Total Macroinvertebrate Density Research Articles

What Are the Relationships between Plankton and Macroinvertebrates in Reservoir Systems?

Macroinvertebrates and plankton play crucial roles in reservoir food webs; however, their relationships have received limited attention. This study investigates the associations between plankton and macroinvertebrates in fifty selected reservoirs. During the spring season, significant concordances were observed in species richness between phytoplankton and zooplankton, as well as between zooplankton and macroinvertebrates. In contrast, during the summer season, the concordance in species richness between phytoplankton and macroinvertebrates was higher compared to other assemblages. Although macroinvertebrates showed a strong connection with phytoplankton in terms of species richness in both seasons, the congruencies were not statistically significant. Partial least squares regression (PLSR) analysis revealed that the densities of phytoplankton, Chlorophyta, Cyanophyta, and protozoans significantly influenced the total macroinvertebrate density in both seasons. Additionally, the densities of mollusks and aquatic insects were affected by the densities of Chlorophyta and Cyanophyta, while the density of oligochaetes was influenced by the density of Chlorophyta. These findings indicated that phytoplankton and zooplankton serve as primary food sources for macroinvertebrates, highlighting the close relationship between plankton and macroinvertebrates in reservoir systems. Moreover, the results of formative measurement models indicated a strong association between zooplankton and macroinvertebrates during the spring, whereas phytoplankton and macroinvertebrates exhibited a close association during the summer. The substantial concordance in density between phytoplankton and zooplankton revealed by the formative measurement models confirmed that assemblages with similar body sizes exhibit stronger concordance compared to those with significant differences in body size.

Ecological characterisation of urban ponds in the Netherlands: a study based on data collected by volunteers

Blue space in the urban environment can positively contribute to public health and well-being. Many urban freshwater systems, however, are exposed to anthropogenic stressors, resulting in deteriorated water quality and biodiversity. Private garden ponds are essential elements of this blue space but little is known about their water quality since they are not monitored by water professionals. The Dutch citizen science initiative Waterdiertjes.nl focusses on biological water quality assessment using macroinvertebrates and launched a campaign to investigate garden ponds in 2021. The campaign yielded macroinvertebrate recordings in 60 garden ponds and limited additional information on dimensions, and presence of water vegetation and fish. Volunteers also investigated 92 public urban ponds in 2021. Combining both data allowed for evaluation of the similarity between both pond types. Analyses were also performed to discover the importance of pond dimensions and presence of aquatic vegetation or fish for the macroinvertebrate biodiversity and water quality. Multivariate analyses showed a considerable overlap in macroinvertebrate community composition between garden and public urban ponds. Results showed high variability in taxon richness, total macroinvertebrate density and water quality scores A significant, nonlinear relation was observed between pond depth and macroinvertebrate taxon richness with the highest richness at a depth of 0.5-1m. Submerged vegetation correlated significantly with taxon richness with little vegetation having the lowest richness. Presence of fish or floating vegetation was not significantly related to taxon richness, total density and water quality scores possibly due to unnatural conditions that underlie in garden ponds. Since water professionals and academic scientists do not monitor garden ponds, citizen science may provide valuable data on water quality and biodiversity in these waters. The present initiative showed that volunteers can successfully monitor understudied ecosystems and gather data on temporal and spatial scales complementary to professional data that lead to new (ecological) insights.

Road effects on benthic macroinvertebrate assemblages in boreal headwater streams

Roads constitute a worldwide network of ecological barriers traversing countless streams and rivers. A large fraction of the land area lies in close proximity to roads. Ecological effects of roads likely extend well beyond the road network, suggesting wide ranging impacts on lotic ecosystems. Road impacts are multifaceted including fragmentation, changing hydrology, sedimentation and pollution. Yet, the ecological impacts are incompletely documented. We examined the effects of roads traversing lotic ecosystems on the structure and function of benthic macroinvertebrates in small temperate headwater streams. Ecological effects differed between reaches upstream and downstream of roads compared to upstream and downstream reaches in control streams. Total macroinvertebrate density and mayfly density were lower downstream of roads than upstream of roads, but they were similar at downstream and upstream reaches of control streams. Species density, but not species richness, tended to be lower downstream than upstream of roads, likely due to the lower macroinvertebrate densities at downstream sites. There were no comparable effects in control streams. Species composition and species abundances differed between road impacted streams and control streams likely because streams that were traversed by roads selected for a different set of species compared to control streams as indicated by checkerboard distribution of species in streams that were traversed by roads. Functional impacts included a greater prevalence of predators in control streams, and a higher proportion of grazers and shredders in streams that were traversed by roads. The study is inconclusive regarding the mechanisms mediating the ecological impact of roads. The ecological effects are likely caused by a combination of factors including fragmentation, pollution and hydrological change among others. Given the vast global road network, the quantitative significance of road effects driving freshwater biodiversity loss may be highly underestimated especially in smaller headwater streams comprising the major part of fluvial ecosystems.

Contribution of alien peracarid crustaceans to the biocontamination of benthic macroinvertebrate assemblages in Croatian large rivers

Peracarid crustaceans (orders Amphipoda, Isopoda and Mysida) are one of the most important groups of invaders in fresh and brackish waters. Although large rivers in Croatia have been heavily invaded by peracarid crustaceans, little is known about their impact on local benthic macroinvertebrate assemblages. The main aim of this study was to investigate the contribution of alien Peracarida to the biocontamination of macroinvertebrate assemblages in Croatian large rivers as a proxy measure of their impact. Quantitative sampling was conducted twice (2015 and 2016/2017), at 48 sites on four large rivers (Danube-4, Sava-21, Drava-20, Mura-3). Physicochemical parameters were measured eight times during 2015 and 2016. In total, 16 species were recorded, five native and 11 alien species. The highest number (10 alien species, most from genus Dikerogammarus and Chelicorophium) were found in the Danube River, while subsets of alien species were found in the Sava (5 spp.) and Drava Rivers (6 spp.), and no alien species were found in the Mura River. The most upstream reaches of the Mura, Drava, and Sava Rivers in Croatia have not yet been colonized by invasive peracarids and the native peracarids are still abundant there. In the Drava River, alien Peracarida had the highest densities. Significant negative correlations were established between the number of native taxa and alien Peracarida species. Proportions of alien peracarids in the total density of benthic macroinvertebrates were spatially variable, the highest average values in the Drava River (24.4 %), and lower in the Danube (20 %) and the Sava (17.7 %) Rivers. Alien Peracarida had the most important contribution to the richness and abundance contamination of macro¬invertebrate assemblages. The upstream spread of invasive peracarids will increase biocontamination and could cause a decline of native species richness and abundance in the most upstream reaches of the Sava and Drava Rivers. To prevent further up¬stream spread of alien Peracarida, “check, clean and dry” protocols should be included in the national regulations.

Macroinvertebrate responses to differing riparian treatments following forest harvest in the headwaters of Trask River watershed

Although it is well-established that macroinvertebrates are an integral part of a healthy stream ecosystem, studies designed to inform forest harvest best management practices for sustainability of macroinvertebrate communities in small streams have been limited. Current riparian management practices for headwater streams generally focus on providing adequate wood supply, reducing debris flows and transport of sediment, and maintaining water quality in larger streams that contain fish. Here we studied the effects of contemporary forest harvest practices on benthic macroinvertebrate density and community composition in 12 small headwater streams as part of the Trask River Watershed Study. To account for seasonal and year-to-year variability in macroinvertebrate densities, we sampled each site at the same time of year for six years before and four years after harvest. Three watersheds were clearcut with variable riparian buffers, three were clearcut with 12 m riparian buffers, and one was thinned with 15 m buffers. Five adjacent watersheds were not treated and were studied as reference sites. All sites had approximately 50 yr old conifer and alder forests, which had revegetated following fires and harvest in prior decades.In these steep mountain streams, benthic macroinvertebrate density and community composition were generally similar across watersheds prior to harvest. Collectors were the most abundant functional feeding group, followed by shredders; scrapers were the least abundant. After harvest, in two of the three clearcut watersheds with variable buffers, the total benthic density and percentage of collectors increased, primarily due to greater numbers of Chironomidae. We also observed more abundant emergence post-harvest at these two watersheds. In the third clearcut watershed with a variable buffer and in the three clearcut watersheds with uniform 12 m riparian buffers, we did not see changes in density or functional feeding groups after harvest. We explored the spatial and temporal aspects of the data using both non-parametric and parametric statistical methods. High variability swamped the treatment effect when watersheds were grouped by riparian treatment for the repeated measure analyses, while NMDS showed a significant shift post-harvest for the watersheds with variable buffers. In the clearcut watersheds with uniform buffers, macroinvertebrates densities and community composition did not shift. At two of the clearcut watersheds with variable buffers, we observed increased density for the first two years after harvest, and chironomids comprised up to 80% of the abundance in samples. In the subsequent years, we documented mixed responses for two watersheds. It was invaluable to have multiple pre- and post-harvest sampling periods in both harvested and reference watersheds in order to better identify site specific responses to treatment and to separate background variability from responses to harvest. We show that retention of riparian vegetation on headwater streams during clearcut harvesting minimized changes in total macroinvertebrate densities and community composition. Small buffers may be key to maintenance of diverse stream invertebrate communities in headwaters.

Effects of urban demand for food and water on physicochemicals and biotic structure of riverine wetlands in the Pampean plain

ABSTRACT Riparian areas of riverine plains develop extensive floodable areas named riverine wetlands, which are essential to the water cycle balance and ecosystem dynamics. In this study, we contrasted the hydrological and physicochemical variables of riverine wetlands of both peri-urban areas impacted by intensive farming and those of rural areas with the indicators of the biotic structure (taxonomic richness, Shannon diversity and total density) of benthic diatoms, phytoplankton, zooplankton, macroinvertebrates, chironomids, fishes, turtles, and birds. The study was performed on riverine waters of the Pampean plain, Argentina, with four seasonal samplings conducted in 2017–2018. Our results showed that the significant deepening of the groundwater level caused by aquifer overexploitation in peri-urban areas, as well as the declining surface water quality with higher phosphorus and total nitrogen concentrations, affected the taxonomic richness, diversity, and total density of the biotic assemblages of riverine wetlands. The taxonomic richness of birds, turtles, phytoplankton, chironomids, and fishes was the most sensitive to land use. Phytoplankton, chironomid, and fish diversity showed the greatest differences between rural and peri-urban riverine waters, while the total density of chironomids and birds showed the greatest differences according to land use. The results suggest that the socioeconomic development in those riverine wetlands that still maintain conditions close to the natural ones needs to be subject to guidelines derived from integrated basin management and sustainable urban planning.

Fish vs. Aliens: predatory fish regulate populations of Limnoperna fortunei mitigating impacts on native macroinvertebrate communities

Limnoperna fortunei, an invasive mussel altering the structure of benthic communities, is preyed upon by several fish species in South America. To investigate the impact of predatory fish on populations of this mussel, and the effects of this top-down interaction on native macroinvertebrates, we performed an in situ experiment in the Uruguay River. By comparing benthic communities of artificial substrates colonised in treatments allowing or excluding fish access, it was demonstrated that fish significantly reduce colonisation by L. fortunei (i.e. its density, biomass and body size). In the absence of mussels (before settlement), fish preyed upon the native macroinvertebrate community inhabiting artificial substrates, reducing their densities compared to the fish exclusion treatment. However, it was found that in the presence of golden mussel (after settlement), the total density of benthic macroinvertebrates, densities of scrapers, and densities of dipterans and gastropods strongly decreased in fish exclusion treatments, suggesting a strong effect of L. fortunei in reducing the native fauna. By preying on L. fortunei, fish favoured the persistence of native macroinvertebrates. Further studies focused on predatory fish species and their efficiency in removing L. fortunei may contribute to advancing towards using native fish as mitigating agents.

Recent invasion of Didymosphenia geminata (Lyngbye) M. Schmidt in a Patagonian regulated river promotes changes in composition and density of macroinvertebrate community

Didymosphenia geminata is a stalked freshwater diatom, which forms large blooms in ultra-oligotrophic conditions, and it has been declared a nuisance species in many lotic systems worldwide. Its presence is verified in Argentine Patagonia since 2010. To understand the differences in the community of macroinvertebrates between non-invaded sites and D. geminata blooms, three non-invaded sites and three sites with 80–90% blooms coverage were sampled seasonally at Futaleufu River. Physical and chemical variables (pH, suspended solids, total dissolved solids, conductivity, dissolved oxygen, and nutrients) showed no significant differences between sites. Sites with D. geminata blooms were associated with significantly higher values of periphyton biomass and chlorophyll a. Macroinvertebrate community differed between D. geminata infected sites and sites with native periphyton. Higher total macroinvertebrate density, higher tolerant groups (Orthocladiinae and non-insect taxa) density, and total richness were found in the presence of blooms. Trophic structure changed at D. geminata blooms, where shredders and collector-gatherers increased in abundance. The diatom blooms may constitute a new complex micro-habitat that provides refuge from harsh current and predators, as well as new foraging opportunities, producing a bottom-up effect on the benthic community.

Structure of macroinvertebrate communities and bioassessment of water quality in the Weihe River mainstream and its typical tributaries from the northern Qinling Mountains

为摸清渭河干流及源于秦岭北麓典型支流的大型底栖动物群落特征，本研究于2017年10月和2018年5月对渭河干流及秦岭北麓5条典型支流共40个样点的大型底栖动物进行调查，并利用Margalef丰富度指数和生物指数BI生物指数对河流水质进行评价.共鉴定大型底栖动物210种，属于5门8纲75科187属.水生昆虫为优势类群，其物种数占总物种数的89.0%，且四节蜉属一种（Baetis sp.）作为绝对优势的物种出现在所有调查河流中.源于秦岭北麓的支流石头河底栖动物总密度最高（616.3 ind./m²），总生物量最大（5.265 g/m²）；而渭河干流底栖动物总密度最低（125.6 ind./m²），总生物量最小（0.289 g/m²）.水质较好的秦岭北麓典型支流底栖动物的Shannon-Wiener多样性指数、Margalef丰富度指数显著高于渭河干流，而Pielou均匀度指数在干支流间的差异性不大.通过Pearson相关分析和多元逐步回归分析得出，淤泥型底质、电导率、pH和硝酸盐氮是影响调查河流底栖动物群落特征的主导因子.丰富度指数法和生物指数法水质评价结果分别显示，渭河干流有73.3%和80.0%的采样点呈中度-重度污染状态，秦岭北麓典型支流有80.0%和68.0%的采样点呈无污染-轻度污染状态.本研究可为渭河流域生态管理与保护提供基础的数据支撑.;For exploring the macroinvertebrate community characteristics of the Weihe River mainstream and its typical tributaries originating from the northern Qinling Mountains, investigation of water environment and macroinvertebrates was conducted in 40 sampling sites in October 2017 and May 2018. Furthermore, Margalef richness and biological index (BI) biological indices were used to assess the water quality of studied rivers. Altogether 210 macroinvertebrates species were identified, belonging to 187 genera, 75 families, 8 classes and 5 phyla. Aquatic insects were the dominant group, accounting for 89.0% of the total species number, and the Baetis sp. was the dominant species in all studied rivers. The tributary Shitou River, had the highest values of total density(616.3 ind./m²), and the highest total biomass(5.265 g/m²). Whereas the total density (125.6 ind./m²) and total biomass (0.289 g/m²) of macroinvertebrates were both lowest in the Weihe River mainstream. The Shannon-Wiener diversity index(H')and Margalef richness index(R)of five typical tributaries were characterized by good water quality and significantly higher than those of the Weihe River mainstream, whereas the Pielou evenness index(J)showed insignificant difference between mainstream and tributaries. Pearson correlation analysis and the multiple linear regression analysis showed that “Silt plus clay” type substrate, conductivity, pH and nitrate nitrogen were the primary environment factors effecting the macroinvertebrate community characteristics in studied rivers. According to the water quality evaluation results of the richness index and the BI method, 73.3% and 80.0% of the mainstream sites were identified as moderately to heavily polluted, but 80.0% and 68.0% of tributary sites were identified as non-polluted to slightly polluted. This study can provide basic data supports for ecological management and protection in the Weihe River Basin.

Time budgets of Torrent Ducks (Merganetta armata) in the Central Andes of Colombia in relation to precipitation and food availability

ABSTRACT Torrent Ducks (Merganetta armata) inhabit fast-flowing rivers in the Andes. Rainfall causes rivers to swell, increasing water velocity, turbulence, and turbidity. These changes may affect the ducks' foraging ability because of the harsher conditions or alteration of the aquatic macroinvertebrate resource base. We examined the relationship of Torrent Duck time budgets with food availability and rainfall in the central Andes of Colombia. Time spent foraging was not correlated with total macroinvertebrate density but was negatively correlated with density of 4 preferred families. Monthly precipitation was negatively correlated with total macroinvertebrate density but not correlated with the 4 preferred families. Time spent foraging correlated with rainfall the day before. Torrent Duck time budgets result from interactions among several factors: the ducks' foraging tactics, prey type, and river conditions that affect ducks directly, and indirectly through prey availability. Three of the 4 preferred i...

Time budgets of Torrent Ducks (Merganetta armata) in the Central Andes of Colombia in relation to precipitation and food availability

ABSTRACT Torrent Ducks (Merganetta armata) inhabit fast-flowing rivers in the Andes. Rainfall causes rivers to swell, increasing water velocity, turbulence, and turbidity. These changes may affect the ducks' foraging ability because of the harsher conditions or alteration of the aquatic macroinvertebrate resource base. We examined the relationship of Torrent Duck time budgets with food availability and rainfall in the central Andes of Colombia. Time spent foraging was not correlated with total macroinvertebrate density but was negatively correlated with density of 4 preferred families. Monthly precipitation was negatively correlated with total macroinvertebrate density but not correlated with the 4 preferred families. Time spent foraging correlated with rainfall the day before. Torrent Duck time budgets result from interactions among several factors: the ducks' foraging tactics, prey type, and river conditions that affect ducks directly, and indirectly through prey availability. Three of the 4 preferred i...

Effects of Aquaculture on Lakes in the Central Yangtze River Basin, China, II: Benthic Macroinvertebrates

AbstractThere is limited information available on the effects of extensive aquaculture or “fish ranching” operations on lake ecosystems. To study the effects of aquaculture on lake ecosystems, benthic macroinvertebrate communities were investigated from July to September 2015 in 23 lakes within the middle reach of the Yangtze River basin. The lakes represented four lake management strategies: fish ranching supported by low (LOW), medium (MEDIUM), or high (HIGH) stocking rates; or fallowing (FALLOW) in which previously ranched HIGH lakes had not been stocked for 2 years. Total macroinvertebrate densities did not vary significantly but were highest in the FALLOW lakes (2,352 individuals/m2), lowest in the LOW lakes (544 individuals/m2), and intermediate in the HIGH (1,734 individuals/m2) and MEDIUM lakes (1,208 individuals/m2). Chironomid densities were significantly lower in LOW lakes compared to all others, and mollusks were not observed in LOW lakes. Chironomid and total macroinvertebrate biomasses were also significantly lower in LOW lakes than in the other lakes. The FALLOW lakes had significantly greater biomasses of mollusks, oligochaetes, and total macroinvertebrates than all other lakes. Two pollution‐tolerant taxa, Tubificidae and Chironomidae, were dominant in all lakes regardless of management strategy, indicating that all study lakes were experiencing some degree of eutrophication. Results indicated that fish ranching does not affect macroinvertebrate communities in a predictable manner based on stocking density, but allowing for a fallowing period could potentially benefit lake macroinvertebrates. Canonical correspondence analysis indicated that chlorophyll a, chloride, conductivity, and total nitrogen were affecting macroinvertebrate density in these lakes, while total suspended solids, alkalinity, turbidity, total hardness, and water depth affected macroinvertebrate biomass.

River ecosystem resilience to extreme flood events.

Floods have a major influence in structuring river ecosystems. Considering projected increases in high‐magnitude rainfall events with climate change, major flooding events are expected to increase in many regions of the world. However, there is uncertainty about the effect of different flooding regimes and the importance of flood timing in structuring riverine habitats and their associated biotic communities. In addition, our understanding of community response is hindered by a lack of long‐term datasets to evaluate river ecosystem resilience to flooding. Here we show that in a river ecosystem studied for 30 years, a major winter flood reset the invertebrate community to a community similar to one that existed 15 years earlier. The community had not recovered to the preflood state when recurrent summer flooding 9 years later reset the ecosystem back to an even earlier community. Total macroinvertebrate density was reduced in the winter flood by an order of magnitude more than the summer flood. Meiofaunal invertebrates were more resilient to the flooding than macroinvertebrates, possibly due to their smaller body size facilitating greater access to in‐stream refugia. Pacific pink salmon escapement was markedly affected by the winter flood when eggs were developing in redds, compared to summer flooding, which occurred before the majority of eggs were laid. Our findings inform a proposed conceptual model of three possible responses to flooding by the invertebrate community in terms of switching to different states and effects on resilience to future flooding events. In a changing climate, understanding these responses is important for river managers to mitigate the biological impacts of extreme flooding effects.

A benthic macroinvertebrate multimetric index for Chilean Mediterranean streams

Increased anthropogenic disturbances affecting streams worldwide have resulted in declines of freshwater biodiversity. Mediterranean ecoregions are very sensitive to such disturbances because of their high levels of natural hydrological variability and increasing trends in human population growth. The use of aquatic macroinvertebrate assemblages as bioindicators is a commonly applied approach for evaluating water body condition. However, extensive use of macroinvertebrates across similar ecoregions may be limited because of natural local differences in biodiversity and differing anthropogenic disturbances. Here, we present a multi-metric index (MMI) based on macroinvertebrate assemblages from Chilean Mediterranean streams. To evaluate the relative level of disturbance among sampling sites with respect to multiple anthropogenic perturbations, we used an integrated disturbance index based on catchment and local scale disturbances. We sampled 95 sites from streams and rivers during the 2016 austral summer including 26 least-disturbed reference sites, 13 highly disturbed sites, and 56 intermediately disturbed sites. In addition, we re-sampled 14 sites during winter and spring to validate our findings. Using a set of screening criteria, we evaluated 74 candidate macroinvertebrate metrics, representing diversity, composition, trophic structure, and tolerance to pollution. The resulting MMI included Diptera taxa richness, total macroinvertebrate density, number of Ephemeroptera-Plecoptera-Trichoptera individuals, and predator taxa richness. The final MMI scores classified the 95 sampling sites into three categories of biotic condition, including good (n = 46), fair (n = 18), and poor (n = 31). Our approach is transferable to other rivers in the region and is a sufficient tool to evaluate the condition of sites affected by several human perturbations at both local and catchment scales in Chilean Mediterranean streams.

Responses of macroinvertebrate communities to small dam removals: Implications for bioassessment and restoration

Abstract Small dam removals are increasing on a global scale; yet, general predictions of organism response to dam removal are constrained by heterogeneity of study designs, implementation strategies, geographies, and characteristics of dams and their removals. Macroinvertebrate data extracted from 29 studies including 34 small dam removals over a broad geographical range were re‐analysed utilizing dam removal effect sizes (a quantified change from before to after removal). Effect sizes of 10 metrics of community structure were calculated to investigate the spatiotemporal extent of small dam removal effects and if responses differ with characteristics of the dam and environmental settings. We found that dam removal had initial negative effects on total macroinvertebrate density and Ephemeroptera, Plecoptera and Trichoptera (EPT) density, both downstream and upstream; however, recovery to pre‐removal values was reached and exceeded after c. 15–20 months. Mean annual discharge, land use in the catchment and distance from the dam affected the magnitude and direction of responses of four community metrics: total density, EPT density, %EPT density and family biotic index. Synthesis and applications. Our study provides evidence that macroinvertebrate community recovery from dam removal is mediated by catchment characteristics and system size, which may correlate with sediment flushing efficiency. Negative impacts were observed in smaller systems or those with a high percentage of undisturbed catchment areas, conditions that may benefit from sediment management prior to dam removal. Significant responses in reaches upstream of the impoundment clearly indicate that caution be applied to interpretations of response in sampling designs that utilize upstream sites for reference condition.

Fishing-induced changes in predation pressure by perch (Perca fluviatilis) regulate littoral benthic macroinvertebrate biomass, density, and community structure

We aimed to study whether the varying changes in predation pressure by perch (Perca fluviatilis) reflect the biomass, density, and community structure of the benthic macroinvertebrates. Prey preference is size-dependent, and overall predation pressure is density dependent, and thus the size structure of the P. fluviatilis population should affect the structure of the macroinvertebrate community, and the population density of P. fluviatilis should reflect the overall density of benthic macroinvertebrates. We sampled the littoral benthic community in a boreal lake that had been divided into two parts that were subjected to two different fishing procedures during 2007–2012 period and analyzed the macroinvertebrate diet of fish. The benthic macroinvertebrate community reflected the predation pressure. Total macroinvertebrate biomass increased during the study period in the lake division with a non-size-selective fishing procedure (NSF), i.e., all invertivorous perch size-classes targeted, but decreased in the section with negatively size-selective fishing procedure (SSF), i.e., large invertivorous individuals ≥ 16 cm were not targeted. This difference was a result of the increase in large-sized species, such as Odonata, for the NSF procedure and decrease in the SSF procedure. In contrast to total biomass, total macroinvertebrate density did not show a response to predator size structure but rather total macroinvertebrate density decreased with increasing fish density. The study demonstrates the effect of predation pressure of P. fluviatilis on benthic communities, thus highlighting the keystone predator role of the species in boreal lakes and gives more insight on the multiple effects of fish predation on littoral benthic communities.

Fish predation and macroinvertebrate abundance on snags in low-gradient blackwater streams

AbstractInvestigations into how fish affect macroinvertebrates in lotic ecosystems have produced equivocal results, and few researchers have examined fish effects on invertebrates in sandy-bottomed blackwater streams. We measured the responses of macroinvertebrate density, biomass, and body size to varying levels of fish predation on snags in 2 southeastern USA blackwater streams. We manipulated fish densities in 3 large enclosures (46–64 m2) in each of 2 streams and included treatments without fish (0X = control), with fish at ambient density (1X), and with fish at 2× ambient density (2X). Macroinvertebrates in enclosures were sampled using 20 tag alder (Alnus serrulatus) snags, ½ of which were allowed to colonize for 2 wk (colonizing community) and ½ for 2 mo (established community). Increasing invertivorous fish biomass resulted in a significant decrease in total macroinvertebrate density, but not macroinvertebrate biomass, in both types of communities (colonizing and established). We found that the bi...

Impacts of flood-driven water level fluctuations on macroinvertebrate assemblages in different zones of a long and narrow subtropical reservoir-bay

Macroinvertebrate communities of reservoirs are known to be affected by water level fluctuations (WLF), however, studies on the effects of WLF within the profundal zones of reservoirs are rarely reported. We examined the impacts of WLF caused by floods in the Three Gorges Reservoir (TGR) on the macroinvertebrate assemblages within different regions along the longitudinal axis of the Xiangxi Bay – a tributary of the TGR. Before the floods, macroinvertebrate density, biomass and diversity all displayed a spatial pattern of increase from the edges to center of the bay, similar to that of sediment organic matter (OM). After the floods and associated WLF, macroinvertebrate density declined substantially. In the downstream region, the flood-driven WLF did not cause obvious changes to the macroinvertebrate community. In the middle region, Chironomidae abundance increased with WLF, but total macroinvertebrate density declined due to a decline in the abundance of Tubificidae. In the upstream region, taxonomic richness increased after the floods, which may have been due to flood-driven inputs of macroinvertebrates arriving from further upstream. Pearson correlation analysis indicated that OM was positively associated with macroinvertebrate density. However, OM content in the middle and the upstream regions increased after the floods while macroinvertebrate density declined. This suggested the effect of the sedimentation and water disturbance exceeded that of OM. Although average Shannon-Wiener diversity of the Xiangxi Bay increased after the floods, beta diversity declined, implying that the dramatic flood-driven WLF caused negative effects on the stability of the Xiangxi Bay ecosystem.

Benthic macroinvertebrate community and chlorophyll a (chl-a) concentration in sediment of three polluted sites in the Lagos Lagoon, Nigeria

This paper reports the benthic macroinvertebrate community and chlorophyll a (chl-a) concentration in sediment of three polluted sites in the Lagos Lagoon, Nigeria. Values observed for DO ranged between 3.0 and 4.5 mg/L, while transparency varied from 3 cm to 32 cm. Turbidity ranged between 28 and 80 NTU and depth of the study stations fluctuated between 196.16 and 317.5 cm. Two major macroinvertebrate groups (Annelida and Mollusca) made up of eight species were identified from a total density of 7820 ind/m2. Mollusca were the most abundant group with a density of 7800 ind/m2 and accounted for 99.7 % of the total macroinvertebrate density. Density of benthic macroinvertebrate varied among the study stations, while the variations observed in the values ofchl-a in sediment were mainly in relation to sampling periods. Transparency of water correlated positively and significantly with chl-a in sediment (rs= 1; p< 0.01) while turbidity and depth of water related negatively and significantly with chl-a in sediment. Results obtained in this study suggest that pollution in the three study sites impacted negatively on the benthic community.Key Words: Chl-a, benthic macroinvertebrate, pollution, estuarine ecosystem

<strong>Caddisflies (Trichoptera) in benthic communities of southern Sakhalin rivers, Far East Russia</strong>

During one year we studied caddisfly assemblages in benthic macroinvertebrate communities of mountain (Frikena River) and piedmont (Partizanka River) reaches of the Lyutoga River Basin. For most of the year in the mountain reaches, the scraper Neophylax ussuriensis Martynov dominates. Maximum caddisfly density (403 ind./m2) and biomass (14,441 g/m2) was recorded in July before mass emergence of that dominant species. The density of caddisflies in the benthic community was more significant in November (32%), and caddisfly biomass was most significant in July (69%). In the piedmont reaches of Lyutoga River Basin in various seasons, Rhyacophila (Hyporhyacophila) sp., Hydatophylax sp., Hydropsyche orientalis Martynov, and Stenopsyche marmorata Navás dominated. Maximum density and biomass of caddisflies (451 ind./m2, 1,576 g/m2) were recorded in 5 September. The density of filterers H. orientalis and S. marmorata occurs in the salmon spawning season and seems to be correlated with the increased abundance of suspended organic substances in the water column as salmon spawn. In the piedmont reaches the role of caddisflies are the most significant in September (49% of total macroinvertebrate density and 56% of biomass).