Chironomid Emergence Research Articles

Effects of ivermectin-spiked cattle dung on a water–sediment system with the aquatic invertebrates Daphnia magna and Chironomus riparius

A two-species test using a water–sediment test system was performed to investigate chronic effects of the parasiticide ivermectin on Daphnia magna and Chironomus riparius. To simulate exposure by direct excretion of cattle into surface waters, ivermectin was applied via spiked cattle dung. The parasiticide was applied once, at concentrations ranging from 11 to 1314 μg kg −1 dung dry weight. The highest concentration corresponds to the maximum concentration in dung 3 days after topical application to cattle. Test vessels were stocked with chironomid larvae and daphnids of defined, mixed age. Replicates were sampled 10, 24, 38 and 51 days post application. Survival, growth and emergence of chironomids, and abundance and biomass of daphnids were evaluated. In case of extinction of the D. magna population in all replicates of a concentration level, daphnids were re-introduced into the remaining vessels of this concentration to simulate immigration. In addition, a second batch of chironomid larvae was introduced into the vessels on day 27 post application. At 1314 μg ivermectin kg −1 dung dry weight, survival, larval growth and emergence of the initially stocked chironomids were strongly affected. A significant effect on emergence was also observed for the second batch of chironomids. The two highest test concentrations led to 100% mortality of the initially stocked daphnids. At 1314 μg kg −1 dung dry weight, no daphnids survived following re-introduction on days 11, 28 and 42. At 263 μg kg −1 dung dry weight, the daphnids that were re-introduced on day 11 survived and reproduced, but abundance and biomass were reduced. The results of the present study indicate that following single application, toxic ivermectin concentrations persisted for an extended period. Possible effects on aquatic invertebrates, which may be caused by direct excretion of ivermectin-containing dung into surface water, deserve further attention.

Phenological patterns of neotropical lotic chironomids: Is emergence constrained by environmental factors?

Abstract In this paper we analyzed the emergence phenology of a highly diverse chironomid assemblage to test for association between emergence and some environmental variables and for the presence of synchrony in emergence. We used a time series of 48 weekly samples from a tropical low order forested stream (south‐eastern Brazil) to describe how this assemblage varied in an intra‐annual scale. An eigenvector‐based filtering approach was adapted to create temporal variables that could be used in our multiple regression analyses, trying to overcome the problems of temporal autocorrelation. Emergence of the Chironomidae, two subfamilies, concordant species, and of dominant species was not related to rainfall, temperature, moon phase or photoperiod. Taxonomic composition and species richness did not change across time. The number of emerging individuals of the subfamily Orthocladiinae was significantly related to temperature and to temporal filters. The inclusion of the temporal filters into the analyses almost eliminated autocorrelation in the regression residuals. We detected interspecific synchrony in a group of species, but an absence of trends and periodicity in chironomid emergence, which was not related to environmental variables. This suggests that unknown factors, differing from those known to control emergence in temperate regions, operate in the tropics. The erratic behaviour of the analyzed series raises the question of whether chaotic dynamics may generate this variability.

Just add water: sources of chironomid drift in a large river floodplain

Although seasonal floodplains represent one of the most dynamic and productive of aquatic ecosystems, the sources of this productivity are poorly understood. We examined composition and sources of chironomid drift in the Yolo Bypass, the primary floodplain of the Sacramento River. We found that invertebrate drift during winter floodplain inundation is dominated by a single species, the newly identified chironomid Hydrobaenus saetheri (Diptera: Chironomidae). In order to determine sources of chironomids in the Yolo Bypass, invertebrates were sampled from several potential sources prior to and during initial floodplain inundation. Rehydration of dried floodplain sediments from several locations showed that H. saetheri dominated insect emergence from this colonization pathway. By contrast, H. saetheri was not a substantial component of inundated floodplain ponds or of tributary inputs to the floodplain. We conclude that the initial pulse of invertebrate abundance in Yolo Bypass floodwaters is dominated by chironomid emergence from sediments in multiple regions of the floodplain.

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.

Biological Assessment of Cannon Creek, Missouri by Use of Emerging Chironomidae (Insecta: Diptera)

A biological assessment was done to determine the impact of heavy metal discharge from the Schuykill Metals Recycling Plant (SMCP) on Cannon Creek, Missouri, its receiving stream. The relationship between sediment chemistry and chironomid emergence was examined. Twenty-four heavy metals and nutrients from the SMCP discharge effluent were examined in Cannon Creek from above the effluent, at the effluent, and below the effluent. Five heavy metals (barium, cadmium, lead, manganese, and zinc) and sodium varied significantly between sites. Changes in community composition, mean abundance of emerging chironomids, and Kansas Biotic Index Values were used to detect impairment by heavy metals and nutrients in Cannon Creek. Concentrations of lead and zinc in Cannon Creek were at levels potentially lethal to chironomids, yet mean abundance of emerging chironomids actually increased with the increase of heavy metals and nutrients and showed a strong and positive correlation with barium and sodium, and a weaker correlation with increases in lead and cadmium. Chironomid diversity patterns did not correlate with the concentrations of heavy metals in Cannon Creek. Community similarity between sites was greatest between the reference site and the site at the SMCP discharge effluent. Low similarity between sites was attributed to gross changes in stream morphology rather than to any effects from the SMCP effluent. Finally, the KBI tolerance values to heavy metals for chironomids in Cannon Creek were above those encountered in the reference condition for the Western Cornbelt Plains Ecoregion, indicating minimal impairment.

Chironomidae (diptera) responses to the experimental flooding of prairie marshes

This study examined chironomid responses to the flooding of ten drained experimental marshes in Delta Marsh, Manitoba, Canada. Emergence traps were used to monitor chironomid emergence from three vegetation types (Symphyotrichum ciliatum, Scolochloa festucacea, and Schoenoplectus tabernaemontani) flooded at two water depths (shallow: 20–40 cm, deep: 50–70 cm) over a four-year period. The greatest number (7,651 m−2 yr−1) and biomass (20.3 g m−2 yr−1) of chironomids emerged from Schoenoplectus-deep sites in the fourth year of flooding. Numbers, biomass, and size classes of emerging chironomids were similar over the four years from the Symphyotrichum habitat. However, chironomid emergence from Scolochloa and Schoenoplectus habitats was dominated initially by the smallest size class but shifted steadily toward production of much larger species over the four-year experiment. The production of chironomids as a potential food resource for waterfowl was high from the Symphyotrichum habitat during all four years of flooding, but emergence from the Scolochloa and Schoenoplectus habitats did not reach comparable levels until the third or fourth year.

Evaluation of a Multi-species Test System for Assessing Acute and Chronic Toxicity of Sediments and Water to Aquatic Invertebrates: Effects of Pentachlorophenol on Daphnia magna and Chironomus prasinus (6 pp)

Single-species toxicity tests are currently used as main tools for assessing effects in ecological risk assessments. Nevertheless, in higher-tier evaluations, alternative ecotoxicological methods can be required. Alternative methods should cover more realistic exposure conditions and/or additional species or endpoints. Water/sediment systems can be considered for covering additional exposure routes. A typical feature of water/sediment systems is the modification of exposure levels with time. The simultaneous exposure of different species within the same system can cover differences in sensitivity and relevance of exposure routes. The aim of this study was to develop a water/sediment test that could detect relevant effects on two selected species and explore the relevance of sediment and waterborne exposure routes. This alternative method may provide relevant information facilitating the design of microcosm and mesocosm studies. A multi-species water/sediment system was designed using two invertebrates: Chironomus prasinus a benthic detritivore invertebrate and Daphnia magna a pelagic filtering invertebrate was designed. Seven static water/sediments systems were built up: two controls and five treatments where sediments were spiked with NaPCP at nominal concentrations of 1.25, 2.5, 5, 10 and 20 mg/kg, respectively. Each system contained caged and free (unrestrained) Daphnia magna organisms to consider differences in the exposure route (through sediment and/or water column) and Chironomus prasinus organisms. Fate and partitioning of PCP within the water/sediment compartments were assessed. Acute (lethality) and chronic effects (reproduction) for Daphnia magna were monitored after 48 h and 16 days of exposure, respectively. Adult emergence and oviposition success of Chironomus prasinus were monitored at the end of test (16 days). Mortality and reproduction inhibition of Daphnia magna occurred at the two higher doses, corresponding to maximum measured PCP water concentrations of 1.95 and 0.746 mg/l, respectively. Chironomus prasinus was less sensitive to PCP than Daphnia magna. Concentrations inhibiting reproduction and provoking almost 100% adult mortality in D. magna only reduced slightly the emergence and reproduction of chironomids. The experimental design focussed on suitability of the system for assessing simultaneously assessing effects on D. magna and C. prasinus instead of calculations of toxicity endpoints for PCP. The results indicate that this experimental design can be useful to the field of sediment/aquatic toxicity testing, particularly through the comparison with single- species results. Assessment of relative contribution of two exposure routes for Daphnia magna and complementary chronic endpoints derived from two different species can be achieved. Another advantage is that differences in reproduction strategies of selected species (sexual vs. parthenogenetic) should permit one to detect mechanisms of action associated to with endocrine disrupters. The feasibility of a two-species test built-up in an artificial sediment/water system has been demonstrated. This experimental design represents a cost/effective test which can assess effects through water and sediment pathways and incorporates several relevant chronic endpoints in a single assay. By building on the experience gained, improvements for further test designs are discussed. Test validation with a set of model chemicals will contribute to address the effectiveness of the test developed as comparing compared to single- species tests.

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 sediment toxicity and arsenite concentration with bacterial and traditional methods

Three sediment samples LP (pool where logs are stored), LF (brook through landfill area), KN (Kaskesniemi) which is in Lake Pyhäselkä downstream from the mill, were taken from an old sawmill area and one from the unpolluted Lake Höytiäinen. The arsenite concentration was measured by GFAAS and two arsenite biosensing bacterial strains Pseudomonas fluorescens OS8 (pTPT31) and Escherichia coli MC1061 (pTOO31). The toxicity of sediment and pore water samples was determined by using luminescent bacteria (Flash test) and, further, whole sediment toxicity was measured using 10 days growth test and 50 days emergency test with midges ( Chironomus riparius). With the flash test a lowered EC50 value was found only in sediment LF (EC50=0.17 v/v%). The Flash test indicated that all sediment samples taken from the sawmill area were highly toxic to bacteria, whereas growth and the emergence of chironomids showed no effects in other samples than LF. The midges tolerate well the contaminated environment. In contrast, bioavailability of arsenite of sediment samples KN and LF was quite high determined using the biosensor-strains in a direct contact assay. The bioavailable fraction of sediment LP was 6–10% out of the total arsenite concentration obtained with GFAAS (0.46–0.77 μg g −1 dw). The results show that the choice of analysis method grossly affects the outcome without any of the method giving an incorrect result. Different methods measure different parameters of a toxic sample and can thus be used to complement each other.

Toxicity of 4-Nonylphenol to Tubifex tubifex and Chironomus riparius in 28-Day Whole-Sediment Tests

Concern has been growing recently over the toxicity and the mimicking properties of 4-nonylphenol (4NP), the most persistent breakdown product of the nonionic surfactant nonylphenol ethoxylates, broadly used in industrial cleaning processes. Twenty-eight-day tests were performed to evaluate the toxicity and the effects on reproduction of 4NP spiked sediment to the benthic invertebrates Tubifex tubifex and Chironomus riparius. 4NP was directly added to the wet sediment, avoiding any solvent. The EC 50 value for the emergence of chironomids was 380 μg 4NP g −1 dry weight (dw); the EC 50 values for the deposition of cocoons and the development of young worms were very similar (428 and 420 μg g −1 dw, respectively). Regarding NP estrogenic activity and its effects on reproduction and development, no significant differences were noted in the sex ratio of the emerged chironomids when exposed to 4NP compared to the controls, but the emerged chironomids did not lay eggs at concentrations higher than the EC 10 (250 μg 4NP g −1 dw). Furthermore, at concentration of 610 μg 4NP g −1 dw an interference in the development of the gonads of adult worms was observed, but it was impossible to determine whether this effect was due to 4NP toxicity or to its hormone mimicking properties.

Effects of deposited sediment on invertebrate drift: An experimental study

The effect of deposited sediment on invertebrate drift was experimentally assessed by adding fine sediment to three of six cobble‐lined artificial channels. One invertebrate species, Deleatidium spp., was added to the channel after the addition of sediment, whereas other taxa had colonised the channel naturally before the addition of sediment. Invertebrate drift was collected from each channel after the added sediment had worked its way into the interstitial spaces of the cobbles. Drift was collected every evening and morning for 3 days, after which time benthic densities in the channels were assessed. The percentage of benthos in the drift was significantly higher from sediment‐treated channels than from untreated channels for Paracalliope fluviatilis, Oxyethira albiceps, Hydrobiosis sp., and chironomid larvae. Drift of these animals from sediment‐treated channels was more than double that from untreated channels, with an average of over 5% of the benthos drifting from the sediment‐treated channels per day. Although there was no difference in the percentage of Deleatidium in the benthos that drifted from treated or untreated channels, significantly more individuals drifted from treated channels. Deposition of fine sediment had no significant effect on chironomid emergence or diurnal drift patterns for the taxa in the experiment. Periphyton communities in sediment‐treated channels were characterised by reduced chlorophyll a and increased inorganic content. We could not determine whether increased drift caused by deposited sediment reflected decreases in suitable habitat, reductions in food quality of the algae, or both.

Did chironomid emergence release Daphnia from fish predation and lead to a Daphnia-driven clear-water phase in Lake Towada, Japan?

The emergence of the chironomid pupae into the water column may potentially allow Daphnia to be released from positively size-selective fish predation and indirectly cause a Daphnia-driven clear-water phase in lakes. We studied these processes in Lake Towada, Japan, from April to October 1998. The biomass of the Daphnia longispina population was stable from April through June and increased by 3-fold in mid-July. This coincided well with the onset of the clear-water phase in the lake. The sharp decline of chironomid larvae in the sediment in June suggested that the major emergence occurred. Stomach contents of kokanee (Oncorhynchus nerka) and pond smelt (Hypomesus transpacificus nipponensis) also shifted from D. longispina to the chironomid pupae at that time. However, mean individual body size, mean ovigerous female size and clutch size of D. longispina declined rapidly in mid-June and stayed smaller thereafter compared to those in April–May, suggesting that fish predation was stronger after mid-June. It is probable that lower water temperatures in April–May suppressed fish feeding activity as well as reproduction in D. longispina, which resulted in the stable biomass of D. longispina. The increased water temperatures resulted in the stable biomass of D. longispina. This would lead to a mid-July peak of less predation-sensitive young adults. Therefore, the chironomid emergence seemed neither to release D. longispinafrom fish predation nor to be associated with the clear-water phase in the present study.

Influence of sexual dimorphism in Chironomus riparius Meigen on toxic effects of cadmium

AbstractSecond instars of Chironomus riparius Meigen were exposed to different concentrations of Cd‐spiked sediment to determine effects on males and females. The wet weights of the larvae were determined after 10 d of exposure. The animals were then returned to the sediment and allowed to emerge. Time to emergence, sex, and adult survival time were recorded. Larval weights declined with increasing Cd concentrations, but the concentration–weight responses of males and females were similar. Hence, the impact of sexual dimorphism on growth measurements in sediment toxicity tests is likely to be small. The cumulative emergence of male and female chironomids did not differ significantly between sexes, except at Cd at 3,200 mg/L (measured sediment concentration 317 μg/kg). Adults emerged from controls between days 9 and 10 and from treatments up to and including Cd at 3,200 mg/L treatment within 18 d. Only one adult emerged from the treatment with Cd at 12,800 mg/L (measured sediment concentration 446 μg/kg), and time to emergence was delayed until day 30. This study has confirmed that Cd in sediments can reduce the survival, growth, development, and emergence of C. riparius, and that emergence patterns may differ between the sexes at higher concentrations of Cd. However, the difference between sexes in effects on larval growth will not greatly influence the results of toxicity tests if test treatments contain different proportions of males and females. Whether survivorship of the sexes differs when larval stages are exposed to Cd remains unclear.

Abundance and Seasonal Trend of Dominant Chironomid Adults and Horizontal Distribution of Larvae in Eutrophic Lake Suwa, Japan.

The abundance and seasonal trend of chironomid emergence and the horizontal distribution of larvae were studied in Lake Suwa from April 1990 to December 1991. A total of 18 species of chironomid adults were captured with a light trap set up on the eastern shore of the lake, and 11 species with bottom-type emergence traps at 2.5 m water depth. Abundant species in the light trap were Chironomus plumosus, Einfeldia dissidens, Propsilocerus akamusi, Procladius choreus, and Glyptotendipes tokunagai. In particular, the former three species constituted 86% of all adults captured with the light trap. E. dissidens was first reported from this lake in the present study. C. plumosus had three emergence periods in 1990, but only two in 1991. The emergence of P. akamusi took place during October to November in both years. The emergence periods of E. dissidens, P. choreus and G. tokunagai occurred during May to October in both years without a marked emergence peak.In a grid survey of 68 points located at intervals of ca. 250-500 m, C. plumosus larvae were mainly distributed in the profundal zone. P. akamusi larvae had the widest distribution with high densities at all stations. E. dissidens was more abundant in the littoral zone, showing significant negative correlations with water depth and loss on ignition.

Sensitivity ofDaphnia carinataSensu Lato to the Insect Growth Regulator, Pyriproxyfen

This paper reports the sensitivity ofDaphnia carinatasensu lato to pyriproxyfen, a promising chironomid control agent. Neonates exposed to pyriproxyfen in acute toxicity trials produced 48-hr LC50of 0.08 ppm, eight times the concentration known to control the emergence of nuisance chironomids. However, continuous exposure to pyriproxyfen (0.01 ppm) during a 3-brood, 14-day life cycle test, suppressed the growth ofD. carinataand reduced reproduction by as much as 80%.

Experimental acidification of a poor fen in northwestern Ontario: effects on emergence of Chironomidae (Diptera)

The effects of experimental acidification and N fertilization on chironomid emergence from a poor fen in northwestern Ontario were studied from 1984 to 1989. Experimental treatments did not affect the numbers of chironomids emerging weekly, the timing of emergence, or species composition of emergence during the study period. Weekly emergence counts were higher (P < 0.05) from the periphery of the fen than the central part. Total seasonal emergence was higher from the area previously burned in a forest fire than the unburned part of the fen, although the difference was not statistically significant. Stability of species composition, despite experimental treatments and physiographic differences in the fen, may be a widespread characteristic of Canadian acidic peatlands.

Chironomids fail to emerge from LAS-contaminated water

: The effect of the surfactant LAS was investigated on chironomid emergence using six outdoor artificial channels. The concentrations of LAS were mostly between 1 and 2 mgl(-1) in the three treated channels. Chironomus yoshimatsui, Cricotopus tamapullus, Eukiefferiella coerescens, Eukiefferiella sp. and Thienemanniella majuscula were the major chironomids obtained with emergence traps. The number of midges trapped did not differ significantly between the treatment and the control for either of the species. On the other hand, the ratios of midges failing to emerge to the total midges trapped was significantly higher in the treatment than in the control for all of the species. The results show that chironomids emergence is difficult as a result of LAS treatment probably due to the lowered surface tension.

The non‐lethal effects of predators and the influence of food availability on life history of adultChironomus tentans(Diptera: Chironomidae)

SUMMARY1. We used a laboratory experiment to determine effects of a predator (other than straightforward prey consumption) and food availability, during the larval stage, on adult size, age at emergence and fecundity ofChironomus tentans.2. Predator presence and decreased food availability resulted in reduced adult emergence.3. Predator presence and food availability resulted in smaller size and greater age at emergence of male and female chironomids. There were no significant interactions between effects of predator presence and food availability.4. Predator presence had no significant effect on fecundity.5. Smaller size and greater age at emergence can have important implications for adult survival, size and age at first reproduction and, thus, intrinsic rate of population growth.

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

Relative Importance of Algae and Emergent Plant Litter to Freshwater Marsh Invertebrates

We test the hypotheses that (1) algae are a major food source for marsh invertebrates and (2) plant litter serves mainly as cover for invertebrates and a substrate for algal growth rather than as a direct source of nutrition. Twelve enclosures (5-m diameter) were deployed in May in a nutrient-poor marsh of the Interlake region of Manitoba, six of which were fertilized to increase algal levels. The hardstem bulrush (Scirpus lacustris glaucus) litter present was replaced with a nonnutritive artificial substrate in half of the fertilized and unfertilized enclosures. Dominant taxa of nektonic herbivores–detritivores increased in abundance and biomass following algae manipulations but were not affected by the replacement of plant litter with a nonnutritive substrate. Epiphytic herbivores–detritivores responded to changes in both detritus and algal food sources, the importance of each factor varying among taxa. Fertilization resulted in early peaks of emergence for chironomids. In the first weeks of the study, chironomid emergence was not affected by the replacement of plant litter with a non-nutritive substrate. In August, however, more chironomids emerged in the treatments where plant litter was provided when compared with the artificial litter treatments.