Abundance Of Benthic Macroinvertebrates Research Articles

Influence of seasonal hydrological regimes on benthic macroinvertebrates in two the Brazilian biodiversity hotspots

Global warming has changed climate patterns worldwide causing an increase of extreme weather conditions that have altered annual seasonal hydrological regimes. These extreme climate-driven shifts modify habitat availability and can influence freshwater communities in disruptive ways. Our study investigates how changes in annual seasonal hydrological regimes affect the community structure and the Functional Feeding Groups (FFG) of benthic macroinvertebrates in two Brazilian biodiversity hotspots, the Brazilian Tropical Savannas (a.k.a., Cerrado) and Atlantic Forest biomes. We investigate whether annual variation in precipitation between biomes influence composition, richness, and abundance of benthic macroinvertebrates and their proportions of FFG. We demonstrate that differences in annual precipitation rates affect the composition and abundance, but not richness of benthic macroinvertebrates. Changes in community structure are related to changes in annual precipitation, which modify stream variables. Our findings suggest that annual seasonal changes in hydrological precipitation modify benthic macroinvertebrate communities, especially in Cerrado, where dry seasons are more pronounced. Therefore, annual changes in precipitation rates may disrupt the benthic macroinvertebrate communities in tropical savannas, potentially leading to biodiversity loss.

Effects of mining activities on fish communities and food web dynamics in a lowland river.

Fish communities of streams and rivers might be substantially subsidized by terrestrial insects that fall into the water. Although such animal-mediated fluxes are increasingly recognized, little is known about how anthropogenic perturbations may influence the strength of such exchanges. Intense land use, such as lignite mining, may impact a river ecosystem due to the flocculation of iron (III) oxides, thus altering food web dynamics. We compared sections of the Spree River in North-East Germany that were greatly influenced by iron oxides with sections located downstream of a dam where passive remediation technologies are applied. Compared to locations downstream of the dam, the abundance of benthic macroinvertebrates at locations of high iron concentrations upstream of the dam was significantly reduced. Similarly, catch per unit effort of all fish was significantly higher in locations downstream of the dam compared to locations upstream of the dam, and the condition of juvenile and adult piscivorous pike Esox lucius was significantly lower in sections of high iron concentrations. Using an estimate of short-term (i.e., metabarcoding of the gut content) as well as longer-term (i.e., hydrogen stable isotopes) resource use, we could demonstrate that the three most abundant fish species, perch Perca fluviatilis, roach Rutilus rutilus, and bleak Alburnus alburnus, received higher contributions of terrestrial insects to their diet at locations of high iron concentration. In summary, lotic food webs upstream and downstream of the dam greatly differed in the overall structure with respect to the energy available for the highest tropic levels and the contribution of terrestrial insects to the diet of omnivorous fish. Therefore, human-induced environmental perturbations, such as river damming and mining activities, represent strong pressures that can alter the flow of energy between aquatic and terrestrial systems, indicating a broad impact on the landscape level.

Mt. Apo Biotic Index (MABI): a macroinvertebrate-based multimetric index for assessing stream biotic integrity of wadeable streams within a geothermal production field in Mindanao, Philippines.

Monitoring the ecological integrity of streams is a challenge, especially in the tropics, which experience high rates of degradation. Multimetric scoring systems have been widely used in other countries in evaluating current stream conditions; however, it has never been done in the Philippines. This study focuses on the development of a benthic macroinvertebrate-based multimetric index for the overall assessment of streams in Mt. Apo, Mindanao, Philippines. The index was used to develop existing physicochemical and biological data obtained during 2010 to 2015 surveys from 15 monitoring sites within the Mt. Apo Geothermal Project (MAGP). Metrics related to benthic macroinvertebrate abundance, richness, composition, functional habit groups, functional feeding groups, and pollution tolerance were screened for their range, temporal stability, sensitivity, discrimination efficiency (DE), redundancy, and responsiveness to anthropogenic impacts. The resulting multimetric index, the Mt. Apo Biotic Index (MABI), is computed as the sum of the individual metric scores after metric transformation using the discrete scoring method DRQ1 (D = discrete, R = reference, Q1 = 25th percentile) of the six core metrics: (1) number of Coleoptera individuals (abundance), (2) number of taxa (richness); (3) [%] Coleoptera taxa (composition), (4) number of sprawler individuals (functional habit group), (5) [%] collector-filterer taxa (functional feeding group), and (6) the Biological Monitoring Working Party Thai version (BMWP-Thai; pollution tolerance). MABI scores were classified into five condition ratings of stream biotic integrity: very poor (6 to 10), poor (11 to 15), fair (16 to 20), good (21 to 25), and excellent (26 to 30). The study demonstrated that the resulting pilot index may provide useful information that will benefit policymakers and resource managers in formulating more comprehensive stream management approaches and conservation plans for priority sites in the region.

Distribution of artisanal fishing gears with impacts on sedimentation and benthic macroinvertebrate assemblages in Songkhla Lake, the largest lagoon in Thailand

The present study investigated the distribution and diversity of stationary fishing gears in Songkhla Lake and assessed the effects of the most abundant gear in the lake, the standing trap, on sedimentation and the abundance of benthic macroinvertebrates. Our survey revealed that six types of fishing gear were used: standing traps, fyke nets, fish aggregating devices, seabass net cages, small traps and stationary lift nets. The type of fishing gear used depended on the depth of water. The density of installed standing traps reached a maximum of 357 traps/km2, which was the highest density of any fishing gear installed on the lake. They were mainly set in the middle part of the lake, where the water was less than 2 m deep. Sedimentation was examined inside and outside the areas influenced by standing traps. Sediment samples were collected with sediment traps in the northeast and southwest monsoon seasons. Sedimentation rates inside and outside the areas influenced by standing traps differed at some sites but the pattern was not consistent across seasons. Sedimentation rates were higher in the northeast monsoon season with the average rate 1132.32 ± 43.73 (mean ± SE) g m−2day−1 when precipitation and run-off were higher and 323.98 ± 10.68 g m−2day−1 in the southwest monsoon or dry season. Moreover, the proportion of finer clay particles was greater in the sediment from the areas influenced by traps. Benthic macroinvertebrate communities between the two areas were different. A bivalve, Potamocorbula sp., which dominated benthic macroinvertebrate assemblages, had a higher abundance in areas influenced by traps. The effects of stationary fishing gears on sedimentation and benthic macroinvertebrates highlighted in this study suggest that the long-term deployment of these gears may affect food chain dynamics in this lagoon system. Ultimately, a proper regulation of the use of these gears may be needed.

Evaluation by benthic macroinvertebrates of the state of health of some rivers in the south Cameroon region

Benthic macroinvertebrates are the best indicators of the ecological quality of watercourses because of their specific diversity, their sensitivity, their variable life span and their capacity to adapt to all types of environments. In order to determine the health status of some rivers in the Southern Cameroon Region, a study was conducted in Kribi in the Ocean Department between February 2022 and February 2023. Physicochemical analyses were carried out according to conventional methods. Sampling of benthic macroinvertebrates was done using the multihabitat approach. The results of physicochemical parameters revealed that the water courses were well oxygenated, with a slightly acidic pH with little disturbances from anthropic activities. The abundance of benthic macroinvertebrates showed 17055 individuals collected belonging to 2 phyla, 3 classes, 19 orders, 59 families and 113 genera. The class of Crustacea dominated with 7693 individuals or 45.10% of relative abundance, followed by Gastropods with 5174 individuals or 30.33% of relative abundance and Insects with 4188 individuals or 24.55% of relative abundance. The taxonomic diversity, coupled with the EPT, EPTD, EPTC and EPTH indices, revealed that the water from these water courses is of good ecological quality.

An argument in support of the development of regionalized standard taxonomic efforts for benthic Macroinvertebrate-Based monitoring

Taxonomic harmonization for benthic macroinvertebrate abundance data is time consuming. If undertaken lightly it can lead to erroneous inferences regarding taxon-specific responses to environmental gradients, variation in benthic index scores, and increased noise in community comparison efforts. Standardization of taxonomic efforts and nomenclature is intended to minimize between and among lab data reporting variability, and therefore optimize the effectiveness of data analyses related to complex aquatic communities. Here we present an argument for the development of regional standard taxonomic efforts, and encourage data consumers to accept infra-rank nomenclature when it is accompanied by a well-documented and repeatable source such as a standard taxonomic effort. We present this argument from our collective experiences from within the boundaries of the United States of America but these concepts can be applied to any ecological region globally and transcend jurisdictional boundaries.

Human-Induced Impact on the Distribution and Diversity of Benthic Macroinvertebrates and Fish Fauna in the Tropical Ikang River, Nigeria

Abstract South-eastern Nigeria’s tropical water ecosystems typically consist of mangrove swamps and riparian forests, both of which have become endangered in the last six decades. The purpose of this research was to determine the extent of human-induced impact and activities on the effect of water quality on the distribution and diversity of benthic macroinvertebrates and fish fauna in the Tropical River (Ikang). The river’s surface water, benthic macroinvertebrates, and fish fauna were sampled and identified to create a database of reference information. Twelve (12) species of benthic macroinvertebrates from two (2) phyla were identified. Station 1 had the highest benthic macroinvertebrate abundance of 58 (35.65%), while Station 3 had the lowest abundance of 52 (31.70%). Uca tangeri was the most abundant benthic macroinvertebrate with a percentage abundance of 28 (17.07%), while Dinocras sp., Macromia sp., and Gomphus sp. were the least abundant benthic macroinvertebrates with a percentage abundance of 3.66%. In addition, seven (7) fish species from six (6) families were identified. During the study, the family Claroteidae was the most abundant, while the family Carangidae was the least abundant. The temperature of the river had a positive correlation with the families Carangidae and Mugilidae, a negative correlation with the family Clupeidae, and no correlation with the family Claroteidae. Total dissolved solids (TDS) correlated positively with the families Carangidae, Mugilidae, and Clariidae, while conductivity correlated positively only with the family Sciaenidae and negatively with the families Carangidae, Mugilidae and Clariidae. The abundance and diversity of benthic macroinvertebrates and fish fauna were generally influenced by the physical and chemical characteristics of the water, the availability of food, and the extent of human impacts and activities. In order to ensure sustainable water quality and biodiversity conservation in our environment, it is necessary to manage the river and the surrounding ecosystem appropriately.

Does experimental seaweed cultivation affect benthic communities and shorebirds? Applications for extensive aquaculture.

Extensive seaweed aquaculture is a growing industry expected to expand globally due to its relatively low impact and benefits in the form of ecosystem services. However, seaweeds are ecosystem engineers that may alter coastal environments by creating complex habitats on previously bare mudflats. These changes may scale up to top-consumers, particularly migratory shorebirds, species of conservation concern that regulate trophic webs at these habitats. Understanding how habitats are transformed and how this affects different species is critical to direct ecological applications for commercial seaweed management. We experimentally assessed through a Before-After Control-Impact design the potential changes exerted by Gracilaria chilensis farming on bare mudflats on the abundance, biomass, and assemblage structure of benthic macroinvertebrates, and their scaled-up effects on shorebirds' habitat use and prey consumption. As predicted, experimental cultivation of G. chilensis significantly affects different components of biodiversity that scale-up from lower to upper trophic levels. The total biomass of benthic macroinvertebrates increased with seaweed cultivation and remained high for at least 2 months after harvest, boosted by an increase in the median size of polychaetes, particularly Nereids. Tactile-foraging shorebirds tracked these changes at the patch level increasing their abundance and spending more time foraging at seaweed cultivated plots. These results suggest that seaweed farming has the potential to impact shorebird populations by favoring tactile-foraging species which could lead to a competitive disadvantage to species that rely on visual cues. Therefore, the establishment of new seaweed farms in bare mudflats at key sites for shorebirds must be planned warranting habitat heterogeneity (i.e., cultivated and non-cultivated areas) at the landscape level and based on a previous experimental approach to account for local characteristics. Fostering properly designed extensive seaweed farming over other aquaculture industries with greater negative environmental impacts would provide benefits for human well-being and for ecosystem functions.

The past is never dead: legacy effects alter the structure of benthic macroinvertebrate assemblages

Land use is the most common and widespread threat to lotic ecosystem health and freshwater biodiversity conservation. The legacy effects of past anthropogenic land use and cover may also affect the structure and functioning of current lotic ecosys¬tems. Therefore, the aim of this study was to use benthic macroinvertebrate assemblages to evaluate the potential legacy effects of anthropogenic land use on headwater streams in the Neotropical Savanna. We tested three hypotheses. (1) The legacy effects on macroinvertebrates of the riparian zone are more important than those of the entire catchment. (2) Recent deforestation has a stronger effect on the current taxonomic structure of benthic macroinvertebrate assemblages than historical deforestation. (3) Sen-sitive taxa respond more readily than tolerant taxa to historical deforestation. To test these hypotheses, we estimated deforestation over the last 30 years for 97 stream sites in 5 hydrological units and tested it against benthic macroinvertebrate abundance, taxa richness, EPT abundance, EPT richness, Shannon-Wiener diversity, and Simpson diversity. The two first hypotheses were cor¬roborated, as Shannon-Wiener and Simpson diversity indices were significantly correlated with deforestation in the riparian zone (p < 0.05) and these diversity variables were positively correlated with older deforestation, meaning that such sites tended to recover their diversity over time after a deforestation event. The third hypothesis was only partially supported because EPT (sensitive taxa) did not represent most taxa with significant correlations with historical deforestation at catchment scale, but were the only taxa to do so at the 200 m riparian buffer. We conclude that recent deforestation has more significant effects, but past deforestation still plays a significant role in the structure and functioning of lotic ecosystems.

Evaluation of benthic macroinvertebrate communities in upstream and downstream of Kulekhani Multipurpose Reservoir, Makawanpur, Nepal

Reservoir construction in the natural waterways can disrupt the structure and function of riparian ecosystems with the alteration in abundance and composition of aquatic organisms. This study assessed the variation in Benthic Macroinvertebrates (BMIs) communities in upstream (Chitlang and Seti Streams) and downstream (spillway) of Kulekhani multipurpose reservoir, Makawanpur, Nepal. Multi-habitat qualitative samplings with Ganga River System Biotic Score (GRSBIOS) index was used for the biological water quality assessment. Out of total 25 families and 8 orders of identified BMIs, Diptera and Coleoptera order are abundant whereas Oligochaeta and Odonata order are lowest. Taxa richness and abundance of BMIs were estimated to be higher upstream. Number of EPT taxa (6 to 2) and percentage of EPT (35.07 to 28.04 %) abundance were recorded in decreasing order of response toward downstream. The upstream showed a high Shannon and Simpson’s diversity index. Chitlang Stream is found slightly polluted as Average Score Per Taxa (ASPT) score is calculated as 6.1 (River Water Quality Status (RWQS)-I)). Similarly, immediate downstream is critically polluted with RWQS-III whereas Seti Stream and spillway after 4 km were found to be moderately polluted as RWQS-II. Canonical Correspondence Analysis (CCA) showed that pH, temperature, and dissolved oxygen have a high influence in BMIs assemblages. The study depicts the ecological health of the stream immediately downstream of the reservoir is disturbed with presence of tolerant BMIs assemblages. The implication of the study can be in the assessment of impact caused by the reservoir in the ecological status of the water transfer.

Developing environmental flow targets for benthic macroinvertebrates in large rivers using hydraulic habitat associations and taxa thresholds

Holistic environmental flows frameworks are built on our understanding of key flow-ecology relationships that support sensitive taxa and critical ecosystem functions under different flow and water level scenarios. Most research on flow-ecology relationships has typically focused on small systems, with less known about flow associations, indicator taxa, and environmental thresholds of assemblage change along hydraulic gradients of large non-wadeable rivers. We assessed benthic macroinvertebrate assemblage structure and applied Taxa Indicator Threshold ANalysis (TITAN) on biomonitoring data collected during a six-year period in the Wolastoq | Saint John River in Atlantic Canada. Flow velocity was strongly associated with the distribution and relative abundance of benthic macroinvertebrates in the river, and taxon associations reflected functional adaptations to flow. We identified 33 genus-level indicator taxa that were either positively or negatively associated with flow velocity. Weaker taxa responses were shown for the gradient in median substrate particle size where 22 negatively and positively responding taxa were identified. We predicted changes in indicator taxon abundance under different flow scenarios using a hydrodynamic model, and characterised the distribution and availability of suitable hydraulic habitat patches within a 20 km reach downstream of a large hydropower generating station. These observations set the stage for the development of ecologically-based flow targets to support holistic environmental flow management in large rivers.

Benthic biodiversity near brine discharge sites in the Port of Rotterdam

The Port of Rotterdam is a heavily man-modified estuarine system, Europe's major seaport and home to a large number of chemical and petrochemical plants, many of which are supplied with distilled water from two demineralized water plants in Botlek and Maasvlakte. In this study, we assessed the ecological conditions near the brine outfalls and at a reference site unimpacted by brine, focusing on the benthic macrofaunal composition. Overall, the analysis of the communities and species revealed a similar macrobenthic composition, although with lower abundance and diversity compared to the nearby North Sea environment. The outfall area of the Botlek demineralized water plant, which is a dead-end entirely marine waterway with no to little currents in contrast to the well flushed brackish environment of the outfall of the Maasvlakte demineralized water plant, was characterized by the lowest abundance of benthic macroinvertebrates, species richness and Shannon diversity index. Higher biodiversity values at the Maasvlakte demineralized water plant compared to the reference site were also associated with the presence of a large biogenic reef of the Pacific oyster Crassostrea gigas with specimens of over 8 years estimated age being observed, however with many dead individuals recorded at the time of surveys. The outfall area of the Botlek demineralized water plant also had the highest disturbance levels according to the results of AZTI's Marine Biotic Index (AMBI) in conjunction with Benthos Ecosystem Quality Index (BEQI). Its community was dominated by the opportunistic native species Capitella capitata and Varicorbula gibba, and species typical for organic matter enrichment such as Alitta succinea (native), Streblospio cf shrubsolii (native) and Theora lubrica (invasive), which correlates well with higher levels of anthropogenic pollution in this area. Generalized linear model (GLM) and distance-based multivariate linear model (DistLM) showed that the distance from the outfalls was an important factor in terms of brine impacts however explaining a small part of the variation observed. Similarity percentage analysis (SIMPER), multivariate analysis, and permutational multivariate analysis (PERMANOVA) showed low similarity between and within study sites, confirming that high levels of heterogeneity exist within the estuarine system in terms of natural conditions and anthropogenic stress.

Impact of Seasonal Changes in the Abundance of Benthic Macroinvertebrates & Physico-Chemical Conditions of a Major River in Western India

The study is focused on the seasonal assessments of riverine water quality and the distribution of benthic macroinvertebrates community at Mahisagar river, India. 27 physiochemical indicators and benthic macroinvertebrates community were identified as per aquatic ecological health criteria to evaluate water quality. Indices like Margalef’s species richness Fisher’s alpha diversity, Saprobic score, Diversity score were calculated to understand the effect of seasonal changes on the pollution tolerance levels of benthic macroinvertebrates. PCA was performed for identifying major pollutants. Applications of such statistical tools and scores, a solution toward the sustainable management of the ecological health of a river can be developed.

The Environmental Effects of the Innovative Ejectors Plant Technology for the Eco-Friendly Sediment Management in Harbors

A sediment bypassing plant based on innovative jet pump, ejectors, has been tested in the first-of-a-kind demo application at the harbor of Cervia (Italy, Northern Adriatic Sea). The ejector is a jet pump aimed to reduce sediment accumulation in navigation channels and coastal areas. Herein we present results of the first study assessing the potential ecological effects of the ejectors plant. Sediment characteristics, benthic, and fish assemblages before and after the plant activation have been analyzed in the putatively impacted (the sediment removal and discharge) areas and four control locations, one time before and two times after plant activation. Ejectors plant operation resulted in a reduction of the mud and organic matter content in the sediment, as well as in changes in shell debris amount in the impacted areas. Abundance and species richness of benthic macroinvertebrates, initially reduced in the impacted areas, probably due to the previous repeated dredging, returned to higher values during demo plant continuous operation. Higher diversity of fish fauna was observed in the study area during plant operation period. Observed dynamics of the ecological status of the marine habitat suggest that an ejectors plant could represent an eco-friendly solution alternative to dredging operations to solve harbor siltation problems.

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.