Ortega-Flores et al. 2023 - Mexican Sargassum arsenic

Ortega-Flores et al. measured inorganic arsenic in stranded holopelagic Sargassum biomass from the Mexican Caribbean over a full seasonal cycle. The same sample set had total arsenic reported previously, and this paper adds iAs by morphotype and season. The values are raw stranded biomass on a dry-weight basis, not washed or processed seaweed food.

Key numbers

The abstract and conclusion summarize the full dataset as iAs 12.7 to 62.9 mg kg-1 dw, representing 14.1% to 81.7% of TotAs. The introduction states that the same samples had previously reported TotAs 9.5 to 255 mg kg-1 dw.

Section 3.1 reports iAs by morphotype in mg kg-1 dw:

Section 3.1 also reports seasonal iAs summaries in mg kg-1 dw:

Section 3.2 reports annual mean TotAs of 91.8 mg kg-1 dw for S. natans VIII, 90.7 mg kg-1 dw for S. fluitans, and 68.2 mg kg-1 dw for S. natans I. The highest TotAs concentrations occurred during the rainy season, with August values above 200 mg kg-1 dw for S. natans VIII and S. fluitans.

The iAs proportion increased over the study period. Section 3.2 reports iAs:TotAs ranges of 14-32% for June-September and 56-80% for March-May. It also states that iAs proportions remained below 40% in samples with TotAs above 100 mg kg-1 dw, whereas iAs proportions over 50% occurred in samples with TotAs below 50 mg kg-1 dw.

Table 1 summarizes the present study row as stranded Mexican Caribbean S. fluitans, S. natans I, and S. natans VIII with iAs 12.7-62.9 mg kg-1, TotAs 21.7-255 mg kg-1, and iAs:TotAs 14-82%.

Methods (brief)

Samples were collected monthly from June 2018 to May 2019 at Puerto Morelos, Quintana Roo, Mexico. Raw stranded biomass was collected from ten 0.5 x 0.5 m² quadrats along a 50 m transect, classified into the three morphotypes, visually cleaned of sand by hand, oven-dried at 60°C for 24 h, crushed with an agate mortar, and stored for analysis. TotAs was measured by HG-AAS in the earlier Ortega-Flores et al. 2022 work, with IAEA-392 algae reference-material recovery greater than 90% and As LoD 0.5 mg kg-1. For iAs, dried ground biomass was extracted in ultrapure water under sonication for 30 min at a 1:100 sample/water mass ratio, centrifuged, and analyzed by anodic stripping voltammetry using standard additions of As(V). The iAs method LoD was 0.2 µg L-1, precision was ~6%, NMIJ CRM 7405-b Sargassum fusiforme was used for accuracy control, and each extract was analyzed in triplicate.

Implications

This source is high-value inorganic-arsenic evidence for raw stranded Sargassum biomass that may enter seaweed valorisation streams. It should not be treated as a ready-to-eat seaweed food result without preserving the raw stranded-biomass matrix and dry-weight basis. Downstream extraction should keep TotAs and iAs distinct, and should preserve the morphotype and seasonal stratification where row fit permits.

Wiki pages this source may touch

• seaweed-kelp-foods
• supplements-algae-seaweed-based
• seaweed
• arsenic-total
• arsenic-inorganic

Verification notes

• Identity checks before writing found no existing source page for DOI 10.1016/j.aquabot.2023.103674, raw handle MFK_103189, or cite key ortega-flores2023-mexican-sargassum-arsenic.
• All Key numbers were rechecked against /tmp/hmi-seaweed-008.txt, extracted with pdftotext -layout, especially Sections 2.1, 2.2, 3.1, 3.2, the conclusion, and Table 1.
• Source-side inconsistency: the abstract/conclusion and Table 1 give the overall iAs range as 12.7-62.9 mg kg-1 dw, but Section 3.1 gives morphotype/season ranges spanning 11.9-71.5 mg kg-1 dw. Both are reported rather than reconciled.
• Speciation check: TotAs and iAs are kept separate. The paper states the iAs method indicates As(V) and not As(III); no total arsenic value is substituted for inorganic arsenic.
• Units and basis are preserved as mg kg-1 dw, %, µg L-1, and mg kg-1; no conversions were performed.
• Evidence tier A reflects peer-reviewed primary iAs data with n=101, seasonal/morphotype structure, reference material checks, detection limits, and triplicate extract measurements.
• Brand firewall: no sampled brands are reported; company names in the discussion are not attached to contamination values and are not used in Key numbers.

Page history

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