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Twentieth-century historic industrial activity in Cornwall, ON loaded high amounts of metals and metalloids to the St. Lawrence River. Despite industrial improvements and the eventual closure of point-source polluters, sedimentary contamination in the Cornwall waterfront remains above provincial guidelines, causing concern for ecosystem management. We analysed chironomid (Order: Diptera) subfossils from modern-day surface-sediment samples and a sediment core from the Cornwall waterfront in order to better understand historic pollution impacts and potential recovery. Modern-day chironomid assemblages were diverse (48 genera, >70 species) and overall assemblage structure was weakly related to sedimentary zinc concentrations, with Procladius, Paratanytarsus, and Ablabesmyia identified as zinc-tolerant and Rheotanytarsus, Polypedilum and Paratendipes identified as zinc-sensitive. The sediment core showed peak total mercury (THg) concentrations were an order of magnitude higher than in modern-day surface sediments. In sections of the core below 10 cm in depth, THg concentrations were high (~30–50 µg/g) and chironomids were nearly absent from the record. Above 10 cm (c. 1980) THg concentrations decreased and chironomid taxa returned in low abundances. Subsequent intervals displayed an increase in diversity, abundance, and the relative abundance of metal-sensitive taxa. This study provides evidence of ecological change which co-occurs with Cornwall’s historic industrial activity and indicates progress toward related ecological goals identified in the current management strategy.

Multi-proxy analysis of a sediment core recovered from Lago Ditkebi in Chirripo National Park, Costa Rica, was undertaken to develop a multi-decadal to sub-centennial-scale reconstruction of Holocene hydroclimate and environmental change for the region. Analyses of sub-fossil chironomid assemblages, macroscopic charcoal, and bulk sediment geochemistry suggest that the glacial highlands in Chirripo National Park experienced notable hydroclimate variability, periodical burning by wildfires and climate-related vegetation change during the last ~8100 years. A single chironomid taxon, Procladius, most commonly associated with cold glacial lakes in Costa Rica, dominates the Holocene sub-fossil chironomid assemblage in Lago Ditkebi. Inferred from the proxy records, the interval between ~8100 and 5270 cal yr BP at the glacial highlands was relatively cold and dry with low effective moisture and limited fire activity. Cool and dry conditions were also observed between ~2820 cal yr BP and present but co-occurred with more frequent, low-severity fires. The highest fire frequency occurred between ~3300 and 1600 cal yr BP. The shifts in the chironomid assemblage and the low δ13C values detected between ~5270 and 2820 cal yr BP suggest a warm and wet climate and a decrease in abundance of Muhlenbergia, a C4 grass during that time. Concurrent maxima in C/N, charcoal accumulation and the abundance of thermophilous chironomid taxon, Polypedilum N type, at ~5200 cal yr BP are indicative of an abrupt climate change event that was characterized by rapid warming, quickly increased effective moisture and intense wildfires in the glacial highlands of Costa Rica.

The non-biting midge subfamily Tanypodinae (Diptera: Chironomidae) is species-rich, ecologically diverse, and near-globally distributed. Within the subfamily, aspects of generic and species-level taxonomy remain poorly understood, in particular the validity of assignment of Australian and New Zealand taxa to genera erected for northern hemisphere (Holarctic) fauna. Here, we place the austral diversity within this global context by extensive geographical and taxonomic sampling in concert with a multilocus phylogenetic approach. We incorporated sequence data for mitochondrial COI, and nuclear 28S and CAD, and conducted Bayesian and maximum likelihood phylogenetic inferences and Bayesian divergence time estimation. The resolved phylogeny supported many associations of Australian taxa with their proposed Holarctic congeners, with the exception of Apsectrotanypus Fittkau, and validates several taxa as endemic. Three of four New Zealand sampled taxa had their sister groups in Australia; New Zealand Monopelopia Fittkau was sister to a German congener. This included the first record of Procladius Kieffer from New Zealand. Most nodes connecting austral and Holarctic taxa clustered around the Cretaceous-Tertiary boundary (60-80 mya), whereas New Zealand-Australia nodes were generally slightly younger (53-57 mya). Together, these data contribute substantially to our understanding of the taxonomy, systematics and biogeography of the Australian Tanypodinae and more broadly to knowledge of Australia’s aquatic insect biodiversity.

Fish may affect macrobenthic communities through trophic interactions and modification of habitat conditions. We compared the density, diversity and taxonomic composition of larval chironomids under low vs high fish impact, created by stocking semi-natural ponds with either young/small common carp Cyprinus carpio at low biomass densities or with high biomass densities of older/large common carp, supplemented by other cyprinids and predatory fish species. Over the study season, May–August, total chironomid abundance was considerably lower in ponds with high fish biomass than in low fish biomass ponds. In July–August larval densities declined significantly, irrespective of the fish status of the ponds. The composition of larval communities diverged between ponds with different fish status. Chironomus riparius and C. plumosus accounted for most of the observed dissimilarity. C. plumosus densities were not affected by the fish status of the pond, constituting on average >38 % of chironomid specimens in both types of ponds. C. riparius was abundant in ponds with low fish biomass (on average 30 %), but rare in ponds with high fish biomass (4 %). Other common taxa were Glyptotendipes pallens (15 % and 13 %, respectively) and Procladius sp. (14 % in ponds with low fish impact). Canonical correspondence analysis showed that fish biomass was more important in determining chironomid community composition than environmental variables indicative of pond eutrophication (total N, P, chlorophyll a and conductivity). Despite adverse effects on total abundance, chironomid diversity was higher under apparently stronger trophic pressure by fish. Fish may have relieved some chironomid species from invertebrate predation and competition with dominant Chironomus larvae. Other important drivers of chironomid assemblage and diversity patterns may include species-specific feeding modes and prey size selectivity of fish, the ability of chironomid larvae to attain size- and depth-refuge from small fish but not larger fish, and differential vulnerability of free-living and tube-dwelling larvae relative to ontogenetic niche shifts of fish.

Sediment cores were recovered from Stella Lake and Baker Lake, sub-alpine lakes located in Great Basin National Park, NV, in 2005 and 2007, respectively. The cores were analyzed for subfossil chironomid (Insecta: Diptera: Chironomidae) remains. Chronologies for the sediment cores, developed using 210Pb, indicate the cores span the 20th century. The midge communities present in the lakes experience muted compositional change through much of the 20th century; however, the post-AD 1980 interval is notable due to rapid lake-specific faunal turnover. The recently deposited sediment in Baker Lake is characterized by decreases in the relative of abundance of Psectrocladius semicirculatus/sordillelus, Cladotanytarsus mancus group and Procladius, the local extirpation of Chironomus, and an increase the proportion of Sergentia, Tanytarsus type G and Tanytarsus type B. The Stella Lake midge community experienced a shift post-AD 1990 from an assemblage dominated by Tanytarsus type G to a P. semicirculatus/sordillelus dominated community. Application of a chironomid-based inference model for mean July air temperature (MJAT), based on a calibration set developed for the Inter-Mountain West of the United States consisting of 79 lakes and 54 midge taxa (rjack2 = 0.55 °C, RMSEP = 0.9 °C, maximum bias = 1.66 °C), provided a means to reconstruct the 20th century temperature regime for the region. Stella Lake and Baker Lake experience large fluctuations in MJAT during the early to mid-20th century and consistently above average temperature during the late-20th century. The chironomid-inferred MJAT reconstructions for Stella Lake and Baker Lake track observed July temperature in the region encompassed by Nevada Climate Division #2 during the late-20th century.

Located in the Yunnan-Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211 km(2), with maximum depth of 155 m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824 ind/m(2) in density, 3.72 g/m(2) in biomass) than in the profundal region (23 ind/m(2) in density, 0.10 g/m(2) in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos. (C) 2008 Elsevier GmbH. All rights reserved.

We conducted an extensive survey of the benthic macroinvertebrate fauna of the heavily polluted Buffalo River (New York) Area of Concern (AOC), with specific emphasis on assessment of morphological deformities of aquatic larval midges (Chironomidae: Diptera). Sediments were sampled on seven occasions during 1990 - 1991, from as many as 20 sites. Abnormal mouthparts (menta) were most frequent among larvae of the genus Chironomus, occurring in 29.0% of all specimens in the Buffalo River (n = 755), and 22.4% in the adjacent Ship Canal (n = 98). Individual sites in the downstream section of the river yielded even higher deformity frequencies; 36.9% (n = 84), 48.1% (n = 27), and 66.7% (n = 9). The frequencies of abnormalities in this genus at all sites within the AOC were well above levels normally observed (0 - 3%) at non-industrial sites. Additionally, abnormal mouthparts (ligulae) were seen in 3.1% of larvae of the genus Procladius (n = 1,677). While individual downstream samples of Procladius were occasionally as much as 15.4% abnormal (n = 26), this genus was much less prone to morphological deformities than Chironomus. Abnormal menta were also noted in the genera Polypedilum, Cryptochironomus, and Dicrotendipes, but were infrequent. Community parameters such as richness and diversity of the chironomid fauna, and the prevalence of oligochaetes, provide further evidence of decreased environmental quality within the downstream reaches of the Buffalo River. The data presented here provide one biologically relevant measure against which to gauge the effectiveness of pollution abatement strategies within the AOC.

The benthic macroinvertebrates of the nearshore zone of Lake Erie in the vicinity of Cleveland, Ohio, were sampled at 12 stations in October 1988 and May 1989 to determine the present pollutional status of the benthic community and to record changes over the past decade. The most abundant macroinvertebrates were, respectively, oligochaete worms, sphaeriid clams, and chironomid larvae. Of 75 taxa identified, 22 were oligochaetes, 16 were chironomids, and 11 were mollusks. Community composition in most of the harbor was suggestive of highly organically enriched sediments and was dominated by five tubificid worm species and pill clams (Pisidium spp.). The open water community, representative of less enriched conditions, was dominated by the tubificid Limnodrilus hoffmeisteri as well as Pisidium spp. and midges of the Chironomus anthracinus? group. Improvement in the habitat quality of the study area, including the harbor, since the late 1970s was evident from a dramatic increase in the number of taxa at all sites, a reduction in the proportion of oligochaete worms, a large increase in the abundance of sphaeriid clams and midge larvae, and the widespread distribution though low abundance in open water sediments of caddisfiy larvae (Oecetis sp.) which were absent in the late 1970s. Midges of the genus Chironomus remained largely absent from the harbor, and the abundance of the genus Procladius remained low around the mouth of the Cuyahoga River. The abundance of oligochaete worms has increased substantially around the river mouth over the decade. This increase may indicate an actual improvement of conditions overall, as might be expected with declining concentrations of toxic substances but continued organic enrichment of the sediments.

Morphological deformities in Procladius (Holotanypus) sp., Procladius (Psilotanypus) bellus (Loew), Clinotanypus, Coelotanypus, Psectrocladius (Psectrocladius) type sp. 2, Chironomus plumosus type, Chironomus thummi type, Cryptochironomus sp. 1, Cryptotendipes, Dicrotendipes, Parachironomus arcuatus group sp. 1, Paralauterborniella, Paratendipes, Polypedilum, Tribelos, and Tanytarsini type a larvae are described and compared. The most severely deformed larvae in Lac St. Louis were found in close proximity to the industrial complex around Beauharnois, Quebec, an area known to be seriously contaminated by PCBs and heavy metals. Further away, and particularly in areas shielded from the main flow of the St. Lawrence by the Iles de la Paix complex, the frequency and severity of deformities decreased. Interpretation of contaminant responses was less easily accomplished in the Laprairie basin where the introduction of untreated domestic sewage imposed extremely severe environmental conditions for benthos. Comparison of contemporary and subfossil community diversities indicate that extensive changes have taken place in the structure of these communities in recent times. The presence of deformities in contemporary chironomid communities suggests that these changes have been brought about, in part at least, by chemical contaminants.

The benthic macroinvertebrates of the central basin of Lake Erie were sampled with a Ponar grab in the summers of 1978 and 1979 along a 155-km reach of the nearshore zone (≤ 12 km offshore) in Ohio, U.S.A., at depths of less than 20 m. The major groups and their most abundant species were, in order of overall abundance, Oligochaeta (Limnodrilus hoffmeisteri, L. cervix-L. claparedeianus group, L. maumeensis), Sphaeriidae (Pisidium casertanum, P. henslowanum, Sphaerium corneum, Musculium transversum), and Chironomidae (Procladius sp., Chironomus spp.). The average abundance of oligochaetes in the harbors was 21,000 individuals m−2 in 1978 and 12,700 m−2 in 1979, compared with 1,500 m−2 and 1,200 m−2, respectively, in the areas outside of harbors. Comparison of the macrobenthic assemblages with those in other regions of the Great Lakes, using several numerical indices as well as indicator species distributions, indicated that the general area of the nearshore zone outside of harbors possesses a moderate degree of organic enrichment, with a gradient of decreasing pollution in an offshore direction. The harbors appeared to be severely degraded, as reflected by the high densities of oligochaetes and the almost complete absence of all but the most pollution-tolerant species. The documentation of species distributions will enable future assessments of changes in the nearshore benthic communities.

Association analysis of data on benthic macroinvertebrates in 257 samples from Georgian Bay, followed by discriminant analysis of water and sediment characteristics, facilitated a quantitative description of trophic variability within a relatively unpolluted system. Discriminating variables were bottom water temperature, water pH and Ca, sediment organic matter, sand, silt, clay, total P, Zn, Pb, and Hg. Four discriminating functions, accounting for 86% of variance, indicated the importance of temperature first, concentrations of organic matter and silt (with sand negative) second, and, in the third and fourth functions, water pH and Ca. Associations which occurred at cooler temperatures consisted of Pontoporeia hoyi with dominant oligochaetes and chironomids generally determined by sediment richness (organic matter and silt content primarily). These associations were P. hoyi — Limnodrilus hoffmeisteri — Chironomus spp. and Procladius spp. at highest sediment richness, P. hoyi — Spirosperma ferox-Micropsectra spp. at intermediate richness and P. hoyi — Stylodrilus heringianus — Heterotrissocladius sp. at lowest richness. Associations in warmer waters consisted of a Chironomus spp. — Chaoborus spp. association in richer sediments and an association of Caecidotea racovitzae and Amnicola spp. at lower sediment richness. A Hexagenia limbata––Hyalella azteca association occurred over a broad range in concentrations of organic matter and silt, but, in terms of sediment texture represented by sand content, this association was intermediate between the other two groups in warmer waters. Finally, a Zalutschia zalutschicola — Chaoborus spp. association, which occurred in only one bay where seasonal acidification was suspected, was related to water pH and Ca in discriminant analysis. These observations on distribution of benthic macroinvertebrates in response to abiotic gradients in a relatively unpolluted system should assist in interpretation of observations on enriched systems where influences of natural and cultural factors often may be confounded.

The benthic community in an outdoor model stream was exposed to the organophosphorus insecticide temephos, at a concentration of 5 mg litre−1 for 30 min, or chlorphoxim at 2 mg litre−1 for 3 h. Three species of chironomids were predominant in this stream in the first experiment, together with Hydropsychodes brevilineata in the second experiment. Both insecticides killed the majority of the zoobenthos, and resulted in a bloom of epilithic algae. The extent of grazing pressure by chironomids on algae was assessed. The chironomid populations recovered quickly but the trichopteran larvae recovered slowly. There were some differences in the toxicity between the two insecticides. Paracyclops fimbriatus and Procladius sp. were affected only by chlorphoxim.