Holocene climatic and environmental changes inferred from midge records (Diptera: Chironomidae, Chaoboridae, Ceratopogonidae) at Lake Berkut, southern Kola Peninsula, Russia
Bibliographic record
Abstract
A radiocarbon-dated sediment sequence from Lake Berkut in the southern part of the Kola Peninsula, northwest Russia, was investigated by means of midge analysis in order to reconstruct the Holocene climatic and environmental history of the region. Past mean July air temperatures at the study site and hypolimnetic oxygen contents of the lake water were inferred from chironomid-based transfer functions. The early Holocene ( c. 10 100-8400 cal. yr BP) is characterized by summer temperatures and hypolimnetic oxygen concentrations broadly similar to present-day conditions. The midge records give evidence of a lake-level fall at c. 7000 cal. yr BP, resulting in weakened thermal stratification of the lake water, and improvement of the hypolimnetic oxygen conditions. After c. 4000 cal. yr BP midge assemblages suggest a lake-level rise related to increased effective moisture. A secondary mid-Holocene climatic optimum with inferred mean July air temperatures of c. 12.1° C was recorded between 6000 and 4400 cal. yr BP, followed by minimum values (c. 11.3°C) between 3500 and 1500 cal. yr BP, accompanied by the onset of natural acidification of the lake. The late-Holocene midge assemblages suggest weakly acidic conditions, low hypolimnetic oxygen contents and a general warming trend during the last c. 1500 years, although paludification and natural acidification may have influenced the temperature reconstruction at this stage. However, the modern chironomid-inferred mean July air temperature (12.5°C) is consistent with meteorological data from a nearby station. In general, the midge records reflect relatively warm and moist conditions at Lake Berkut before c. 7000 cal. yr BP, a relatively warm and dry climate at c. 7000-4000 cal. yr BP, and a shift to cooler and wetter climatic conditions in the region after c. 4000 cal. yr BP.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".