Peat sequence diatoms from Kedarnath, Central Himalaya, used to reconstruct mid-late Holocene hydroclimatic conditions

Abstract

Diatoms preserved in peat can preserve valuable evidence of palaeoenvironmental changes due to their sensitivity to climatic changes and their crucial role in high productivity and nutrient cycling. We present total diatom concentrations and diatom community composition preserved in a high-altitude peat deposit located in the headwaters of the Mandakini River, Central Himalaya, India, to reconstruct the hydroclimatic conditions which prevailed during the mid-late Holocene. Since diatom productivity is associated with water table height/elevation, the high diatom concentrations during ∼5656–5307 cal yr BP, ∼4310–4264 cal yr BP, ∼3515–3024 cal yr BP and ∼ 1679–988 cal yr BP are inferred to have been periods of relatively high water table, denoting improved hydrological conditions. Conversely, low concentrations of diatoms occurred during ∼8077–5866 cal yr BP, ∼5263–4332 cal yr BP, ∼4241–3570 cal yr BP, ∼2970–1715 cal yr BP, and ∼ 697–370 cal yr BP. The temporal changes in the diatom suggest stressed hydrological conditions. The water table fluctuations inferred from diatom concentration variability show a positive correlation with the Indian summer monsoon (ISM) intensity and a negative correlation with the westerlies. The observed low concentrations of diatoms was associated with the relatively dry climatic conditions, which is detrimental to the peat environment and therefore suggests the need for in-situ data monitoring for the Indian peat deposits. As dry conditions can result in the deterioration of peat deposits, which may prove a significant source of atmospheric carbon dioxide in a changing climate, their conservation strategies will help limit carbon emissions.