Macroinvertebrate Production Research Articles

Effects of process‐based floodplain restoration on aquatic macroinvertebrate production and community structure

AbstractRecent stream restoration approaches, such as Stage 0 restoration, aim to restore natural processes to regain lost ecosystem functions, but project implementation can also represent a reach‐scale disturbance. Assumed outcomes of these restoration actions, like greater biological productivity, are rarely evaluated. In this study, we examined the short‐term effects of Stage 0 floodplain restoration on the secondary production of aquatic macroinvertebrate communities in the South Fork McKenzie River, Oregon, 1–2 years following project implementation. We seasonally sampled macroinvertebrates from benthic and submerged wood surfaces in the restored reach, and two unrestored reference reaches located upstream, to estimate annual secondary production. Macroinvertebrate production estimates were 3× lower on a per‐meter‐squared basis in the restored reach than in the upstream unrestored reference reaches (9764 vs. 29,636 mg DM/m2/yr). However, because there was 4.5‐times greater wetted area available in the restored reach, overall macroinvertebrate production per unit of valley length was 3.4× higher in the restored reach than in unrestored reference reaches (2744 vs. 802 kg DM/km). Additionally, the mosaic of aquatic habitats created via restoration (main‐channel, side‐channel, and wetted forest habitats) supported a diversity of macroinvertebrate assemblages both within and among reaches. Our findings suggest Stage 0 project implementation, which can include dewatering and filling incised channels, may reduce aquatic macroinvertebrate production on a per‐unit‐area basis for at least 1 or 2 years following restoration. However, this short‐term disturbance effect may be offset by channel aggradation and widening, which can provide a more wetted area for macroinvertebrate production and may support greater macroinvertebrate community diversity. Future studies are needed to examine the longer term (2–10 years) aquatic macroinvertebrate response to Stage 0 restoration, and the impacts of shifting resource availability on stream fishes.

Effects of incomplete sampling on macroinvertebrate secondary production estimates in a forested headwater stream

Estimates of secondary production depend on the efficiency of sampling methods in capturing abundances and body lengths of the entire macroinvertebrate community. The efficiency of common sampling methods in fulfilling these criteria is poorly understood. We compared the effects of a Surber sampler (250 µm mesh size) and a Freeze corer in capturing abundance, biomass, and secondary production of macroinvertebrates in a forested headwater stream. We then examined how the use of nets with different mesh sizes could affect estimates of secondary production. Macroinvertebrate abundance was three times lower, and biomass was three times higher with the Surber than with the Freeze corer. Neither method captured the entire length distribution, and incomplete sampling of body lengths and abundance resulted in underestimating total secondary production by 48% (Surber) and 49% (Freeze corer). We estimated that reducing the mesh size from 250 to 100 µm would reduce the underestimation of production from ~ 48 to ~ 12% due to the inclusion of smaller individuals. Our results improve the efficiency of common sampling methods, allowing a reliable quantification of the role of macroinvertebrates in stream ecosystem functioning.

Structure, biomass, and secondary production of benthic macroinvertebrates in subtropical Andean rivers.

Secondary production is the formation of heterotrophic biomass across time, which integrates several important ecological processes that affect the life of organisms, populations, communities and ecosystems, but its study has poor developed in South America. The objectives of this work were to describe the diversity of benthic macroinvertebrate assemblages in terms of abundance and biomass, and to quantify their secondary production for the first time in Andean rivers. A quantitative sampling scheme was implemented, using a Surber sampler, in three forested streams. Physical-chemical variables, nutrients, organic matter and chlorophyll were measured also. The macroinvertebrates were separated and identified mostly at the species level. Each taxon was assigned to a functional feeding group. Secondary production was estimated for 38 taxa, mostly Diptera, Trichoptera, Coleoptera, and Ephemeroptera. The annual production varied from 3769 to 13916 mg dry mass m-2 y-1. Most abundant taxa were also those with higher production, dominated by Ephemeroptera (Baetidae), Trichoptera (Hydropsychidae) and Diptera (Chironomidae and Simuliidae). Density, biomass, and production of collectors and predators were much higher than the other feeding groups. We expect that our results will be useful to evaluate the effects on stream functioning produced by global warming and other anthropogenic disturbances in our region.

Influence of Suspended Mussel Aquaculture and an Associated Invasive Ascidian on Benthic Macroinvertebrate Communities

Many benthic macroinvertebrates are associated with cultured bivalves but are normally excluded from studies on the environmental effects of bivalve aquacultures. We evaluated the hypothesis that mussel aquaculture increases overall “benthic” macroinvertebrate productivity by considering both sediment- and mussel sock-associated macroinvertebrates. It was predicted that the presence of the invasive ascidian Styela clava would increase this effect by increasing the mussel sock’s biogenic structure. Macroinvertebrates in sediments and on mussel socks were sampled in eight bays on Prince Edward Island, Canada: three were invaded by Styela clava and there were five where it was absent. Infaunal macroinvertebrates associated with benthic sediments (sediment macroinvertebrates) within leases were less abundant relative to the control locations outside of leases and showed a trend towards decreased biomass and productivity. Abundance of mussel sock-associated macroinvertebrates was greater in bays with S. clava than in bays without it. When sediment and mussel sock macroinvertebrates were considered together as “benthic” communities within mussel leases and compared to sediment macroinvertebrate communities outside of leases, “benthic” macroinvertebrate abundance, biomass, and productivity were greater inside mussel leases than in areas outside of them. The presence of S. clava did not influence this trend. Although the ecological role of the macroinvertebrates associated with suspended mussels is likely not equivalent to those associated with benthic sediments, the presence of macroinvertebrates on suspended mussels, in some measure, offsets the impacts on the abundance, biomass, and productivity of macroinvertebrate communities at the farm-scale.

Rehabilitating Valley Floors to a Stage 0 Condition: A Synthesis of Opening Outcomes

Degraded floodplains and valley floors are restored with the goal of enhancing habitat for native fish and aquatic-riparian biota and the protection or improvement of water quality. Recent years have seen a shift toward “process-based restoration” that is intended to reestablish compromised ecogeomorphic processes resulting from site- or watershed-scale degradation. One form of process-based restoration has developed in the Pacific Northwest, United States, that is intended to reconnect rivers to their floodplains by slowing down flows of sediment, water, and nutrients to encourage lateral and vertical connectivity at base flows, facilitating development of dynamic, self-forming, and self-sustaining river-wetland corridors. Synergies between applied practices and the theoretical work of Cluer and Thorne in 2014 have led this form of restoration to be referred to regionally as restoration to a Stage 0 condition. This approach to rehabilitation is valley scale, rendering traditional monitoring strategies that target single-thread channels inadequate to capture pre- and post-project site conditions, thus motivating the development of novel monitoring approaches. We present a specific definition of this new type of rehabilitation that was developed in collaborative workshops with practitioners of the approach. Further, we present an initial synthesis of results from monitoring activities that provide a foundation for understanding the effects of this approach of river rehabilitation on substrate composition, depth to groundwater, water temperature, macroinvertebrate richness and abundance, secondary macroinvertebrate production, vegetation conditions, wood loading and configuration, water inundation, flow velocity, modeled juvenile salmonid habitat, and aquatic biodiversity.

Resource supply and organismal dominance are associated with high secondary production in temperate agricultural streams

Abstract Agricultural land‐use affects the environmental and biological characteristics of stream ecosystems through multiple pathways including nutrient and pesticide contamination, riparian clear‐cutting and hydromorphological degradation. These changes in the abiotic environment can have a direct effect on the productivity of macroinvertebrate communities through environmental filtering and via altered resource conditions encompassing a shift from allochthonous to autochthonous primary production and changes in elemental stoichiometry and food quality. Additionally, macroinvertebrate productivity can be affected indirectly via biological mechanisms, such as changes in species interactions, richness, competition, and predation. We studied the effects of agriculture on structural and functional descriptors of macroinvertebrate communities by assessing environmental characteristics and macroinvertebrate secondary production (MSP), biomass and density in two forested and two agricultural streams and investigated underlying biotic mechanisms. On average, MSP was 1.6–3.6, biomass 2.8–6.2 and density 5–13 times higher in agricultural than in forested streams. This pattern was associated with higher nutrient concentrations, standing crops of riparian herbaceous vegetation, suspended particulate organic carbon, quantity and quality of epilithic biofilms and chlorophyll‐a concentrations in seston and biofilm of the agricultural streams. Species richness and evenness were significantly lower in agricultural than in forested streams. A negative relationship between MSP and species richness and evenness indicated that density compensation and trait dominance were the prevalent mechanisms facilitating higher MSP in agricultural streams. Our findings suggest that the loss of riparian canopy and excess nutrient conditions are the major environmental drivers contributing to homogenization of ecological niches and dominance of highly productive non‐insect generalist species. This study highlights the importance of an ecosystem approach to understanding how complex aggregate stressors affect the regulation of consumer–resource interactions. There is an urgent need to preserve or restore natural riparian vegetation, fostering habitat and resource diversity and limiting nutrient contamination to stream ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

Periphyton as a key diet source of essential fatty acids for macroinvertebrates across a nutrient and dissolved organic carbon gradient in boreal lakes

AbstractWe studied how physiologically important long‐chain polyunsaturated fatty acids (PUFA) in benthic macroinvertebrates (Asellus aquaticus, Chironomidae, and Oligochaeta) were related to those in periphyton and terrestrial organic matter (tree leaves), collected from littoral areas of 17 boreal lakes that differed in their dissolved organic carbon (DOC) and nutrient (phosphorus and nitrogen) concentrations. We also analyzed fatty acid (FA)‐specific stable carbon isotopes (δ13CFA) to investigate the dietary origin (periphyton vs. terrestrial organic matter) of PUFA in the consumers. In contrast to periphyton, terrestrial organic matter was deprived of long‐chain PUFA, such as eicosapentaenoic acid (EPA), but rich in short‐chain PUFA. The FA composition of macroinvertebrates was primarily taxon‐specific despite the large differences in DOC and nutrient concentrations of the lakes. An increase in DOC concentration had a negative impact on the EPA content of Asellus, chironomids, and oligochaetes as well as the total FA content of chironomids and oligochaetes. However, the FA content of macroinvertebrates was not related to lake total phosphorus concentrations, although the total FA and EPA content of periphyton increased with the trophic status of the study lakes. The δ13CPUFA values of macroinvertebrates were positively related with the δ13CPUFA of periphyton and weakly with δ13CPUFA of terrestrial leaf material. The results indicate that EPA in the studied macroinvertebrate taxa was mainly derived from an algal‐based diet and not via biosynthesis from allochthonous precursor FA. Thus, macroinvertebrate production in lakes may be limited by the available algae‐based food sources.

Effects of a lagoon on performances of a freshwater fishpond in a multi-trophic aquaculture system

Integrated multi-trophic aquaculture (IMTA) is a way to help preserve the environment while maintaining a good level of total production. An ecologically semi-intensive pond system was designed in which a polyculture fishpond was associated with a lagoon planted with macrophytes to bioremediate the water. The properties of this “semi-intensive coupled” system (SIC) were compared to those of semi-intensive (SI) and extensive (E) systems, each of which was contained in a single fishpond with the same fish polyculture (common carp (Cyprinus carpio), roach (Rutilus rutilus), and perch (Perca fluviatilis)) as SIC. E differed in that it had half the initial density of fish, and the fish were not fed. Fish growth performances, water quality (chemical and biological indicators), chlorophyll concentrations, and invertebrate production were measured. The systems were compared based on fish production performances and physicochemical and biological characteristics, and were then described using principal component analysis (PCA). Carp and roach in the two fed systems had higher growth performances than those in E. Compared to SI, the planted lagoon in SIC, induced a decrease of 15% in fish growth performances and of 83% in total chlorophyll concentration (a proxy for phytoplankton) but improved water quality (−34%, −60% and −80%, for the concentrations of total nitrogen, total phosphorus, and blue green algae (for micro-algae in class Cyanophyceae), respectively). According to the PCA, SIC clearly differed from SI in benthic macro-invertebrate production and concentrations of total nitrogen, total phosphorus, and brown algae (for micro-algae in class Dinophyceae or a branch of Bacillariophyta) in the water. SIC differed from E in oxygen parameters (dissolved and saturation), estimated annual zooplankton production, and pH. In conclusion, the properties of a lagoon reveal perspectives for environmentally friendly practices, while using biodiversity and secondary production in order to enhance fish production.

The ultimate peanut butter on crackers for Hyalella: diatoms on macrophytes rather than bacteria and fungi on conditioned terrestrial leaf litter

Abstract It is well established that terrestrial and aquatic ecosystems are interlinked in a myriad of ways, yet understanding of the role terrestrial particulate organic matter (OM) plays in supporting aquatic macroinvertebrate production is still incomplete and debated. We investigated the role of terrestrial particulate OM (leaf litter) and autochthonous OM (macrophytes) with and without biofilm as food sources for the model benthic macroinvertebrate Hyalella (Amphipoda). We hypothesised that biofilm (algae, fungi, bacteria) associated with terrestrial and aquatic plants is the main food source for benthic primary consumers. First, we microbially conditioned the leaf litter insitu for 10‐weeks. Then, we performed a laboratory feeding experiment with nine treatments: no food, conditioned leaf litter from two native terrestrial plants, non‐conditioned leaf litter from these plants, two freshly collected macrophyte species with periphyton, and these macrophytes without periphyton. We measured the growth and analysed the fatty acid (FA) composition of field‐collected and experimental amphipods reared on these diets. We found that amphipods fed food sources without biofilm grew poorly and had a FA content and composition resembling that of starved animals. The same was observed for amphipods fed one leaf litter type with biofilm. However, animals fed the other leaf litter type with biofilm grew during the feeding experiment and showed a characteristic FA composition linked to the higher fungal biomass in this food source. We showed that amphipods fed macrophytes with biofilm resembled field‐collected animals regarding FA amounts and composition; monounsaturated FA representing >40% of total FA, with 16:1n‐7 (palmitoleic acid) and 18:1n‐9 (oleic acid) being the most abundant, and polyunsaturated FA representing 30% of total FA. The FA data indicated algae, particularly diatoms, as evidenced by large quantities of its biomarker 16:1n‐7, were the main food for the amphipods. We conclude diatoms were the peanut butter on crackers for the amphipods, and diatom consumption supported its somatic growth and polyunsaturated FA composition. In contrast, bacteria and fungi on conditioned leaf litter were lower quality food sources because they do not provide essential FA for macroinvertebrates growth and physiology. These results have important ecological implications from a food web perspective.

Secondary production of macroinvertebrates as indicators of success in stream rehabilitation

AbstractHydromorphological rehabilitation is increasingly being used to reverse degradation of stream and river ecosystems. River rehabilitation projects have nevertheless been criticised for not meeting their goals or for not being monitored sufficiently well to assess whether their goals were met. There is therefore an urgent need to develop robust approaches to assessing treatment efficacy and to thus guide the increasing investment in rehabilitation. A headwater tributary of the River Welland in Leicestershire, UK was rehabilitated in summer 2014. Rehabilitation included removal of weirs and the creation of a distinct and meandered low‐flow channel with pool‐riffle sequences. Macroinvertebrates were collected in random sampling protocols stratified at in‐stream biotope level. The rehabilitated reach was compared with a semi‐natural upstream reach as a reference, and a similarly degraded reach as a control. This study demonstrated that rehabilitation of the River Welland had clear beneficial effects on ecological processes. It demonstrated that active re‐creation of lost biotope heterogeneity improved macroinvertebrate biodiversity and secondary production, which is the formation of heterotrophic biomass through time. The rehabilitated reach yielded higher production estimates for Gastropoda, Bivalvia, Malacostraca, Odonata, Arachnida and Ephemeroptera, Plecoptera and Trichoptera, and a lower estimate for Chironomidae relative to the control reach. The rehabilitated reach also had higher estimates of production for Shredder, Scraper, Filter‐feeder and Predator feeding groups relative to the control reach. Rehabilitation works transformed the reach from a condition more akin to the degraded reach to being more similar to the semi‐natural reach. These outcomes demonstrate recovery of the reach's entire macroinvertebrate community structure and function after rehabilitation. The results provide a clear message to river rehabilitation practitioners: rehabilitation of the function of a physically degraded river ecosystem is possible if the rehabilitation is planned to actively restore the lost in‐stream biotope diversity.

Patterns of macroinvertebrate production and energy flow in headwater streams of the Brazilian Savanna

AbstractSecondary production estimates are an important element of ecosystem ecology because they facilitate quantification of the roles of consumers in material and energy cycling. We estimated pr...

Experimental N and P additions relieve stoichiometric constraints on organic matter flows through five stream food webs.

Human activities have dramatically altered global patterns of nitrogen (N) and phosphorus (P) availability. This pervasive nutrient pollution is changing basal resource quality in food webs, thereby affecting rates of biological productivity and the pathways of energy and material flow to higher trophic levels. Here, we investigate how the stoichiometric quality of basal resources modulates patterns of material flow through food webs by characterizing the effects of experimental N and P enrichment on the trophic basis of macroinvertebrate production and flows of dominant food resources to consumers in five detritus-based stream food webs. After a pre-treatment year, each stream received N and P at different concentrations for 2years, resulting in a unique dissolved N:P ratio (target range from 128:1 to 2:1) for each stream. We combined estimates of secondary production and gut contents analysis to calculate rates of material flow from basal resources to macroinvertebrate consumers in all five streams, during all 3years of study. Nutrient enrichment resulted in a 1.5× increase in basal resource flows to primary consumers, with the greatest increases from biofilms and wood. Flows of most basal resources were negatively related to resource C:P, indicating widespread P limitation in these detritus-based food webs. Nutrient enrichment resulted in a greater proportion of leaf litter, the dominant resource flow-pathway, being consumed by macroinvertebrates, with that proportion increasing with decreasing leaf litter C:P. However, the increase in efficiency with which basal resources were channelled into metazoan food webs was not propagated to macroinvertebrate predators, as flows of prey did not systematically increase following enrichment and were unrelated to basal resource flows. This study suggests that ongoing global increases in N and P supply will increase organic matter flows to metazoan food webs in detritus-based ecosystems by reducing stoichiometric constraints at basal trophic levels. However, the extent to which those flows are propagated to the highest trophic levels likely depends on responses of individual prey taxa and their relative susceptibility to predation.

Coupled reservoir-river systems: Lessons from an integrated aquatic ecosystem assessment

Sustainable reservoir-river management requires balancing complex trade-offs and decision-making to support both human water demands and ecological function. Current numerical simulation and optimization algorithms can guide reservoir-river operations for optimal hydropower production, irrigation, nutrient management, and municipal consumption, yet much less is known about optimization of associated ecosystems. This ten-year study demonstrates an ecosystem assessment approach that links the environmental processes to an ecosystem response in order to evaluate the impact of climatic forcing and reservoir operations on the aquatic ecosystems of a coupled headwater reservoir-river system. The approach uses a series of numerical, statistical, and empirical models to explore reservoir operational flexibility aimed at improving the environmental processes that support aquatic ecosystem function. The results illustrate that understanding the seasonal biogeochemical changes in reservoirs is critical for determining environmental flow releases and the ecological trajectory of both the reservoir and river systems. The coupled models show that reservoir management can improve the ecological function of complex aquatic ecosystems under certain climatic conditions. During dry hydrologic years, the high post-irrigation release can increase the downstream primary and macroinvertebrate production by 99% and 45% respectively. However, this flow release would reduce total fish biomass in the reservoir by 16%, providing management tradeoffs to the different ecosystems. Additionally, low post-irrigation flows during the winter season supports water temperature that can maintain ice cover in the downstream river for improved ecosystem function. The ecosystem assessment approach provides operational flexibility for large infrastructure, supports transparent decision-making by management agencies, and facilitates framing of environmental legislation.

Feeding behavior of the ocypodid crab Macrophthalmus japonicus and its effects on oxygen-penetration depth and organic-matter removal in intertidal sediments

This study examined the poorly understood feeding behavior of the ocypodid crab Macrophthalmus japonicus in the field to explore its effects on oxygen-penetration depth (OPD) and organic-matter removal from intertidal sediments. An in situ investigation was conducted on an upper mud flat in the mouth of the Han River estuary, on the western coast of Korea. The behavior of M. japonicus and variation in the OPD within its habitat were surveyed and contents of organic materials such as organic carbon (OC), organic nitrogen (ON) and δ15N in its feeding pellets were compared as contrasted with non-feeding sediments during the daytime ebb in summer. We continuously recorded the surface activity of the crab during two main feeding periods and during a resting period, when the crabs remain immobile on the surface. Feeding periods exceeded 1 h; crabs fed on sediments more actively during the first feeding period (45 pseudo-pellets individual−1 h−1) than during the second feeding period (19 pseudo-pellets individual−1 h−1). The feeding period duration increased as body size decreased. Adult crabs devoted more of their time to basking in sunlight to dry their bodies, whereas young crabs spent most of their time feeding. Crab feeding activity on the surface generally enhanced the OPD. Conversely, OPD decreased during basking, when most crabs were immobile. Crab feeding greatly altered sediment geochemistry in the intertidal flat. In feeding pellets, OC and ON concentrations decreased to 55% and 60%, respectively, of those in non-feeding sediments. OC and ON were removed at rates of 1.89 mmol C m−2 h−1 and 0.24 mmol N m−2 h−1, respectively. The removal rate of OC by crab feeding was three-fold higher than that of OC mineralization by diffusive oxygen uptake (average: 0.56 mmol C m−2 d−1) and was comparable with the rate of anaerobic carbon mineralization (1.74–3.83 mmol m−2 h−1) in this region. The increase in the C/N ratio (10.6%–12.5%) and decrease in δ15N (7.21‰–5.99‰) in feeding pellets compared with non-feeding sediments indicate that M. japonicus removed N more selectively to meet requirements. These results imply that in situ crab activity significantly influenced OC and ON cycles; therefore, it is necessary to consider processes such as macroinvertebrate production and consumption when evaluating the purification function of intertidal sediments.

Influences of fish on food web structure and function in mountain lakes

Abstract Introduction of new fish species to lakes that contain fish is known to disrupt food webs, but few studies have quantified the effects of introduced fish on flow of organic matter and mechanisms governing food web structure in historically fishless lakes. Contrasting flow of organic matter and food web structure in macroinvertebrate communities in lakes with and without fish provides an opportunity to characterise resiliency of macroinvertebrate food web function when there are changes in community composition and reductions in biomass. Organic matter flow and food web structure were characterised in six lakes with and six lakes without fish at high elevation in the southern Rocky Mountains of Colorado, U.S.A. Carbon (δ13C) and nitrogen (δ15N) were used to determine the proportionate contribution of organic matter from primary organic matter sources (periphyton, phytoplankton, terrestrial plants) to consumers including herbivores and higher trophic levels. Contributions of organic matter sources to macroinvertebrates were combined with estimates of littoral macroinvertebrate production in quantifying the contribution of each primary source to total invertebrate production. Although introduced fish altered community composition, body size, and biomass, they did not alter contributions of the organic matter sources to production of macroinvertebrates. The dominant resources contributing to macroinvertebrate production were periphyton and phytoplankton, which combined contributed to 80% of macroinvertebrate production. Despite occupying the highest trophic position (difference in δ15N relative to primary sources), fish did not alter trophic structure of littoral macroinvertebrate communities in maximum macroinvertebrate trophic position and community trophic position. Community trophic position weighted by production for macroinvertebrates was related to macroinvertebrate production per unit area but was independent of lake area. In lakes with fish, maximum macroinvertebrate trophic position was similar to that of lakes without fish because large predators (predaceous beetles and dragonflies) were replaced by small predators (tanypod chironomids). The present study indicates that macroinvertebrate food webs can exhibit resilience to introduced or invasive fish even when there are changes in community composition and biomass. This suggests that changes in structure (e.g. biomass, community composition) associated with introduced or invasive species do not necessarily equate to changes in food web function (e.g. flow of organic matter, maximum trophic position). Further, the present study suggests that although maximum trophic position has been shown to increase with lake size for lakes containing fish, the pattern is unlikely to extend to lakes without fish. The relationship between lake size and maximum trophic position for lakes containing fish may occur because fish have expandable niches associated with high motility and indeterminate growth, in contrast to macroinvertebrates.

Main stem and off‐channel habitat use by juvenile Chinook salmon in a sub‐Arctic riverscape

Abstract Poor growth and survival in freshwater and marine environments have been implicated as responsible for Chinook salmon (Oncorhynchus tshawytscha) declines across Alaska. Lateral connectivity of river main stems with off‐channel habitats may play an integral role in sustaining Alaskan salmonid populations because off‐channel habitats commonly provide greater growth opportunities than main stem habitats through greater macroinvertebrate productivity and warmer water temperatures. However, off‐channel habitats may impose greater mortality risks to juvenile salmonids, as these habitats are typically more susceptible to drying and are often occupied by potential predators. We used a hierarchical Bayesian count model to describe juvenile Chinook salmon distributions throughout the Chena River, Alaska in main stem and off‐channel habitats and employed diet, prey availability, and bioenergetic analyses to explain these habitat selection decisions from data collected in the summer of 2015. We found salmon to be most abundant in off‐channel habitats as summer temperature increased, which suggested that salmon dispersed to off‐channel habitats to take advantage of energetically favourable growth conditions as indicated by the higher prey biomass in benthic and diet samples collected within off‐channel habitats. Our results could have significant implications for juvenile salmon under a warming Alaskan climate as access to productive off‐channel habitats may be important to offset increased energetic costs as temperature warms.

Benthic life in karst spring—The life cycle and secondary production of benthic macroinvertebrates under the effects of constant water temperature

Because of the thermal stability and the persistence over geological time scales of their aquifers, the permanent karst springs may act as a glacial refuge, as well as serve as “in vivo” laboratories for the testing of various ecological hypotheses. For these reasons, our main hypotheses were: i) to the constant water temperature benthic species will response by specific voltinism and life-cycle length will be different from those that the species usually have in non-spring habitats; ii) under the constant water temperature the particular species and whole community will have higher biomass turnover like in similar non-spring habitats. Investigation was performed in large cave karst spring “Vyvieranie” in the Western Carpathians. In total, 40 species of benthic macroinvertebrates were identified in the studied karst spring. The trajectory of the annual change of the benthic community structure clearly showed a returnable pattern at the species density and biomass level. The constant water temperature throughout the year was reflected by specific life-history trajectories in certain benthic species. While some species had fixed voltinism (e.g. Ephemerella mucronata, Isoperla sudetica), others indicated having a flexible life-cycle pattern. In the species with a flexible life cycle, the trajectory of larval development occurred in two different ways. In the first case, a constant water temperature extended larval development (e.g. Protonemura auberti, Leuctra albida). In the second case, the addition of a winter cohort was recorded (e.g. Gammarus fossarum, Rhyacophila tristis, Protonemura austriaca). The productivity of this benthic community was considerably higher than that previously found in other submountain limestone streams in the Western Carpathians.

Lakeshore modification reduces secondary production of macroinvertebrates in littoral but not deeper zones

AbstractLittoral macroinvertebrates are an integral component of lake food webs, but their productivity may be affected by shoreline alteration. We hypothesized that human modification of lake shor...

Disturbance, nutrients, and antecedent flow conditions affect macroinvertebrate community structure and productivity in an Arctic river

AbstractClimate change is expected to alter disturbance regimes and biogeochemical cycles that underlie the structure and function of ecosystems worldwide. In the Arctic, rapid warming is already affecting these processes via changes in precipitation and thawing permafrost. We assessed how anticipated changes in disturbance regimes and nutrient availability may affect an arctic river ecosystem (Kuparuk River, Alaska) by analyzing temporal patterns of biofilm chlorophyll mass and macroinvertebrate community structure and productivity. Our study incorporated an upstream reach (sampled 2001–2012) and a downstream reach (sampled 2011–2012) to which phosphorus (P) was added to simulate increases in nutrient supply that are anticipated as permafrost thaws. Greater hydrologic disturbance during the open‐water season correlated with reduced algal biomass and invertebrate secondary production (range ∼ 2–7 g DM m−2 yr−1) in the following spring and summer. Bed disturbing flows also altered macroinvertebrate community structure with distinct “high‐flow” and “base‐flow” assemblages documented. Recovery time was shorter for chlorophyll mass and macroinvertebrate production (∼ 1 yr) than community structure (∼ 3 yr). Experimental P‐addition increased algal biomass and invertebrate production, but also resulted in a third macroinvertebrate assemblage dominated by mobile grazers rather than filter‐feeders. Our results suggest that a decrease in the return interval for bed disturbing floods to < 4 yr will result in persistent changes in macroinvertebrate community structure and fundamental alterations to the food web. These results also demonstrate how arctic river communities may be affected by increases in the magnitude and variability of river discharge and nutrient supplies that are anticipated as the climate warms.

Seasonal and spatial variations of stream insect emergence in an intensive agricultural landscape

A growing amount of literature exists on reciprocal fluxes of matter and energy between ecosystems. Aquatic subsidies of winged aquatic insects can affect terrestrial ecosystems significantly, but this issue is rarely addressed in agroecosystems. By altering the production of benthic macroinvertebrates, agricultural practices could increase or decrease the strength of aquatic subsidies and subsequently the provision of several ecosystem services to agriculture. Effects of seasons and environmental variables on aquatic insect emergence were investigated in third-order agricultural streams in northwestern France. Most emerging dry mass (DM) of caught insects belonged to Trichoptera (56%), Chironomidae (25%) and Ephemeroptera (19%). We estimated that annual emerging dry mass of aquatic insects ranged between 1445 and 7374 mg/m2/y depending on the stream. Seasonal variations were taxon-specific, with Ephemeroptera emerging only in spring, Trichoptera emerging in spring and early summer, and Chironomidae emerging throughout the year. The percentage of watershed area covered by agriculture, ammonium concentration and hypoxia positively influenced emerging DM of Chironomidae but negatively influenced Ephemeroptera. Emerging DM of Trichoptera and Ephemeroptera increased significantly as water conductivity and temperature increased. Channel openness increased the emerging DM of all taxonomic groups, but Chironomidae were more abundant in narrow, incised streams. Assuming that the biomass of aquatic invertebrates ultimately disperse toward terrestrial habitats, nutrient accumulations on land near streams were estimated to reach 0.5–2.3 kg C ha−1 y−1, 0.1–0.5 kg N ha−1 y−1 and 0.005–0.03 kg P ha−1 y−1, depending on the stream. This suggests a significant flux of aquatic nutrients to agroecosystems and the need for future studies of its potential influence on the ecosystem services provided to agriculture.