1 Factors Controlling the Net Ecosystem Production of Cryoconite on Western Himalayan Glaciers 1 2 Monica Sharma Shamurailatpam 1 , Jon Telling 2 , Jemma L Wadham 3,4,5 , AL. Ramanathan 1 , Chris Yates 5 , N 3 Janardhana Raju 1 4 1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India 5 2 School of Natural and Environmental Sciences, Newcastle University, Newcastle, UK 6 3 Centre for Arctic Gas Hydrate, Environment and Climate, UiT the Arctic University of Norway, Tromsø, 7 Norway 8 4 Centre for ice, Cryosphere, Carbon and Climate, UiT the Arctic University of Norway, Tromsø, Norway 9 5 School of Geographical Sciences, University of Bristol, Bristol, UK 10 Corresponding author email: monica.shamurai@gmail.com 11 12 Abstract: 13 In situ experiments were conducted to determine the Net Ecosystem Production (NEP) in cryoconite holes from 14 the surface of two glaciers (Patsio glacier and Chhota Shigri glacier) in the Western Himalaya during the melt 15 season from August to September 2019. The study aimed to gain an insight into the factors controlling microbial 16 activity on glacier surfaces in this region. A wide range of parameters, including sediment thickness, TOC %, TN 17 %, chlorophyll-a concentration, altitudinal position, and grain size of the cryoconite mineral particles were 18 considered as potential controlling factors. From redundancy analysis, the rate of Respiration observed in 19 cryoconite at Chhota Shigri glacier was predominantly explained by sediment thickness in cryoconite holes (37.1 20 % of the total variance, p < 0.05) with Photosynthesis largely explained by the chlorophyll-a content of the 21 sediment (39.6 %, p < 0.05). NEP was explained primarily by the TOC content and sediment thickness in 22 cryoconite holes (35.8 % and 22.1 % respectively, p < 0.05). The altitudinal position of the cryoconite is strongly 23 correlated with biological activity, suggesting that the stability of cryoconite holes was an important factor driving 24 primary productivity and respiration rate on the surface of Chhota Shigri glacier. We calculated that the number 25 of melt seasons required to accumulate organic carbon in thin sediment layers (<0.3 cm), based on our measured 26 NEP rates, ranged from 11 to 70 years, indicating that the organic carbon in cryoconite holes largely derives from 27 allochthonous inputs, such as elsewhere on the glacier surface. Phototrophic biomass in the same thin sediment 28 layer of cryoconite was estimated to take atleast 4 months to be produced in situ (with mean estimated time upto 29 1.7 ± 1.5 years). Organic matter accumulated inside the cryoconite holes both through allochthonous deposition 30