Ma et al. 2018 - total and inorganic arsenic contents in seaweeds

Ma and colleagues reviewed published total arsenic and inorganic arsenic measurements in seaweeds, grouping the literature by Rhodophyta, Phaeophyta, and Chlorophyta. This is secondary evidence: it compiles prior studies and does not add new sample measurements. The values below are useful for seaweed/kelp food and algae/seaweed supplement context, but downstream occurrence pooling should trace and de-duplicate the underlying primary studies.

Key numbers

All concentration values below are reported by the review as mg kg-1 DW; no unit conversion was performed. The review states that records were collected from published studies available up to June 2017 and that the same seaweed species collected from different geographic zones was treated as a different datum.

Table 1 summary by phylum:

The abstract and Section 3 report that tAs in the top 10 Phaeophyta species is over 100 mg kg-1 DW, while the top 7 Rhodophyta species range from 20 to 50 mg kg-1 DW and the top 3 Chlorophyta species range from 10 to 15 mg kg-1 DW. Section 3.2 reports that Phaeophyta iAs is significantly higher than Rhodophyta and Chlorophyta (P<0.05), while Rhodophyta and Chlorophyta do not differ significantly (P>0.5).

Table 2 high-tAs species:

The Table 2 footnote defines high-tAs species thresholds as above 100, 20, and 10 mg kg-1 DW for Phaeophyta, Rhodophyta, and Chlorophyta, respectively.

Table 3 high-iAs species:

The Table 3 footnote defines high-iAs species thresholds as above 50, 1, and 0.3 mg kg-1 DW for Phaeophyta, Rhodophyta, and Chlorophyta, respectively; the extracted footnote prints AsT in this sentence, but the table title and body are for inorganic arsenic.

Additional source-reported context:

• The review states that typical ocean-water arsenic is 1 to 3 µg l-1, with an average of 1.7 μg l-1.
• It states that seaweed tAs levels are approximately 1,000-50,000 times higher than ocean water, depending on species.
• It reports that most species of Rhodophyta, Phaeophyta, and Chlorophyta have tAs below 30, 100, and 20 mg kg-1 DW, respectively.
• It cites one Sargassum sinicola case near Gulf of California hydrothermal venting as above 600 mg kg-1; this is environmental context from a cited study, not a Table 1-3 occurrence summary row.
• It reports that arsenosugars make up >85% of soluble arsenic in most species, citing Rose et al. 2007 and Kalia and Khambholja 2015.

Methods (brief)

This is a peer-reviewed literature review, not a primary measurement study. The authors compiled published seaweed arsenic studies available up to June 2017, summarized total and inorganic arsenic by phylum, and listed high-tAs and high-iAs species with the methodology and cited primary reference where available. Samples of the same species from different geographic zones were treated as separate data points so that each species-zone record corresponded to one datum. Analytical methods in the compiled studies include AFS, ICP-MS, HPLC-ICP-MS, FI-HG-AAS, AAS, GS, HG-AFS, ICP-OES, and INAA.

Implications

This source supports seaweed/kelp food and algae/seaweed supplement context by identifying phylum- and species-level patterns in total arsenic and inorganic arsenic. The review’s most relevant routing signal is that Phaeophyta values, especially hijiki, Sargassum piluliferum, Laminaria spp., and several brown algae, carry much higher secondary-summary iAs than Rhodophyta or Chlorophyta. Because the paper aggregates prior literature and several underlying primary sources are separately ingested in the wiki, these values should not be pooled as independent occurrence measurements without source-level de-duplication.

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.aquaculture.2018.07.040, raw handle MFK_ma2018, title text, or cite key ma2018-seaweed-arsenic-contents.
• Text was extracted to /tmp/hmi-seaweed-046.txt with pdftotext -layout; the title page, abstract, body, Tables 1-3, and figure legend were readable.
• All Key numbers were checked against /tmp/hmi-seaweed-046.txt, especially Tables 1-3 at the end of the extracted text. The Gayralia oxysperma zone is recorded as “not reported in extracted table” because the table text layer prints 12.68 where the zone column should be.
• Units and bases are preserved as mg kg-1 DW, %, µg l-1, and μg l-1; no conversion to ppb or wet-weight basis was performed.
• Speciation check: total arsenic (AsT/tAs), inorganic arsenic (AsI/iAs), arsenosugars, As(III), and As(V) are kept distinct. No total arsenic value is promoted to inorganic arsenic.
• Brand firewall: the review names no consumer brands. Species names, zones, analytical methods, and cited primary-study authors are retained as scientific context.
• Missing-slug check: no missing product or ingredient slug blockers. Exact seaweed species and phylum names remain in prose/tables while frontmatter uses broad seaweed/kelp and algae/seaweed supplement slugs.
• Evidence-fitness note: this page is secondary literature context. The sample_n field is null because the review does not report primary samples; n values in Table 1 are compiled literature records and should not be treated as primary sample counts.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.