Variability in carbon uptake and (re)cycling in Antarctic cryptoendolithic microbial ecosystems demonstrated through radiocarbon analysis of organic biomarkers
Bibliographic record
Abstract
Abstract Cryptoendolithic lichens and cyanobacteria living in porous sandstone in the high‐elevation McMurdo Dry Valleys are purported to be among the slowest growing organisms on Earth with cycles of death and regrowth on the order of 10 3 –10 4 years. Here, organic biomarker and radiocarbon analysis were used to better constrain ages and carbon sources of cryptoendoliths in University Valley (UV; 1,800 m.a.s.l) and neighboring Farnell Valley (FV; 1,700 m.a.s.l). Δ 14 C was measured for membrane component phospholipid fatty acids (PLFA) and glycolipid fatty acids, as well as for total organic carbon (TOC). PLFA concentrations indicated viable cells comprised a minor (<0.5%) component of TOC. TOC Δ 14 C values ranged from −272‰ to −185‰ equivalent to calibrated ages of 1,100–2,550 years old. These ages may be the result of fractional preservation of biogenic carbon and/or sudden large‐scale community death and extended period(s) of inactivity prior to slow recolonization and incorporation of 14 C‐depleted fossil material. PLFA Δ 14 C values were generally more modern than the corresponding TOC and varied widely between sites; the FV PLFA Δ 14 C value (+40‰) was consistent with modern atmospheric CO 2 , while UV values ranged from −199‰ to −79‰ (calibrated ages of 1,665–610 years). The observed variability in PLFA Δ 14 C depletions is hypothesized to reflect variations in the extent of fixation of modern atmospheric CO 2 and the preservation and recycling of older organic carbon by the community in various stages of sandstone recolonization. PLFA profiles and microbial community compositions as determined by molecular genetic characterizations and microscopy differed between the two valleys (e.g., predominance of biomarker 18:2 [>50%] in FV compared to UV), representing microbial communities that may reflect distinct stages of sandstone recolonization and/or environmental conditions. It is thus proposed that Dry Valley cryptoendolithic microbial communities are faster growing than previously estimated.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".