compared to the control location. Family Biotic Index score showed that all sites were substantially polluted with organic pollution, with the control site being much less polluted. In conclusion, benthic macroinvertebrates assemblage was affected by effluent originating from aquaculture farm outlets. It is therefore necessary to conduct aquaculture farming using methods that are deemed to be environmentally friendly.

Restoration of rapids habitat in a Great Lakes connecting channel, the St. Marys River, Michigan

Aquatic habitat has been extensively altered throughout the Laurentian Great Lakes to increase navigation connectivity. In particular, the St. Marys River, a Great Lakes connecting channel, lost >50% of its historic rapids habitat over the past century. In 2016, the natural flow was restored to the Little Rapids area of the St. Marys River. The goal of our study was to evaluate physical and ecological responses to the restoration of the Little Rapids area. Extensive habitat and biological data were collected prior to restoration (2013 and 2014), and after restoration (2017 and 2018). Measured parameters included total suspended solids, current velocity, benthic macroinvertebrates, and larval, juvenile, and adult fishes. Total suspended solids stayed low (<4 mg/L) following restoration, with the exception of a single construction‐related event. Pre‐restoration data indicated that all measured velocities were below the target flow rate of 0.24 m/s, whereas 70% of the measured habitat was above the target flow post‐restoration. Abundance and richness of benthic macroinvertebrates were reduced following restoration (>90% reduction). We observed a 45% increase in richness of larval fish 2 years after restoration and a 131% increase in catch per unit effort. For adult fishes, the proportion of individuals with a preference for fast‐moving waters increased from 1.5 to 45% in the restored area, and from 7 to 15% upstream of the restored area; a similar response was observed for lithophilic spawners. The physical and biological conditions of the Little Rapids improved and resembled conditions typical of rapids habitat extent in other areas of the river and other systems.

Variability in benthic invertebrate community structure near warm water effluents of a power plant in the southern Caspian Sea

Anthropogenic changes to the temperature regime of a water body, including but not limited to climate change and thermal pollution, may influence the community structure of species living therein. Among these, benthic communities, due to their limited movement and long life span, are one of the best biological indicators to reflect the impact of environmental stressors. In this regard, the thermal pollution of Pare-Sar power plant in the southern Caspian Sea was used as a natural laboratory to assess the effects of warming on macrobenthic communities’ biomass, abundance, richness, and structure throughout the year. Water temperature near the effluents of the power plant was on average 1.29 °C higher than the control sites. We observed that warming led to an increase in the abundance and species richness of benthic macroinvertebrates. However, benthos biomass was significantly lower in the impact site rather than the control sites, probably due to the increased proportion of small-bodied taxa and decreased growth rate of biomass determinant taxa. Therefore, our findings may be an indication of potential benthic community response to thermal pollution and may provide a baseline for future projections under global climate change scenarios.

How Does Mining Salinisation Gradient Affect the Structure and Functioning of Macroinvertebrate Communities?

Elevated salinity creates degrading conditions for the development of aquatic biota in different regions of the world. There is a need for research on freshwater salinisation in order to understand how this stressor alters ecosystem function and to predict changes in biodiversity globally. Such data are missing from Central Europe, and therefore, the presented study was performed in inland anthropogenic ponds with different salinity levels located in the second largest European hard coal basin. The researcher indicated a positive correlation between water salinity and the biomass and density of macrozoobenthos as well as the percentage of shredders and the abundance of alien species, whereas there was a decrease in taxa diversity and richness and the abundance of filtering and gathering collectors and predators along with increasing salinity. The survey showed that a high level of nutrients and organic matter were also significantly correlated with the distribution of the macroinvertebrate taxa and functional feeding groups. The conducted research confirmed that mining salinisation acts as a strong filter that shapes the biodiversity because it affects the composition, abundance, biomass and functional traits of benthic macroinvertebrates and significantly contributes to the invasion of alien species.

Seasonal changes in the abundance of benthic macroinvertebrates & physico-chemical condition of Moussa Stream Bida, Nigeria

Seasonal changes in the abundance of benthic macroinvertebrates and physico-chemical condition of Moussa Stream, Bida Nigeria, were studied monthly from January to August 2017. Macroinvertebrates were sampled using modified kick sampling techniques. Three different sampling stations were selected along the course of the Stream. The results from the stream showed that water temperature (24.9-27.50C), Depth (14.7-45.8cm), Flow velocity (0.14-0.23m/s), Biochemical oxygen demand (2.0-7.0mg/L), pH (6.33-8.6), Conductivity (20-63μ/cm), Alkalinity (8-30mg/L), Turbidity (61-285NTU), Nitrate (0.87-3.85mg/L) and Phosphate (0.31-1.01mg/L) were within the maximum permissible limit (WHO, SON) except Dissolved oxygen (3.1-10mg/L). Most of the parameters investigated with the exception of depth and flow velocity showed no significant difference (p>0.05) among all the sampling stations. Temperature, depth and flow velocity showed no significant differences with season. pH, DO, BOD5, Turbidity, Conductivity, Alkalinity, Nitrate, and Phosphate were significantly higher during wet season. A total of 471 individuals from 30 species and 20 families of invertebrates were recorded. The overall macroinvertebrates recorded from station 1, 2 and 3 were 166(35.24%), 149(31.63%) and 156(33.12%). Overall, there was significant difference (P<0.05) in number of individuals among the sampling stations. The abundance according to the Orders revealed that Coleopterans, Odonata and Hemipterans were the most common groups encountered. Ephemeroptera Diptera, Mollusca and Oligochaeta were sparingly found in all stations. The percentage and total number of individuals of macroinvertebrates recorded during the study period shows 67.09% (316 individuals) in dry season and the remaining 32.90% (155 individuals) were recorded in rainy season. CCA result correlated positively between species abundances and measured environmental variables. Low density of pollution sensitive macro invertebrates groups and the deteriorating water quality were implications of pollution stress caused by anthropogenic activities.
 Key words: seasonal changes, macroinvertebrates, stream, Bida.

Spatial and temporal variations in the species composition and abundance of benthic macroinvertebrates along the coast of the Eastern Black Sea

ABSTRACT The species composition and abundance of benthic macroinvertebrates in the Eastern Black Sea were determined seasonally, between May 2013 and February 2014. Sediment was collected using a Van Veen grab, at different depths: 5–15 m, 15–25 m, 25–35 m and >35 m. A total of 320 hauls were undertaken at 80 stations, and 90 species were identified, from seven phyla and 47 families. Overall, Mollusca was the most diverse phylum, with 32 species, followed by Annelida (32) and Arthropoda (13). The most abundant species was Chamelea gallina, which accounted for 37% of the total number of individuals, followed by Gouldia minima (25%) and Pitar rudis (10%). Based on seasonal variations, 62 species were identified in winter, 59 in summer, 54 in spring and 46 in autumn. The highest abundance was recorded in summer, representing 37.8% of the total abundance, followed by spring (25.2%). The species with the highest abundance in all four seasons was C. gallina followed by G. minima. Also, C. gallina followed by G. minima was the most abundant species in Samsun, Ordu, Giresun and Trabzon, whereas in Rize and Artvin, the most abundant species was G. minima followed by C. gallina. The results of this study should provide baseline data for future monitoring, to understand the consequences of natural or anthropogenic disturbance on the species composition and abundance pattern of the benthic macroinvertebrate community along the coast of the Eastern Black Sea.

Ecological consequences of shoreline armoring on littoral fish and benthic macroinvertebrate communities in an Eastern Ontario lake

Shoreline erosion in lakes is a pressing issue for many landowners, yet common erosion mitigation practices that involve armoring can alter littoral habitat and potentially diminish near-shore biodiversity. We studied the effects of two armoring methods (i.e., riprap, retaining walls) on habitat, taxonomic richness, relative abundance, and total abundance of fishes and benthic macroinvertebrates at shorelines on Big Rideau Lake in eastern Ontario, Canada. Snorkel surveys were conducted to assess aquatic habitat characteristics and fish diversity, and benthic infauna were sampled using kick-nets. Submergent and emergent macrophytes were more abundant at natural rocky shorelines compared to shorelines modified with riprap or retaining walls. Coarse woody debris was also more abundant at natural shorelines compared to riprap and retaining wall shorelines. Relative abundances of some fish species varied between shoreline types, but overall species richness and total abundance did not. Largemouth Bass (Micropterus salmoides) were more abundant at natural sites than armored sites. Conversely, Rock Bass (Ambloplites rupestris), Pumpkinseed (Lepomis gibbosus), Bluegill (Lepomis macrochirus), Yellow Perch (Perca flavescens), and baitfish from the family Cyprinidae were more abundant at both types of armored sites compared to natural sites. Taxonomic richness of benthic macroinvertebrates did not vary among shoreline types, however abundance of Amphipoda, Isopoda, Ephemeroptera, and Cladocera was greater at armored shorelines. These results suggest that human modification of shorelines is altering littoral ecosystems and potentially leading to shifts in the community structure of littoral nekton. More study is needed to fully understand the community level effects of shoreline erosion mitigation involving armoring in freshwater lakes and determine the effectiveness of alternative mitigation strategies that preserve natural habitat features.

Kolonisasi Makrozoobentos pada Kolam Habitat Semi Ex Situ (HSE) di Kawasan Maninjau, Sumatera Barat

Semi Ex-Situ Habitat (HSE) Pond is a pond that is designed for spawning native fish in Lake Maninjau, particularly in Bada fish ( Rasbora argyrotaenia ) in semi ex situ condition. This study aims to determine the benthic macroinvertebrates colonization in HSE ponds. The source of the water came from Lake Maninjau and the springs nearby. The study was conducted in August, October, and November 2018. Benthic macroinvertebrates samples were taken from some artificial substrate stainless steel- wire mesh (the size are 20 cm x 20 cm, mesh size 30), which was placed at the bottom of the ponds for 20—30 days. The result shows that there are five classes of benthic macroinvertebrates in an HSE pond with the water springs and HSE pond with the water of Lake Maninjau. Chironomidae was the most abundant Family in both the springs-HSE pond and the lake Maninjau-HSE pond. The abundance of benthic macroinvertebrates in these two ponds respectively, are 2207 individuals/m 2 and 4138 individuals/m 2 . The Shanon-Wiener diversity index value is low, they are 0,38 in the springs-HSE pond and 0,29 in the lake Maninjau-HSE pond. The Bray Curtis similarity index values in those two HSE Ponds ranged from 47% to 63%, furthermore its categories from “not similar to similar”.

HEM Impoundment—A Numerical Prediction Tool for the Water Framework Directive Assessment of Impounded River Reaches

A novel prediction tool is presented as a component of the Habitat Evaluation Model (HEM), which allows the assessment of the ecological status of impounded water bodies based on environmental factors that were shown in literature to correlate with the abundance of benthic macro-invertebrates. Main model parameters are the observed grain sizes and depth-averaged flow velocities obtained from a hydrodynamic simulation. The tool was tested in three Austrian river reaches. It was found that the river lengths predicted to be ecologically affected by the impoundments were substantially shorter for mean flow conditions than previously assessed when employing a physical mapping approach. The differences disappeared for low discharge conditions. The numerical prediction tool allows us to perform a status assessment for discharge conditions, which are potentially more representative of the annual discharge spectrum than those within the in-situ observable range. This property, thus, bears the potential to facilitate the recommendation of sediment management strategies in impounded river reaches in the future.

Variation of benthic macroinvertebrate communities in streams of three landscapes of South Brazilian grasslands

Introduction: Aquatic ecosystems in southern Brazil are presently under great environmental pressure. Changes in land use result in negative impacts on the ecosystem, affecting the functioning of stream communities. Objective: To compare the benthic macroinvertebrate community richness, abundances and compositions in streams of three South Brazilian grassland landscapes and correlate community patterns with environmental and spatial variables. Methods: Fifteen streams along riparian forests were selected in three landscapes (mean geographical distance of 285.1 km) inserted in the Paraná and Uruguai river basins. Of the three landscapes, two are inserted in conservation units (State Park of Guartelá and Palmas Wildlife Refuge). Invertebrates were collected in 20 kick net points along 150 m of the streams between June and November 2015. Invertebrates were sorted in the laboratory with three sieves and were identified to the lowest taxonomic level possible. The taxa were classified in functional feeding groups of shredders/detritivores, predators, scrapers, collectors/filters and gatherers/collectors. For each stream, we measured the environmental variables width and velocity, pH, dissolved oxygen, and temperature; and the relative cover of forest, grassland, plantation and silviculture in the catchments. Results: We found a total of 1 058 individuals, divided in 53 morphospecies and 34 families. Lower abundance of benthic macroinvertebrates was found in the northernmost landscape with higher temperature, and forest in the catchment. These streams were described mainly by predator groups, while streams inserted in the other two landscapes showed a more diverse guild composition of shredders/detritivores, gatherers/collectors, collectors/filterers, and scrapers. Geographical distance was the main factor influencing differences in community compositions among landscapes. Conclusions: Lower abundance of the northernmost landscape may be explained by (i) the low habitat heterogeneity due to dominance of sandy substrates, and by (ii) the anthropogenic land use of agriculture and extensive cattle breeding in the region that is ongoing and started before the creation of the conservation unit. Additionally, composition of macroinvertebrates may be correlated with environmental differences among landscapes that, in turn, are related to the geographical distance. Therefore, macroinvertebrate community responses may reflect different biota biogeographical histories that can also be associated with historical land use practices.

Comparisons Between Laboratory Sediment Toxicity Test Results and Assessment of Benthic Community Changes for a Lake with Mild Metal Contamination.

Effects of moderate-to-severe sediment contamination may be readily discernable in both sediment toxicity bioassays and benthic community assessments. However, the impact may be less obvious under conditions of relatively mild contamination and significant variation of natural environmental variables. This study evaluated sediment toxicity and benthic community impacts for a shallow eutrophic lake system with relatively low levels of sediment metal contamination. We evaluated selected sediment physical and chemical properties, as well as benthic community structure, for 50 sites along a sediment Pb contamination gradient in the lake. We tested the toxicity of sediment from 20 of the sites, using a standardized 42-days sediment bioassay with Hyalella azteca survival, reproduction, and growth endpoints. Using principal component and correlation analyses we found negative relationships for both Pb and Cu, between sediment metal concentrations and the diversity and abundance of benthic macroinvertebrates. Taxa known to be metal-sensitive (e.g., Hyalella sp. and Physa sp.) were less abundant at sites with relatively higher Pb and Cu concentrations. However, amphipod performance in the chronic toxicity test was not related to sediment Pb or Cu concentrations (but was influenced by sediment organic content). Our results demonstrate that an assessment of community-level effects may be warranted even when sediment metal concentrations are too low to elicit detectable toxic effects in standardized laboratory tests.

Do oyster breakwater reefs facilitate benthic and fish fauna in a dynamic subtropical environment?

Oyster breakwater reefs used for coastal protection have shown to enhance local biodiversity. Particularly, macro-invertebrate and fish assemblages can benefit directly from reefs providing structurally complex habitats and indirectly through alteration of soft-sediment environment near the reef areas. To test this hypothesis, a manipulative field experiment was carried out on an eroding intertidal flat in the southeastern coast of Bangladesh by deploying replicate units of each 20 m long oyster breakwater reefs specially designed to protect adjacent shorelines. Transient fishes and resident intertidal macro-invertebrate communities were assessed monthly for a period of 18 months. On the intertidal flat, five transects were setup for faunal and environmental data collection, three crossing the breakwater reefs and two along the control areas without reefs. Prior to the deployment of the reefs, both the macro-invertebrate and fish assemblage were not significantly different among the five transects, indicating a rather uniform distribution of species in all tidal flats. Data collected post-reef deployment revealed that oyster breakwater reefs supported a greater biomass as well as abundance of benthic macro-invertebrates on the landward mudflat behind the reefs than the mudflat of control sites. The community structure, and seasonal variation of the macrobenthic community were associated with the variations in the sediment accumulation, as influenced by the breakwater reefs. Additionally, higher abundance of transient finfish and mobile macro-invertebrates at the reef sites suggest that the faunal communities were attracted by the higher abundance of prey resources (i.e. polychaetes, small crustaceans, juvenile gastropods and bivalves) as supported by the reefs. Thus, the reef areas served as shelter, nursery, and foraging grounds for different species. Though the ecological benefits of using oyster breakwater reefs only span adjacent to the reefs, this study confirms the importance of reef structure in facilitating local coastal biodiversity in a subtropical region.