Benthic invertebrates of some saline lakes of the Sud Lipez region,Bolivia

The benthic invertebrates fauna of most of the saline lakes of the Sud Lipez region (Bolivia, Altiplano) has been until now quite unstudied. Samples collected during an extensive survey of 12 lakes and two small inflow rivers allow a first list of the main macroinvertebrates living in these biotopes.The heterogeneous nature of these saline lakes with their freshwater springs and phreatic inflows offers a variety of habitats to macroinvertebrates. The benthic fauna in lakes with salinities > 10 g l^–1 is not so low in density but includes few species and is dominated by Orthocladiinae and Podonominae larvae. In contrast, the freshwater springs and inflows are colonized by a diverse fauna, with a mixture of both freshwater and saline taxa, but dominated by Elmidae and Amphipoda. The lakes are quite isolated and, apart from some cosmopolitan organisms, their fauna can be quite distinctive.     

Assessment of eutrophication pressure on lakes using littoral invertebrates

Until the E.U. Water Framework Directive listed benthic invertebrates as a biotic element to be used for ecological classification of lakes, techniques for the assessment of the response of littoral invertebrates to anthropogenic pressures were extremely limited compared with those of rivers and lake profundal zones. We describe here the development of an ecological classification model based on changes of littoral invertebrate assemblages across a gradient of eutrophication, which is the most widespread anthropogenic pressure on lakes across Europe. The model comprises three derived parameters, two of which were developed from taxon-specific optima along a total phosphorus gradient calculated using canonical correspondence analysis, and the third based on invertebrate abundance. Combining the parameter metrics, we can estimate the ecological quality ratio (EQR), relative to those from paleolimnologically-confirmed reference lakes. The model was tested using independent samples collected from both hard and soft substrata and across two seasons from 45 lakes, comprising three alkalinity groups (n = 15 in each), and across gradients in water column total phosphorus concentrations. For hard substrata, EQRs were related consistently and highly significantly to water column concentrations of total phosphorus, accounting for the majority of the variance in every alkalinity group. For samples taken from soft substrata, a significant relationship was found only for high alkalinity lakes, accounting for a moderate proportion of the variability in water column total phosphorus concentrations. Our results compare highly favourably with those from other aquatic ecological assessment methods, irrespective of the faunal or floral group upon which they are based, demonstrating that littoral invertebrate assemblages can provide a statistically robust prediction of nutrient status when samples are collected from hard substrata. While the method was developed specifically to assess nutrient pressures on littoral invertebrates, many lakes are subject to multiple pressures. The development of classification models that incorporate multiple pressures presents a particularly significant challenge for the implementation of the Water Framework Directive, requiring both reliable identification of minimally-impacted reference states and incorporation of pressures that are unlikely to interact in predictable ways.     

Effects of macrophyte growth forms on invertebrate communities in saline lakes of the Wyoming High Plains

In saline lakes, areal cover and both species and structural diversity of macrophytes often decline as salinity increases. To assess effects of the loss of certain macrophyte growth forms, we characterized benthic and epiphytic invertebrates in three growth forms (thin-stemmed emergents, erect aquatics, and low macroalgae) in oligosaline lakes (0.8–4.2 mS cm⁻¹) of the Wyoming High Plains, USA. We also measured the biomass and taxonomic composition of epiphytic and benthic invertebrates in two erect aquatics with very similar structure that are found in both oligosaline (Potamogeton pectinatus) and mesosaline (9.3–23.5 mS cm⁻¹) (Ruppia maritima) lakes. Although total biomass of epiphytic invertebrates varied among oligosaline lakes, the relative distribution of biomass among growth forms was similar. For epiphytic invertebrates, biomass per unit area of lake was lowest in emergents and equivalent in erect aquatics and low macroalgae; biomass per unit volume of macrophyte habitat was greatest in low macroalgae. For benthic invertebrates, biomass was less beneath low macroalgae than other growth forms. Taxonomic composition did not differ appreciably between growth forms for either benthic or epiphytic invertebrates, except that epiphytic gastropods were more abundant in erect aquatics. Total biomass of epiphytic and benthic invertebrates for the same growth form (erect aquatic) did not differ between oligosaline (Potamogeton pectinatus) and mesosaline (Ruppia maritima) lakes, but taxonomic composition did change. In the oligosaline to mesosaline range, direct toxic effects of salinity appeared important for some major taxa such as gastropods and amphipods. However, indirect effects of salinity, such as loss of macrophyte cover and typically higher nutrient levels at greater salinities, probably have larger impacts on total invertebrate biomass lake-wide.     

Benthic macro- and meso-invertebrates of a sandy riverbed in a mountain stream, central Japan

Quantitative samples of benthic invertebrates were collected from a sandy riverbed of a mountainous stream (Kozu site of Takami-gawa stream, Nara Prefecture), central Japan by core samplers in five sampling occasions through the years 2008–2009. A total of 120 taxa were identified, representing 55 families and 97 genera. Insects formed about 92% of the total recorded taxa and 88% of individuals’ abundance. A total of 111 taxa of aquatic insects, belonging to 49 families and 92 genera, were identified and represented by ten orders. Oligochaeta and Acari were dominant non-insect invertebrates. Diptera was the most diverse insect group, followed by Trichoptera and Ephemeroptera. Dominant taxa were mesoinvertebrates, younger stages of macroinvertebrates, both of which predominantly inhabit the interstitial zone of a sandy riverbed. Both taxon richness and invertebrate abundance were higher in February 2009 and lower in April and August 2008. A few major invertebrate taxa demonstrated distinct seasonal trends; i.e. Nymphomyia alba, Rheosmittia, and Corynoneura were abundant in February 2009. Newly hatched larvae of Larcasia akagiae were abundant in May 2008. This study also demonstrated the effectiveness of core samplers to collect small-sized benthic fauna that inhabit the interstitial or hyporheic zone of the sandy riverbed.     

Effects of methoprene and Bti (Bacillus thuringiensis var. israelenis) on non-target insects

The effects of mosquito larvicides Bacillus thuringiensis israelensis (Bti) and methoprene, on non-target benthic invertebrates were studied in a divided pond experiment in south-central Minnesota, USA, during the spring and summer of 1989. Density and biomass of insects and other benthic macroinvertebrates were quite low in all sections of the three ponds studied, which may have been due to three consecutive years of drought, but richness appeared to be high and we observed no evidence of dominance by a particular group. We also saw no evidence of negative effects of larvicide treatment on density or biomass of any invertebrate group, nor was there a treatment-related decrease in richness of benthic invertebrate taxa under these drought conditions.     

Benthic invertebrate recolonization of small-scale disturbances in the littoral zone of a subtropical Florida lake

Construction of spawning beds by the exotic cichlid fish, Sarotherodon aurea, produces numerous small-scale disturbances in shallow Florida lakes. Two experimental methods were used to simulate these disturbances (containers filled with defaunated sediment and disturbed natural substratum) and to determine benthic invertebrate recolonization patterns and rates.Recolonization of experimental containers was rapid and densities of macroinvertebrates reached equilibrium with the control habitat by Day 6 following disturbance. However, Chironomidae and miscellaneous taxa usually were more abundant (p < 0.05) in the experimental containers, and Oligochaeta always were more abundant (p < 0.01) in the control. Species of the planktonically dispersed insects either attained equilibrium rapidly or showed significantly higher densities in the experimental containers (i.e. opportunistic species).In the second experimental approach, disturbance of natural substratum removed 91% of the benthic invertebrates. The common species of chironomids reached equilibrium by Day 6 but the two predominant oligochaetes, Limnodrilus and Pristina, reached equilibrium at 9 and 15 days respectively. For the entire community, similarity on Day 6 was 87.1% and over the remainder of the sample period averaged 86.8%. Chironomid instar analyses showed significantly higher proportions of early instars in the disturbed patch indicating that colonization is principally by younger organisms. Thus, small-scale disturbance in freshwater benthic communities may be more important in ordering the biomass or age-group structure than the numerical abundance.     

Cladocera (Crustacea) from Nicaragua

Thirty-one Cladocera taxa are recorded from lakes, rivers and ponds of Western Nicaragua. They include Alona bromelicola sp. nov. found in water accumulations in epiphytic Bromeliads. The Cladocera recorded are neotropical and circumtropical. Other invertebrates found are also listed.     

The lentic and lotic characteristics of habitats determine the distribution of benthic macroinvertebrates in Mediterranean rivers

1. The importance of flow‐related factors to benthic organisms, as well as the role of habitat conditions in shaping aquatic communities during low‐flow periods, have been recognised. Despite this, the preferences of macroinvertebrates to the ratio of lentic to lotic habitats at the reach scale have not been accurately quantified in most instances.
2. Aquatic invertebrates and habitat features in a range of temporary rivers in Sardinia were investigated. The investigation focused on the flow‐related characteristics that contribute to defining the lentic–lotic condition of the river reaches. The relation of habitat features to benthic taxa distributions was assessed using multidimensional scaling. The main aim of the paper was to quantify the responses of taxa to the different lentic and lotic habitat conditions by applying hierarchical logistic regressions. Finally, taxon optima were aligned along the lentic–lotic gradient and the responses of different taxonomic groups compared.
3. Unbroken waves and imperceptible flow were correlated with benthic taxa variability, suggesting local hydraulics and turbulence have a major role in regulating community composition. The overall lentic–lotic character of the river reaches was also clearly related to the benthic taxa distribution. More than 80% of taxa were significantly related to the lentic–lotic gradient, and an asymmetrical response curve was the predominant model.
4. Benthic groups showed taxon optima clustered in different ranges of the lentic–lotic gradient. Odonata, Coleoptera, Hemiptera, and Mollusca preferred clearly lentic conditions. Diptera mainly ranged on the lotic side of the gradient, while Trichoptera were relatively uniformly distributed across the gradient. Ephemeroptera taxa clustered in intermediate lentic–lotic conditions, with two species preferring extremely lentic habitats. In general, optima converged at intermediate and extremely lentic conditions, presumably due, respectively, to the coexistence of different lentic and lotic features and to the highly diverse environmental characteristics under extremely lentic situations.
5. These results support the conclusion that dissimilar ecological factors act on benthic taxa along the lentic–lotic range and species favouring different lentic–lotic conditions are subjected to pressures of different nature. This should not be ignored when defining species preferences and studying community structure or relationships between species in Mediterranean rivers, which cyclically vary their habitat composition. In addition, the uneven distribution of optima of different groups along the lentic–lotic gradient might affect macroinvertebrate metrics when assessing ecological status or establishing reference conditions under variable climatic conditions.

     

Hydromorphological degradation impact on benthic invertebrates in large rivers in Slovenia

Large rivers are amongst the most degraded ecosystems. We studied a relationship between hydromorphological degradation and benthic invertebrates in large rivers in Slovenia. Five indices of the Slovenian hydromorphological assessment methodology were used to develop a HM stressor gradient. Natural type-specific habitat diversity was considered in the hydromorphological stressor gradient building and thus two hydromorphological types of large rivers were defined. CCA ordination with five HM indices and 315 benthic invertebrate taxa revealed variations in taxa response along the HM stressor gradient. First CCA axis species values were used to develop a taxon-specific river fauna value (Rf_i), whereas tolerance values (biplot scaling) were used to determine a hydromorphological indicative weight (HW_i). Rf_i, HW_i, and log₅ abundance classes were combined using weighted average approach to construct a River fauna index for large rivers (RFI_VR). Several additional benthic invertebrate-based metrics were also tested against the HQM. A Slovenian multimetric index for assessing the hydromorphological impact on benthic invertebrates in large rivers (SMEIH_VR) was constructed from the RFI_VR and a functional metric %akal + lithal + psammal taxa (scored taxa = 100%). The strong relationship between hydromorphological stressor gradient and SMEIH_VR index provides us with an effective assessment system and river management tool.     

Interaction of a biotic factor (predator presence) and an abiotic factor (low oxygen) as an influence on benthic invertebrate communities

We examined the response of benthic invertebrates to hypoxia and predation risk in bioassay and behavioral experiments. In the bioassay, four invertebrate species differed widely in their tolerance of hypoxia. The mayfly, Callibaetis montanus, and the beetle larva, Hydaticus modestus, exhibited a low tolerance of hypoxia, the amphipod, Gammarus lacustris, was intermediate in its response and the caddisfly, Hesperophylax occidentalis, showed high tolerance of hypoxia. In the behavioral experiments, we observed the response of these benthic invertebrates, which differ in locomotor abilities, to vertical oxygen and temperature gradients similar to those in an ice-covered pond. With adequate oxygen, invertebrates typically remained on the bottom substrate. As benthic oxygen declined in the absence of fish, all taxa moved above the benthic refuge to areas with higher oxygen concentrations. In the presence of fish mayflies increased activity whereas all other taxa decreased activity in response to hypoxia. Mayflies and amphipods remained in the benthic refuge longer and endured lower oxygen concentrations whereas the vertical distribution of caddisflies and beetle larvae was not influenced by the presence of fish. As benthic oxygen declined in the presence of fish, all but the beetle larva reduced activity over all oxygen concentrations compared to when fish were absent. As benthic oxygen continued to decline, mayflies and amphipods moved above the benthic refuge and were preyed upon by fish. Thus, highly mobile taxa unable to tolerate hypoxia (mayflies and amphipods) responded behaviorally to declining oxygen concentrations by migrating upward in the water column. Taxa that were less mobile (beetle larvae) or hypoxia-tolerant (caddisflies) showed less of a response. Taxa most vulnerable to fish predation (mayflies and amphipods) showed a stronger behavioral response to predator presence than those less vulnerable (caddisflies and beetle larvae). Because invertebrates differ in their ability to withstand hypoxia, episodes of winter hypoxia could have long-lasting effects on benthic invertebrate communities either by direct mortality or selective predation on less tolerant taxa.     

Littoral benthic macroinvertebrates of mountain lakes in the Tatra Mountains (Slovakia,Poland)

Littoral benthic macroinvertebrates of 45 mountain lakes in the Tatra Mountains were sampled using a semi-quantitative method in September 2000. A total of 32,852 specimens were identified to 93 taxa belonging to 14 higher taxonomic groups. Multivariate statistics (CCA, RDA) and nine biotic metrics (AQEM/STAR) were used to explain relationships between macroinvertebrate assemblages and environmental variables. Up to 57% of the ecological position of littoral macroinvertebrate assemblages were explained by variance of environmental variables divided into chemical, trophic, physical, catchment and location. Five types of Tatra lakes were recognized using CCA: A — strongly acidified lakes (small catchment, low pH, high concentration of TP, DOC, highest amount of POM in littoral); B — alpine acidified lakes (low amount of POM, low values of biotic metrics); C — alpine non-acidified lakes (high value of diversity index, predominance of Diptera); D — subalpine acidified lakes (high values of biotic metrics: number of families, proportion of crenal and rhithral taxa/total taxa); E — subalpine non-acidified lakes (high values of biotic metrics: number of families, number of genera, BMWP score, number of taxa and abundance of EPT taxa). RDA was used to design five levels of macroinvertebrate taxa acidification tolerance. The Tatra Acidification Index (TAI) was established to assess the acidification status of the lakes in the Tatra Mts.     

Benthic nematodes in acidified lakes: case of a neglected grazer

Abundance and composition of nematode fauna were examined in the benthic microbial mats and upper sediment layer of the littoral of acidified (pH 4.6 to 5.7) lakes. Nematodes constituted from 58% to 90% of all the invertebrates present (excluding protozoans and rotifers). In the examined material, the majority of nematodes was represented by 3 taxa of which Ironus was found specifically associated with the mats. It was concluded that the persistence of benthic mats may be linked to the metabolic activity of the associated nematode fauna.     

Thermal stratification and benthic foraging patterns of white sucker

Abundances of white sucker, 100–500 mm FL, were not significantly different among the epilimnia, metalimnia and portions of the hypolimnia shallower than 20 m in each of two lakes. However, small suckers < 200 mm were captured most frequently in the epilimnion and no white suckers were captured in the deepest region, 20–38 m, of the two lakes. White suckers consumed prey from all three temperature zones in each lake. Prominent food items were Hyalella azteca and the chironomid larvae Heterotrissocladius, Djalmabatista and Procladius. Despite differences in relative densities of benthic invertebrates among thermal zones of the two lakes, suckers in neither lake foraged exclusively on prey of epilimnetic origin. Suckers captured in the metalimnia foraged on invertebrates that were common to all three thermal zones. And, only 0–4% of the suckers captured in the hypolimnia of the two lakes contained prey that were unique to the epilimnia. Suckers caught in the hypolimnia mainly consumed deep water invertebrates; 83% of the suckers foraged in the metalimnion and hypolimnion of Islets Lake and 45% foraged in the hypolimnion in Burnt Island Lake. Consequently there was little evidence of a massive inshore feeding migration followed by a post-feeding return to the hypolimnion. Northern pike and lake trout rarely fed on white suckers in these lakes and thus piscivory was an unlikely factor in the observed distribution of suckers.     

Aquatic macroinvertebrate community structure of aNymphoides peltata-dominated and macrophyte-free site in an oxbow lake

The aquatic macroinvertebrates in two freshwater biotopes,viz. aNymphoides peltata-dominated site and a macrophyte-free site, were studied quantitatively in a shallow alkaline oxbow lake of the river Waal, the main branch of the river Rhine in The Netherlands. The research comprised the analysis of water, sediment and macrophyte samples.In the macrophyte-free site Oligochaeta and Nematocera, particularly of the collector gatherer functional feeding group, dominated the prevailing benthic community. The total macroinvertebrate biomass ranged here from 0.3 to 0.9 g ash-free dry weight per m² of biotope.Species richness, densities, and biomass of macroinvertebrates were considerably higher in the biotope dominated byNymphoides peltata. Many taxa were found associated with the aboveground macrophyte. The sediment compartment, however, contributed most to the total density and biomass of macroinvertebrates. Nematocera and Oligochaeta were the most abundant fauna groups, whereas the largest share in total biomass was provided by clams (Mollusca). The biomass of the total macroinvertebrate community in theNymphoides-dominated site ranged from 6.2 to 7.5 g ash-free dry weight per m² of biotope. The biomass of the aboveground phytophilous fauna ranged from 0.1 to 0.6 g ash-free dry weight per m² of biotope. In September, when theNymphoides peltata vegetation was in its senescent phase, the largest numbers and the highest biomass of phytophilous macroinvertebrates were observed. The contribution of the shredder functional feeding group was high in this period. This, and the overall high abundance of fauna with a detritivorous mode of life, indicates the importance of macrophyte detritus as input to food chains.     

Development of a regional macroinvertebrate index for large river bioassessment

Large river bioassessment protocols lag far behind those of wadeable streams and often rely on fish assemblages of individual rivers. We developed a regional macroinvertebrate index and assessed relative condition of six large river tributaries to the upper Mississippi and Ohio rivers, Midwest USA. In 2004 and 2005, benthic macroinvertebrates, water chemistry, and habitat data were collected from randomly selected sites on each of the St. Croix, Wisconsin, Minnesota, Scioto, Wabash, and Illinois rivers. We first identified the human disturbance gradient using principal components analysis (PCA) of abiotic data. From the PCA, least disturbed sites showed strong separation from stressed sites along a gradient contrasting high water clarity, canopy cover, habitat scores, and plant-based substrates at one end and higher conductivity and nutrient concentrations at the other. Evaluation of 97 benthic metrics identified those with good range, responsiveness, and relative scope of impairment, as well as redundancies with other metrics. The final index was composed of Diptera taxa richness, EPT taxa richness, Coleoptera taxa richness, percent oligochaete and leech taxa, percent collector-filterer individuals, predator taxa richness, percent burrower taxa, tolerant taxa richness, and percent facultative individuals. Each of the selected metrics was scored using upper and lower thresholds based on all sites, and averaging across the nine metric scores, we obtained the Non-wadeable Macroinvertebrate Assemblage Condition Index (NMACI). The NMACI showed a strong response to disturbance using a validation data set and was highly correlated with non-metric multidimensional scaling (NMDS) ordination axes of benthic taxa. The cumulative distribution function of index scores for each river showed qualitative differences in condition among rivers. NMACI scores were highest for the federally protected St. Croix River and lowest for the Illinois River. Other rivers were intermediate and generally reflected the mixture of land use types within individual basins. Use of regional reference sites, though setting a high level of expectation, provides a valuable frame of reference for the potential of large river benthic communities that will aid management and restoration efforts.     

Response of American dippers (Cinclus mexicanus) to variation in stream water quality

1. Semi‐aquatic birds may be sensitive to altered water quality. While avian species are not used in the bioassessment of streams, they may complement the more common use of benthic macroinvertebrates and fish. We estimated the extent to which water quality can predict attributes of the populations of one common semi‐aquatic bird, the American dipper (Cinclus mexicanus). 2. First, we estimated dipper presence/absence in relation to water quality as measured by a multimetric assessment index and individual bioassessment metrics. Second, we estimated dipper territory area and reproductive success in response to variation in water quality. We studied the diet, territory area and fecundity of dippers and sampled benthic macroinvertebrates, water chemistry and physical variables at 32 sites with and 17 sites without nesting dippers. 3. Dipper presence was only weakly related to chemical, physical and commonly recorded bioassessment metrics such as per cent Ephemeroptera, Plecoptera and Trichoptera (%EPT). Dippers were strongly related to the abundance of their common prey, Drunella and Heptageniidae, which are only a small component of the commonly recorded bioassessment metrics. The variances in territory area and reproductive success were weakly predicted by water quality variables. 4. Dipper presence reflected disturbance as measured by their common prey, showing that lower abundance of these stream invertebrates affected this semi‐aquatic bird. We suggest dipper presence/absence might be used in multimetric indices of biotic integrity for the bioassessment of streams.     

Macroinvertebrate Diversity in Alpine Lakes: Effects of Altitude and Catchment Properties

Lakes are common features of alpine landscapes, and the attention given to alpine lakes has increased recently in response to increased recognition of the important role that these freshwaters play as sensible indicators of climate change. Despite this general research interest, there is nevertheless a general lack of information about zoobenthos especially of lakes in the Alps, and only few published data are available, which has made it nearly impossible to draw general conclusions in respect to benthic community structure, profundal and/or littoral food webs. This paper aims to explore the relationships between main environmental/catchment properties of 55 lakes and their littoral benthic fauna across three regions of the Alps. We provide updated information on relative abundance, species richness, distribution and ecology of macroinvertebrates which occur and are typical in the littoral of high-mountain lakes of the Alps. These lakes were located in the Lago-Maggiore Watershed (Italy and Switzerland), in South Tyrol (Italy) and in North/East Tyrol (Austria), between 1840 and 2796 m a.s.l., in catchments undisturbed by human activities. As the studied lakes are situated above the tree line, they were characterised by low nutrient levels indicating an oligotrophic status. Lake water chemistry corresponded closely to the geo-lithology of the catchment and some parameters (especially nutrient concentrations) differed between the regions. The macroinvertebrates were dominated by insects which to a high degree were chironomid larvae and pupae. Other insect orders were typical cold stenotherm species of Ephemeroptera, Plecoptera and Trichoptera. Non-insect macroinvertebrates contributed to the 144 taxa found. Other than lake size and catchment area, the faunal parameters exhibited a clearer pattern along altitude. Macroinvertebrates per sample increased with higher elevation, reached their maximum in lakes between 2400 and 2600 m a.s.l., but decreased strongly above 2600 m. The altitudinal pattern of species richness and Shannon diversity resembled each other being highest between 2001 and 2200 m a.s.l., but decreased when going lower and higher, respectively. Various patterns and trends along altitude were also evident when individual groups were analysed within the individual sampling regions. The somewhat conflicting trends of various biocoenotic indices let assume that factors other than altitude are also responsible for the structure of faunal assemblages in the littoral of alpine lakes. Six variables (“bare rocks” and “nitrate”, “alkalinity”, “ammonia” and “peat bog”) were selected by the CCA analysis where these three groups of lakes were identified: (1) lakes with a higher alkalinity (higher pH, conductivity, ion concentration), a higher relative vegetation cover (compared to the “bare rocks” on the opposite side) and lower nitrate levels; (2) lakes with a higher portion of “bare rocks” in their catchments and higher nitrate levels; and (3) a smaller group of lakes with higher ammonia levels and a boggy environment. Geographical patterns seemed to have weak effects on the presence of taxa while catchment properties had evident impacts on macroinvertebrate communities in these lakes. In this way, the present study contributes to the overall understanding of environmental settings and effects on high mountain lake ecosystems and assists in refining research and conservation strategies for an important landscape aspect in the Alps.     

Interim Responses of Benthic and Snag‐Dwelling Macroinvertebrates to Reestablished Flow and Habitat Structure in the Kissimmee River,Florida, U.S.A.

A critical component in the effort to restore the Kissimmee River ecosystem is the reestablishment of an aquatic invertebrate community typical of free‐flowing rivers of the southeastern United States. This article evaluates early responses of benthic and snag‐dwelling macroinvertebrates to restoration of flow and habitat structure following Phase I construction (interim period) of the Kissimmee River Restoration Project. Replicate benthic and snag samples were collected from remnant river channels in Pool A (Control site), and Pool C, the site of the first phase of restoration (Impact site). Samples were collected quarterly for 2 years prior to construction (baseline) and monthly or quarterly for 3 years following Phase I construction and restoration of flow. Baseline benthic data indicate a community dominated by taxa tolerant of organic pollution and low levels of dissolved oxygen, including the dipterans Chaoborus americanus (Chaoboridae) and the Chironomus/Goeldichironomus group (Chironomidae). Baseline snag data indicate a community dominated by gathering‐collectors, shredders, and scrapers. Passive filtering‐collector invertebrates were rare. Following restoration of flow, benthic invertebrate communities are numerically dominated by lotic taxa, including bivalves and sand‐dwelling chironomids (e.g. Polypedilum spp., Cryptochironomus spp., and Tanytarsini). Snags within the Phase I area support an invertebrate community dominated by passive filtering‐collectors including Rheotanytarsus spp. (Chironomidae) and Cheumatopsyche spp. (Hydropsychidae). Results indicate that restoration of flow has resulted in ecologically significant changes to the river habitat template not observed in Pool A. Observed shifts in benthic and snag macroinvertebrate community structure support previously developed hypotheses for macroinvertebrate responses to hydrologic restoration.     

Aquatic macrophytes, macroinvertebrate associations and water levels in a lowland Tasmanian river

Aquatic macrophytes are a common habitat for macroinvertebrates and may occupy depth zones in the littoral region of lowland rivers. Studies have indicated that different species of macrophyte typically support different assemblages, abundances and numbers of species of macroinvertebrates. This has often been attributed to differences in the dissectedness of stems and leaves of the macrophytes, resulting in differences in the surface area and/or the number of microhabitats available to invertebrates. I set out to measure the abundance and taxonomic richness and to describe the macroinvertebrate assemblages associated with three species of aquatic macrophyte in a pool in the Macquarie River, Tasmania and to examine responses of these variables to changes in water levels over summer. The macrophyte species sampled wereMyriophyllum simulans/variifolium, Triglochin procera} and Eleocharis sphacelata, each one differing in the dissectedness of its stems and leaves and its location in the littoral zone. Whereas the greatest abundance of macroinvertebrates was found associated in all months (i.e. at all water levels) with the structurally complex and shallowest macrophyte species, Myriophyllum, the number of taxa associated with this species was in several cases lower than for the structurally simpler and deeper water Triglochin and Eleocharis. While water depth and total plant biomass of samples were often correlated with invertebrate abundance and richness, these relationships were different for each macrophyte species. Of the nine most common invertebrate taxa collected from all samples, the abundances of more than half showed consistent differences among macrophyte species across months, two showed differences among macrophytes, but with an interaction with month and two showed no differences among macrophytes. There were major differences in the invertebrate assemblages associated with each macrophyte species in any one month, however, there was also a large turnover of taxa associated with the species of macrophytes from one month to the next. Changes in water level and concomitant changes in environmental variables are suggested as factors influencing the invertebrate fauna in the littoral zone of the pool of the Macquarie River. It is thus important for river managers to be aware that species of macroinvertebrates are not evenly distributed across species of macrophyte and that water levels and their influence on macrophytes as invertebrate habitat may play an integral part in determining the abundance, richness and assemblage of invertebrates in rivers.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of Wilmot Creek

The effects of the lampricide, TFM, on the abundance of macroinvertebrates in the benthos of Wilmot Creek, a hardwater tributary to Lake Ontario, was examined over 1 year. Drifting macroinvertebrates were also collected before, during and after TFM treatment. Significant decreases in benthic abundance were exhibited by Dolophilodes sp., Tubificoidea, Cricotopus sp. and Macrotendipes sp. throughout the 350 days following treatment. Only the decrease in abundance of Dolophilodes sp. and Tubificoidea could be attributed to TFM treatment. Increases in drift abundance observed during treatment were generally an accurate indicator of TFM-sensitive macroinvertebrates. The most sentive taxa (Dolophilodes sp., Dugesia sp. and Tubificoidea) responded immediately following the introduction of TFM. Branchiobdellida, Diamesa sp., Dicranota sp., Lumbricidae and Nemouridae exhibited increases in drift abundance 8–10 h after the introduction of TFM, however, were considered less sensitive than the former taxa because a decline in their abundance in the benthos was not detected.The response of the benthic invertebrates found in this hardwater creek was similar to those observed during studies of softwater streams. Only the most severely affected taxa were not present in the benthos 350 days after treatment.