Factors controlling the net ecosystem production of cryoconite on Western Himalayan glaciers

Abstract

In situ experiments were conducted to determine the Net Ecosystem Production (NEP) in cryoconite holes from the surface of two glaciers (Patsio glacier and Chhota Shigri glacier) in the Western Himalaya during the melt season from August to September 2019. The study aimed to gain an insight into the factors controlling microbial activity on glacier surfaces in this region. A wide range of parameters, including sediment thickness, TOC %, TN %, chlorophyll-a concentration, altitudinal position, and grain size of the cryoconite mineral particles were considered as potential controlling factors. From redundancy analysis, the rate of Respiration observed in cryoconite at Chhota Shigri glacier was predominantly explained by sediment thickness in cryoconite holes (37.1 % of the total variance, p < 0.05) with Photosynthesis largely explained by the chlorophyll-a content of the sediment (39.6 %, p < 0.05). NEP was explained primarily by the TOC content and sediment thickness in cryoconite holes (35.8 % and 22.1 % respectively, p < 0.05). The altitudinal position of the cryoconite is strongly correlated with biological activity, suggesting that the stability of cryoconite holes was an important factor driving primary productivity and respiration rate on the surface of Chhota Shigri glacier. We calculated that the number of melt seasons required to accumulate organic carbon in thin sediment layers (<0.3 cm), based on our measured NEP rates, ranged from 11 to 70 years, indicating that the organic carbon in cryoconite holes largely derives from allochthonous inputs, such as elsewhere on the glacier surface. Phototrophic biomass in the same thin sediment layer of cryoconite was estimated to take atleast 4 months to be produced in situ (with mean estimated time upto 1.7 ± 1.5 years). Organic matter accumulated inside the cryoconite holes both through allochthonous deposition 2 and via biological activity on the glacier surface in these areas may have the potential to export dissolved organic matter and associated nutrients to downstream ecosystems. Given the importance of Himalayan glaciers as a vital water source for millions of people downstream, this study highlights the need for further investigation in aspects of the quantification of in situ produced organic matter and its impact on supraglacial melting in the Himalaya.

A preliminary investigation of microbial communities on the Athabasca Glacier within deposited organic matter

“…69 However, the accumulation of organic pollutants, as shown in this study, represents an important source of carbon and therefore may have a significant impact on microbial communities of these ecosystems. 70,71…”

“…69 However, the accumulation of organic pollutants, as shown in this study, represents an important source of carbon and therefore may have a signicant impact on microbial communities of these ecosystems. 70,71 3.4 Nutrient proling of glacier samples Amounts of total organic carbon (TOC) varied among samples of glacier materials (Table 2). Surface sediment had the greatest TOC percentage (16.0%), with cryoconite holes having a similar percentage of 13.7%.…”

The distribution and drivers of microbial pigments in the cryoconite of four Tibetan glaciers

“…We compared the chlorophyll a concentration from the present study with those obtained in the Longyearbreen glacier, Arctic (Langford et al, 2014) and glaciers of the Western Himalayans (Shamurailatpam et al, 2023). Chlorophyll a concentration ranges between 0.64 and 2.68 μg g −1 in Longyearbreen Glacier, which is within the same range as our findings.…”

“…In comparison, chlorophyll a concentration in the Western Himalayan Chhota glaciers (Altitude 4562-4789 m) and Patsio glaciers (5050 m) ranges from 3.60 to 12.6 μg g À1 , which are comparable to that in QY and TGL, but higher than that in PL and JMYZ. The varied chlorophyll a concentration might be explained by the lower temperature of the Chhota and Patsio glaciers (Shamurailatpam et al, 2023), as temperature and chlorophyll a concentration are negatively correlated (Figure 3).…”