Article

# Classification, assessment and trophic reconstruction of Danish lakes using chironomids

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## Abstract

1. Surface-sediment assemblages of subfossil chironomid head capsules from fifty-four primarily shallow and nutrient-rich Danish lakes were analysed using multivariate numerical techniques. The species data, comprising forty-one chironomid taxa, were compared to environmental monitoring data in order to establish a relationship between chironomid faunal composition and lake trophic state. 2. The subfossil assemblages were compared to the chironomid bathymetric distributions along transects from four lakes. Correspondence analysis and similarity coefficients showed that the subfossil assemblages, sampled in the lake centre, reflect the chironomid communities in the littoral at a depth of 2–7 m. 3. Two-way indicator species analysis (TWINSPAN) was used to classify the Danish lakes into five groups defined by trophic state, lake depth and pH. Eighteen chironomid taxa showed significant differences in abundance among the five groups. Canonical correspondence analysis (CCA) showed the chlorophyll a concentration ([Chl a]) and Secchi depth to be the variables best correlated to the faunal data, and fourteen taxa were significantly correlated to [Chl a]. 4. The strong correlation between chironomid data and the ln-transformed ([Chl a]) was used to create a weighted averaging (WA) model to infer lake trophic state. Several models were tested by cross validation (leave-one-out jack-knifing), and a simple WA model using inverse de-shrinking had a RMSEPjack of 0.65 (ln units) and a r2jack of 0.67. 5. The results can be used in the assessment and reconstruction of lake trophic state for long-term monitoring and palaeoecological investigations of shallow, temperate lakes in the mesotrophic to hypertrophic nutrient range.

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... Two minor reorganisations in the chironomid fauna occur during CM-C5 at 622-617 cm (13 710 ± 210 to 13 550 ± 150 cal a BP) and 612-608 cm (13 330 ± 320 to 13 120 ± 450 cal a BP) with Corynocera ambigua increasing markedly to 31% and 14%, respectively. C. ambigua thrives in cold, unstable, transitional environments (Brodersen and Lindegaard, 1999). A change in the composition of aquatic macrophytes may also be partially responsible as C. ambigua is often associated with charophytes (Brodersen and Lindegaard, 1999). ...
... C. ambigua thrives in cold, unstable, transitional environments (Brodersen and Lindegaard, 1999). A change in the composition of aquatic macrophytes may also be partially responsible as C. ambigua is often associated with charophytes (Brodersen and Lindegaard, 1999). Chara oospores were encountered during HC picking at depths where C. ambigua increased in abundance. ...
... Conditions may have been ultra-oligotrophic as inferred from the dominance of M. radialis-type (Brodin, 1986), which forms up to 52% of the assemblages. Another discrete peak of 58% in C. ambigua occurs at the start of this zone indicating another period of instability (Brodersen and Lindegaard, 1999). ...
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Three clearly defined abrupt cooling events (ACEs) can be observed within Greenland Interstadial (GI)-1 in the Greenland ice-core records. However, the spatial variation in amplitude and timing of these ACEs is poorly understood due to the paucity of well-dated records with quantified temperature reconstructions. This study presents high-resolution chironomid-inferred July air temperature (T Jul) and oxygen isotope (δ 18 O) records from Crudale Meadow (Orkney Isles, UK). Three centennial-scale ACEs punctuate the Windermere Interstadial at Crudale Meadow. The largest ACE shows an amplitude of 5.4°C and a 1% isotopic decline and is centred on~14.0 ka BP, consistent with the timing of the GI-1d event in the Greenland stratigraphy. The two other observed ACEs are of smaller magnitude and are centred on~13.6 ka BP and~13.2 ka BP, with these smaller magnitude events tentatively correlated with the GI-1cii and GI-1b events, respectively, but lack sufficient chronological constraint to fully assess their timing. When comparing the Crudale Meadow record with other locations in the British Isles a strong relationship can be observed between the magnitude of T Jul cooling and latitude, with a reduced signal in more southerly locations, indicating that oceanic forcing may be a key driver of the ACEs.
... All these factors indicate that each lake may respond individually and heterogeneously to these processes, as their chironomid assemblage composition differ from one to another, as well as their morphological and environmental characteristics. Moreover, such processes may affect certain taxa more strongly than others, leading to overor underrepresentation of certain taxa (Frey 1988;Brodersen and Lindegaard 1999;Eggermont et al. 2007). In fact, redeposition processes by sediment erosion and transportation are considered one of the most important sources of disturbance of chironomid remains (Kansanen 1986), which may lead to a misinterpretation of the environmental factors shaping subfossil assemblages. ...
... Whereas some studies found that most subfossil chironomids tend to remain where the larvae lived (Iovino 1975;Walker et al. 1984), van Hardenbroek et al. (2011) found that the remains are transported and redeposited offshore. The same contradictory patterns have been showed by studies focusing exclusively on the subfossil assemblage: whereas several studies found significant changes of the subfossil assemblage with depth (Frey 1988;Heiri et al. 2003;Heiri 2004;Kurek and Cwynar 2009;Luoto 2010;Cao et al. 2012;Karmakar et al. 2014), others (Frey 1988Schmäh 1993;Brodersen and Lindegaard 1999;Eggermont et al. 2007;Langdon et al. 2008;Holmes et al. 2009) did not found any significant depth pattern. ...
... This is an important finding, since assessing the ability of a single core to properly represent the whole assemblage should be a prerequisite to any paleolimnological study. Concordantly, other studies that did not find any depth-related pattern or threshold of the recent subfossil assemblage (Schmäh 1993;Brodersen and Lindegaard 1999;van Hardenbroek et al. 2011). Also, Heiri (2004) found that sediment cores taken at any part of the basin in shallow Norwegian lakes included the dominant taxa, although with varying abundances. ...
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Paleolimnological studies often rely on a single sediment core for reconstructing past environmental changes of an entire lake system. This involves a number of assumptions about the correct representativeness of the living assemblage by the subfossil assemblage. This paper is aimed at understanding the main drivers affecting the dispersion and transportation of Chironomidae head capsules, which may affect the correct interpretation of downcore changes through overrepresentation or underrepresentation of certain taxa. We analyzed the chironomid living assemblage of Enol Lake (Picos de Europa National Park, Spain) and compared the subfossil assemblage at different depths. We found a highly homogeneous composition and density of recent subfossil assemblage along the depth transect (i.e. dominance of the Tanytarsini Paratanytarsus austriacus-type), which would indicate that a single core retrieved at any depth would be representative of the lake community. However, the composition of the benthic living assemblage changed significantly with depth, suggesting the existence of a driving force behind the dominance of P. austriacus-type in the subfossil assemblage. We argue that the dense mats of Characeae present in the sublittoral area (from 2 to 8 m) are most likely responsible for this homogenization, since this is the preferred habitat of Paratanytarsus, which was found at very high densities at this depth. Thus, we conclude that the interpretation of past changes in the lake conditions should be made with caution due to the overrepresentation of P. austriacus-type head capsules along the depth transect. Our findings show that it is important to explore the relationship between the living and the recent subfossil fauna of each lake in paleolimnological studies, since understanding deposition and transport patterns can help to avoid misinferring past environmental and limnological conditions.
... Profundal; eutrophic X X X Pinder and Reiss (1983), Brodersen and Lindegaard (1999), Moller Pillot (2009) ...
... Oligotrophic X X Pinder and Reiss (1983), Brodersen and Lindegaard (1999), Moller Pillot (2013) Protanypus Profundal; oligomesotrophic X X Pinder and Reiss (1983), Brodersen and Lindegaard (1999) mucedo and Plumatella spp. as was the final post-1981 interval ( Fig. 6b; Table 2). K-means analysis for daphnid ephippia resulted in three time intervals in which assemblages differed significantly (ESM4e) at c. pre-1900-1955, 1956-1990 and 1991-present. ...
... Oligotrophic X X Pinder and Reiss (1983), Brodersen and Lindegaard (1999), Moller Pillot (2013) Protanypus Profundal; oligomesotrophic X X Pinder and Reiss (1983), Brodersen and Lindegaard (1999) mucedo and Plumatella spp. as was the final post-1981 interval ( Fig. 6b; Table 2). K-means analysis for daphnid ephippia resulted in three time intervals in which assemblages differed significantly (ESM4e) at c. pre-1900-1955, 1956-1990 and 1991-present. ...
Article
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Aquatic biodiversity is commonly linked with environmental variation in lake networks, but less is known about how local factors may influence within-lake biological heterogeneity. Using a combined ecological and multi-proxy palaeoecological approach we investigated long-term changes in the pathways and processes that underlie eutrophication and water depth effects on lake macrophyte and invertebrate communities across three basins in a shallow lake—Castle Lough, Northern Ireland, UK. Contemporary data allow us to assess how macrophyte assemblages vary in composition and heterogeneity according to basin-specific factors (e.g. variation in water depth), while palaeoecological data (macrophytes and co-occurring invertebrates) enable us to infer basin-specific impacts and susceptibilities to nutrient-enrichment. Results indicate that variability in water depth promotes assemblage variation amongst the lake basins, stimulating within-lake macrophyte assemblage heterogeneity and hence higher lake biodiversity. The palaeo-data indicate that eutrophication has acted as a strong homogenising agent of macrophyte and invertebrate diversities and abundances over time at the whole-lake scale. This novel finding strongly suggests that, as eutrophication advances, the influence of water depth on community heterogeneity is gradually eroded and that ultimately a limited set of eutrophication-tolerant species will become homogeneously distributed across the entire lake.
... It shows overall high occurrences in the mid-part of the lake sequence (local zones II-1 and II-2) with more stable T jul inferences. The modern distribution of C. ambigua in Finnish lakes is related to cold oligo-mesotrophic waters, but it is known to have a complex ecology (Brodersen & Lindegaard 1999). It is reported to dominate the assemblage in temperate lakes aswell (Brodersen & Lindegaard 1999), and in the Holocene record from Lake Loitsana, high numbers of C. ambigua have been related to macrophyte density, particularly of Myriophyllum (Shala et al. 2014b). ...
... The modern distribution of C. ambigua in Finnish lakes is related to cold oligo-mesotrophic waters, but it is known to have a complex ecology (Brodersen & Lindegaard 1999). It is reported to dominate the assemblage in temperate lakes aswell (Brodersen & Lindegaard 1999), and in the Holocene record from Lake Loitsana, high numbers of C. ambigua have been related to macrophyte density, particularly of Myriophyllum (Shala et al. 2014b). Myriophyllum is also well represented in the macrofossil record of local zone II-2 (Fig. 3B), but the high abundances of C. ambigua in the early half of local zone II-1 might be related to clear alkalinity water conditions. ...
Article
Few fossil‐based environmental and climate records in northern Europe are dated to Marine Isotope Stage (MIS) 5a around 80 ka BP. We here present multiple environmental and climate proxies obtained from a lake sequence of MIS 5a age in the Sokli basin (northern Finland). Pollen/spores, plant macrofossils, NPPs (e.g. green algae), bryozoa, diatoms and chironomids allowed an exceptionally detailed reconstruction of aquatic and telmatic ecosystem successions related to the development of the Sokli Ice Lake and subsequent infilling of a relatively small and shallow lake confined to the Sokli basin. A regional vegetation development typical for the early half of an interglacial is recorded by the pollen, stomata and plant macrofossil data. Reconstructions of July temperatures based on pollen assemblages suffer from a large contribution of local pollen from the lake's littoral zone. Summer temperatures reaching present‐day values, inferred for the upper part of the lake sequence, however, agree with the establishment of pine‐dominated boreal forest indicated by the plant fossil data. Habitat preferences also influence the climate record based on chironomids. Nevertheless, the climate optima of the predominant intermediate‐ to warm‐water chironomid taxa suggest July temperatures exceeding present‐day values by up to several degrees, in line with climate inferences from a variety of aquatic and wetland plant indicator species. The disequilibrium between regional vegetation development and warm, insolation‐forced summers is also reported for Early Holocene records from northern Fennoscandia. The MIS 5a sequence is the last remaining fossil‐bearing deposit in the late Quaternary basin infill at Sokli to be studied using multi‐proxy evidence. A unique detailed climate record for MIS 5 is now available for formerly glaciated northern Europe. Our studies indicate that interglacial conditions persisted into MIS 5a, in agreement with data for large parts of the European mainland, shortening the Last Glacial by some 50 ka to MIS 4‐2.
... Algal growth and availability were not specifically examined in this study, but in other studies have been found to be an important variable in influencing chironomid community structure in lakes (e.g. Moore 1981, Aagaard 1986, Brodersen and Lindegaard 1999. Also, macrophyte presence and distribution could lend further insight into chironomid community structure of the clearwater study lakes as AL had a littoral zone with an abundant mixture of macrophyte species not found in the same density, or at all, in the other lakes. ...
... Woodward and Shulmeister (2006) concluded that temperature and lake productivity, measured as chlorophyll-a concentration, were the most significant variables that influenced chironomid taxa in New Zealand. Brodersen and Lindegaard (1999) found that Secchi depth and chlorophyll-a concentration were best correlated to chironomid faunal data in Danish lakes. Moore (1981) showed algal density and availability stimulated by highly transparent water played an important role in chironomid communities in a northern Canadian lake. ...
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Chironomidae (Diptera) surface-floating pupal exuviae were collected monthly during the ice-free season in 2010-2011 from six lakes in the North Temperate Lakes Long-Term Ecological Research site in northern Wisconsin. The goal of this study was to determine whether chironomid community structure reflected differences in lake morphometry (i.e. depth, area, shoreline development, etc.), water chemistry and/or landscape position (i.e., elevation). Forty-six genera were identified from four subfamilies: Chironominae (57%), Orthocladiinae (28%), Tanypodinae (11%), and Diamesinae (4%). Tanytarsus, Ablabesmyia, and Psectrocladius were found in all six study lakes; whereas certain genera, such as Omisus, Protanypus, and Epoicocladius were each observed in only one lake. An analysis of abiotic variables revealed that pH, total phosphorus, and Secchi depth were the most important factors structuring chironomid communities in the NTL-LTER site clearwater study lakes, but a more complete suite of habitat variables that includes biotic factors (i.e., algal growth and availability and macrophyte characteristics) should be sampled in future studies to determine the importance of these variables. Elucidating the factors that influence chironomid community structure can lead to an improved understanding of chironomid ecology and distribution patterns in north temperate lakes and will be a valuable asset in examining the interplay of landscape position and biological communities in lakes.
... Such reconstructed past environmental conditions are based on multi-proxy studies combining sedimentary characteristics and biotic variables (Birks & Birks, 2006). For trophic state reconstruction, diatom and chironomid indicators are often used for their sensitivity to diverse aspects of trophic conditions (Brodersen & Lindegaard, 1999;Hall & Smol, 2010). Diatom and chironomid species composition is also affected by other factors including the abundance and diversity of macrophytes (Sayer et al., 1999;Brodersen et al., 2001;Sayer et al., 2010;Vermaire et al., 2013;Tarrats et al., 2018), water depth (Bennion, 1995;Barley et al., 2006) and chironomids additionally to the oxygen level (Brodersen & Quinlan, 2006). ...
... The most abundant chironomids of our record, namely Chironomus anthracinus-type, C. plumosus-type and Procladius (Fig. 5, Table 2), often produce very abundant populations in highly productive lakes with low clarity and oxygen depletion or anoxia near the bottom (Nagell & Landahl, 1978;Matěna, 1989;Hamburger et al., 1994). Characteristic cold stenothermic taxa inhabiting oligotrophic and well-oxygenated waters (e.g. the Heterotrissocladius grimshawi-type or Micropsectra spp.) are missing, although reported in many European records, including LG sediments of lowland shallow lakes (Brooks et al., 1997;Brodersen & Lindegaard, 1999;Płóciennik et al., 2011;Bos et al., 2017) or Czech LG lakes situated in elevations of above 900 m a. s. l. (Kletetschka et al., 2018). Furthermore, mesotraphentic species (e.g. the Derotanypus or Corynocera ambigua-type) present in regional mid-altitude lakes (400-900 m a. s. l.) (Hošek et al., 2014;Hájková et al., 2016) are also absent from Lake Komořany records. ...
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Shallow lowland lakes undergo long-lasting natural eutrophication processes, which can be studied through the development of communities of aquatic organisms. However, records showing millennial-scale trophic status variability in these water bodies are rare. Two radiocarbon-dated sedimentary profiles from former (now destroyed by brown coal mining) Lake Komořany (Central Europe, Czech Republic) served for a multi-proxy study of biological remains (diatoms, chironomids, pollen) supplemented by X-ray fluorescence (XRF) and loss-on-ignition (LOI). The age–depth model and palynostratigraphy confirm a continuous Late-Glacial to Early-Holocene record. The results suggest consistent in-lake conditions with high nutrient availability since the lake origin in the Late-Glacial period. A distinct shift at the Late-Glacial/Holocene boundary evidenced by an enhancement in diatom valve concentration and a lithological interface was foregone by a qualitative change in diatom and chironomid assemblages along with rise in LOI. It suggests that a major transformation occurred before the onset of the Holocene. As this qualitative change was characterized by a decrease in relative abundance of nutrient-demanding species, we propose an indirect climatic control by means of nutrient availability as the main driver of the aquatic species composition.
... The chironomid composition indicates a shift to more productive lake conditions, with the presence of mesotrophic-eutrophic taxa Endochironomus albipennis-type, Glyptotendipes pallens-type and Dicrotendipes nervosustype (Moller Pillot 2009). The appearance of Chironomus plumosus-type further highlights a shift to more productive lake conditions, as C. plumosus-type is a eutrophic taxon that has been used as an indicator of hypereutrophic conditions in Danish lakes (Brodersen and Lindegaard 1999) and is an early coloniser in the profundal of highly eutrophic lakes (Moller Pillot 2009). The substantial increase in NAPp between 3670 and 3425 BC along with proportional increases in eutrophic chironomid taxa signify intensification of early Neolithic farming at Cooney Lough. ...
... Chironomus anthracinus-type, Glyptotendipes pallens-type, Cladotanytarsus mancus-type and Tanytarsus mendax-type are the main responsive taxa at Lough Dargan, and Chironomus anthracinus-type, Cladotanytarsus mancus-type and Tanytarsus lugenstype are the main responsive taxa at Templevanny Lough. Each of these taxa is either associated with agriculturally active lake catchments in western Ireland today (Potito et al. 2014), or has been associated with productive mesotrophic-eutrophic lake systems (Moller Pillot 2009), and/or hypereutrophic conditions in other regions of Europe (Chironomus plumosus-type and Glyptotendipes; Brodersen and Lindegaard 1999). ...
Article
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This study explored the utility and performance of chironomid (Diptera: Chironomidae) autecology in the investigation of prehistoric farming impacts on freshwater lake systems. Chironomid subfossils, lake sediment geochemistry (δ¹³C, δ¹⁵N and C:N), pollen and macroscopic charcoal analyses were used in a comparative limnological assessment of three archaeologically rich study sites in northwest Ireland. At all three study sites, pastoral farming and its associated nutrient inputs, as represented by non-arboreal pollen indicative of grassland/pasture (NAPp) and lake sediment geochemistry, are concomitant with increases in eutrophic chironomid taxa. Redundancy analysis (RDA) and partial RDAs established that δ¹⁵N and NAPp were controlling factors of chironomid community compositional change during the Neolithic (4000–2500 BC) and Bronze Age (2500–600 BC). Bronze Age farming had a considerably greater impact on the lake systems than Neolithic farming, as indicated by a higher proportion of eutrophic taxa and increases in δ¹⁵N, C:N and δ¹³C values, consistent with increased erosion and agricultural inputs. Findings emphasise the importance of identifying the natural, pre-impacted state of a lake system to determine the extent of agricultural impact accurately. The timing and magnitude of change show that Neolithic and Bronze Age farming exhibited a strong control over chironomid communities at all three sites.
... For example, pioneering work by Thienemann (1918;1928) showed that the composition of profundal macroinvertebrate communities was strongly related to dissolved oxygen (DO) concentrations. This early work inspired the use of profundal macroinvertebrate communities to classify the trophic status of lakes (Thienemann, 1921;Saether, 1979;Brodersen and Lindegaard, 1999;Langdon et al., 2006). ...
... In conclusion, trophic state influenced the composition of the macroinvertebrate community of the eulittoral zone, but not as much as has been previously reported for profundal communities (Thienemann, 1921;Saether, 1979;Brodersen and Lindegaard, 1999;Langdon et al., 2006). Furthermore, our study showed that the effects of trophic state were nested within habitat type, and were partially superseded by biotic interactions and small-scaled habitat complexity (Fig. 5). ...
Thesis
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Das litorale Makrozoobenthos ist eine bedeutende biotische Komponente in Seen und trägt substantiell zur Biodiversität und Funktion von Seeökosystemen bei. Allerdings unterliegt das Litoral zunehmenden anthropogenen Nutzungen, deren ökologische Auswirkungen jedoch kaum quantifiziert wurden. In dieser Doktorarbeit wurde untersucht, welche Bedeutung maßgebliche Umweltfaktoren auf die Zusammensetzung des litoralen Makrozoobenthos haben, und wie sich anthropogene Nutzungen auf die Zusammensetzung und Funktion des Makrozoobenthos auswirken. Die Zusammensetzung des Makrozoobenthos wurde durch die Uferstruktur, Trophie und das hydrodynamische Regime bestimmt. Die faunistische Ähnlichkeit zwischen Habitaten war jedoch signifikant geringer als zwischen Trophiestufen, so dass die Uferstruktur, und nicht die Trophie, einen größeren Einfluss auf das Makrozoobenthos hat. Strukturelle Degradation führte zu einer Reduktion der Habitatheterogenität, was eine signifikante Verringerung der Diversität und eine signifikant veränderte Artenzusammensetzung verursachte. Infolgedessen war die Komplexität der Makrozoobenthos-Nahrungsnetze an degradierten Ufern signifikant geringer als an natürlichen Ufern. Erhöhte Wasserstandsschwankungen führten zum Ausfall von Wurzelhabitaten und der damit assoziierten Makrozoobenthos-Gemeinschaft. Schiffsinduzierter Wellenschlag führte zur Verdriftung des Makrozoobenthos von ihren Habitaten bereits bei geringen Sohlschubspannungen. Die Effekte von Wasserstandsschwankungen und schiffsinduziertem Wellenschlag wurden jedoch durch Habitate mit hoher struktureller Komplexität verringert. Mit dieser Doktorarbeit konnte ich ein mechanistisches Verständnis darüber erarbeiten, wie anthropogene Nutzungen die Wirkungsbeziehungen zwischen Umweltfaktoren und Artengemeinschaften verändern und welche ökologischen Auswirkungen dies hat. Diese Kenntnisse können als wissenschaftliche Basis zur Bewertung von anthropogenen Beeinträchtigungen des Litorals dienen.
... While temperature is clearly an important variable in determining chironomid community structure, they also respond to changes in a wide variety of other environmental variables , and transfer functions have been developed for a number of different parameters including salinity (Heinrichs et al., 2001), dissolved oxygen (Quinlan & Smol, 2002;Quinlan et al., 1998) and nutrient status (Brodersen & Lindegaard, 1999;Brooks et aI., 2001). If chironomid abundance and diversity can be influenced by so many environmental variables then it is reasonable to ask whether it is really possible to attribute community variance to just one primary driver, temperature. ...
Thesis
p>Peatland palaeoclimate studies typically involve two steps: 1) reconstruction of bog surface wetness (BSW) and 2) palaeoclimatic inference based on interpretation of the BSW record. This investigation is a test of the relationship using proxy data from northern England. BSW is reconstructed from Hulleter Moss in southern Cumbria and Malham Tarn Moss in North Yorkshire, using plant macrofossil, testate amoebae and peat humification analysis. The bog sites are paired with proximal lake sites, Bigland Tarn in southern Cumbria and Malham Tarn in North Yorkshire, and palaeotemperature estimates produced using chironomid analysis. Both bog sites displayed an impressive degree of internal consistency between proxy measures of BSW. A high degree of covariance was also found between the two sites and with the wider literature. Chironomid records were produced for lake sites and modern temperatures were accurately inferred from core-top samples. A combination of <sup>14</sup>C, <sup>210</sup>Pb and spheroidal carbonaceous particles were used to date the cores, although the radiocarbon chronology of Malham Tarn was problematic. Nevertheless, comparison of the well constrained Bigland Tarn palaeotemperature estimates with an earlier study from Cumbria revealed a high degree of similarity, corroborating the idea that temperature is the primary signal recorded in the chironomid stratigraphy. Comparison between the BSW and chironomid-inferred temperature records therefore provides an empirical test of the closeness of the relationship between temperature and BSW. While similarities between the two records are evident there are also significant differences and the data do not support a dominant temperature control over BSW.</p
... This capacity, together with their specific ecological preferences and narrow tolerances to environmental variables makes chironomids the most reliable aquatic group for reconstructing past climate and environmental conditions. The close relationship between chironomids and environmental variables, has allowed the development of chironomid-based quantitative models to reconstruct trophic status (Lotter et al. 1998;Langdon et al. 2006), oxygen level (Quinlan and Smol 2002), salinity (Henrichs et al. 2001;Eggermont et al. 2006), depth (Korhola et al. 2000;Engels et al. 2012), lake size and acidification (Mousavi 2002;Pegler et al. 2020), chlorophyll-a (Brodersen and Lindegaard 1999), and especially, air or water temperature (Eggermont and Heiri 2012). The performance and robustness of these models depend on many aspects, one of them is the taxonomic resolution. ...
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We provide a photographic guide and taxonomic diagnosis of Chironomidae larval remains obtained from surface sediments and short cores of 92 waterbodies situated on the Yucatan Peninsula and in Central America, namely Mexico, Belize, Guatemala, El Salvador and Honduras. A total of 101 morphotypes belonging to 64 genera were identified. Chironominae was the most species-rich subfamily represented by 57 morphotypes of 34 genera. The most widespread and abundant genus was Goeldichironomus followed by Chironomus and Polypedilum. Orthocladiinae were represented by 26 morphotypes and 17 genera, with the most common one being Cricotopus. Remains of this subfamily were recorded in only 15\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${^{1} \!\mathord{\left/ \!{\vphantom {\left(d+4\right)}} \right.} _{5}}$$\end{document} of the surveyed lakes. Tanypodinae included 17 morphotypes belonging to 12 genera. Labrundinia along with Ablabesmyia and Coelotanypus were the most common genera. Subfamily Podonominae was represented by the genus Parochlus. We believe that our study includes most of the Chironomidae genera of Central America and will have broad applicability for both paleolimnologists and aquatic ecologists.
... The rise in Microtendipes pedellus-type may indicate more minerogenic sedimentation (Hofmann, 1984;Brodersen and Lindegaard, 1999a) connected with climatic deterioration and sparse vegetation, which agrees with pollen results indicating more open forests than in the preceding Allerød period (i.e. lower AP/NAP ratio, more Artemisia, Chenopodiaceae and other indicators of open vegetation; Pokorný, 2002). ...
Article
We present a new chironomid record from sediments of former Lake Švarcenberk in South Bohemia (412 m asl, Czech Republic), located in the oceanic-to-continental macroclimatic transitional zone of eastern Central Europe. We provide estimates of Weichselian Late Glacial and Early Holocene (ca. 15–8 ka BP) mean July air temperatures on the basis of changes in the fossil assemblage using a joint Norwegian-Swiss transfer function. In our study, the climate was found to be relatively cold during the Late Pleniglacial, with July temperatures ranging between 11.2 and 12.3 °C. With the exception of the youngest section of this interval, temperatures during the Bølling-Allerød interstadial were relatively stable and warm, with values around 13.3–14.5 °C. During the Younger Dryas (YD), July temperatures varied between 12.7 and 16 °C, and these particular results are in agreement with other climatic reconstructions from the central to the eastern part of the European continent showing no or moderate summer temperature decrease during the YD, or even a slightly warming trend. A relatively warm and climatically stable early YD phase was followed by a variable and overall cooler younger phase. At the beginning of the Early Holocene, our reconstructed July temperatures increased to 17.7 °C. We demonstrate that general patterns of temperature changes inferred from chironomids during the Last Glacial Termination are similar to various multi-proxy reconstructions in Europe but we observe two unusually strong and abrupt cooling events: one that may be linked with the Gerzensee oscillation at the end of the Bølling-Allerød Interstadial and another that probably corresponds to the Preboreal Oscillation, although the temperature decreases in these intervals were much more pronounced than observed in other chironomid records from Europe, suggesting that local climatic factors and ecosystem responses may have overamplified these cold events in the temperature reconstruction. However, other proxies (geochemistry, pollen) support the interpretation of climatically driven palaeoenvironmental changes such as the development of vegetation cover, changes in lake productivity, pedogenesis and erosion.
... Many other studies found that chironomid assemblages vary across a lake's basin ( Heiri, 2004;Luoto, 2010Luoto, , 2011Engels and Cwynar, 2011). However, opposite results (Brodersen and Lindegaard, 1999;Van Hardenbroek et al., 2010) also have been reported. Water depth in our data is an important variable that explains 25.12% of the variance in chironomid assemblages. ...
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Subfossil chironomid (Diptera, Chironomidae) remains are often used as indicators of lake level changes in palaeolimnological studies. However, their usefulness as a water depth proxy can vary between the sites, depending on the lake morphology, mode of taphonomic processes or amplitude of past water level fluctuations, among other factors. In this study, we have examined the distribution of subfossil chironomids in the shallow Lake Spore (northern Poland) to assess the influence of water depth on the fauna. Our aim was to evaluate the site-specific utility of subfossil chironomids for lake level reconstruction at Lake Spore. The subfossil chironomid assemblages in Lake Spore have heterogeneous distribution, suggesting they are predominately composed of remains deposited close to the sampling location. A strong relationship between the water depth and the chironomids is marked by the 25.12% variance explained by water depth in the taxonomic data. Moreover, according to generalized linear models (GLMs) out of 44 dominant taxa, 12 have significant relationships with water depth. However, the sensitivity of our chironomid fauna to water depth changes is not continuous along the entire depth gradient. The most abrupt assemblage change occurs at 2.6-3.7 m water depth, in proximity to the depth where macrophytes become less dense and finally disappear. We conclude that, despite these strong chironomid-water depth relationships, only major water level fluctuations can be satisfactorily reconstructed due to the limited turnover rates of the fauna along a depth gradient and relatively small amplitude of the lake level variations characteristic for East-Central Europe.
... flexilis (Kolada et al., 2014), the bryozoans P. articulata and P. fruticosa (Økland & Økland, 2002) and the chironomids Stempellina spp., Pseudochironomus spp., and Protanypus spp. (Brodersen & Lindegaard, 1999). During this time, there was high between-lake variation in both macrophyte and invertebrate communities, but low macrophyte within-lake compositional variation over time, resulting in a non-significant macrophyte space-time interaction. ...
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Aim To investigate if connectivity and zebra mussel (Dreissena polymorpha) occurrence can mitigate effects of eutrophication in a lowland lake landscape. Location Upper Lough Erne, Northern Ireland, UK. Methods Data on environment, macrophytes and invertebrates were assembled for three basins of a large central lake and its satellite floodplain lakes via field surveys and palaeolimnological analyses. Space–time interaction analyses of palaeoecological data were compared pre‐1950 and post‐1950. Multivariate analyses examined how connectivity, environment and zebra mussels influenced contemporary lake communities, and explain their divergence from historical communities in the past. Results Pre‐1950, we found high community variation across sites and low within‐lake variation in macrophytes, but progressive eutrophication accentuated within‐lake community variation after 1950. Partitioning analysis showed larger effects of connectivity than nutrient enrichment on contemporary macrophyte composition, while local effects structured invertebrate communities. Three clusters of lakes were revealed according to variation in macrophyte composition, isolation from the central lake and nutrient enrichment: Group 1– the central lake and six nearby lakes were meso‐eutrophic (TP = 66.7 ± 47.6 μg/L; TN = 0.79 ± 0.41 mg/L) and had the highest zebra mussel abundances and organismal biodiversity; Group 2– Eight eutrophic (TP = 112±36.6 μg/L; TN = 1.25 ± 0.5 mg/L) and connected lakes; Group 3– Seven isolated and hypertrophic (TP = 163.2 ± 101.5 μg/L; TN = 1.55 ± 0.3 mg/L) lakes. Pre‐1950 palaeolimnological data for macrophytes and invertebrates for 5 lakes and a basin in the central lake most resembled extant lake communities of Group 1. However, palaeo‐records revealed that macrophytes and invertebrates subsequently converged towards those of Groups 2 and 3. Main conclusions Our study reveals that the central “mother” lake acts as a hub for preserving biodiversity via shared hydrological connectivity with satellite lakes and high zebra mussel abundances. These may buffer the impoverishing effects of eutrophication and sustain unexpectedly high biodiversity in the short term. Such protective buffering, however, cannot be relied upon indefinitely to conserve biodiversity.
... In terms of trophic status preference, almost all four categories differed markedly among the lake groups, indicating the chironomid classification based on trophic status preference may have a great potential for the bioassessment of freshwater lakes. Historically, chironomids were of particular importance in the assessment of lakes and running water (especially in hypereutrophic environments where other invertebrate groups are scarce or absent), because of their high resistance and resilience to environmental gradients (Brodersen and Lindegaard, 1999;Saether, 1979). Our results also indicated that algal lakes were characterized by the numerical dominance of haemoglobinpresent chironomids, whereas the four lake groups shared roughly identical median abundance of the chironomids with abdominal tubules. ...
... The presence of C. plumosus-type throughout this period indicates that the profundal zone received greater quantities of fresh phytoplankton material (Prat et al., 1992). Together with the presence of Procladius larvae this indicates eutrophic conditions (Brodersen and Lindegaard, 1999) connected to oxygen depletion during periods of stagnation. The higher trophic status of the reservoirs is reflected by the dominance of P. nubeculosum-type and C. mancus-type, both being considered indicators of eutrophy (Langdon et al., 2006). ...
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Chironomid stratigraphic changes were studied in three man-made reservoirs situated in a region intensely used for mining in the past (Banska Stiavnica, Central Europe). The reservoirs were built in the first half of the 18th century and are remnants of a former hydro-energetic system that provided water for mining and smelting facilities until the 1920s. Sediment cores spanning the last 170-200 years were sampled and dated. A total of 58 taxa were identified, Accepted Article with the most common taxa being Cladotanytarsus mancus-type, Polypedilum nubeculosum-type, Procladius spp. and Tanytarsus spp. Changes in the subfossil assemblages suggest that all reservoirs followed similar developmental trends. The low number of chironomid remains and the prevalence of littoral and rheophilic taxa characterize the initial phase, with severe water level fluctuations and unproductive conditions. A dramatic shift in both the qualitative and quantitative structure of the chironomid assemblages accompanied the decline of mining activities in the region. The second period of reservoir development was linked to changes in sediment composition and an increase of sediment organic content. In this phase, chironomids indicate nutrient enrichment, and the development of a hypoxic profundal zone, and complex littoral habitats. Since the 1970s, changes in the assemblage structure indicate a reduction in the profundal fauna and an increasing importance of the littoral taxa. Despite the significantly different usage of the reservoirs after the mining phase (recreation and angling vs drinking water supply) the changes in chironomid assemblages were fairly similar and indicated nearly identical developmental trajectories.
... To cope with this situation, some paleoecologists have tended to focus their studies on shallow lakes with little or no obvious thermal stratification (e.g., Smith et al., 1998). In instances where shallow lakes are thermally stratified, most subfossils are still likely to have been derived from organisms in the warm epilimnetic and upper littoral regions, and at some later stage to have undergone transport to and redeposition in the deep-water sediments in the central part of the basin (e.g., Walker et al., 1991;Brodersen, 1998;Brodersen and Lindegaard, 1999). ...
Article
Using miniature thermistors with integrated data loggers, the decrease in summer lake surface water temperature (LSWT) with increasing altitude a.s.l. was investigated in 10 Swiss Alpine lakes located between 613 m a.s.l. and 2339 m a.s.l. The LSWTs exhibit essentially the same short-term structure as regional air temperature, but are about 3 to 5°C higher than the air temperature at the altitude of the lake. LSWTs decrease approximately linearly with increasing altitude at a rate slightly greater than the surface air temperature lapse rate. Diel variations in LSWT are large, implying that single water temperature measurements are unlikely to be representative of the mean. Local factors will affect LSWT more than they affect air temperature, possibly resulting in severe distortion of the empirical relationship between the two. Several implications for paleoclimate reconstruction studies result. (1) Paleolimnologically reconstructed LSWTs are likely to be higher than the air temperatures prevailing at the altitude of the lake. (2) Lakes used for paleoclimate reconstruction should be selected to minimize local effects on LSWT. (3) The calibration of organism-specific quantitative paleotemperature inference models should not be based on single water temperature measurements. (4) Consideration should be given to calibrating such models directly against air temperature rather than water temperature. (5) The primary climate effect on the aquatic biota of high-altitude lakes may be mediated by the timing of the ice cover.
... To avoid possible biases in the past environmental reconstructions, especially in deep stratified lakes, it is very important to consider the origin of subfossil remains collected from the offshore (Millet et al., 2010). As discussed above, littoral sediment erosion and transport to offshore areas are frequent mechanisms occurring in clastic lakes (Brodersen & Lindegaard, 1999;Heiri, 2004), but the range to which organism remains are susceptible to be transported to offshore zones depends mostly on the particular processes of erosion/transport/deposition of sediments occurring in each lake. For example, Wang et al. (2012) examined the taxonomic distribution of subfossil assemblages of a deep-water lake in China and found that most organisms in deep assemblages had been transported out from the littoral zone or from the slope to offshore areas. ...
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Until recently, the distribution of diatom and chironomid assemblages and their attributes (species richness/diversity) in relation to water depth and sedimentary environments have been identified but not quantified. The influence of environmental variables on assemblage distribution and taxa richness in a deep, monomictic lake in São Miguel Island is assessed. Attention is given to community variation along a water-depth gradient. Sediment core samples were analysed for diatom content, chironomids, and grain-size clastic particles along three transects from the shoreline to the central deep basin of the lake at a resolution of 1 m water depth. Linear and unimodal regressions were used to test taxon richness, taxon diversity and taxon evenness versus water depth of each transect. A hump-shaped relationship between species richness and water depth was noted, with a peak occurring at mid-depth, meaning that samples located at that depth better represented the total subfossil assemblage living in lake Azul. Moreover, data indicate that both assemblages in Lake Azul, and taphonomic effects, were influenced by processes of clastic transport depending on the lake morphology. Results from this study allow us to access the spatial distribution of biological assemblages in clastic-dominated lakes with a high topographic gradient, and provide us with principal criteria that will allow us to determine coring locations that capture the true species diversity for studies in lakes.
... Due to the problems with species-level sorting, little is known about species turnover of chironomid communities (Delettre & Morvan, 2000) in tropical environments, and even less is known about the environmental variables that structure chironomid communities (Cranston et al., 1997;Helson et al., 2006). More information is available for temperate lake systems (e.g., Brodersen & Lindegaard, 1999;Wazbinski & Quinlan, 2013;Tarkowska-Kukuryk & Mieczan, 2014) while the response of chironomids to physicochemical variables in the tropics is poorly ...
Thesis
Non-biting midges (Chironomidae: Diptera) are an important component of freshwater ecosystems. However, most freshwater quality assessment or conservation biology studies rarely incorporate species-level information on midges. This is because traditional methods for sorting and identifying midges are too expensive. Here, I optimize, test, and use a new DNA barcoding technique that is based on Next Generation Sequencing (NGS). I use “NGS barcodes” for >30,000 individual specimens to demonstrate how NGS barcodes can improve analyzing the community structure of specimen- and species-rich invertebrate taxa. I first demonstrate that the midge fauna of a reservoir can be characterized by barcoding 500–1000 specimens (Chapter 2). I recommend that biomonitoring programs could cheaply gather data with only a small number of NGS-barcoded specimens or metabarcoded bulk samples. Next, I show how a new sequencing technique (MinION™) can be used for obtaining NGS barcodes within 24 hours (Chapter 3). I estimate that a single run of MinIONTM can generate >100 barcodes and conclude that an estimate of species composition can be obtained 10 hours since sample handling. Lastly, I reveal that Singapore’s biggest swamp forest remnant (Nee Soon Swamp Forest) maintains a rich and largely unique fauna (>400 chironomid species) that is resilient against the invasion of species from surrounding artificial reservoirs (Chapter 4). I show that the x chironomid occurrence in the swamp forest is associated with several physicochemical variables rather than the presence of or distance to the reservoirs. These findings suggest that even small or fragmented swamp forests can be suitable habitats for chironomids. This has an important conservation implication for many other swamp forests in Southeast Asia that are under threat. Overall, these studies expose the enormous power of NGS barcoding in ecological research, to study ecosystem health, biological diversity, and habitat conservation.
... 0.1-1 mm year -1 (Gell et al., 2006). Samples were taken from the deepest point in the wetland (Schmäh, 1993;Brodersen & Lindegaard, 1999;Real et al., 2000;Heiri, 2004) as other studies have shown that samples from the deepest part of a wetland provides an integrated sample of the whole waterbody assemblage (Heiri, 2004). The deepest point was located visually in temporary systems, and measured using a ruler in permanent systems. ...
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Subfossil chironomid head capsules have been used extensively as proxies to characterise past environmental conditions of waterbodies. To date, their potential to distinguish between temporary and permanent waterbodies has not been determined. This study set out to assess if subfossil chironomid head capsules could be used to distinguish between temporary and permanent floodplain wetlands from the Ovens River, south-eastern Australia. Twenty-six taxa were collected in both wetland types: one taxon (Paracladopelma spp.) was found exclusively in permanent wetlands; and five taxa (Cladopelma spp., Cryptochironomus spp., Microchironomus spp., Microtendipes spp. and Cricotopus spp.) were found exclusively in temporary wetlands. The overall concentrations of chironomid head capsules were greater in permanent than temporary wetlands. Furthermore, eight taxa were found in significantly higher concentrations in permanent than temporary wetlands but, apart from the unique taxa, the concentrations of no other taxa were significantly greater in the temporary than permanent wetlands. The temporary and permanent wetlands had distinct chironomid assemblages, as evidenced by the abundance and presence/absence data. This study highlights the importance of heterogeneity in the environment to maintain chironomid diversity and suggests that chironomid subfossils have the potential to be useful in palaeoecological studies aiming to reconstruct past changes in hydrology.
... Chironomids (Diptera: Chironomidae) are useful indicators of environmental conditions in inland waters (Walker 2001). The ecosystems they occupy are exceptionally wide-ranging (Porinchu and MacDonald 2003), as they occur across large gradients of environmental variables, such as temperature (Fortin et al. 2015), oxygen (Brodersen and Quinlan 2006), productivity (Brodersen and Lindegaard 1999;Medeiros et al. 2015), hydrology (Balasubramaniam et al. 2017), salinity (Dickson et al. 2014;Fenoy and Casas 2015) and turbidity (Greffard et al. 2012). ...
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Reliable estimates of Holocene temperatures are important for understanding past climate dynamics, the response of biota to climate change, and validating climate models. Chironomids in lake sediment cores are used widely to quantify past summer temperatures, for which high-latitude and/or high-altitude lakes, remote from human influence, are usually considered appropriate. Temperature inferences from lowland lakes are likely influenced by other variables, specifically eutrophication and industrial pollution, but their reliability has never been tested. We used a Norwegian chironomid-based transfer function (r² = 0.91; RMSEP = 1.01 °C) to infer mean July air temperature over the last 200 years, using chironomid assemblages in a core collected from a polluted, nutrient-enriched lake at Speke Hall, Liverpool, England. The chironomid-inferred temperatures correlate significantly with the local instrumental temperature record and follow long-term national temperature trends. These results show that chironomids can be used to produce reliable estimates of past mean July air temperature, even when other variables have also influenced the composition of the chironomid community. These findings underline the value of chironomids as sensitive and reliable quantitative proxies for summer temperature.
... The former has the third lowest WA temperature optimum of all dominating taxa in the CS, and the latter has the lowest optimum with a value of 10.6 ± 1.4°C (Figure 6). The modern distribution of C. ambigua in Finnish lakes is related to cold oligo-mesotrophic waters, but it is known to have a complex ecology (Brodersen and Lindegaard, 1999). In the sediment sequence of Lake Loitsana, it appears to be favoured by dense macrophyte communities of, for example, Myriophyllum (Shala et al., 2014b, Figure 2). ...
Article
Four biotic proxies (plant macrofossils, pollen, chironomids and diatoms) are employed to quantitatively reconstruct variations in mean July air temperatures (Tjul) at Lake Loitsana (northern Finland) during the Holocene. The aim is to evaluate the robustness and biases in these temperature reconstructions and to compare the timing of highest Tjul in the individual reconstructions. The reconstructed Tjul values are evaluated in relation to local-scale/site-specific processes associated with the Holocene lake development at Loitsana as these factors have been shown to significantly influence the fossil assemblages found in the Lake Loitsana sediments. While pollen-based temperatures follow the classical trend of gradually increasing early-Holocene Tjul with a mid-Holocene maximum, the aquatic/wetland assemblages reconstruct higher-than-present Tjul already during the early Holocene, that is, at the peak of summer insolation. The relatively low early-Holocene July temperatures recorded by the pollen are the result of site-specific factors possibly combined with a delayed response of the terrestrial ecosystem compared with the aquatic ecosystem. Our study shows that all reconstructions are influenced at least to some extent by local factors. This finding stresses the need to evaluate quantitatively reconstructed climate values against local lake development and highlights the benefit of using multi-proxy data in Holocene climate reconstructions.
... The emergence of Chironomus plumosus-type and an increase in δ 15 N from c. 2530 BC coincide in an increase in PPI at c. 2550 BC, signifying substantial nutrient input to the lake system. Chironomus plumosustype is a eutrophic taxon that has been used as an indicator of hypertrophic conditions in Danish lakes (Brodersen and Lindegaard, 1999). ...
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This study provides the first decadally resolved chironomid and organic geochemistry record of the Irish Neolithic from a small lake adjacent to the Carrowkeel-Keshcorran complex in County Sligo, Ireland. Chironomid (non-biting midge fly) sub-fossils and lake sediment geochemistry (δ¹³C, δ¹⁵N and C:N) from the Templevanny Lough core were used to assess the timing and magnitude of within-lake responses to Neolithic farming activity. When compared with decadally resolved pollen and macroscopic charcoal records from the same core, the limnological data show a direct influence of prehistoric farming on a freshwater lake system through nutrient loading and lake eutrophication. Elevated nutrient levels, suggesting a more productive lake system, and a subsequent turnover in the chironomid community indicate a period of intensive farming activity from c. 3790–3620 BC in the early Neolithic. This was followed by a decline in farming with short periods of small-scale human activity, exemplified through nutrient loading and short-lived increases in eutrophic chironomid taxa during the middle to late Neolithic. A return of farming activity can be seen in all proxy data in the late Neolithic (c. 2720–2480 BC). The chironomid community composition typically lagged land-use change by c. 10–20 years and exhibited predictable and proportional responses to agricultural activity. The timing and magnitude of limnological changes show that land-use, rather than climate, is the main control on chironomids at Templevanny Lough, thus showing the potential prominence of the anthropogenic signal during the Neolithic.
... Chironomids (Insecta: Diptera: Chironomidae) are non-biting midges recognized to be sensitive to a variety of environmental variables. Recent developments, driven by the need to better predict climate change effects on the environment, have increased the use of chironomid transfer functions to reconstruct quantitatively physical and chemical variables such as air and water temperature (Walker et al. 1991Walker et al. , 1997 Lotter et al. 1997; Olander et al. 1999; Larocque et al. 2001; Porinchu et al. 2002; Heiri et al. 2003; Velle et al. 2005, Larocque et al. 2006), total phosphorus ( Langdon et al. 2006), chlorophyll a (Brodersen and Lindegaard 1999), oxygen availability (Quinlan et al. 1998), lake depth (Korhola et al. 2000) and metal contamination (Brooks et al. 2005). Chironomids have also been used for dating sediments (Fallu et al. 2004) and to reconstruct past temperature from d 18 O (Wooller et al. 2004). ...
... In addition, Chironomidae larvae feed on algae, detritus, macrophytes, and microorganisms associated with the substrate (Hirabayashi & Wotton, 1999). These characteristics have made Chironomidae larvae a widely used tool in biomonitoring studies (Saether, 1979;Johnson, 1995) and lake classification (Thienemann, 1925;Brodersen & Lindegaard, 1999;Rossaro et al., 2012). ...
Article
Several limnological variables including sediments affect community structure in lotic and lentic environments. In general, Chironomidae larvae are dominant in macroinvertebrate communities both in abundance and in species richness in floodplains. Using granulometric texture as a surrogate for heterogeneity, we hypothesised that the diversity and distribution of Chironomidae larvae is higher in more heterogeneous environments. For this study, samples were collected quarterly from February to December 2008 at 12 stations in a tropical floodplain including both lotic and lentic stations in the Paraná River. We recorded 66 morphospecies belonging to three subfamilies. Density, species richness and alpha diversity were greater in lotic versus lentic environments. Granulometric data were more diverse in lotic environments according to the Shannon-Wiener index. Different species dominated each environment, and these taxonomic differences were demonstrated by detrended correspondence analysis (DCA). The link between granulometric characteristics and chironomid assemblages were further established by a significant correlation between granulometric variables and one or both of the DCA axes. Thus, the results support our hypothesis and suggest that the diversity and distribution pattern of Chironomidae larvae can be related to sediment heterogeneity due to the higher values of the assemblage attributes found in the lotic environments.
... However, increased phosphorus concentrations were not so distinctly reflected in the species composition of chironomids since the proportion of eutrophic and oligotrophic taxa was rather equal in this zone (Fig. 6) and oligotrophic taxa distinctly increased their abundances compared to the previous zone. It was documented that the reaction of heterotrophic chironomids to changes in lake water nutrients is not as predictable as the reaction of autotrophic organisms because chironomids are influenced by increased productivity indirectly through the food availability (macrophytes, algae, but also other invertebrates and organic detritus) and oxygen concentrations (Brodersen and Lindegaard, 1999;Brodersen and Quinlan, 2006), which could be influenced also by other factors than phosphorus availability. Moreover, fossil chironomid records from the central part of small lakes are composed by species from both, the littoral and the profundal, where different environmental conditions can occur (Van Hardenbroek et al., 2011). ...
... Myös aikaisempien tutkimusten valossa voidaan ravinnepitoisuutta pitää tärkeänä järvien pohjaeläinten koostumukseen vaikuttavana tekijänä niin litoraali-kuin profundaalivyöhykkeessäkin (Macan & Maudsley 1969, Kansanen et al. 1984, 1990, Kornijów 1988, Brodersen et al. 1998, Brodersen & Lindegaard 1999 Kuva 23. Painotetun keskiarvon (WA) menetelmällä ennustettujen Lahden Vesijärven ja Saimaan EPT-taksonien fosforipitoisuusoptimien ja Tanskan järvien EPT-taksonien klorofyllia -pitoisuusoptimien (Brodersen et al. 1998) Useiden jo edellä mainittujen eutrofiaa suosivien taksonien WA-optimit klorofylli-apitoisuuden suhteen olivat ravinnegradientin eutrofisessa päässä myös tanskalaisten järvien kivikkorannoilla [Brodersen et al. (1998) Sietokykyalueen on havaittu olevan laajempi ravinnegradientin eutrofisessa päässä myös profundaalivyöhykkeen surviaissääskillä (Chironomidae) (Saether 1979, Kansanen et al. 1984. ...
... Finally, Chironomidae assemblages change along the river continuum similarly to EPT taxa (Ephemeroptera, Plecoptera and Trichoptera) (e.g. Prat et al., 1983;González, 1990, 1991;Lindegaard and Brodersen, 1995;Puntí et al., 2009) and according the lake typology (Saether, 1979;Brodersen and Lindegaard, 1999;Mousavi, 2002). ...
... Lobinske et al. 2002) and are found preserved in lake cores (e.g. Brodersen and Lindegaard 1999) and so would be expected to persist in platypus cheek pouch samples. Chironomids were found in 37% of the cheek pouches examined (Table 2). ...
Article
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The unique Australian monotreme, the platypus (Ornithorhynchus anatinus) potentially exerts a strong top-down influence on riverine food webs in eastern Australia. However, despite considerable interest in the evolutionary history and physiology of the platypus, little is known of its trophic relationships. To address this lack of knowledge we used stable isotope analysis, in combination with the analysis of food items stored in cheek pouches, to determine its position in a typical riverine food web. This was the essential first step in the process of designing a larger study to investigate the relative importance of top-down and bottom-up effects in rivers where the platypus occurs. We found that platypuses were feeding on a wide range of benthic invertebrates, particularly insect larvae. The similarity of δ13C and δ15N values recorded for the platypus, a native fish (Galaxias sp.) and the exotic mosquitofish (Gambusia holbrooki) indicated dietary overlap and potential competition for the same resources. Although cheek pouch studies identify most of the major groups of prey organisms, the potential for contribution of the soft-bodied organisms such as larval dipterans, is suggested by stable isotope analysis, indicating that the use of both techniques will be important in future ecological investigations.
... The development of assessment tools for monitoring the ecological integrity of European lakes has focused mainly on quantifying the impacts of eutrophication on biotic communities based on phytoplankton (Phillips. et al., 2011;Søndergaard et al., 2011;Mischke et al., 2012), and sublittoral and profundal invertebrate abundances and composition (Saether, 1979;Brodersen & Lindegaard, 1999;Langdon et al., 2006). Although the impacts of anthropogenic shoreline alterations on lake ecological status have been increasingly studied in recent years and several monitoring programmes have been developed (e.g. ...
Article
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Lake shores are characterised by a high natural variability, which is increasingly threatened by a multitude of anthropogenic disturbances including morphological alterations to the littoral zone. The European Water Framework Directive (EU WFD) calls for the assessment of lake ecological status by monitoring biological quality elements including benthic macroinvertebrates. To identify cost- and time-efficient sampling strategies for routine lake monitoring, we sampled littoral invertebrates in 32 lakes located in different geographical regions in Europe. We compared the efficiency of two sampling methodologies, defined as habitat-specific and pooled composite sampling protocols. Benthic samples were collected from unmodified and morphologically altered shorelines. Variability within macroinvertebrate communities did not differ significantly between sampling protocols across alteration types, lake types and geographical regions. Community composition showed no significant differences between field composite samples and artificially generated composite samples, and correlation coefficients between macroinvertebrate metrics calculated with both methods and a predefined morphological stressor index were similar. We conclude that proportional composite sampling represents a time- and cost-efficient method for routine lake monitoring as requested under the EU WFD, and may be applied across various European geographical regions. http://link.springer.com/article/10.1007/s10750-015-2500-1
... The Chironomidae represent a highly speciose group consisting of more than 5000 described species with an estimated additional 5000 undescribed species (Cranston, 1995;Cranston & Martin, 1996). Chironomids are common in freshwater environments, and at both the species and genus levels, they vary in their sensitivity to pollution and environmental characteristics (Rosenberg, 1992;Brodersen & Lindegaard, 1999;Mousavi, Primicerio & Amundsen, 2003;Carew et al., 2007;Carew, Miller & Hoffmann, 2011b). The group is often considered difficult to identify due to morphological similarity among species, and like many taxa, it would benefit from DNA barcode identification. ...
Article
DNA barcoding has proven useful for identifying species, and there is increasing interest in this approach to determine species compositions for routine biological monitoring. Generally, DNA barcodes applied to taxa used for monitoring are clearly linked to species, but where taxa are closely related separation using DNA barcodes can be ambiguous. This raises challenges for monitoring, especially if closely related taxa are not recognised as separate species and these species have different environmental responses.Here we examine whether separation of closely related taxa with DNA barcodes is supported by other gene sequences and whether morphological and environmental differences occur among related species that cannot be easily separated. We selected six Chironomidae genera where initial neighbour-joining analysis of DNA barcodes produced monophyletic groups supported by high bootstraps (>95%), but groups were separated by low nucleotide divergence of 3–7%. Taxon separation based on DNA barcodes and mitochondrial cytochrome b (CytB) gene sequences were compared to delineations based on nuclear sequences from the carbomoylphosphate synthase-like gene region 1 (CAD1) and the zinc metalloproteinase (ZMP) gene.Species delineations with DNA barcodes were not always the same as those defined with nuclear sequences, morphological variation or differences in pollution and salinity tolerance. Morphological differences and some environmental differences were often in agreement with taxon separation based on nuclear CAD1 (and ZMP) sequences rather than DNA barcodes (and CytB variation).This study suggests that nuclear sequence data when used in combination with DNA barcodes can help separate closely related taxa into groups useful for routine biological monitoring.
... These results agree with comparable lake records from South and Southwest Greenland (Massa et al., 2012;Perren et al., 2012) Overall, we found evidence for reliable chironomidbased inferences of temperature trends for the region, especially from the two headwater lakes. �hese findings are consistent with the well-established relationships between chironomids and both air and water temperature at high latitudes (Brodersen and Lindegaard, 1999;Luoto et al., 2014). Indeed, many studies have illustrated the accuracy of using chironomids for quantitatively reconstructing air temperature. ...
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Sediment cores from three lakes located in the northernmost region of Ungava, Québec (Canada) were examined to define aquatic community and ecosystem variability during the Late Holocene period. A chironomid-based transfer function was used to reconstruct August air temperature trends, and lacustrine primary production was inferred from sedimentary biogenic silica content and siliceous microfossil abundances. Trends in primary production, sediment organic matter content (estimated through loss on ignition), and chironomid-inferred temperature were compared to explore potential effects of environmental change on biotic assemblage composition at centennial to millennial time scales. Although no direct correlation between chironomid-inferred August air temperature and primary production was observed, we found indications that both chironomid and diatom communities were responding to the same overarching regional climatic and environmental processes. Over the last decade, northern Québec has been undergoing notable, rapid warming that contrasts with the relative inertia of the past few millennia. This study provides a baseline against which recent and future environmental changes in this region can be compared.
... In warmer climatic conditions, limnological factors can have a dominant influence, such as lake trophic status (e.g. Brodersen & Lindegaard 1999. Few studies have previously been performed on chironomids as palaeo-oxygen indicators (e.g. ...
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We examined the relationship between fossil chironomid assemblages and environmental variables in 30 lakes in southern Finland with particular attention to hypolimnetic oxygen. Ordination techniques (DCA, CCAs) and Monte Carlo permutation tests were used to identify the most important parameters controlling the chironomid distributions. Based on the λ1:λ2 ratios of the variables, the greatest potential for quantitative inferences was with hypolimnetic oxygen (λ1:λ2 = 0.767). Therefore, inference models for past late-winter hypolimnetic oxygen were developed using weighted-averaging partial least squares (WA- PLS) techniques. The best model used one WA-PLS component, with a cross-validated coefficient of determination (r2jack) of 0.72 and a root-mean-squared error of prediction (RMSEP) of 2.351 mg l-1. The model was tested on two short-core sediment sequences. The results indicated that quantitative estimations of hypolimnetic oxygen changes provide a useful tool for palaeolimnology and lake management in assessments of lake ecosystems, and in restoration projects in southern Finland.
Article
Aim While we understand broad climate drivers of insect distributions throughout the Arctic, less is known about the role of spatial processes in determining these relationships. As such, there is a need to understand how spatial controls may influence our interpretations of chironomid environment relationships. Here, we evaluated whether the distribution of chironomids followed spatial gradients, or were primarily controlled by environmental factors. Location Eastern Canadian Arctic, Greenland, Iceland. Taxon Non‐biting midges (Chironomidae). Methods We examined chironomid assemblages from 239 lakes in the western North Atlantic Arctic region (specifically from the Arctic Archipelago of Canada, two parts of west Greenland (the southwest and central west) and northwest Iceland). We used a combination of unconstrained ordination (Self Organizing Maps); a simple method with only one data matrix (community data), and constrained ordination (Redundancy Analysis); a canonical ordination with two datasets where we extracted structure of community related to environmental data. These methods allowed us to model chironomid assemblages across a large bioregional dimension and identify specific differences between regions that were defined by common taxa represented across all regions in high frequencies, as well as rare taxa distinctive to each region found in low frequencies. We then evaluated the relative importance of spatial processes versus local environmental factors. Results We find that environmental controls explained the largest amount of variation in chironomid assemblages within each region, and that spatial controls are only significant when crossing between regions. Broad‐scale biogeographic effects on chironomid distributions are reflected by the distinct differences among chironomid assemblages of Iceland, central‐west Greenland, and eastern Canada, defined by the presence of certain common and low‐frequency, rare taxa for each region. Environmental gradients, especially temperature, defined species distributions within each region, whereas spatial processes combine with environmental gradients in determining what mix of species characterizes each broad and geographically distinct island region in our study. Main conclusions While biogeographic context is important for defining interpretations of environmental controls on species distributions, the primary control on distributions within regions is environmental. These influences are fundamentally important for reconstructing past environmental change and better understanding historical distributions of these insect indicators.
Article
Aim: while we understand broad climate drivers of insect distributions throughout the Arctic, less is known about the role of spatial processes in determining these relationships. As such, there is a need to understand how spatial controls may influence our interpretations of chironomid environment relationships. Here, we evaluated whether the distribution of chironomids followed spatial gradients, or were primarily controlled by environmental factors. Location: Eastern Canadian Arctic, Greenland, Iceland. Taxon: non-biting midges (Chironomidae) Methods: we examined chironomid assemblages from 239 lakes in the western North Atlantic Arctic region (specifically from the Arctic Archipelago of Canada, two parts of west Greenland (the southwest and central west), and northwest Iceland). We used a combination of unconstrained ordination (Self Organizing Maps); a simple method with only one data matrix (community data), and constrained ordination (Redundancy Analysis); a canonical ordination with two data sets where we extracted structure of community related to environmental data. These methods allowed us to model chironomid assemblages across a large bioregional dimension and identify specific differences between regions that were defined by common taxa represented across all regions in high frequencies, as well as rare taxa distinctive to each region found in low frequencies. We then evaluated the relative importance of spatial processes versus local environmental factors. Results: we find that environmental controls explained the largest amount of variation in chironomid assemblages within each region, and that spatial controls are only significant when crossing between regions. Broad-scale biogeographic effects on chironomid distributions are reflected by the distinct differences between chironomid assemblages of Iceland, central-west Greenland, and eastern Canada, defined by the presence of certain common and low-frequency, rare taxa for each region. Environmental gradients, especially temperature, defined species distributions within each region, whereas spatial processes combine with environmental gradients in determining what mix of species characterizes each broad and geographically distinct island region in our study. Main conclusions: we outline that while biogeographic context is important for defining interpretations of environmental controls on species distributions, the primary control on distributions within regions is environmental. These influences are fundamentally important to know for reconstructing past environmental change and better understanding historical distributions of these insect indicators.
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The potential of applying the analysis of freshwater midges (Chironomidae) for current questions in geographical research is examined. Chironomids are cosmopolitan in distribution and frequently the most abundant insects found in freshwater ecosystems. The capacity of the family to tolerate large gradients of pH, salinity, depth, oxygen concentration, temperature and productivity enables members of the Chironomidae to occupy virtually every available niche present in freshwater environments. In addition to wide distribution and abundance, Chironomidae are well suited for paleolimnological studies because the larvae possess chitinous head capsules which are well-preserved in lake sediment and relatively easily recovered and identified. As a result, chironomids are increasingly being used to track a number of natural and anthropogenically induced limnological changes resulting from atmospheric contamination, eutrophication and increased lake water salinity. Other areas in which subfossil chironomid analysis has provided valuable insight include climate change, phylogentics and biogeography and aquatic ecosystem dynamics and development. Details describing the biology and ecology of the Chironomidae that are directly relevant to their use in paleoenvironmental and biogeographical studies are presented. The methodology describing the recovery and identification of subfossil chironomid remains is reviewed. A generalized overview of the statistical methods that are commonly employed in relating the modern distribution of chironomids to specific aspects of the environment, i.e., the calibration dataset approach, is briefly discussed. Case studies that highlight the various uses and applications of chironomid analysis in areas of paleoenvironmental and biogeographical research relevant to geographers are described. Lastly, the current status of chironomid research in academic geography is discussed and suggestions of potential future research directions are made.
Chapter
Die im Dezember 2000 in Kraft getretene Wasserrahmenrichtlinie der EU verlangt eine Bewertung des ökologischen Zustands von Gewässern auf der Basis der biologischen Qualitätskomponenten Fische, benthische wirbellose Fauna, Makrophyten und Phytobenthos sowie Plankton. Da es in Deutschland bisher keinen einheitlichen und allgemein anerkannten Ansatz gibt, Stehgewässer mit Hilfe ihrer Makrozoobenthos-Besiedlung zu bewerten, wurde eine entsprechende Literaturstudie durchgeführt. Die Studie soll die Durchführbarkeit einer Makrozoobenthosbewertung gemäß den Anforderungen der Wasserrahmenrichtlinie für Deutschland prüfen.
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В книге представлены методические обзоры по основным группам биологических индикаторов, применяемым в палеоэкологии: пыльца, диатомовые водоросли, личинки хирономид, ракообразные, остракоды, губки – и кратко охарактеризованы прочие группы беспозвоночных животных. В книгу также вошел обзор по применению педогумусового метода для палеоэкологических реконструкций. Обсуждаются современные подходы к использованию биологических индикаторов в качестве показателей палеоклиматических изменений и проблемные стороны проведения экологических и температурных реконструкций. Представлены примеры палеореконструкций, выполненных с применением различных индикаторных групп из различных регионов: Степной и Горный Алтай, Центральная и Северная Якутия, Северный Урал, Западная Сибирь, Байкал, Тянь-Шань, Среднее Поволжье и пр. Книга рассчитана на специалистов в области палеоэкологии и на студентов
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The study of subfossil Chironomidae assemblages from a 2.50 in long core spanning the entire Late-glacial period in Lake Lautrey (Jura, France) displays the main climatic events of this interval, i.e. Oldest Dryas, Bolling/Allerod Interstadial and Younger Dryas. Each climatic event was characterized by a particular chironomid community associated with a corresponding trophic state of the lake. Oligotrophic conditions prevailed during the Oldest Dryas, whereas a strong eutrophication characterized the Bolling/Allerod Interstadial. Moreover, the chironomid biostratigraphy appears not monotonous during this Interstadial. Two large developments of macrophyte belt were proposed at the beginning of the Bolling and the end of the Allerod, respectively. Furthermore, from their particular chironomid fauna two short intervals were identified displaying comparatively lower organic content. These intervals correspond to the Older Dryas and the Intra Allerod Cold Phase (I.A.C.P.). The beginning of the Younger Dryas is shown by a strong and rapid change in chironomid assemblages. The pelagic primary production appeared much reduced whereas the benthic production was rather favored. The progressive change in chironomid assemblages and specially the decline of C. ambigua (Zetterstedt) during the rest of the Younger Dryas, is interpreted as an improvement of the environmental conditions.
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Updated version of bibliography to 20.12.16
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The macrobenthic invertebrate community of a shallow Mediterranean lake (Lake Golcuk, Izmir, Turkey) was studied in order to (a) describe the intra-annual and spatial variability in benthic communities, (b) relate possible community changes to environmental conditions and (c) evaluate the responses of the lake’s ecological status on community indices. The benthic assemblage was sampled seasonally at six sites during a period of 2 years (June 2008-March 2010). Additionally, hypolimnetic water quality variables were monitored over the same period at each site. The benthic fauna of Lake Gölcük was found to be very limited with 16 species belonging to four taxonomic groups. Potamothrix hammoniensis was the dominant benthic species and represented more than 72% of the total benthic fauna. Depth, dissolved oxygen, pH, conductivity, transparency, and water temperature seemed to be the main environmental factors affecting community indices. Benthic communities are affected by human disturbances in Lake Gölcük shifting their composition to more tolerant taxa, reflecting also the eutrophic to hypertophic character of the lake.
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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.
Article
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).
Article
The study of subfossil Chironomidae assemblages from a 2.50 m long core spanning the entire Late-glacial period in Lake Lautrey (Jura, France) displays the main climatic events of this interval, i.e. Oldest Dryas, Bølling/Allerød Interstadial and Younger Dryas. Each climatic event was characterized by a particular chironomid community associated with a corresponding trophic state of the lake. Oligotrophic conditions prevailed during the Oldest Dryas, whereas a strong eutrophication characterized the Bølling/Allerød Interstadial. Moreover, the chironomid biostratigraphy appears not monotonous during this Interstadial. Two large developments of macrophyte belt were proposed at the beginning of the Bølling and the end of the Allerød, respectively. Furthermore, from their particular chironomid fauna two short intervals were identified displaying comparatively lower organic content. These intervals correspond to the Older Dryas and the Intra Allerød Cold Phase (I.A.C.P.). The beginning of the Younger Dryas is shown by a strong and rapid change in chironomid assemblages. The pelagic primary production appeared much reduced whereas the benthic production was rather favored. The progressive change in chironomid assemblages and specially the decline of C. ambigua (Zetterstedt) during the rest of the Younger Dryas, is interpreted as an improvement of the environmental conditions.
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The chironomid compositions and spatial configuration were first assessed through the analysis of 41 surface sediment samples from Lake Chaohu. Chironomid assemblages were mainly dominated by Microchironomus tabarui, Chironomus plumosus, Microchironomus and Harnischia, denoting totally eutrophicated conditions throughout the whole lake. Hierarchical cluster analysis and MDS (non-metric multidimensional scaling) ordination analysis categorized all sampling sites into three groups. The difference of fauna diversity and evenness index (i.e., H, d and J) among the three clusters were not statistically significant. Common taxa in individual samples showed high similarities (72.5-93.3%) with total chironomid fossils in the basin. The resuspension and redistribution of sediments might not enough to bring about the fully homogenization of chironomid remains. Effective explanation for the even distribution of chironomid was the totally eutrophication in the whole lake. The rapid and accurate response of organism communities to environment changes in habitats confirmed the importance of biological monitoring. The researchers should pay more attention to evaluation results just based on chemical proxy which may not reflect the real situation of aquatic systems. Comprehensive counter measures should be carried out for improving water quality in Lake Chaohu.
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Scent marking activities in many ungulate species involve some aggression directed towards the vegetation. Both Thar ungulates Chinkara (Gazella bennetti) and Blackbuck (Antelope cervicapra) maintain their territory by different activities mainly during rutting period. We studied scent marking patterns of the both ungulates from August,2003 to July,2005. The present paper attempts to provide some quantified information, based on a case study undertaken at Guda, Jajiwalarea of Jodhpur and Ren site of Nagaur district of Rajasthan. On the basis of time spent on different aged animals, focal animal sampling method was used. During present study 675 different scents marking activities have been recorded. Out of this, 558 noted were from different territorial activities displayed by Blackbuck while Chinkara showed 117 territorial episodes. The bush hitting activity was more frequent during rutting season of Blackbuck and it performed highest 33.15% bush hitting among all the observed patterns at the same time as Chinkara displayed 23.07% only. Chinkara showed highest 45.26% bed site path fixation followed by 27 episode of bush hitting whereas both Blackbuck and Chinkara showed the eye rubbing activity similarly 11.82% and 11.11% respectively of the total territorial scent marking activities.
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Using miniature thermistors with integrated data loggers, the decrease in summer lake surface water temperature (LSWT) with increasing altitude a.s.l. was investigated in 10 Swiss Alpine lakes located between 613 m a.s.l. and 2339 m a.s.l. The LSWTs exhibit essentially the same short-term structure as regional air temperature, but are about 3 to 5°C higher than the air temperature at the altitude of the lake. LSWTs decrease approximately linearly with increasing altitude at a rate slightly greater than the surface air temperature lapse rate. Diel variations in LSWT are large, implying that single water temperature measurements are unlikely to be representative of the mean. Local factors will affect LSWT more than they affect air temperature, possibly resulting in severe distortion of the empirical relationship between the two. Several implications for paleoclimate reconstruction studies result. (1) Paleolimnologically reconstructed LSWTs are likely to be higher than the air temperatures prevailing at the altitude of the lake. (2) Lakes used for paleoclimate reconstruction should be selected to minimize local effects on LSWT. (3) The calibration of organism-specific quantitative paleotemperature inference models should not be based on single water temperature measurements. (4) Consideration should be given to calibrating such models directly against air temperature rather than water temperature. (5) The primary climate effect on the aquatic biota of high-altitude lakes may be mediated by the timing of the ice cover.
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This study was based on sedimentary midge (Diptera: Nematocera) assemblages from multilake datasets along environmental transects from Finland (regional), southern Finland (semiregional), and Helsinki district (local) and an intralake dataset from eastern Finland (site-specific). The aim was to examine scale-dependencies in midge distribution. The results imply that distribution and abundance of midge taxa are related to scale: on the regional scale the forcing factors are related to prevailing climate conditions, on semiregional scale they are related to water quality, on more local scales predation pressure is the key variable and on site-specific scales habitat characteristics determine the species assemblages. Although the number of study sites was not equal and not all environmental parameters were possible to measure from all spatial scales, it is apparent that caution is required in midge-based environmental assessments, because changes in faunal composition are driven by factors operating at different spatial scales.
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The effects of submerged macrophytes and light on the foraging behaviour and capture rate of perch Perca fluviatilis, bream Abramis brama and roach Rutilus rutilus, were studied. Attack frequency and number of captured chironomid larvae decreased for all species with increasing complexity of the artificial vegetation. Perch was, however, less affected by vegetation density. Capture efficiency of perch was reduced markedly in darkness, however, whereas capture efficiencies of bream and roach were unaffected by absence of light. In a turbid, highly productive lake, abundance of chironomid larvae increased with increasing submerged macrophyte complexity. Perch was most abundant in Chara tomentosa, whereas bream and roach preferred the unvegetated part of the lake. Perch seem to be the superior foragers on macroinvertebrates in dense littoral vegetation; bream and roach are superior in turbid waters lacking submerged macrophytes. Changes in the physical environment induced by eutrophication (decrease in submerged vegetation and increase in turbidity) should affect the competitive interactions among perch, bream and roach, promoting the observed succession from percids to cyprinids in lakes undergoing eutrophication. -from Author
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We used multivariate statistical techniques to analyse the distributions of surface sediment chironomid assemblages with respect to surface-water temperature, and an additional set of 27 environmental variables, in 30 freshwater lakes of northern Fennoscandia. Our study transect spans boreal coniferous forest to subarctic tundra and includes a steep temperature gradient. Canonical correspondence analysis (CCA) with forward selection and associated Monte Carlo permutation tests revealed that there were statistically significant (P
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Eighteen lakes were added to a published training set of 46 British Columbia (BC) lakes in order to expand the original range of total phosphorus (TP) concentrations. Canonical correspondence analysis (CCA) was used to analyze the relationship between diatom assemblages and environmental variables. Specific conductivity and [TP] each explained significant (P≤0.05) directions of variance in the distribution of the diatoms. The relationship between diatom assemblages and [TP] was sufficiently strong to warrant the development of a weighted-averaging (WA) regression and calibration model that can be used to infer past trophic status from fossil diatom assemblages. The relationship between observed and inferred [TP] was not improved by the addition of more eutrophic lakes, however the [TP] range and the number of taxa used in the transfer function are now superior to the original model. Diatom species assemblages changed very little in lakes with TP concentrations greater than 85 µg 1−1, so we document the development of a model containing lakes with TP≤85 µg 1−1. The updated model uses 59 training lakes and covers a range of species optima from 6 to 41.9 µg 1−1 TP, and a total of 150 diatom taxa. The updated inference model provided a more realistic reconstruction of the anthropogenic history of a highly eutrophic BC lake. The model can now be used to infer past nutrient conditions in other BC lakes in order to assess changes in trophic status.
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Distribution and composition of the epilithic macroinvertebrate fauna was studied on 21 different sites situated in the surf zone of Lake Esrom. A relative degree-of-exposure (windinduced wave activity) was calculated for each station from the specific number of wind days, wind velocity and a measured wind fetch. Macroinvertebrate abundance averaged 20 200 ind. m–2 stone bottom, and was composed primarily of six taxa (70% of the mean densities). The distribution patterns of the 48 most common taxa were compared to exposure, the amount of filamentous algae and shore slope, by regression, cluster analysis and ordination analysis (PCA and RDA). The abundance of 25 taxa was significantly correlated to the amount of filamentous algae, and a protectional effect of algae growth was suggested for the exposed sites. Seventeen taxa showed significant difference in abundance between sheltered western stations and exposed eastern stations. Stations with a gentle slope were characterised by sand covered stones and a fauna that qualitatively was similar to the fauna at greater depth in the littoral. Redundancy analysis (RDA) showed filamentous algae and slope to be the most important factors controlling the species distribution, whereas the gradient of exposure in Lake Esrom was too short to explain the species tolerance range.
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Three commonly used measures of diversity, Simpson's index, Shannon's entropy, and the total number of species, are related to Renyi's definition of a generalized entropy. A unified concept of diversity is presented, according to which there is a continuum of possible diversity measures. In a sense which becomes apparent, these measures provide estimates of the effective number of species present, and differ only in their tendency to include or to ignore the relatively rarer species. The notion of the diversity of a community as opposed to that of a sample is examined, and is related to the asymptotic form of the species-abundance curve. A new and plausible definition of evenness is derived.
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Using an expanded surface sample data set, representing lakes distributed across a transect from southernmost Canada to the Canadian High Arctic, a revised midge-palaeotemperature inference model was developed for eastern Canada. Modelling trials with weighted averaging (with classical and inverse deshrinking; with and without tolerance downweighting) and weighted averaging partial least squares (WA-PLS) regression, with and without square-root transformation of the species data, were used to identify the best model. Comparison of measured and predicted temperatures revealed that a 2 component WA-PLS model for square-root transformed percentage species data provided the model with the highest explained variance (r$$_{jack}^2$$= 0.88) and the lowest error estimate (RMSEPjack = 2.26 °C). Comparison of temperature inferences based on the new and old models indicates that the original model may have seriously under-estimated the magnitude of late-glacial temperature oscillations in Atlantic Canada. The new inferences suggest that summer surface water temperatures in Splan Pond, New Brunswick were approximately 10 to 12 °C immediately following deglaciation and during the Younger Dryas. During the Allerod and early Holocene, surface water temperatures of 20 to 24 °C were attained. The new model thus provides the basis for more accurate palaeotemperature reconstructions throughout easternmost Canada.
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The ecological themes that can be addressed by an analysis of the sediment record include species and assemblage persistence and antiquity, rates and directions of change in lake-basin morphometry. Suggests that contemporary short-term seasonal and inter-annual studies cannot be fully understood without a consideration of the medium-term decadal and longer trajectories provided by palaeoecological analyses. -from Authors
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The profundal chironomid associations in 9 Finnish lakes were analyzed using a hierarchical cluster analysis technique. The lake typology of Brundin is shown to be a valid base for monitoring stratified lakes. Availability of food is the primary controlling mechanism. In the shallow water region the difficulties in creating benthic lake typologies are apparent. The best classification results in relation to the water quality and trophic status were achieved at a depth of 3-5 m. It is necessary to divide the littoral and sublittoral into subzones and to compare lakes separately in them.-from Authors
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The distribution among Labrador (Canada) lakes of remains from 21 chironomid taxa was analysed by means of canonical correspondence analysis (CCA). Tests with partial CCA of three hypotheses revealed that the distributions of chironomid taxa were significantly correlated with summer surface-water temperature and maximum lake depth, but not sediment organic content. In addition, an exploratory CCA revealed possible relationships of chironomid fauna with residual longitude and Fe concentration. -from Authors
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The paper discusses the rationale behind the use of biological variables in environmental monitoring of lakes, as well as the principles of variable selection and the limitations of data usability. Profundal benthic communities are suggested to be an integral measure of autotrophic and heterotrophic lake processes. Measures of community structure and their relationship to morphometric and edaphic factors are presented and discussed, including indicator species/communities, diversity/species richness, oligochaete/chironomid ratio, and oligochaete abundance.
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Systematiek De indeling van de Orthocladiinae levert zo mogelijk nog meer problemen op dan die van de andere subfamilies van de Chironomidae. Momenteel is het algemeen gebruikelijk de groep in vier subfamilies te splitsen: Diamesinae, Prodiamesinae, Orthocladiinae en Telmatogetoninae (zie bijv. Saether, 1979a; Ferrarese & Rossaro, 1981; Cranston, 1982). In oudere literatuur worden deze subfamilies vaak niet onderscheiden of wordt een andere indeling gemaakt (Brundin, 1956; Pankratova, 1970; Fittkau & Reiss, 1978). De Telmatogetoninae leven uitsluitend marien en zullen hier buiten beschouwing blijven. De verschillen tussen de larven van de overige subfamilies zijn voor een determineerwerk onpraktisch. Zo is het belangrijkste kenmerk van de Diamesinae-larven gelegen in de bouw van de hypopharynx en het verschil in de bouw van de antenne is niet bij alle soorten duidelijk. Daarom zijn in dit hoofdstuk de drie subfamilies nog als vanouds tesamen genomen en bij de beschrijvingen als één geheel alfabetisch gerangschikt. De alfabetische in plaats van systematische rangschikking is ingegeven door het grote aantal
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In temperate regions many species of Chironomidae are uni- or bivoltine, but 3 or 4 annual generations are not uncommon. For most species the overwintering capability is not restricted to a particular instar, and in temperate regions development of some species may continue throughout winter. The pupal stage is short-lived. The developed pupa swims to the surface where the adult quickly emerges. For most species the adult phase lasts only a few days, and a single egg batch is usual. The influence of environmental conditions on the larval stages is shown, with attention focusing on substrate, water quality, food, predation, parasitism and competition. The value of chironomids as indicators of water quality is shown.-P.J.Jarvis
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Consideration of the dipteran family Chironomidae is an important aspect of microfossil analysis of lake sediments because chironomids provide information on the ecological characteristics of an earlier period of lake development.Chironomids are of particular interest because some species are typical of the profundal zone of eutrophic lakes and other of oligotrophic lakes. As a result, the major part of the literature on chironomid analysis deals with the use of these animals as indicators of trophic states during earlier periods of lake histories. Indeed, some studies have shown that an “oligotrophic” profundal fauna was completely replaced by “eutrophic” species during lake development.The chironomid fauna is not only influenced by factors connected with eutrophication but also by other events occurring during lake development, such as changing climatic conditions, which, until now, have hardly been discussed.
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The theory of gradient analysis is presented in this chapter, in which the heuristic techniques are integrated with regression, calibration, ordination and constrained ordination as distinct, well-defined statistical problems. The various techniques used for each type of problem are classified into families according to their implicit response model and the method used to estimate parameters of the model. Three such families are considered. First, the family of standard statistical techniques based on the linear response model is dealt with, because they are conceptually the simplest and provide a basis for what follows, even though their ecological application is restricted. Second, a family of somewhat more complex statistical techniques are outlined which are formal extensions of the standard linear techniques and incorporate unimodal (Gaussian-like) response models explicitly. Finally, the family of heuristic techniques is considered based on weighted averaging. These are not more complex than the standard linear techniques, but implicitly fit a simple unimodal response model rather than a linear one. Ordination diagrams and their interpretation on bi plots and joint plots are also given in the chapter. This chapter has discussed which response model to choose from direct and indirect gradient analysis, and then in direct system, which one to choose from regression and constrained ordination.
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1. Scales of temporal analysis in limnology generally cover dial through to interannual changes, with occasional longer studies with up to 50 years continuous sampling data. Lakes, however, have been changing over much longer time periods than this, as is apparent from palaeolimnological studies. Temporal scales are, however, largely relative, with an individual's perspective controlling what is deemed short or long term. 2. Phytoplankton populations are variable over a variety of timescales, and the sediment record can readily record these changes from interannual through to 103-year timescales. Because of anthropogenic influences, such as acidification and eutrophication, phytoplankton communities probably have been altered dramatically in many lakes, often before routine sampling began. Records of changing phytoplankton populations at timescales relevant to limnologists can be derived from, for example, varved sediments and used to address specific problems, such as the degree of long-term interannual variability and timescales of sexual reproduction. 3. Palaeolimnologists tend to interpret changes in sediment assemblages in terms of ecological and physiological processes which are relevant at scales that may not be resolvable in lake sediments. There is a clear need for sediment records to be interpreted in terms of the processes which operate at timescales that match the resolution of that sediment sequence. 4. Increasingly fine sampling resolutions are being attempted by palaeolimnologists, often without consideration of the reasons for such an approach or to the repeatability of the results. The increased variability associated with high-resolution sampling can make it difficult to separate noise from the ecological signal. There is a clear need for replication. 5. The necessary temporal resolution is defined by the aim of any given palaeolimnological study. If the main emphasis of a study is, for example, establishing background phosphorus concentrations, a coarser sampling resolution is probably acceptable than that required for many ‘ecological’studies.
Article
1. The macroinvertebrate fauna living on stones in the exposed stony littorals of thirty-nine Danish lakes were examined by multivariate numerical methods. The data were derived from 125 semi-quantitative samples and a species list of 126 taxa. The mean number of individuals per sample was 960, and among the most common taxa were Asellus aquaticus, Gammarus, Oulimnius, Tinodes, Cricotopus and Dicrotendipes.2. The total number of species and fourteen individual taxa were positively correlated to mean depth of the lakes and eleven taxa were correlated to the total phosphorus concentration. The Shannon diversity was negatively correlated to the chlorophyll a concentration ([Chl a]).3. Community patterns were examined by detrended correspondence analysis (DCA), and the relationship between species data and selected environmental variables was analysed by canonical correspondence analysis (CCA). Mean lake depth was found to be the strongest environmental variable in explaining the species data. The [Chl a] and Secchi depth also explained significant variation in the distribution of the stony littoral invertebrates. Wind fetch and relative exposure did not explain any variation in the faunal composition among sites.4. The abilities of the macroinvertebrates to predict the lake trophic state, expressed as log ([Chl a]), were explored by means of weighted averaging (WA) regression and calibration. Two tolerance-weighted WA models using inverse and classical regression for deshrinking are presented. The models were assessed by the root mean square error (RMSE) of prediction, using bootstrapping as cross validation, and by the correlation between observed and inferred log ([Chl a]). The model using inverse deshrinking had a RMSEboot = 0.41 and r2 = 0.63. By using classical regression, the predictability in the ends of the gradient was improved but the RMSE increased: RMSEboot = 0.46.5. Although the factors determining faunal distribution patterns in the Danish lowland lakes were highly multivariate and difficult to disentangle, it seems reasonable to use the WA estimated species optima and tolerances to [Chl a] in a bio-assessment model.
Article
Recent mathematical indices summarizing biological communities of indicators are recapitulated. Improvements of these indices based on weighting according to width of trophic ranges of each species are suggested. Their principle deficiencies, however, are pointed out. Revised lists of characteristic profundal as well as littoral and sublittoral chironomids in Nearctic and Palearctic lakes show that at least 15 characteristic chironomid species communities can be delineated, 6 in each of the oligotrophic and the eutrophic ranges and 3 in the mesotrophic range. It is proposed that these communities be lettered consecutively in the Greek alphabet from α (alpha) to o (omikron). A key to the 15 divisions based on the species associations in the profundal zone of harmonic lakes is put forward. There is very good correlation between the 15 divisions and the ratios of average total phosphorus to mean lake depth and average chlorophyll a to mean lake depth. The ratio of chironomids to oligochaetes and the distribution patterns of single species have proven useful in pin-pointing localized areas of pollution. The primary mechanism governing the distribution of chironomid communities in oligotrophic and mesotrophic lakes appears to be the availability of food materials rather than the annual hypolimnetic oxygen concentration. In eutrophic lakes the relationships between organic matter accumulation and oxygen levels are so interdependent as to be inseparable.
Article
A computer program for reconstructing environmental variables (e.g. lake-water pH) from fossil assemblages (e.g. diatoms) by weighted averaging regression and calibration is described. The estimation of sample-specific errors of prediction by bootstrapping is outlined. The program runs on IBM-compatible personal computers.
Article
The relative species composition of subfossile chironomidheadcapsules in surface sediments from ten shallow Danishlakes ofdifferent trophic status were analysed through similarityindicesand multidimensional scaling. It was possible to distinguishbetween high and low productivity lakes by means of subfossileremains. The low productivity shallow lakes (TP–1) were characterised by the taxa Psectrocladius,Pseudochironomus, Microtendipes and Pentaneurini. The highproductivity lakes (TP>150 g P l–1) showsimilaritiesto littoral communities in eutrophic stratified lakes and arerepresented by genera such as Cricotopus, Procladius, Microchironomus and Chironomus.In surface samples from Lake Stigsholm subfossile speciescomposition was compared with species composition in samplesoftrapped adult midges and samples of living larvae. Therelativespecies composition between the three sample types variedconsiderably. Samples of living larvae showed a high degree ofvariation within the lake while surface sediment samples ofsubfossile chironomid remains seemed to be a persistent andreliable tool in classification of shallowlakes.
Article
Changes in the composition of chironomid remains from three 65–76 cm deep cores of profundal sediments reflect changes in the lake's trophic state during a period of approximately 150 years. A long period of moderate eutrophication and successively increasing chironomid numbers was followed by a rapid change in productivity resulting in the disappearance of characteristic oligotrophic-mesotrophic members of the chironomid fauna. Nutrient and chlorophyll concentrations during different periods of the lake's history are reconstructed from sediment data and general chemical and biological relationships in Scandinavian lakes. Prospective effects of nutrient reduction are assessed.
Article
Effective management of aquatic resources requires long-term environmental data. However, because long-term observations are rarely available, indirect proxy methods must be used to substitute for these missing historical data sets. Major advances have been made in paleolimnology over the last decade, and many of these advances can be applied directly to integrated and cost-effective assessments of aquatic ecosystem health. This commentary uses the analogy of human health to argue that paleolimnological data provide information crucial to the decision-making processes of ecosystem managers.
Article
The remains of diatoms, cladocerans, and midges are usually the most abundant of freshwater organisms and to now have been most useful in interpreting past conditions in a lake. Each taxocene consists of two separate communities, one in the warm littoral zone and the other offshore. Remains of inshore organisms are moved offshore by wind-generated currents, the amount of transport varying with individual characteristics of the lakes. Nowhere do remains of the two communities become completely integrated numerically, although the remains of the littoral chydorid Cladocera become integrated by species before they are incorporated into the sediments. The taxa of the planktonic Eubosmina and of the offshore midges correspond to levels of productivity in present-day lakes, and hence changes in the fossil record are commonly regarded as indicating eutrophication over time. The deepwater midges respond to the concentration of dissolved oxygen in deep water, which may be controlled more by a decrease in volume of deep water through accumulation of sediments than by any real increase in edaphic productivity. While such changes are going on offshore during the Holocene, the littoral communities of cladocerans and midges are scarcely changing at all, suggesting a different response of the inshore from the offshore communities to longterm changes resulting from increasing productively or from other functions. Thus, considering these different responses of the two communities of organisms and their incomplete mixing, the remains of littoral and offshore taxa recovered from an offshore core of sediments must be tabulated separately and interpreted separately. For any studies involving accumulation rates, there must be an understanding of the integration of inshore and offshore remains, its variation over the lake bottom, and how it may have varied with marked fluctuations in water level.
Article
Interpreting sedimentary phosphorus profiles in terms of changes in the historical P load is difficult due to variable retention and post-depositional diagenesis. An alternative approach is to use diatom assemblages in surface sediments and derive a transfer function for epilimnetic SRP and total P concentrations using weighted average regression and calibration. The obtained relationship can then be applied to down-core changes in sedimentary diatom assemblages and diatom-inferred P (DI-P) used to assess historical changes in epilimnetic P-concentrations. A diatom-phosphorus calibration data set for 43 eutrophic lakes in Northern Ireland has been constructed and applied to two small eutrophic lakes (Lough Mann, White Lough). DI-total P (i.e. predicted) is highly correlated with observed TP (r 2 = 0.75) for the surface-sediment training data-set. The resultant changes in DI-P derived from application of the transfer function to down-core changes in diatom assemblages are compared to sedimentary P concentrations. The latter are highly variable, presumably due to redox-derived effects, while DI-P profiles are more readily interpretable, and agree with other stratigraphic records of lake eutrophication. The method offers a good possibility of defining pre-disturbance (i.e. natural) phosphorus concentrations in lakes with associated implications for lake-restoration programmes.
Article
Based on data from 233 Danish lakes, enclosure experiments, full-scaleexperiments and published empirical models we present evidence that top-downcontrol is more important in shallow lakes than in deep lakes, excepting lakeswith a high abundance of submerged macrophytes. The evidence in support is: (1)That at a given epilimnion total phosphorus concentration (TP) the biomass offish per m2 is independent of depth, which means that biomassper m3is markedly higher in shallow lakes. (2) That the biomass of benthic invertebratesis higher in shallow lakes, which means that the benthi-planktivorous fish areless dependent on zooplankton prey than in deep lakes. By their ability to shiftto zooplankton predation their density can remain high even in periods whenzooplankton is scarce and they can thereby maintain a potentially high predationpressure on zooplankton. (3) That the possibilities of cladocerans to escapepredation by vertical migration are less. (4) That the zooplankton:phytoplanktonmass ratio per m2 is lower and presumably then also thegrazing pressure onphytoplankton. (5) That nutrient constraints appear to be weaker, as evidenced bythe fact that at a given annual mean TP, summer TP is considerably higher inshallow lakes, especially in eutrophic lakes lacking submerged macrophytes. (6)That negative feedback on cladocerans by cyanobacteria is lower as cyanobacterialdominance is less frequent in shallow lakes and more easily broken (at least inNorthern temperate lakes), and (7) That top-down control by benthi-planktivorousfish is markedly reduced in lakes rich in submerged macrophytes because theplants serve as a refuge for pelagic cladocerans and encouragepredatory fish at the expense of prey fish. We conclude that manipulation of fishand submerged macrophytes may have substantial impact on lake ecosystems, inparticular in shallow eutrophic lakes. On the contrary, if the conditions formore permanent changes in plant abundance or fish community structure are lackingthe feed-back mechanisms that endeavour a return to the original turbid state willbe particularly strong in shallow lakes.
Article
The frequency and the importance of wind-induced resuspension were studied in the shallow, eutrophic Lake Arresø, Denmark (41 km2, mean depth 3 m). During storm events in autumn 1988 lake water samples were collected every 2–8 hours by an automatic sampler at a mid-lake station. The concentration of suspended solids and Tot-P was found to increase markedly. During storms up to 2 cm of the superficial sediment was resuspended, and the concentration of resuspended solids in the water column rose to 140 mg l−1. The resuspended particles had a relatively high settling velocity and on average, a relatively short residence time in the water column of 7 hours. A model which describes the concentration of resuspended solids as a function of wind velocity and of settling velocity of the resuspended particles is presented. Using additional wind velocity data from a nearby meteorological station, the model has been used to calculate the frequency of resuspension events and concentration of resuspended solids for the period from May to November 1988. These calculations show that resuspension occurred about 50% of the time. Average flux of suspended solids from the sediment to the water was 300 g m−2 d−1 and during 50% of the time lake water concentration of suspended solids was more than 32 mg l−1. A relationship between concentration of suspended solids and Secchi-depth is presented. Because of resuspension, Secchi-depth in Lake Arresø is reduced to 0.5 m. Resuspension also had a marked effect on Tot-P concentration in the lake water, and P input to the lake water being totally dominated by resuspension events.
Article
In order to evaluate short-term and long-term effects of fish manipulation in shallow, eutrophic lakes, empirical studies on relationships between lake water concentration of total phosphorus (P) and the occurrence of phytoplankton, submerged macrophytes and fish in Danish lakes are combined with results from three whole-lake fish manipulation experiments. After removal of less than 80 per cent of the planktivorous fish stock a short-term trophic cascade was obtained in the nutrient regimes, where large cyanobacteria were not strongly dominant and persistent. In shallow Danish lakes cyanobacteria were the most often dominating phytoplankton class in the P-range between 200 and 1 000µg P l−1. Long-term effects are suggested to be closely related to the ability of the lake to establish a permanent and wide distribution of submerged macrophytes and to create self-perpetuating increases in the ratio of piscivorous to planktivorous fish. The maximum depth at which submerged macrophytes occurred, decreased exponentially with increasing P concentration. Submerged macrophytes were absent in lakes>10 ha and with P levels above 250–300µg P l−1, but still abundant in some lakes<3 ha at 650µg P l−1. Lakes with high cover of submerged macrophytes showed higher transparencies than lakes with low cover aboveca. 50µg P l−1. These results support the alternative stable state hypothesis (clear or turbid water stages). Planktivorous fish>10 cm numerically contributed more than 80 per cent of the total planktivorous and piscivorous fish (>10 cm) in the pelagical of lakes with concentrations above 100µg P l−1. Below this threshold level the proportion of planktivores decreased markedly toca. 50 per cent at 22µg P l−1. The extent of the shift in depth colonization of submerged macrophytes and fish stock composition in the three whole-lake fish manipulations follows closely the predictions from the relationships derived from the empirical study. We conclude that a long-term effect of a reduction in the density of planktivorous fish can be expected only when the external phosphorus loading is reduced to below 0.5–2.0 g m−2 y−1. This loading is equivalent to an in-lake summer concentration below 80–150µg P l−1. Furthermore, fish manipulation as a restoration tool seems most efficient in shallow lakes.
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