Fate of dissolved organic matter across the permafrost–nearshore water continuum: role of the intertidal sediments
Bibliographic record
Abstract
Abstract. Increasing rates of coastal erosion and permafrost thaw along the Arctic coastline represent a major lateral source of dissolved organic matter (DOM) to the coastal environment, where it can meet multiple fates depending on its origin and composition. Along the (ground)water flow path, Iron (Fe)-hydroxides play an important role in the retention of terrestrial organic matter, but its role on DOM released from coastal thawing permafrost specifically remains poorly understood. To address this gap, we sampled permafrost meltwater, beach groundwater, and seawater samples from several coastal bluffs transects up to 2 km from the shoreline. Across the salinity gradient – from permafrost meltwater to nearshore waters - we found that dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) concentrations decreased drastically, indicating significant removal processes along this continuum. Optical indices (aCDOM350, SUVA254, HIX) reflected changes in DOM composition and aromaticity, suggesting microbial degradation and mineral-organic interactions occur to transform DOM. Furthermore, a PARAFAC analysis of fluorescent DOM indicated that permafrost-derived DOM had a high molecular weight (HMW), humic, and terrigenous origin, while coastal ocean-derived FDOM was protein-rich, low molecular weight (LMW), and from microbial (autochthonous) origin. The optical signature of permafrost meltwater faded along the permafrost-nearshore water continuum. Controlled experiments with excess Fe2+ along constant oxygen bubbling showed a rapid (within 6 hours) and major decrease in DOC and CDOM, suggesting interaction with reactive Fe-hydroxides, acting as a permanent or temporary trap of permafrost-derived DOM. Overall, our findings highlight the role of intertidal and nearshore zones where subsurface flows regulate the persistence and reactivity of terrestrial DOM as it transits from permafrost to marine environments in the Arctic.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
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".