The Distribution of Benthic and Hyporheic Macroinvertebrates from the Heads and Tails of Riffles

The spatial distribution of benthic (up to 0.05 m depth) and hyporheic (0.25 and 0.5 m depth) macroinvertebrates from downwelling zones at the heads of riffles and upwelling zones at the tails of riffles was examined in two studies on a 4th order chalk stream in Dorset, England. In the first study, differences in benthic and hyporheic macroinvertebrate community composition between the head and tail of a single riffle were investigated. In the second study, a replicated design involving eight riffles was used to compare benthic and hyporheic macroinvertebrate community composition both between heads and tails of the same riffles and between riffles. In the first (single riffle) study there were significantly higher mean numbers of benthic invertebrates and families at the riffle head (715 individuals and 13.8 families per 0.0225 m²) compared to the tail (192 individuals and 8.7 families). ANOSIM analysis also showed that the community structure of head and tail benthic samples was significantly different. In the second (replicated riffle) study, there were also significantly more benthic invertebrates at riffle heads ( = 594 per 0.0225 m²) compared to tails ( = 417 per 0.0225 m²), although this was not the case for families, and community structure also differed significantly between riffle heads and tails. In contrast, in the hyporheic zone, there were no significant differences between the total numbers of invertebrates in the riffle heads and tails, or between riffles, although a significant difference in family richness between riffle head and tail samples was identified in the first study. Community analysis revealed progressively poorer separation of riffle head and tail samples at 0.25 m and 0.5 m hyporheic depths. Whilst being able to identify clear differences in benthic communities from riffles heads and tails, the physically heterogeneous nature of the riffle habitats studied made it difficult to account for the consistent differences in macroinvertebrate communities observed with the physical variables measured.     

Biological,chemical and physical characteristics of downwelling and upwelling zones in the hyporheic zone of a north-temperate stream

Along a single stream riffle, there is a typical flow pattern in which surface water enters the hyporheic zone in a downwelling zone at the head of the riffle and hyporheic water returns to the stream surface in an upwelling zone at the tail of the riffle. Distinct patterns of physical and chemical conditions in the hyporheic zone are likely to determine patterns of microbial activity and occurrence of hyporheic fauna. Interstitial water and core samples were taken at three depths in the downwelling and upwelling zones of a single riffle in the Speed River, Southern Ontario, Canada. Physical and chemical characteristics of the hyporheic water, bacterial density, protein content, detritus content and faunal composition of the hyporheic sediment were analysed. The downwelling and upwelling zones differed significantly in temperature, pH, redox potential, dissolved oxygen and nitrate with significant positive correlations occurring among the latter three. There were no differences in bacterial density or detritus content between the two zones nor between depths in either zone, but protein content, considered to be a measure of biofilm biomass, was significantly higher in the downwelling zone. Total density of hyporheic fauna and the number of taxa decreased with increasing depth in both upwelling and downwelling zones, and were positively correlated with surface water characteristics (oxygen, temperature and nitrate), sediment protein content and detritus; however, only a weak correlation was found with zone. The composition of taxa differed between the two zones, and faunal distribution was correlated with dissolved oxygen, detritus, protein content and depth.     

A Large-scale Comparative Analysis of Riffle and Pool Fish Communities in an Upland Stream System

Fishes were sampled in riffle and pool habitats at 74 upland localities in the Little River system, southeastern Oklahoma and southwestern Arkansas, U.S.A. I asked how these two habitat-defined communities differed with regard to species abundance and incidence patterns, and how these differences varied along othree environmental gradients: elevation, stream gradient, and stream size. Riffle and pool communities showed distinct and significant differences when ordinated in multivariate space defined by species abundance patterns. Sites with similar pool communities did not have similar riffle communities, and riffle and pool communities responded to environmental gradients in different ways. Elevation was the best predictor of pool community structure, whereas stream size was the best predictor of riffle communities. Overall, riffle habitats had fewer species than pool habitats and formed significant subsets of pool communities at 12 of 74 sites. I predicted that at small stream localities where riffles were unstable, riffle species would form subsets of the pool species communities, and both community types should show high similarities. The presence of faunal subsets was not associated with stream size, but faunal similarities were significantly higher at small stream localities. At the species level, 14 species were significantly associated with pool habitats, while only two were associated with riffle habitats. Riffle and pool communities, although linked by a continuous habitat gradient at the local scale, responded differently to large-scale environmental gradients. Local differences between these communities were predictable based on stream size.     

Can an indicator of river health be related to assessments from a catchment-scale sediment model?

The accumulation of sand and fine gravel (<5 mm diameter) on riverbeds can adversely affect benthic macroinvertebrates, which are good indicators of the ecological health of rivers. The possibility arises, therefore, that predictions of sedimentation could form a useful proxy for indicating the health of a river. The Sediment River Network Model (SedNet) constructs sediment budgets to predict the depth of bed material accumulation (BMA) in each link of a river network. This study tests whether the predicted BMA depth was associated with spatial differences in macroinvertebrate community structure, in the Upper Murrumbidgee River catchment of southeast Australia. There was a significant, albeit limited, correlation. Riffle sites with low BMA depth (0–0.01 m) had a significantly different macroinvertebrate community structure compared to sites with medium (0.01–0.3 m) or high (>0.3 m) BMA depth. At these sites, taxa sensitive to habitat were in greater abundance when BMA depth was low. Additionally, riffle sites with high predicted BMA depth had lower values for three macroinvertebrate community structure measures—AUSRIVAS observed-to-expected (OE) taxa ratio, Ephemeroptera abundance and Plecoptera abundance. There was no significant difference in macroinvertebrate community structure between sites with medium and high levels of BMA depth. Possible reasons for this result are: (1) there may have been few sites in the high and medium categories to provide sufficient statistical power to detect a significant difference; (2) spatial variation in BMA depth within SedNet river links; or (3) only a minimal amount of BMA is required to change community structure. To further define spatial variation in biological damage from BMA, data are required on the spatial scale of variations in BMA depth and damage to macroinvertebrate community structure.     

Benthic and hyporheic invertebrate assemblages along a flow intermittence gradient: effects of duration of dry events

1. A large proportion of the total river length on Earth comprises rivers that are temporary in nature. However, the effects of periodical dry events have received far less attention from ecologists than those of floods and low flows. 2. This study concomitantly examined the effects of flow intermittence on invertebrates from the streambed surface and from a depth of 30 cm in the hyporheic zone. Invertebrates were collected during 3 years in the Albarine River, France, before and after summer dry events from 18 sites (seven were perennial) distributed along a longitudinal flow intermittence gradient. 3. I predicted benthic and hyporheic density and taxonomic richness to decrease, and assemblage composition to shift from desiccation‐sensitive to desiccation‐resistant taxa with increased dry event duration. Second, I predicted benthic and hyporheic assemblages from sites that dried for longer periods to be nested subsets of assemblages from sites that dried for shorter periods. Last, I predicted a convergence in benthic and hyporheic assemblage composition with increasing duration of dry events, resulting from increased vertical migration of benthic taxa into the hyporheic sediments to cope with dry events. 4. Increased dry event duration in the Albarine River led to a decrease in both benthic and hyporheic density and taxonomic richness. Invertebrate assemblage composition shifted along the gradient of increasing flow intermittence, but broad taxonomic overlap between perennial and temporary reaches and nestedness patterns indicated that these shifts were because of the loss of taxa susceptible to drying rather than selection for desiccation‐resistant specialists. 5. Assemblage composition between benthic and hyporheic invertebrates diverged with increasing dry event duration, suggesting that the hyporheic zone did not act as a refuge during dry events in this river. 6. Quantitative studies on the relationships between ecology and intermittence are still rare but are needed to predict the consequences of future changes in flow intermittence. The relationships found in this study should be tested across a wide range of temporary rivers to better evaluate the generality of these findings.     

The effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community

We investigated the effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community, together with changes in the hyporheic geomorphology, physico-chemistry and biofilm activity. Hyporheic invertebrates were collected, together with environmental data, on seven sampling occasions from June 2004 to May 2005, at two river reaches—at the site of in-stream gravel extraction and at a site 2.5 km upstream. The hyporheic samples were taken from the river bed and from the gravel bars extending laterally from the stream channel. The invertebrate community was dominated by insect larvae (occasional hyporheos), followed by meiofauna (permanent hyporheos). Stygobionts were present at low species richness and in low densities. Gravel extraction from the stream channel led to changes in the patterns of water exchange between surface and subsurface and changes in the sediment composition at the site. Immediate reductions in density and taxonomic richness of invertebrates were observed, together with changes in their community composition. The hyporheic invertebrate community in the river recovered relatively fast (in 2.5 months) by means of density and taxonomic richness, while by means of community composition invertebrates needed 5–7 months to recover. The impact of fine sediments (<0.1 mm) on biofilm activity measured through ETS activity and hyporheic invertebrate density and taxonomic richness was strongly confirmed in this study.     

Longitudinal patterns of invertebrates in the hyporheic zone of a glacial river

1. Longitudinal changes in physicochemical factors and the composition of the invertebrate community were examined in the hyporheic zone of a glacial river (Val Roseg, Switzerland) over a distance of 11 km from the glacier terminus. Multivariate analysis was used to determine the habitat preferences of taxa along an upstream‐downstream gradient of increasing temperature and groundwater contribution to river flow. 2. The hyporheos conformed to the longitudinal distribution model described for zoobenthic communities of glacial rivers in that taxonomic richness increased with distance from the glacier terminus. Spatial variation in taxonomic richness was best explained by temperature, the influence of groundwater, and the amount of organic matter. The overriding importance of these variables on the distribution of taxa was confirmed by the multivariate analysis. 3. The hyporheic zone contributed significantly to the overall biodiversity of the Roseg River. Whereas insect larvae were predominant in the benthos, hyporheic invertebrates were dominated by taxa belonging to the true groundwater fauna and the permanent hyporheos. Several permanently aquatic taxa (e.g. Nematoda, Ostracoda, Cyclopoida, Harpacticoida, Oligochaeta) appeared exclusively in the hyporheic zone or they extended farther upstream in the hyporheic layer than in the benthic layer. Leuctridae, Nemouridae, and Heptageniidae colonised hyporheic sediments where maximum water temperature was only 4 °C. 4. Despite strong seasonal changes in river discharge and physicochemistry in hyporheic water, the density and distribution of the hyporheos varied little over time. 5. Taxonomic richness increased markedly in the downstream part of a floodplain reach with an extensive upwelling zone. Upwelling groundwater not only maintained a permanent flow of water but also created several species‐rich habitats that added many species to the community of the main channel.     

空间和环境因子对黄河口自然和淡水恢复湿地底栖动物群落的差异影响

生物多样性的形成和维持机制是生态学研究的核心问题,其中环境和空间因子在群落构建中的相对重要性是生态学家面临的重要挑战。为探究黄河口湿地底栖动物群落的关键影响因子,及环境和空间因子对底栖动物群落结构的相对调控作用。于2017年10月与2018年5月对黄河口湿地32个样点（淡水恢复湿地19个和自然湿地13个）的底栖动物和水体理化指标进行采集分析。非度量多维标度排序（NMDS）结果显示,黄河口淡水恢复湿地和自然湿地的底栖动物群落结构显著不同。典范对应分析（CCA）表明,影响淡水恢复湿地底栖动物群落结构的环境因子主要为电导率、盐度和氧化还原电位;而自然湿地底栖动物群落结构主要受pH和无机碳的影响;盐度是两类湿地底栖动物群落组成差异的关键因子。变差分解（VPA）结果显示,环境过滤对淡水恢复湿地底栖动物群落起主导作用;在自然湿地中,空间因子对底栖动物群落具有主要的调控作用,同时环境和空间因子的相互作用也至关重要。本研究明确了黄河口的自然和恢复湿地中环境和空间因素对底栖动物群落特征的相对作用,对黄河三角洲河口湿地中生物多样性的保护和生态系统管理提供参考。     

Spatial responses of hyporheic invertebrates to seasonal changes in environmental parameters

1. Spatial relationships between hyporheic invertebrates and subsurface water flow patterns, sediment characteristics, water physicochemical parameters and several possible food sources were compared over three seasons at one site beneath a riffle. Measures of food sources included particulate organic matter (POM), bacterial activity (aerobic respiration, nitrate respiration and mineralisation of organic nitrogen) and microbial abundance. 2. Patterns of water flow changed significantly over the 9‐month study period, from predominantly upwelling beneath the entire riffle in spring, to distinct differentiation between downwelling and upwelling zones in summer and autumn. Water physicochemical parameters changed accordingly, showing gradually weaker correlations with depth and stronger correlations with zone between spring and autumn. 3. Despite these changes, depth remained the strongest predictor of invertebrate richness, density and taxon composition throughout the study period. However, invertebrate distributions were secondarily correlated with water physicochemical parameters, and a minor gradient in invertebrate distributions between downwelling and upwelling zones became stronger from spring to summer. 4. The correlations between invertebrates and physicochemical parameters changed in both magnitude and direction with season. In spring, invertebrates showed a negative correlation with surface water infiltration, whereas in summer and autumn, the correlation was positive. Correlations were strongest in summer, when interstitial dissolved oxygen concentrations were lowest. 5. No relationships were found between hyporheic invertebrates and POM, microbial abundance or activity. This suggests that at this site, proximity to the streambed surface and physicochemical variables are more important than the abundance of food in controlling invertebrate distributions.     

The Recovery of Benthic Invertebrate Communities Following Dewateringin Two Braided Rivers

The recovery of benthic invertebrates was investigated in the braided Tukituki and Waipawa Rivers (North Island, New Zealand) following extended channel dewatering of sites for 6, 10 or 14 weeks during summer 1997/1998. After rewatering, invertebrates rapidly colonised each denuded site and, although some invertebrates were numerically dominant at different times, 95⁺% of the taxa list were present after 7 days of rewatering. The number of individuals also increased over time, but significantly greater numbers were collected in reference sites and those dry for 6 weeks compared to sites dewatered for longer periods. Taxa such as Tanytarsus spp., Maoridiamesa spp. (Diptera: Chironomidae) and the riffle beetle Elmidae (Coleoptera) were abundant early, while Deleatidium spp. (Ephemeroptera: Leptophlebiidae) dominated communities later. The greater abundance of Deleatidium in sites dewatered for a short time may be because desiccation was less significant at determining taxa present at these sites, or that reference sites provided a closer source of colonists and periphyton propagules to allow a more rapid numerical recovery of this taxon. In contrast, Elmidae dominated communities at sites dewatered for longer periods because Elmidae may be more resilient to desiccation than Deleatidium. These data suggest that the duration of dewatering may regulate taxonomic composition in the short term by subjecting taxa to desiccation and/or food resource restrictions, but not in the long term because food resources recovered over time and sites with similar physicochemical conditions should have similar communities.     

Faunal response to benthic and hyporheic sedimentation varies with direction of vertical hydrological exchange

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Do stream macroinvertebrates use instream refugia in response to severe short-term flow reduction in New Zealand streams?

1. Demand for water is increasing and water managers need to know how much they can remove from a stream before there are significant detrimental effects on its biological integrity. Flow reduction alters a number of habitat variables known to be important to aquatic invertebrates such as depth, velocity, temperature and fine sediment accumulation. Some taxa may attempt to use instream refugia to mitigate the effects of flow reduction.
2. We experimentally manipulated flows by constructing weirs and diversions in three small New Zealand streams. Discharge was reduced by 88–96%. We tested the hypothesis that macroinvertebrates would use pools and the hyporheic zone as refugia during short-term (1-month) periods of reduced flow.
3. We sampled hyporheic invertebrates with colonization chambers and pool invertebrates with kick nets within a before-after, control-impact (BACI) experimental design. A suite of physicochemical parameters was measured concurrently including surface and hyporheic temperatures.
4. Flow reduction significantly decreased velocity (60–69%) in all streams. Depth (18–61%) and wetted width (24–31%) tended to decrease but these changes were not always significant. Sediment cover increased the most in farmland streams (10–80%). Apart from decreasing temperature range (18–26%), flow reduction had little impact on the surface water temperatures.
5. Flow reduction had no impact on the abundance of common pool macroinvertebrates or on the abundance, vertical distribution or community composition of hyporheic macroinvertebrates.
6. Our results suggest that aquatic macroinvertebrates are resistant to short-term, severe flow reduction as long as some water remains.     

The effects of increased flow and fine sediment on hyporheic invertebrates and nutrients in stream mesocosms

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Spatial distribution and population dynamics of a benthic rotifer, Embata laticeps (Murray) (Rotifera, Bdelloidea) in the bed sediments of a gravel brook

• 1 The spatial and temporal distributions of the most abundant bdelloid rotifer, Embata laticeps (Murray), inhabiting the sediment surface and the hyporheic interstitial of a gravel stream were investigated between October 1991 and October 1992. Three temporal peaks of population density occurred during the year at the sediment surface differing in their riming from the density peaks detected within the bed sediments.
• 2 The depth distributions of E. laticeps in pool and riffle areas differed significantly. Higher abundances were found between 10 and 20 cm depth in the pool and between 20 and 30 cm in the riffle area. In these two sites a significant effect of surface discharge (estimated 1 week before sampling) on rotifer densities was found. Discharge greater than 0.424 m³s^?1 significantly reduced the densities in the riffle, while only at values greater than 1.660m³s^?1 were abundances influenced in the pool area.
• 3 The percentages of egg-bearing females were higher within the bed sediment than in the surface layer, and in the pool area than in the riffle. Thus, overall mean values of population increase were higher in the pool habitat (x?= 0.015 ± SE 0.029 day^?1) than in the riffle and at the sediment surface (x?= 0.004 ± 0.025 and 0.005 ± 0.026 day^?1, respectively). In addition, population growth fluctuated more strongly at the sediment surface than within the hyporheic intersiritial. Comparison of the observed values of population increase with a randomization test, where observed densities were randomly permuted, revealed no significant differences between those observed and values from a random model. Thus, a clear trend in population growth of E. laticeps over time could not be demonstrated in this gravel stream.

     

Effects of pollution on benthic invertebrate communities of the St. Marys River, 1985

A survey was undertaken in 1985 to assess spatial and temporal trends in the benthic community structure in relation to sediment contamination and wastewater sources at 70 stations between Whitefish Bay and lower Lake George in the St. Marys River. Cluster analysis identified seven benthic communities. Three were identified as pollution impacted, based on a preponderance of tubificids and nematodes, usually at high densities (up to 259 000 m^-2), but sometimes at low densities (< 100 m^-2) at individual stations. Impacted communities occurred downstream of industrial and municipal sources and in depositional areas, and were confined mainly to Canadian waters. Unimpacted communities had greater numbers of taxa, and occurred upstream of point sources, along the U.S. shoreline, and in most areas of downstream lakes. Impacted and unimpacted communities were separated along particle size and contaminant gradients in river sediments. Despite recent reductions in pollutant loadings and improvements in sediment quality, no major changes were apparent in the status of the benthic community from earlier surveys.     

Evidence of a threshold level of fine sediment accumulation for altering benthic macroinvertebrate communities

When land use practices alter natural hydrologic and sediment delivery regimes, the effects usually are negative to macroinvertebrates. We hypothesized a threshold level of fine sediment accumulation in the substrate may exist where benthic macroinvertebrate abundance and diversity will be significantly reduced. We surveyed seven Appalachian streams with different levels of substrate fine sediment twice yearly from fall 1998 to spring 2000. Three riffles (with 2 replicates each) were sampled with a 0.25 mm Surber sampler in each season and stream. Simple linear regression was used to test relationships between substrate size classes and metrics, and nested ANOVA was used to test macroinvertebrate differences among streams. Consistent negative relationships with the finest substrate particles (<0.25 mm) were observed with EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa richness. In seasons of normal hydrology, EPT taxa richness significantly decreased (p<0.05) in streams where fine substrate particles (<0.25 mm) exceeded 0.8–0.9% of riffle substrate composition. In drought seasons, fine sediment (<0.25 mm) exceeded 0.8–0.9% in most surveyed streams, lowering macroinvertebrate diversity in all streams. In these streams, a threshold for EPT diversity appears to be in excess of 0.8–0.9% fine sediment (<0.25 mm) substrate accumulation. We suggest similar threshold levels exist in other streams where macroinvertebrate taxa are altered with potential effects on trophic webs and nutrient processing.     

The effect of patch disturbance on stream invertebrate community structure: the influence of disturbance history

The effect of disturbance history on the recovery of benthic invertebrate communities following disturbance was investigated in four streams in the Southern Alps of New Zealand. Two of the streams had a history of fluctuating discharge and temperature while the others did not. Recovery from disturbance was tested experimentally using baskets of cobbles, a third of which were disturbed every week for 9 weeks, a further third every 3 weeks and the final third left undisturbed. Algal biiomass, number of invertebrate taxa and total number of invertebrates all declined in baskets disturbed more frequently. Although the relative abundance of some taxa declined with time since the last disturbance, no taxa showed a significant decline in absolute abundance. However, several taxa showed marked increases in relative abundance in the less disturbed treatments particularly at the more stable sites. In contrast to the predictions of ecological theory, numbers of taxa and total invertebrates appeared to recover more quickly in the more complex communities at the stable sites. However, if these communities are considered to represent only stable communities, they do support the view that more complex communities will be more resilient. Community structure at the stable sites was also more similar between baskets in the undisturbed treatment than at the unstable sites, suggesting communities had reached a constant state more quickly. The more rapid recovery of communities measured at the stable sites may have been a consequence of experimental scale; disturbed patches were only 0.045 m² in area and the higher densities of invertebrates at the stable sites meant a larger pool of colonists was available following each experimental disturbance. Nevertheless, ideas of stability in ecological theory and the scale of most spate events suggest this is the appropriate scale for examining community recovery. Furthermore, the larger pool of available colonists could not explain all the differences in community response, as patterns of change in community structure at the stable sites differed considerably more from those expected by purely random colonisation processes than at the unstable sites.     

Seasonal and spatial distribution of ciliates in the sandy hyporheic zone of a lowland stream

The seasonal and spatial distribution of abundance and biomass as well as the taxonomic composition of ciliates inhabiting the sandy hyporheic zone of a lowland stream were studied. The mean abundances varied between 0 and 895 cells ml⁻¹ sediment, and the mean ciliate biomass ranged between 0 and 5.3 μg C ml⁻¹ sediment. Ciliate numbers and biomasses were greatest at the sediment surface and declined significantly with increasing sample depth. Abundance and biomass varied seasonally, with maximum values in late autumn and early winter and minimum values in early summer. The community was dominated by small representatives of the Hymenostomatia and Peritrichia. Ciliate community composition changed with depth from a very diverse community at the sediment surface to a less diverse one at greater sediment depths. Ciliate abundance and biomass were two orders of magnitude lower in the channel water than in the hyporheic zone. Although representatives of all sediment taxa could also be found in the channel water, the greatest concentrations of Peritrichia and Suctoria were in the hyporheic zone. The species of the sandy Ladberger Mühlenbach sediment were ubiquitous; there was no single ciliate fauna that proved to be typical for this kind of freshwater biotope.     

Stable isotopes, mesocosms and gut content analysis demonstrate trophic differences in two invasive decapod crustacea

1. Improving our understanding of dietary differences among omnivorous, benthic crustacea can help to define the scope of their trophic influence in benthic food webs. In this study, we examined the trophic ecology of two non‐native decapod crustaceans, the Chinese mitten crab (Eriocheir sinensis) (CMC) and the red swamp crayfish (Procambarus clarkii) (RSC), in the San Francisco Bay ecosystem to describe their food web impacts and explore whether these species are functionally equivalent in their impacts on aquatic benthic communities. 2. We used multiple methods to maximise resolution of the diet of these species, including N and C stable isotope analysis of field data, controlled feeding experiments to estimate isotopic fractionation, mesocosm experiments, and gut content analysis (GCA). 3. In experimental enclosures, both CMC and RSC caused significant declines in terrestrially derived plant detritus (P < 0.01) and algae (P < 0.02) relative to controls, and declines in densities of the caddisfly Gumaga nigricula by >50% relative to controls. 4. Plant material dominated gut contents of both species, but several sediment‐dwelling invertebrate taxa were also found. GCA and mesocosm results indicate that CMC feed predominantly on surface‐dwelling invertebrates, suggesting that trophic impacts of this species could include a shift in invertebrate community composition towards sediment‐dwelling taxa. 5. Stable isotope analysis supported a stronger relationship between CMC and both algae and algal‐associated invertebrates than with allochthonous plant materials, while RSC was more closely aligned with terrestrially derived detritus. 6. The trophic ecology and life histories of these two invasive species translate into important differences in potential impacts on aquatic food webs. Our results suggest that the CMC differs from the RSC in exerting new pressures on autochthonous food sources and shallow‐dwelling invertebrates. The crab's wide‐ranging foraging techniques, use of intertidal habitat, and migration out of freshwater at sexual maturity increases the distribution of the impacts of this important invasive species.