Chironomids as a paleoclimate proxy Lake deposits have a rich diversity of fossilized insects that trace back to middle Paleozoic era, further increasing in abundance during the Quaternary period. Among the diverse array of aquatic invertebrates, different families of aquatic fly larvae can be extracted from sediments of the Quaternary era. Among them, Chironomids, two-winged flies that belong to the family Chironomidae, are of greatest ecological importance due to their diverse feeding habitat and their role as an important component of the food web. Chironomids complete their larval stage in the water, with their adult life stage outside of the water only lasting a very short time. During their larval stages, Chironomids play an important role in the degradation of material in the aquatic ecosystem. Ecologically they are considered bottom dwellers and are very responsive to any fluctuation in the surrounding environment. Their head capsule and feeding structures are quite commonly fossilized in lake sediments, allowing them to serve as a valuable paleoclimate proxy. Factors influencing chironomid distribution and abundance One of the major factors that affect chironomid distribution is the climate conditions at the local, regional, and global scale . Changes in these conditions are preserved  over large periods of time as a fossil record . Through paleolimnological methods  including chironomid assessment, these changes can be extrapolated to predict future climate change. Chironomids are very responsive to any fluctuation in the surrounding environment, making them good indicators of a variety of factors, including salinity, water depth, stream flow, aquatic productivity, oxygen level, lake acidification, pollution, temperature, and overall ecosystem health. Chironomid distribution can be related to those factors using a transfer function to connect a particular group of organisms to a specific environmental variable. A variety of disparate factors have been influencing the abundance and distribution pattern of chironomids in recent history. Therefore, it is important to be careful when making broader interpretations from their fossil records. Several recent debates have discussed the impact of temperature on chironomid abundance and diversity, along with other associated factors  . Accurate interpretations of chironomid fossil records must consider a wide array of associated factors within the ecosystem. In order to understand the different forces that have been affecting the fossil data of a lake, it is important to reconstruct the physical, chemical, and the nutrient content of the lakes that actually shapes the communities. Their distribution and abundance are highly influenced by the combination of human disturbance and change in the climate. Both of them influence the catchment area that resulted in the changing of vegetation, hydrology, and nutrient cycle . Any change at the regional level, especially temperature, affects the water quality at the local scale and then ultimately has a species-specific effect on habitat. Chironomids and reconstruction of quantitative change in Holocene climate Several factors are considered as controlling factors of chironomid distribution and abundance. Researchers assessing chironomid distribution primarily examine the temperature, while considering supporting factors  such as pH, salinity, nutrient flow, and productivity, especially of the late Pleistocene/Holocene time period. For many years, research has been carried out into the relationship between temperature and chironomid distribution pattern due to the impact of temperature on chironomid emergence. Chironomids are directly and indirectly affected by temperature during their whole life cycle, including larval emergence, growth, feeding and reproduction. According to Eggermont and Heiri, the indirect impact of temperature on different physical and chemical aspects determines chironomid distribution and abundance. There is also a strong relationship between chironomid abundance, emergence, and distribution and mean water and air temperatures. According to research conducted in the high-altitude lake Lej da la Tscheppa in Switzerland, seasonal temperature reconstruction can be done with the help of independent chironomids and diatoms. Any change in the assemblage of chironomids reflects change in the temperature and duration of ice cover of that specific water body due to climate change. According to their findings, chironomids respond mostly to the change in the summer temperature, so seasonal variation in temperature can be inferred from sediment cores. Use of chironomids in assessments of anthropogenic climate change According to the fifth IPCC report (2014), a key factor in the shaping of aquatic biodiversity is the progression of human-induced climate change. Macroinvertebrates, especially chironomids, have been considered an important indicator of past climate change, in particular with regard to temperature. There is a strong correlation between the chironomid assemblage and the water temperature, lake depth, salinity, and nutrient concentrations. Therefore, the impact of climate change on lake water levels can be related to changes in the pattern of chironomid distribution and abundance. This strong correlation indicates the evaporation and precipitation profiles of the lake in the past. Past climatic conditions are reconstructed based on paleolimnology with the help of different fossilized records, especially lake sediments that help differentiate regional and local climate change.
Chironomids as a paleoclimate proxy Lake deposits have a rich diversity of fossilized insects that trace back to middle Paleozoic era, further increasing in abundance during the Quaternary period. Among the diverse array of aquatic invertebrates, different families of aquatic fly larvae can be extracted from sediments of the Quaternary era. Among them, Chironomids, two-winged flies that belong to the family Chironomidae, are of greatest ecological importance due to their diverse feeding habitats and their role as an important component of the food web. Chironomids complete their larval stage in the water, with their adult life stage outside of the water lasting only a very short time. During their larval stages, Chironomids play an important part in the degradation of material in the aquatic ecosystem. Ecologically they are considered bottom dwellers and are very responsive to any fluctuation in the surrounding environment. Their head capsule and feeding structures are commonly fossilized in lake sediments, allowing them to serve as a valuable paleoclimate proxy. Factors influencing chironomid distribution and abundance One of the major factors that affect chironomid distribution is the climate conditions at local, regional, and global scales . Changes in these conditions are preserved as a fossil record over large periods of time . Through paleolimnological methods , including chironomid assessment, these changes can be extrapolated to predict future climate change. Being very responsive to any fluctuation in the surrounding environment, Chironomids are good indicators of a variety of factors, including salinity, water depth, stream flow, aquatic productivity, oxygen level, lake acidification, pollution, temperature, and overall ecosystem health. Chironomid distribution can be related to those factors using a transfer function to connect a particular group of organisms to a specific environmental variable. A variety of disparate factors have influenced the abundance and distribution patterns of chironomids in recent history. Therefore, it is important to be careful when making broader interpretations from their fossil records. The impact of temperature on chironomid abundance and diversity, along with other associated factors , has recently been debated . Accurate interpretations of chironomid fossil records must consider a wide array of associated factors within the ecosystem. In order to understand the different forces that have been affecting the fossil data of a lake, it is important to reconstruct the physical, chemical, and nutrient content that actually shape the lake communities. Their distribution and abundance are highly influenced by the combination of human disturbance and changes in climate, both of which influence the catchment area that resulted in changing vegetation, hydrology, and nutrient cycles . Any change at the regional level, especially temperature, affects local water quality and then ultimately has a species-specific effect on habitat. Chironomids and reconstruction of quantitative change in Holocene climate Researchers assessing chironomid distribution primarily examine the temperature, while considering supporting factors , such as pH, salinity, nutrient flow, and productivity, especially of the late Pleistocene/Holocene time period. For many years, research has been carried out into the relationship between temperature and chironomid distribution due to the impact of temperature on chironomid emergence. Chironomids are directly and indirectly affected by temperature during their entire life cycle, including larval emergence, growth, feeding and reproduction. According to Eggermont and Heiri, the indirect impact of temperature on different physical and chemical aspects determines chironomid distribution and abundance. There is also a strong relationship between chironomid abundance, emergence, and distribution and mean water and air temperatures. According to research conducted in the high-altitude lake Lej da la Tscheppa , Switzerland, seasonal temperature reconstruction can be done with the help of independent chironomids and diatoms. Any change in the assemblage of chironomids reflects change in the temperature and duration of ice cover of that body of water due to climate change. According to their findings, chironomids respond mostly to change in summer temperature, so seasonal variation in temperature can be inferred from sediment cores. Use of chironomids in assessments of anthropogenic climate change According to the fifth IPCC report (2014), a key factor in the shaping of aquatic biodiversity is the progression of human-induced climate change. Macroinvertebrates, especially chironomids, have been considered an important indicator of past climate change, in particular with regard to temperature. There is a strong correlation between the chironomid assemblage and water temperature, lake depth, salinity, and nutrient concentrations. Therefore, the impact of climate change on lake water levels can be related to changes in the pattern of chironomid distribution and abundance. This strong correlation indicates the evaporation and precipitation profiles of the lake in the past. Past climatic conditions are reconstructed based on paleolimnology with the help of different fossilized records, especially lake sediments that help differentiate regional and local climate change.
R
habitat
habitats
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only lasting
lasting only
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role
part
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quite
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scale
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A
as a fossil record
D
as a fossil record
A
,
R
Chironomids are
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making them
Chironomids are
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been influencing
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pattern
patterns
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Several recent debates have discussed the
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, has recently been debated
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the nutrient content of the lakes that actually shapes the
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change in the climate. Both of them
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the changing of
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cycle
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the water quality at the local scale
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Several factors are considered as controlling factors of chironomid distribution and abundance.
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,
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pattern
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whole
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in
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specific water body
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