Macroinvertebrate Trophic Structure Research Articles

Reconnecting a stream channel to its floodplain: implications for benthic diatoms and macroinvertebrate trophic structure

Streams systems draining upland landscapes provide valuable ecosystem services, but they are vulnerable to incision and channelization caused by anthropogenic disturbance. Restoring a degraded stream to its pre‐disturbance condition by reconnecting the channel to its historical floodplain aims to recover lost hydro‐morphological processes and functions. Seeking evidence to indicate whether that aim is met in practice, we examined diatoms and the stream macroinvertebrate trophic structures in three reaches of Whychus Creek, Oregon, United States. Two reaches were reconnected to their pre‐disturbance floodplains in 2012 and 2016. The third, control reach, was not restored and was selected to represent the degraded stream condition prior to restoration. Ordinations showed that benthic diatom species composition shifted from the control reach to the restored reaches. Compared to the control reach, reconnection decreased the percentages of diatoms with nitrogen (N)‐fixing cyanobacterial endosymbionts in the 2012 restored reach and decreased diatoms tolerant to low N conditions in both the restored reaches. δ15N values in both stream macroinvertebrates and tree leaves in the riparian zone were higher in the restored reaches. These findings suggest that floodplain reconnection may modify hydro‐morphological processes and ecosystem functions in ways that enhance organic matter retention and hyporheic exchange, resulting in increased nutrient availability, improved nutrient cycling, and greater primary productivity. More generally, our results suggest that characterizing diatom species composition and trophic interactions using stable isotopes provides the basis for identifying and evaluating the beneficial effects of stream restoration on ecosystem functions and the food‐web.

Macroinvertebrate trophic structure on waterfalls in Borneo

Waterfalls have unique physical characteristics and harbour highly specialised macroinvertebrate communities, but have been the subject of very few ecological studies. There are no previous studies of trophic structure of waterfall assemblages. It was hypothesised that because of the steep gradient of waterfalls and low retention of terrestrial-based resources, the abundant basal food resources would be periphyton. In addition, because of the frequent scouring flood events, it was predicted that periphyton would be a significant source of food for filter feeders. Waterfalls in the Ulu Temburong National Park (Brunei Darussalam) were used in the present case study. Methods included stable carbon (C)- and nitrogen (N)-isotope analyses (SIA; δ13C and δ15N of leaf litter and periphyton) and gut-content analysis (GCA) of the most the abundant macroinvertebrates. With δ15N values ranging from –1.9 to 5.5‰, literature suggests that this indicates that herbivores (Heptageniidae and Blephariceridae), omnivores (Simuliidae and Hydropsychidae) and predators (Buccinidae) live in the waterfalls. Apart from Buccinidae, the taxa had δ13C signatures ranging from –33 to –26‰, with a high dependence on periphyton, which is similar to other tropical-stream biotopes. The present study suggests that despite scouring velocities, waterfalls support animals with a range of diets, based on grazing or scraping, filter feeding and predation.

Changes in macroinvertebrate trophic structure along a land-use gradient within a lowland stream network

Running waters are among the most threatened ecosystems globally, having altered hydrological regimes, homogenized habitat, and impaired water quality. These multiple stressors impact aquatic biodiversity and ecosystem function across space and time, although a clear mechanistic understanding is still lacking. Here, we examined the trophic response of macroinvertebrates among streams in a Swiss lowland catchment encompassing a gradient of land uses. Clear compositional changes were observed as anthropogenic impacts increased from least-impacted to agricultural and urbanized sites. Taxonomic diversity was lowest at sites with morphological and water quality impairment (agricultural sites), whereas taxonomic identity (susceptible vs. generalist species) mainly changed due to water quality degradation (agricultural and urban sites) based on the SPEAR (pesticides) index. Using stable isotopes (δ13C, δ15N), a simplification in macroinvertebrate trophic structure was evident along the land use gradient. At a site receiving wastewater treatment effluent, stable isotopes also revealed trophic shifts in primary consumers that corresponded to changes in available food resources. Results further showed that some taxa losses, e.g., the mayfly Ecdyonurus, to land- use effects may be due to low trophic plasticity. The combination of analyses, including stable isotopes, provided an improved mechanistic understanding of community and population responses to land-use changes along river networks.

Stream macroinvertebrate communities across a gradient of natural gas development in the Fayetteville Shale

Oil and gas extraction in shale plays expanded rapidly in the U.S. and is projected to expand globally in the coming decades. Arkansas has doubled the number of gas wells in the state since 2005 mostly by extracting gas from the Fayetteville Shale with activity concentrated in mixed pasture-deciduous forests. Concentrated well pads in close proximity to streams could have adverse effects on stream water quality and biota if sedimentation associated with developing infrastructure or contamination from fracturing fluid and waste occurs. Cumulative effects of gas activity and local habitat conditions on macroinvertebrate communities were investigated across a gradient of gas well activity (0.2–3.6wells per km2) in ten stream catchments in spring 2010 and 2011. In 2010, macroinvertebrate density was positively related to well pad inverse flowpath distance from streams (r=0.84, p<0.001). Relatively tolerant mayflies Baetis and Caenis (r=0.64, p=0.04), filtering hydropsychid caddisflies (r=0.73, p=0.01), and chironomid midge densities (r=0.79, p=0.008) also increased in streams where more well pads were closer to stream channels. Macroinvertebrate trophic structure reflected environmental conditions with greater sediment and primary production in streams with more gas activity close to streams. However, stream water turbidity (r=0.69, p=0.02) and chlorophyll a (r=0.89, p<0.001) were the only in-stream variables correlated with gas well activities. In 2011, a year with record spring flooding, a different pattern emerged where mayfly density (p=0.74, p=0.01) and mayfly, stonefly, and caddisfly richness (r=0.78, p=0.008) increased in streams with greater well density and less silt cover. Hydrology and well pad placement in a catchment may interact to result in different relationships between biota and catchment activity between the two sample years. Our data show evidence of different macroinvertebrate communities expressed in catchments with different levels of gas activity that reinforce the need for more quantitative analyses of cumulative freshwater-effects from oil and gas development.

Environmental effects and urban impacts on aquatic macroinvertebrates in a stream of central Brazilian Cerrado

The urban effects on macroinvertebrate trophic structure were evaluated in a stream located in central Brazilian Cerrado. Samplings were evaluated from May/2004 to March/2005 in the upper, middle and lower sections. Characterization of ecological conditions and habitat diversity indicated headwater as “natural” site, up and downstream the urban region were “altered” ones, and the sites located nearest to urban area were considered “impacted”. A well oxygenated and transparent water, acid pH, low electrical conductivity (<0.22 µS/cm), and low nutrients concentrations (<0.03 mg/L PO 4 −2 , <0.05 mg/L N–NH4 and <3.0 mg/L N–NO 3 −2 ) was registered for headwater area. Stretches located near the urban region had higher electrical conductivity (48–100 µS/cm), higher ammonium (7.16 mg/L), and poor oxygenated water. The trophic organization was different along the stream and related to environmental preservation degree. Shredders occurred only in the headwater (Phylloicus sp., Trichoptera). Predators were dominant in upstream sites of the urban area (>90 % of biomass). In the sites located near the urban area, an alternative predominance was observed between gathering collectors and predators, with the gathering collectors dominance in the area impacted by city sewage inflow (>90 %). There was a progressive participation of scrapers in stretches located downstream of the city. Biomass was dominated by predators (>50 % in six sites) encompassing larger organisms (>20 mm), and gathering collectors were density dominants (from 53 to 99 %). Predators were the most dominant functional feeding group (22 taxa), followed by scrapers (eight), gathering collectors (seven) and filtering collectors (five). The results state that the Sobradinho stream is under different degrees of environmental impacts with lower preservation levels of its natural conditions, even in areas close to its headwater.

If we build it, will they colonize? A test of the field of dreams paradigm with soil macroinvertebrate communities

Soil invertebrates transfer energy and material between belowground and aboveground systems, but a clear understanding of their recovery following long-term disturbance to soil is lacking. We quantified trophic, taxonomic, and compositional change of soil macroinvertebrates in cultivated fields, prairies restored for 1–21 years, and prairies that had never been cultivated. Taxonomic diversity (H′; based on morphospecies), richness, and evenness did not change across the chronosequence. Average taxonomic richness across all restorations was intermediate to cultivated fields and remnant prairie. Detritivores increased linearly across the chronosequence, while omnivores peaked at 5–8 years following restoration, coinciding with high plant richness. Spiders were the only predators that increased across the chronosequence. Proportional similarity of the macroinvertebrate communities to the average structure of remnant prairies increased across the chronosequence, but this relationship was not upheld when individual remnant prairies with different community structures were used. This study demonstrates that remnants can vary widely in macroinvertebrate trophic structure, diversity, and taxonomic composition and include exotic macroinvertebrate species, indicating a real dilemma for assessing recovery of restorations to a “target” community.

Trophic structure of macroinvertebrates in Amazonian streams impacted by anthropogenic siltation

AbstractThis study assessed the results of anthropogenic sediment input on macroinvertebrate trophic structure in streams located in an area of oil and natural gas exploitation in Brazil's Amazon forest. The results indicate that macroinvertebrate communities both in streams impacted by anthropogenic sediments and in non‐impacted streams are composed mainly of taxa in the following functional feeding groups: predators, gathering‐collectors, scrapers, shredders and filtering‐collectors. The highest densities were observed for collector‐gatherers, followed by scrapers, predators, shredders and filtering‐collectors. However, both the richness and the density of all groups were reduced in impacted streams. The reductions were significantly related to suspended inorganic sediment load and to the colour of suspended sediments. The relative proportion of shredders in streams impacted by anthropogenic sediments was significantly reduced as compared with the proportion observed in non‐impacted streams. This resulted from lower availability of coarse particulate organic matter in these streams owing to burial of leaves and other plant material. These results indicate changes in the functioning and productivity of streams owing to anthropogenic siltation. This is because the benthic macroinvertebrate communities, sampled during this study, were dependent on the degradation of leaves, which are the primary energy source sustaining the benthic foodweb.

Response of algal metrics to nutrients and physical factors and identification of nutrient thresholds in agricultural streams

Many streams within the United States are impaired due to nutrient enrichment, particularly in agricultural settings. The present study examines the response of benthic algal communities in agricultural and minimally disturbed sites from across the western United States to a suite of environmental factors, including nutrients, collected at multiple scales. The first objective was to identify the relative importance of nutrients, habitat and watershed features, and macroinvertebrate trophic structure to explain algal metrics derived from deposition and erosion habitats. The second objective was to determine if thresholds in total nitrogen (TN) and total phosphorus (TP) related to algal metrics could be identified and how these thresholds varied across metrics and habitats. Nutrient concentrations within the agricultural areas were elevated and greater than published threshold values. All algal metrics examined responded to nutrients as hypothesized. Although nutrients typically were the most important variables in explaining the variation in each of the algal metrics, environmental factors operating at multiple scales also were important. Calculated thresholds for TN or TP based on the algal metrics generated from samples collected from erosion and deposition habitats were not significantly different. Little variability in threshold values for each metric for TN and TP was observed. The consistency of the threshold values measured across multiple metrics and habitats suggest that the thresholds identified in this study are ecologically relevant. Additional work to characterize the relationship between algal metrics, physical and chemical features, and nuisance algal growth would be of benefit to the development of nutrient thresholds and criteria.

A model of macroinvertebrate trophic structure and oxygen demand in freshwater wetlands

Abstract We present a model of macroinvertebrate trophic structure, detrital cycling, and dissolved oxygen (DO) dynamics in shallow freshwater wetlands with varying allochthonous subsidies. The model is based on field data of primary and secondary production in municipal wastewater-fed and river-fed constructed wetlands in central Ohio, USA. State variables for primary production include macrophyte, periphyton, and metaphyton biomass. Macroinvertebrate biomass is segregated by functional feeding group and includes collectors, scrapers, shredders, and predators. Model simulations demonstrate the association of water column dissolved oxygen, primary production, allochthonous organic matter, and the structure of the macroinvertebrate community. The quality and quantity of allochthonous carbon is shown to have considerable importance, not only as a food source but also as an oxygen sink. Allochthonous carbon equivalent to 5% of autochthonous production increases the macroinvertebrate standing crop by 4–17%, depending on particle size. A large allochthonous subsidy also reduces the simulated average diel dissolved oxygen and increases the percentage of hypoxia-tolerant macroinvertebrates. Simulations show both the heterotrophic response and the changes in community structure brought about by an allochthonous subsidy.

Spatial and temporal variability of trophic relationships among aquatic macroinvertebrates in a seasonal marsh

We examined macroinvertebrate trophic relationships in stands of two emergent plants, pickleweed (Salicornia virginica) and alkali bulrush (Scirpus robustus), and in epiphytic and benthic habitats within pickleweed stands. Numbers of detritivores, predators, and herbivores were examined throughout the flooding season (October 1990–March 1991). Trophic structure of macroinvertebrate communities differed between epiphytic and benthic habitats; both herbivores and detritivores were abundant in epiphytic habitats, but detritivores alone were numerically dominant in benthic habitats. Macroinvertebrate communities also differed between pickleweed and alkali bulrush stands: (1) all trophic groups were abundant in pickleweed, but detritivores were numerically dominant in alkali bulrush; (2) pickleweed supported higher macroinvertebrate numbers than alkali bulrush. Species composition was similar in both vegetation types, and diversity decreased during the season. Macroinvertebrate trophic structure in the epiphytic habitats changed during the season; detritivores quickly colonized both vegetation types after flooding, and predator and herbivore numbers increased later. Herbivores were an important component of macroinvertebrate communities in these wetlands, indicating that algal herbivory may be more important than previously thought.

The Effects of Wildlife Ungulate Herbivory Upon Riparian and Stream Ecosystems within the Greater Yellowstone Area

This study will investigate the effects of wildlife ungulate herbivory, principally of elk and moose, upon riparian and stream habitats within the Greater Yellowstone Ecosystem, which encompasses both the Grand Teton National Park and the Yellowstone National Park. The emphasis of the research will concern how these effects express themselves within the aquatic macroinvertebrate community. Sampling conducted in August and October of 1996 revealed that sites subject to moderate and minimal herbivore use contain greater quantities of allochthonous material and a more diverse macroinvertebrate trophic structure than streams incurring heavy herbivore use.

Recovery of a Headwater Stream from an Insecticide-Induced Community Disturbance

Faunal assemblages, leaf litter processing rates, and seston export were followed in two streams two years after one was altered with an insecticide. Two years after treatment ended, the macroinvertebrate trophic structure of the treated stream (TS) community had recovered and was similar to that of the reference stream (RS); however, major differences in taxonomic composition persisted. Some taxa, e.g., Diplectrona metaqui and Pseudostenophylax, which were rare or absent in TS before treatment became locally abundant during recolonization. Other taxa (e.g., Peltoperla, Pycnopsyche, Diplectrona modesta, and Fattigia), which were known to be abundant in TS before treatment, remained absent or rare in TS and common in RS. Recovery of shredder functional group biomass in TS was accompanied by restoration of leaf litter processing rates, seston concentrations, and export. These had all decreased significantly in TS, relative to RS, during the treatment period. Despite the recovery of the shredder functional group biomass, the taxa dominating this group remained strikingly different from RS and pretreatment conditions in TS. Biomasses of some shredders (e.g., Lepidostoma spp. and Tipula) were twice as high in TS as in RS, while others (e.g., Peltoperla, Fattigia, and Pycnopsyche) were low or absent in TS. Although taxonomic differences still existed between TS and RS, trophic structure was similar between streams. Restoration of shredder biomass, leaf litter processing, and organic seston concentrations in TS supports the concept that stream ecosystems are resilient to disturbance. Thus recovery of trophic function may occur in a fashion not recognizable solely by taxonomic criteria.