Relationship between benthic insects (Ephemeroptera, Plecoptera, Coleoptera, Trichoptera) and temperature in small and medium-sized streams in Germany: A multivariate study

Benthic insect communities (Ephemeroptera, Plecoptera, Coleoptera, Trichoptera) were studied together with water temperature and environmental parameters in streams between June 2000 and June 2001. The sampling area consisted of 20 sites in small and medium-sized streams located in the lower mountainous area of Central Europe. Temperature was recorded nearly continuously and several physicochemical and environmental variables were assessed. Macroinvertebrates were sampled both in spring and summer. Data-sets of species abundance and occurrence were analysed using multivariate techniques and were correlated to the thermal and environmental conditions of the streams. The temperature preferences of the species were compared to published data-sets on their autecological characteristics. Up to 29% of the variability in the Ephemeroptera, Plecoptera, Trichoptera and Coleoptera community was explained by summer temperature variation in the data-sets for both small and medium-sized streams. A smaller, but significant part of the variability in species distribution was explained by conductivity, substratum type, and the percent coverage of local riparian forest. Compared to small streams, temperature was less important for the macroinvertebrate composition in medium-sized streams. This result is likely due to the more tolerant, eurythermic species composition in larger streams. A total of 33 Ephemeroptera, Plecoptera, Coleoptera and Trichoptera taxa were positively correlated and 28 taxa were negatively correlated to summer temperature patterns. The temperature preferences of taxa considered in this study were related to species traits, such as egg dormancies and life cycle plasticity.     

Longitudinal and seasonal distribution patterns of the benthic fauna of an alpine glacial stream (Val Roseg, Swiss Alps)

1. Seasonal changes in longitudinal patterns of environmental conditions and macroinvertebrate community distributions were examined in an alpine glacial stream (Roseg River, Switzerland). 2. Physico‐chemical parameters reflected seasonal changes in glacial influence via shifts in water sources and flowpaths (glacial meltwater versus ground water), and were best described by turbidity, particulate phosphorus and specific conductance. High nitrogen concentrations indicated snowmelt was the main water source in June. 3. Macroinvertebrate densities and taxon richness were highest during spring (4526 m^–2 and 16 taxa, all sites combined) and late autumn/early winter (8676–13 398 m^–2 with 16–18 taxa), indicating these periods may be more favourable for these animals than summer when glacial melting is maximal. Diamesa spp. (Chironomidae) dominated the fauna at the upper three sites (>95% of zoobenthos) and were abundant at all locations. Other common taxa at lower sites (1.2–10.6 km downstream of the glacier terminus) included other chironomids (Orthocladiinae, Tanytarsini), the mayflies Baetis alpinus and Rhithrogena spp., the stoneflies Leuctra spp. and Protonemura spp., blackflies (Simulium spp., Prosimulium spp.), and Oligochaeta. 4. Co‐inertia analysis revealed a strong relationship between environmental conditions and benthic macroinvertebrate assemblages. Furthermore, it elucidated temporal variability in longitudinal response patterns, as well as a similarity in temporal patterns among individual sites. 5. Our results suggest that zoobenthic gradients are not solely related to temperature and channel stability. Seasonal shifts in sources and pathways of water (i.e. extent of glacial influence), and periods of favourable environmental conditions (in spring and late autumn/early winter) also strongly influenced zoobenthic distributions.     

The distribution of some freshwater planktonic bacteria in two stratified eutrophic lakes

SUMMARY. Changes in bacterial populations and certain physical and chemical variables in Esthwaite Water between June and September 1975 were studied and compared with results obtained from 1972 to 1974 in the hypolimnia of Blelham Tarn and the Lund tubes. The counts of total bacteria ranged between 1 and 7 × 10⁶ml⁻¹ and were highest in the anoxic hypolimnion. The bacterial genera examined in more detail constituted only a small percentage of this count and included Ochrobium (10⁴ml⁻¹), Naumanniella (10³ml⁻¹), Leptothrix (10²ml⁻¹), Planctomyces (10³ml⁻¹), and Metallogenium (10²ml⁻¹). The iron bacteria appear to grow best in the oxycline where there was not only sufficient oxygen for aerobic growth but also a plentiful supply of reduced iron. Planctomyces numbers increased as the thermocline became depressed in September. The results from Blelham Tarn might be interpreted as further evidence of growth by iron bacteria in the absence of dissolved oxygen, but other explanations are possible. Examination of the results by multiple regression analysis showed that it was possible to explain a significant proportion of the bacterial variation (with the notable exception of the Planctomyces counts) in spite of considerable intercorrelation of the regressor variables.     

Experimental Assessment of the Effects of Environmental Factors and Longitudinal Position on Alpha and Beta Diversities of Aquatic Insects in a Neotropical Stream

We evaluated the effect of environmental factors on the abundance and genera richness of aquatic insects colonizing artificial substrates. We also assessed the relative effects of environmental factors on assemblage variation (beta diversity), and contrasted its magnitude with the variation associated with the spatial position of reaches in a Neotropical stream. Homogeneous and heterogeneous bricks were installed in seven stream reaches and removed after 60d. Substrate type and organic matter showed significant effects on abundance. For observed richness, substrate type was the only important variable. For rarefied richness, no explanatory variable was important. A NMDS ordination of bricks revealed the effect of spatial position and substrate type. A partial Redundancy Analysis (pRDA) indicated that the environmental matrix explained 12.44% of the total variation, while reach position explained 7.41%. We conclude that at local scale (reaches 430–920 m apart), environmental factors, especially substrate heterogeneity, were important in determining the alpha and beta diversities of the insect assemblage in the stream (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The composition and importance of the phytoneuston in two floodplain lakes in south-eastern Australia

Normans Lagoon and 3-Gum pond are small floodplain water bodies adjacent to the Murray River, south-eastern Australia, and often have a visible film/sheen across their surface. Since few studies have provided quantitative comparisons of the surface and subsurface layer communities of shallow freshwater lakes, we determined the contributions of the surface and subsurface populations to overall algal biomass when a surface film was visible, and when it was not visible. We examined the algae and cyanobacteria present at the air–water interface of each water body, and compared the findings with those for the water immediately below the surface, and for the overall water column. The algal groupings Trachelomonas spp., other Euglenophyceae (principally Euglena spp.), Chlorophyceae and Cyanobacteria usually comprised >95% of the measured biovolume within all samples. Samples from the air–water interface were considerably enriched (up to 200-fold) with respect to algal biovolume, whether or not a visible surface film was present, and elevated cell counts were observed within the air–water interface for motile organisms such as Trachelomonas spp. and green unicellular flagellates. The reverse was true for the cyanobacterium Planktolyngbya however, with greater concentrations occurring at depth. In terms of its contribution to the overall algal/cyanobacterial populations within each water body, the surface layer was found to be responsible for <1–20% of the biovolume over the entire water column. Multivariate statistical analysis confirmed there were significant differences between the communities of the air–water interface and those of the water below, and that these differences occurred both in the presence and absence of a visible surface film/sheen. Handling editor: D. Ryder     

Geographical distribution of myxomycetes on coniferous deadwood in relation to air temperature in Japan

This study obtained information on the biogeographical distribution of lignicolous myxomycetes in temperate regions in Japan. It examined how climatic variables are related to patterns of occurrence in myxomycete communities. Sixty-four taxa were recorded on coniferous wood in 15 forest sites in summer. Common species that were abundant and widely distributed in Japan included Stemonitis axifera, Lycogala epidendrum, and Cribraria cancellata. In addition, Lindbladia cribrarioides was characteristic on dead Pinus densiflora wood in southwestern Japan. The species diversity index (H′) of the myxomycete communities was positively correlated with the annual mean temperature. The distribution of myxomycete communities was analyzed using nonmultidimensional scaling (NMDS). The ecological nature of the gradients expressed by the first two NMDS axes was that the first axis was found to correspond strongly to changes in the average minimum temperature and the latitude, and the second axis was related to a complex of factors, including altitude. The relative abundance of certain species in a myxomycete community on Japanese red pine changed in relation to the annual mean temperature, e.g., Lycogala epidendrum correlated negatively while Stemonitopsis hyperopta did so positively. We conclude that air temperatures can be used to predict the geographical distribution of lignicolous myxomycetes in this temperate region of Japan.     

Influence of morphohydraulic habitat structure on invertebrate communities (Ephemeroptera,Plecoptera and Trichoptera)

Fluvial geomorphology proposes the methodology of cognition and assessment of the riverine landscape and points to the possibilities of exploitation of its results in hydrobiological research. Habitat structure of two reaches of the Drietomica brook (Biele Karpaty Mts, Slovakia) was assesed at level of morphological and morphohydraulic units in the sense of the River Morphology Hierarchical Classification (RMHC)). Physical habitats were described by flow hydraulics and substrate properties as directly measured variables (current velocity, depth, substrate size) and related variables (flow type, Froude and Reynolds numbers). According to the shear stress (expressed by Fr and Re), the morphological units were divided into two main groups — with low shear stress — pools, glides, edgewaters, bar nooks and bars; with high shear stress — riffles, runs, rapids and scours; characterized also by different Ephemeroptera, Plecoptera and Trichoptera (EPT) communities. The EPT communities were analyzed in relation to the morphological, hydraulic and substrate characteristics of the stream channel. The main environmental gradient responsible for the variation in EPT fauna was found using Principal Component Analysis and was related to gradient of flow in term of current velocity and other hydraulic attributes covered by Fr and Re numbers. The EPT communities (by means of abundance, feeding types, current, microhabitat and zonation preferences) showed preferences for different morphological units, flow type and current velocity. Depth and substrate grain size showed only weak relation to EPT communities.     

Taxonomic revision of the genus Chiloporter Lestage (Ameletopsidae: Ephemeroptera) with notes on its biology and distribution

A taxonomic revision of the genus Chiloporter is presented confronting new material collected in Chile and Argentina, with the literature of the genus. Unknown developmental stages are described; association of larvae and winged stages is confirmed here by rearing. The synonymy of the extant species is proposed. Notes on the biology and distribution are also included.     

Nutrient and hydrologic budgets of a great lakes coastal freshwater wetland during a drought year

A coastal wetland along Lake Erie (Ohio, U.S.A.) was studied to determine hydrologic and phosphorus budgets and spatial and temporal variation of phosphorus and related chemical parameters. The wetland was influenced by changing Lake Erie water levels, seiches, shifting shoreline sediments, and watershed inflow during a year of severe drought. The water budget for a 7-month period (March – September, 1988) had average inflow of 15 200 m³ day^–1 from the watershed and 3.5 m³ day^–1 from Lake Erie. The wetland increased in volume by 700 m³ day^–1 despite a drought that resulted in 80% more evapotranspiration than rainfall as a barrier beach isolated the wetland from Lake Erie for 77% of the study period. Conductivity decreased by 34% as water flowed through the wetland and turbidity and total suspended solids were variable and statistically similar at inflow and outflow. Average total phosphorus concentrations in the inflow and outflow were also similar (247 and 248 µg P l^–1 respectively) although total soluble phosphorus and soluble reactive phosphorus decreased significantly (=0.05) from inflow to outflow (averages 94 to 45 µg P l^–1 and 7.5 to 4.0 µg P l^–1 respectively). Nutrient budgets from field data estimate a retention of 36% of the phosphorus, presumably in the sediments (0.8 mg P m^–2 day^–1). A general nutrient retention model, an estimated deposition rate from a sediment core and a simulation model predicted higher mass retention of phosphorus but similar percentage retention.SommaireUn marecage qui côtoie le lac Erie (USA) a servi de site expérimental pour en déterminer les budgets d'eau et de phosphore, de même que pour la variation spatiale et temporelle du phosphore et d'autres facteurs chimiques. Le marécage a été influencé par: niveaux d'eau qui changeaient; seiches; sédiments mouvants du littoral; et afflux de la ligne de partage des eaux dans une année de grande sécheresse. Le budget d'eau dans une période de 7 mois (mars–septembre 1988) montre un afflux de 15 200 m³ jour^–1 de la ligne de partage, et 3.5 m³ jour^–1 du lac Erie. Le volume du marécage a augmenté par 700 m³ jour^–1 malgré une sécheresse qui a produit plus d'évapotranspiration (80%) que de pluie pendant qu'une plage-obstacle a isolé le marecage du lac Erie pendant 77% de la période d'observation. La conductivité a diminué par 34% pendant que l'eau coulait, et la turbidité et les TSS ont varié, tout en démontrant des statistiques similaires à l'afflux et au déversement. Les moyennes pour les concentrations du total du phosphore à l'afflux et au déversement ont été similaires (247 and 248 µg P l^–1), quoique le TSP et le SRP ont diminué (=0.05) de l'afflux au déversement (donant des moyennes de 94 à 45 µg P l^–1 et de 7.5 à 4.0 µg P l'^–1). Les budgets de substances nutritives pour les données suggèrent une reténtion de 36% du phosphore, évidemment dans les sédiments (0.8 mg P m^–2 jour^–1). Un modèle pour la rétention des nutrients, un taux de déposition, estimé par un noyau de sédiments, et une simulation avaient prédit un plus grand taux de rétention de phosphore, mais un pourcentage similaire pour la rétention.From a paper presented at the Third International Wetlands Conference, 19–23 September, 1988, University of Rennes, France.     

The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes

Summary The annual development of the gonads of Dreissena polymorpha was studied at three sampling sites in two lakes over 3 and 1 1/2 years, respectively. A resting stage occurred after the last spawning in summer/autumn. Oogenesis (accompanied by multiplying segmentation of the oogonia and early growth processes of its oocytes) restarted in specimens at least 1 year old at low temperatures (below 10° C) during winter and early spring. At one location (Fühlinger See) the onset of the spawning season was correlated with an increase of water temperatures above 12° C. At 2 m depth, two main spawning periods in May and August were normally recognized, the first at temperatures of 12–16° C, the second at 16–21° C. It was clearly demonstrated for the first time in Dreissena polymorpha that the oocytes became mature in successive cohorts within one gonad. A female mussel may spawn several times during the reproductive season. At 9 m depth, the onset of spawning also started at about 12° C; this occurred in late summer, with two spawning periods within 1 month at a temperature range of 12–16° C. At another location (Heider Bergsee) the size of the gonads and the oocytes was reduced during April of both years studied, when food supply was low simultaneously with rapidly rising water temperatures in this shallow lake. There was no spawning period during spring. The major spawning period was delayed until July (temperatures 19–22°C). This shows (1) the synchronizing influence of low winter temperatures on the annual reproductive cycle and (2) a temperature threshold of at least 12° C for the start of the spawning processes. The results are discussed with regard to the geographical limits of further spread of Dreissena polymorpha.     

Geochemistry of suspended and settling solids in two freshwater lakes

This study describes the 1987–1992 time variationof the bulk chemical composition, levels of heavymetals, arsenic, nitrogen and phosporous insuspended and settling solids in Lake Volkerak andLake Zoom (The Netherlands). Suspended and setlingsolids were collected with continuous flowcentrifuges and sediment traps, respectively. Therelations between solids characteristics and metalconcentrations in the particles were investigatedusing correlation and factor-analysis. Heavy metals,except manganese, were associated with clay contentof the particles and with organic carbon which wasmainly determined by phytoplankton growth. Manganesewas correlated with Org-C only. Clay and organicmatter with associated heavy metals showed negativetrends on all locations, and a seasonality due toalgal biomass dilution. It is concluded that thetrophic state significantly affects trace metalcycling. Sediment traps collect different types ofparticles than continuous flow centrifuges. Thetraps collect particles with higher clay content,lower Org-C concentrations and higher Org-C/Nelemental ratios than the centrifuges. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal changes in the underwater light climate of two Canadian shield lakes

This study examines the seasonal variation in the underwater spectral distribution of light in a mesotrophic (Lake Cromwell) and an oligo-mesotrophic (Lake Croche) temperate lake. Gilvin is primarily responsible for the strong selective attenuation of blue light in both lakes. As a result of differing gilvin concentrations light transmission maxima of downwelling and upwelling spectra are near 615 nm in Lake Cromwell and 599 nm in Lake Croche. With increases in depth both upwelling and downwelling radiance fluxes decrease, are shifted to longer wavelengths and become more monochromatic. The greatest penetration of light occurs in the summer and spring after which a gradual decrease occurs through fall to a minimum value in winter. Under the winter cover the P ₅₀ of downwelling light shifts 10 to 20 nm towards shorter wavelengths. Seasonal changes in downwelling irradiance are related to solar altitude, concentration of suspended particles, phytoplankton populations, amount of gilvin, mixing and winter cover. The brownish colouration of these lakes is explained by reflectance of spectrally impure orangish-red light.     

Egg characteristics and oviposition behaviour of the aquatic insect orders Ephemeroptera,Plecoptera and Trichoptera in New Zealand: a review

The abundance and distribution of aquatic insects may be controlled by factors at any stage of the life cycle. To understand the potential role of factors affecting egg and adult stages and oviposition, basic information on egg characteristics and oviposition behaviour is required. However, published information on New Zealand Ephemeroptera, Plecoptera and Trichoptera (EPT) is scattered and very limited. This review compiles current knowledge of New Zealand EPT egg characteristics and oviposition behaviour using published information and unpublished observations. Where direct observations are lacking, information on closely related species overseas, and inferences based on female morphology, are included. Eggs show a variety of physical characteristics that may influence egg retention, transport and distribution. Oviposition behaviour is highly selective among some taxa, but appears generalist among others, though the latter may still require specific cues. Identifying and providing for adult, egg and oviposition requirements may be fundamental to re-establishing EPT populations in restored aquatic habitats.     

The effect of water movement on the distribution of Oligochaeta in lakes

The Oligochaeta are more exposed to disturbance under conditions of intense water movement than other invertebrates, particularly when the substrate is unstable. Furthermore, low mobility of bottom water, which can lead to excessive accumulation of organic matter in sediments, and to the formation of sapropel, can also be limiting to the distribution of oligochaetes. Organic contamination in conditions of low water dynamics can result in the absence of Oligochaeta through oxygen depletion. Dynamic water movement can stimulate the mass development of Oligochaeta in organically polluted areas.     

Longitudinal zonation and life cycles of macrozoobenthos in the Mauerbach near Vienna,Austria

A total of 12277 benthic invertebrates were caught from November 1990 to October 1991 at the Mauerbach, a first to fourth order forest brook near Vienna, Austria, using a Surber sampler and a hand net. Five taxa comprised 96.6% of the catch: Diptera larvae (45.6%), Amphipoda (37.6%) and larvae of Ephemeroptera (6.4%), Plecoptera (5.3%) and Trichoptera (1.7%). Mean values of macrozoobenthos density ranged from 39514 specimens m⁻² at upstream sampling site 5 in December to only 286 specimens m⁻² at sampling site 3 in May, shortly after a severe flood. Based on benthic invertebrate population structure, sites 5 and 6 (situated near the source) were clearly separated from the downstream sites 1 to 4. At upstream sites, shredders comprised up to 71.7% of the total, whereas at downstream sites collectors were most abundant. In addition, the proportion of eucrenal species decreased from 12% at site 6 near the source to only 2% at site 1 near the mouth. Among the insect species studied in detail, most were univoltine except Ephemera danica (Ephemeroptera) and Sericostoma personatum (Trichoptera), which had a two-year life cycle.     

Development of aquatic insect eggs in relation to temperature and strategies for dealing with different thermal environments

Average reaction norms relating number of day-degrees required to complete egg development to temperature are described for 95 species (115 populations) of Plecoptera, Odonata, Ephemeroptera, and Diptera (mainly Culicidae, with some Tipulidae and Sciomyzidae). The slope of the average reaction norm is used as an index of adaptation, with positive slopes indicating cold-adapted species, negative slopes indicating warm-adapted species, and slopes around zero indicating generalist species; 57% of the between-taxon variation in slope is associated with differences between orders, 14% among families, 7% among genera, 14% among species, and 8% among populations. Significant differences between congeneric species are found in only 4 of 92 possible comparisons. Only Hecoptera show much cold-adaptation, with 40% of the species having significantly positive slope. However, 26% of the species (mainly in the Systellognatha) have significantly negative slope, suggesting adaptation to warmer waters than those in which the order is believed to have originated. The other orders probably originated in warm water and have generally maintained this adaptation. All Odonata, 71% of the Diptera and 81% of the Ephemeroptera have significantly negative slopes. Diapause is a common alternative to metabolic adaptation to deal with unfavourable thermal environments. We suggest that it occurs widely in eggs of Plecoptera and in the mayfly Rhithrogena hyolaea, cold-adapted species that may use diapause to survive periods of high temperature.     

The distribution,structure, and composition of freshwater ice deposits in Bolivian salt lakes

Freshwater ice deposits are described from seven, high elevation (4117–4730 m), shallow (mean depth <30 cm), saline (10–103 g l^-1) lakes in the southwestern corner of Bolivia. The ice deposits range to several hundred meters in length and to 7 m in height above the lake or playa surface. They are located near the lake or salar margins; some are completely surrounded by water, others by playa deposits or salt crusts. Upper surfaces and sides of the ice deposits usually are covered by 20–40 cm of white to light brown, dry sedimentary materials. Calcite is the dominant crystalline mineral in these, and amorphous materials such as diatom frustules and volcanic glass are also often abundant.Beneath the dry overburden the ice occurs primarily as horizontal lenses 1–1000 mm thick, irregularly alternating with strata of frozen sedimentary materials. Ice represents from 10 to 87% of the volume of the deposits and yields freshwater (TFR <3 g l^-1) when melted. Oxygen isotope ratios for ice are similar to those for regional precipitation and shoreline seeps but much lower than those for the lakewaters. Geothermal flux is high in the region as evidenced by numerous hot springs and deep (3.0–3.5 m) sediment temperatures of 5–10°C. This flux is one cause of the present gradual wasting away of these deposits. Mean annual air temperatures for the different lakes probably are all in the range of -2 to 4°C, and mean midwinter temperatures about 5°C lower. These deposits apparently formed during colder climatic conditions by the freezing of low salinity porewaters and the building up of segregation ice lenses.