Arsenic cycling in freshwater phytoplankton and zooplankton cultures
Bibliographic record
Abstract
Environmental context Understanding how arsenic is changed from toxic to non-toxic chemical forms in lakes and rivers is important in understanding the overall risk from arsenic. Freshwater plankton exposed in laboratory cultures to different sources of toxic inorganic arsenate formed arsenosugars, but at higher exposure levels, in water and through contaminated sediment, inorganic arsenate remained unchanged. In arsenic-contaminated freshwater bodies, plankton may provide a source of toxic inorganic arsenic to consumers. Abstract Freshwater phytoplankton (Chlamydomonas) and zooplankton (Daphnia pulex) were exposed to arsenic to trace the arsenic transformations and the formation of organoarsenic compounds at the base of the freshwater food chain. Plankton were cultured in artificial lake water, and exposed to arsenic through several pathways, hypothesised to be the main exposure sources: through water, food and contaminated sediments. High performance liquid chromatography–inductively coupled plasma–mass spectrometry and X-ray absorption spectroscopy were used to determine arsenic speciation in the studied organisms, and X-ray fluorescence mapping was used to locate the arsenic in a single Daphnia specimen. The results show that the formation of methylated arsenic compounds and arsenosugars by the zooplankton organisms was independent of the exposure route, but instead dependent on arsenic concentration in the environment. Specifically, organoarsenic compounds were dominant in extracts of Daphnia organisms exposed to low arsenic concentrations through water at 10 µg L–1 (67 %), and through contaminated food (75 %), but inorganic arsenic was dominant in Daphnia exposed to high arsenic concentrations, including contaminated sediments. Phytoplankton cultures contained variable amounts of arsenosugars, but on average the dominant compound in phytoplankton was inorganic arsenic. The main implications of the present study for understanding arsenic cycling in the freshwater plankton community are that arsenosugars are formed at possibly both the phytoplankton and zooplankton trophic levels; and that higher arsenic loads in plankton correspond to higher inorganic arsenic concentrations, which could indicate a saturation of the arsenic methylation process by plankton organisms.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".