Chironomid Pupal Exuviae Research Articles

Book Review: A Guide to the Identification of Genera of Chironomid pupal Exuviae Occurring in Britain and Ireland (Including Common Genera from Northern Europe) and Their Use in Monitoring Lotic and Lentic Freshwaters. By Ronald S. Wilson and Leslie P. Ruse

Book Review: A Guide to the Identification of Genera of Chironomid pupal Exuviae Occurring in Britain and Ireland (Including Common Genera from Northern Europe) and Their Use in Monitoring Lotic and Lentic Freshwaters. By Ronald S. Wilson and Leslie P. Ruse

Chironomid Emergence and Relative Emergent Biomass from Two Alabama Streams

Chironomid pupal exuviae were sampled monthly using drift nets and hand sieves over an annual cycle from Hendrick Mill Branch (HMB; Blount County, AL) and Payne Creek (PC; Hale County, AL). Taxon richness, community composition, and emergence phenologies were similar despite marked differences in physical/chemical characteristics of the study streams. The highest emergence rates were observed in spring (PC) or both spring and fall (HMB). However, there was no significant relationship between emergence/emergent biomass and date. Estimates of daily emergence and emergent biomass were much higher in HMB than in PC. These patterns may have resulted from a more consistent flow regime, higher substrate stability, lower variation in temperature/chemical characteristics, greater channel surface area, and a more significant hyporheic zone in HMB than in PC.

The use of chironomid pupal exuviae in river biomonitoring: the importance of sampling strategy

Due to the seasonal variation in the emergence patterns of chironomid taxa, a combination of three monthly samples from spring to autumn has been recommended for biomonitoring of rivers using the Chironomid Pupal Exuvial Technique (CPET). The main purposes of this study were to establish an effective sampling strategy (i. e. strategy that would allow effective discrimination between study sites) for biomonitoring of boreal rivers using the CPET methodology and to estimate the taxonomic coverage of any three monthly sample combinations. First, we collected pupal exuvial samples from three oligo- to mesotrophic study sites in a large boreal River Kymi, southern Finland, in 4-week intervals from the beginning of May to September 2003. The four most effective combinations of three monthly samples resulted in a significant difference between the sites, while the six least powerful combinations indicated no differences in chironomid communities between the sites. A corresponding data set was collected from four oligo- to eutrophic rivers, one sampling site representing each river. In this data set, eight combinations out of ten found significant differences between the rivers. Thus, the sampling strategy seemed more decisive at the within vs. among-river scale of comparison. No single combination of three monthly samples was consistently the most effective one in discriminating among the studied sites and rivers. Nevertheless, a combination of CPET samples from different seasons (i. e. spring, mid-summer and late summer/autumn) clearly constitutes the best sampling strategy for the detection of environmental impacts in boreal rivers. In the studied rivers, and probably in other boreal rivers as well, any combination of three monthly samples from spring to autumn will yield a reasonably high coverage of the available genera (at least 60%). We suggest that the efficiency of different sample combinations and the distribution of the emergence periods of locally abundant intolerant taxa are crucial information when the CPET methodology is used for river biomonitoring.

Aquatic biodiversity and saline lakes: Lake Bogoria National Reserve, Kenya

Lake Bogoria, in the Rift Valley of Kenya is an extreme saline lake (conductivity 40–80 mS cm-1, alkalinity 1500 m equ 1-1). It is hydrologically more stable than the other, endorheic lakes in Kenya, because it is deep — maximum depth at present just over 10 m in an area of 3000 ha — and so does not have periods when it is dry. It is ecologically simple, with only one species dominating the phytoplankton — the cyanobacterium ‘spirulina’, Arthrospira fusiformis. Its biomass and productivity were very high — biomass between 38 and 365 μg 1-1 chlorophyll ‘a’ and 3.4–21 x 103 coils ml-1 and net production between 0.24 and 1 gm C m3 h, the latter in a narrow zone of less than a metre. There were no macro-zooplankton in the plankton and the only grazer of A. fusiformis was the lesser flamingo, Phoeniconaias minor, which occurred irregularly in very high concentrations (in excess of 1 x 106). Detritivory in the benthos was effected by a single chironomid species, Paratendipes sp., at a maximum density of 4 x 104 m-2. The mean daily emergence of adult chironomids was estimated to be 1 x 103 m-2, the maximum 3. There was no littoral plant community within the lake but 44 dicotyledonous and 31 monocotyledonous plant species in the drawn-down zone and adjacent to it. A diverse draw-down terrestrial invertebrate fauna, only superficially described here, processed the flamingo feathers and carcasses, with other detritus such as chironomid pupal exuviae and decaying A. fusiformis scum. About 50 bird species depended upon the chironomids, either as they emerged through the water column as flying adults or later on the shoreline as floating pupal exuvia and dead adults. The lake has high conservation value because of three bird species in particular — lesser flamingo, Cape teal and black-necked grebe. The former provides real economic value in a region otherwise impoverished, because of the spectacle of tens of thousands of flamingos set against the landscape of hot springs and fumaroles at the lake edge, which draws 15 000 visitors per annum. P. minor has experienced three periods during the past ten years when major mortalities have occurred, the last of which killed 700 birds day-1. This could have involved as many as 200 000 birds (about 1/5th of the maximum population at this lake) if mortality was at a constant rate for the nine months it was observed. Causes of mortality have been suggested as avian tuberculosis, poisoning from cyanobacterial toxins or from heavy metal contamination at Lake Nakuru, but it is still not yet clear what contribution each makes to the problem.

Assessing lake functioning using the macrobenthic community with special reference to Chironomidae (Diptera). A subalpine lake (Lake Annecy) as an example

The macrobenthic community of Lake Annecy was investigated through both a study of the total macrobenthic organisms living in the sediments and an extensive study of the chironomid community. Two sampling methods were used. Sediments were sampled in April 1998 with a modified Ekman grab at 36 sampling sites along four isobaths. At the same sites, chironomid pupal exuviae were collected for species identification at the water surface by net-dragging. Quantitative descriptors of the total macrobenthic and the emerging chironomid communities (i.e. total taxon richness, chironomid species richness, littoral biodiversity index, chironomid larval density) showed high values that reflect a high biogenic capacity. Qualitative descriptors of the communities (i.e. bathymetric pattern of taxon richness, specific composition of the chironomid community and bathymetric distribution of chironomid species) indicate that Lake Annecy is an oligohumic lake characterised by a decrease in organic matter content with depth. According to VERNEAUX et al. (1993 a, 1993 b, 1995) biological classification of lakes the bathymetric pattern of the macrobenthic community of Lake Annecy is related to an optimal efficiency of organic matter assimilation within the food web (optimal functioning).

Chironomid pupal exuviae as indicators of lake status

Thirty lakes in England and Wales were characterised by the distribution and abundance of chironomid species, collected as pupal exuviae, in correlation with chemical and physical measurements. Alkalinity and lake volume were the best predictors of chironomid species assemblage among lakes. Conductivity, lake volume and altitude were the best variables discriminating lake classes based on species distribution. A biological classification, constrained by conductivity, was used to calculate indicator species scores. A conductivity gradient of indicator species assemblages was produced to demonstrate how temporal or spatial reference conditions could be inferred. Conductivity, lake area and catchment area were the best predictors of profundal species distribution. Potential lake anoxia increased in explanatory importance after exclusion of littoral species. Alkalinity, catchment area and lake area significantly explained distribution of genera. Compared with a classification derived from 208 littoral and profundal species, discriminant analysis of best subsets of indicator taxa found 97 % of lakes were correctly classified using 15 profundal species and 73 % were correct using 7 genera. It was concluded that the pupal exuvial technique was an easy and effective method for characterising large lakes, as required for implementation of the European Water Framework Directive.

Species assemblages of Chironomidae (Diptera) in acidic Welsh streams

Despite their speciose nature and potential role as ecological indicators, there are few data on the chironomids that characterise upland streams at risk from acidification. Nor has the use of pupal exuviae for typing upland streams been appraised. Therefore, in conjunction with the second Acid Waters Survey for Wales, sixty-one sites on acid-sensitive streams were sampled for chironomid pupal exuviae in June 1995. No exuviae were found at nine of the sites but the remainder produced seventy-three species, the majority of which belonged to the sub-family Orthocladiinae. Sites with three or more species were subjected to two-way indicator species analysis (TWINSPAN). This analysis produced thirteen species assemblages and eight site groups at Level 6, The concepts of constancy and fidelity were used to establish the relative strengths of the relationships between the species assemblages and the site groups. Almost all the species assemblages showed a strong fidelity to one or two site groups. Habitat data collected for each site from October 1994 to September 1995 were used to explore the relationships between the species assemblages and the habitat characteristics of the site groups. It was apparent that pH was only one of several environmental variables that correlated with the distribution of the species assemblages. However, the robustness of these species assemblages and their ecology require further investigation.

Analysis of chlordane-impacted streams using chironomid pupal exuviae (Diptera: Chironomidae)

A method of rapidly assessing streams and rivers using chironomid pupal exuviae was tested on a chlordane-impacted stream near St. Louis, Missouri. Various concentrations of chlordane were found in sediments of Grand Glaize Creek, most likely resulting from soil runoff around housing and business developments throughout the stream's course. Chironomid pupal exuviae and sediment samples were collected concurrently from Grand Glaize Creek on two separate occasions, once in 1988 and again in 1990. Cluster analysis of samples at sites, based on the percent abundances of taxa within habitats and by subfamilies, produced two distinct clusters; one grouping samples with lower chlordane concentrations and the other grouping samples with higher chlordane concentrations. Further analysis showed a trend towards lower percent abundances of taxa living in depositional and transitional/depositional zones (Chironominae and some Tanypodinae) at the higher chlordane site, while the lower chlordane sites had lower percent abundances of taxa within erosional and erosional/transitional zones (Orthocladiinae and some Tanypodinae). These findings support the hypothesis that taxa living in close association to fine organic sediments will be exposed to higher concentrations of chlordane in the stream and more negatively affected than taxa feeding and living in habitats removed from chlordane-bound sediments. Comparisons from the present study were made to related studies revealing similar patterns among the Chironomidae.

Chironomid Assemblages of Three Endoreic Karstic Lagoons (Southern Spain) Determined by Collection of Pupal Exuviae: Importance of the Water Mineralization and Sediment Characteristics

AbstractFloating chironomid pupal exuviae were collected every three months from January 1992 to April 1993 on the windward shore of three endoreic karstic lagoons varying in the mineralization of the water and the characteristics of the sediment.A total of 16 chironomid species were identified in the three lagoons studied. Species richness was rather similar in the lagoons, varying from 8 species in Lagoon Chica to 10 species in Lagoon Caja. The chironomid assemblage of Lagoon Caja seems to be determined by the vast cover of aquatic macro‐phytes (mainly Myriophyllcim spicurum), a substrate widely preferred by the species of the subfamily Orthocladiinae. However, in Lagoon Chica with a similar cover of M. spicurm, only one Orthocladi‐inae species was found with a low relative abundance. The higher salinity may have limited the colonization of more Orthocladiinae species.The chironomid assemblages of the lagoons Chica and Grande are largely determined by the high mineralization of the water, most of the resident species being widely recognized as halophilous or tolerant of a wide range of water mineralization, and by the concomitant high intensity and frequency of disturbance in the sediment. Continuous anoxia, sulphide production and the compact layer of salt precipitates in these lagoons appear to deplete the abundance of sedentary detritivorous‐phytophagous species, but allow a stronger representation of highly mobile facultative predatory taxa (e.g. Proclucliiis) which are more able to withstand this constantly stressed environment, as in the profundal benthos of eutrophic aquatic systems with long‐lasting periods of anoxia.

The Relationship of Habitat Characteristics to the Distribution of Chironomidae (Diptera) as Measured by Pupal Exuviae Collections in a Large River System

ABSTRACT Floating chironomid pupal exuviae were collected throughout the Yakima River (Washington, USA) and tributaries in 1989 and 1990. All samples were taken during the October-November low-flow season and most sites were visited once with a sampling effort of approximately 10 minutes. Sampled stream segments ranged from 3rd to 7th order and elevation ranged from 140–1200 m. The total number of taxa distinguished in 77 samples was 150 with a mean of 24 per site. Species richness was not highly correlated with stream order or elevation. An ecological gradient defined by ordinating the taxa by site data was highly correlated with site elevation (r=.93). Comparison with published attributes of chironomid genera suggested that temperature regime was a dominant environmental variable controlling chironomid distribution in this basin. However, since most measured habitat variables were associated with altitude, their effects could not be separated. Cluster analysis of taxa by site data resulted in groupings ...

Chironomid community structure deduced from larvae and pupal exuviae of a chalk stream

Species abundances of Chironomidae (Insecta: Diptera) have often been excluded from studies of benthic river communities because of difficulties associated with sampling and identifying larvae. Chironomid pupal exuviae are easier to collect and identify and could be used to determine community structure if shown to be representative of local larval assemblages. Larvae were sampled along a 20 m chain secured over mid-channel gravels, upstream of two collection points for pupal exuviae. Proportional taxa abundances of pupal exuviae and larvae sampled from 130 m of stream were directly compared by a χ2 test of independence and also separately fitted to four models of species abundance distribution. Observed proportions of taxa were not independent of the life stage sampled. The greatest discrepancies occurred with species of pupal exuviae that were absent as larvae from the gravel. The log series model provided the best fit with both pupal and larval data. Collections of pupal exuviae had greater species richness and evenness than samples of larvae. This was considered to be a consequence of sampling larvae from the gravel habitat alone.

Chironomid emergence from an English chalk stream during a three year study

Chironomid pupal exuviae were collected from the same site on a third order chalk stream for three years at approximately monthly intervals. During the final year, larvae were core sampled from mid-channel gravel. Below-average flows were interrupted by an abnormally high discharge in February of the second year. Orthocladiinae dominated the list of emerging taxa, three species remained co-dominant for all three years. The proportions of emerging species of Chironominae exceeded those of Orthocladiinae during the two summers with the lowest discharge. Variations in species rank and abundance were correlated with variations in mean monthly discharge for each of the three years. A few emerging species were present in gravel as early instar larvae only, or rarely found as later instars. These early instars may have redispersed to marginal habitats. It was concluded that certain species exhibited temporal stability during perturbations in discharge

Monitoring the Effect of Sewage Effluent on the Oxford Canal Using Chironomid Pupal Exuviae

ABSTRACTCollections of chironomid pupal exuviae from the Oxford Canal were taken monthly from May to October 1991 at stations above and below the sewage effluent discharge at Kidlington, near Oxford.The chironomid exuvial assemblages showed clear changes reflecting the effects of the sewage, notably in the increased dominance of Parachironomus arcuatus and Chironomus riparius and other pollution‐tolerant species downstream from the effluent inflow. A return to the pattern of taxa seen in the upstream stations was noted below the next canal lock, 2.8 km downstream from the effluent discharge.Environmental quality indices, calculated according to the Chironomid Pupal Exuvial Technique, also reflected the effects of the sewage inflow.The results show that chironomid populations, as sampled by collecting pupal exuviae, are potentially valuable for monitoring organic pollution in canals.

Chironomid pupal exuviae and larvae of two storage reservoirs in The Netherlands

For three years chironomid larvae were collected bimonthly with a grab sampler in two deep storage reservoirs in The Netherlands. Chironomid pupal exuviae were collected monthly, from April to November, with a handnet. Net samples yielded more taxa than grab samples. The taxa found in net samples originated from more habitats, than taxa found in grab samples. The relative contribution of Orthocladiinae was much larger in net samples. Based on the results obtained in the two reservoirs, some advantages and disadvantages of both sampling methods are discussed.

Water quality changes of the river Meuse assessed by chironomid pupal exuviae

The chironomid fauna of the river Meuse in Belgium and The Netherlands was studied in order to determine spatial water quality variations. Because the river Meuse serves as a source for drinking water production for about five million people in Belgium and The Netherlands, water quality is an essential factor to be studied. From 1984 till 1989 pupal exuviae were collected. Water quality was assessed by several indices and autecological information of the various taxa. With regard to pollution the general trend through the years was the same. The most upstream sampling site, in the Belgian Ardennes, was relatively unpolluted. As a result of untreated industrial and municipal wastewater discharges in the Liege region, water quality deteriorated dramatically at the Dutch border. At the most downstream sampling site, near the river mouth, a slight recovery was observed. Apart from organic and inorganic pollution other environmental factors such as flow velocity and the nature of the riverbed, also play a significant role in the occurrence of the organisms. It is concluded that protective measures need to be taken to restore the affected river ecosystem.

Diel emergence patterns of drifting chironomid (Diptera) pupal exuviae in the Aude River (Eastern Pyrenees, France)

Two diel emergence patterns (April and October 1990) of chironomids from a hyporhithral site (4th–5th order) in the Aude River are described. In April, 62 species were collected with a mean hourly richness of 31 (±4). The Orthocladiinae (91%) largely dominated the emergence. The total number of exuviae captured by one drift-net varied from 1300 to 11600 per one hour period. There was a clear bimodal pattern with peaks post dawn (07.00–09.00 hrs) and around sunset (18.00 hrs).

Emergence of Chironomidae (Diptera) from a delta-swamp receiving thermal effluent

Chironomid pupal exuviae were collected over an eight-week period from a delta-swamp which receives thermal effluent from a nuclear reactor on the Savannah River Plant, South Carolina, USA. Two sites were sampled using box-type emergence traps. Site 1 was directly in a major thermal plume channel, and site 2 was outside the plume in a stand of stressed bald cypress trees. Sixteen chironomid taxa were collected, of these, species of Chironomus (42%) and Tanytarsus (35%) dominated the warmer site (site 1, maximum temperature 46 °C), whereas Tanypus neopunctipennis comprised > 84 % at site 2 (maximum temperature 43 °C). Emergence substantially increased at both sites after the reactor was shut down and water temperatures returned to ambient (27–28 °C). Tanytarsus sp. 1 and T. neopunctipennis were capable of successfully emerging during water temperature periods of 40–46 °C. The deep organic sediment, characteristic of the delta-swamp apparently served as a refugium for these and other species of midges during high temperature periods. It is suggested that the ability of some taxa to tolerate these elevated temperatures may be a combination of several factors: behavioral and ecological adaptations to utilize available refugia; and physiological adaptations to withstand higher temperatures and low dissolved oxygen concentrations.

A survey of the distribution of chironomidae (Diptera, Insecta) of the river rhine by sampling pupal exuviae

During the period from 1981-07-23 to 1981-08-10, the River Rhine, from the Alps to the North Sea, was sampled for chironomid pupal exuviae. Samples were also taken from the Grande Canal d'Alsace and from selected tributaries. In all 78 samples were taken, of which 9771 exuviae were examined and 135 taxa identified. A species list is given showing the distribution of taxa between the principal regions of the river (Appendix 1). Samples were also taken to show the ‘within-sample’ and ‘between-sample’ variability, and one pair of samples was used to demonstrate the difference between the two banks of the river below the junction with the Main. The Rhine above the Bodensee has a diverse fauna dominated by Orthocladiinae. The Hochrhein near the entry of the River Aare, and the River Aare itself, also have a diverse fauna, but include many sediment-dwelling Chironominae. Below Strasbourg the fauna changes markedly, losing most of its sediment-dwellers, and shows a great increase of pollution-tolerant species. The fauna generally becomes less diverse and of poorer quality throughout the Oberrhein sections, and faunal changes are demonstrated that are related to the inflow of the Rivers Neckar and Main, Samples from the Mittelrhein gorge and the Niederrhein are generally dominated by two species ofRheotanytarsus and show a progressive reduction of diversity coupled to an increase of pollution-tolerant species. The low proportions of sediment-dwellers in the Niederrhein and the Waal, suggests that the sediments are unsuitable for the support of a normal chironomid fauna.

The use of chironomid pupal exuviae in the surveillance of sewage pollution within a drainage system

Collections of chironomid pupal exuviae were made during the summers of 1976 and 1977 above and below a number of sewage effluent discharges in the Bristol R. Avon drainage system. The effluents varied in their qualities, and discharged into rivers of different sizes. It was found that the exuvial collections showed changes in their species composition and relative species abundance which matched the overall polluting effects of the various discharges, the most change occurring below effluents of poor quality discharging into small rivers. The pollutional effects were more marked during 1976 when the rivers had unusually low flow, than in 1977 when the river flows were higher. It is concluded that biological changes consequent on sewage effluent discharge into these rivers can be monitored by sampling the chironomid pupal exuviae above and below the site of discharge.

Chironomid pupal exuviae in the River Chew

SUMMARY. Weekly skim‐net samples of chironomid pupal exuviae were collected at a single station on the River Chew, Avon, England, from September 1972 to September 1973. Eighty‐six types of exuviae were characterized in this study, of which sixty‐four made up only 4% of the year's catch. Thirty ‐eight percent of the year's catch was referable to Micropsectra atrofasciata Kieffer.The samples showed the expected maxima of numbers and species in spring and early summer. The emergence periods for many of the more common species were very extended, with one or more peaks.