Chemical form of arsenic in marine macroalgae

Overview

Morita and Shibata reviewed water-soluble and lipid-soluble arsenic compounds in marine macroalgae and added a HPLC/ICP/MS species-map table for Japanese algae. The paper is useful speciation context for seaweed because it separates total arsenic, lipid-phase arsenic, water-phase arsenic, arsenosugars, arsenate, and unidentified arsenicals. It should not be read as a modern market-occurrence survey, and the symbol-coded species map should not be converted into exact inorganic-arsenic concentrations.

Key numbers

The paper reports algae arsenic concentrations in µg/g dry in Table 2 unless a row is explicitly marked wet base; no unit conversion was performed. Table 2 covers 38 marine algae and one higher plant comparator, with total arsenic, lipid-phase arsenic, water-phase arsenic, and symbol-coded arsenic species.

Table 2 numeric ranges by phylum, excluding the rows footnoted as wet base:

Wet-base purification-study rows in Table 2:

The Table 2 species symbols are semi-quantitative: the paper defines free marks as 0.1-1 µg/g As (dry), 1-10 µg/g As, and more than 10 µg/g As; open circles mark compounds identified by purification studies, and a double circle marks the most abundant species. Those symbols are retained as qualitative speciation context rather than exact concentration values.

Other source-stated figures and findings:

• The introduction states that brown algae contain arsenic at “several tens of ppm” on a dry-weight basis, while green and red algae contain “several ppm” on a dry-weight basis.
• The paper estimates daily arsenic intake through marine algae ingestion in the average Japanese diet at about 100 µg/day.
• The review cites Lunde’s finding that 97% of arsenic in Laminaria hyperborea was organic arsenic and Sanders’s examination of 56 algae species, where arsenic was organic at 53% in Chlorophyceae, 78% in Phaeophyceae, and 57% in Rhodophyceae.
• For Hizikia fusiforme, the paper states that the major methanol-extract arsenical was inorganic arsenate (50%) together with compound As-IV. It also states that inorganic arsenic in H. fusiforme was found only in the surface layer, while arsenic-ribofuranosides were distributed more evenly in tissue.
• For Sphaerotrichia divaricata, the text states a typical arsenic concentration of about 2 ppm on a wet-weight basis; about 25% of methanol-extracted arsenic was lipid soluble and the remainder water soluble.
• For Undaria pinnatifida, the lipid-soluble arsenic was identified as a diacylated derivative of compound As-II, and the text states that 25% of arsenic was in lipid-soluble form.

Methods (brief)

This is a peer-reviewed review article with an embedded HPLC/ICP/MS characterization table. Table 1 lists marine algae collected from Choshi, Chiba Prefecture on May 26, 1987, Hiraiso, Nakaminato, Ibaraki Prefecture on June 17, 1987, and Inamuragasaki, Kamakura, Kanagawa Prefecture on July 11, 1987; species identifications were performed by named phycologists. The review also summarizes prior purification work using methanol extraction, Sephadex/DEAE/CM chromatography, HPLC-ICP methods, NMR, GC/MS, and radiolabel assimilation studies. The PDF itself does not print a DOI; the DOI in source metadata was verified from external bibliographic metadata for the same title, authors, journal, volume, pages, and year.

Implications

This source is a historical speciation anchor for seaweed arsenic. It supports the wiki rule that total arsenic in seaweed cannot be treated as inorganic arsenic and that organic arsenosugars, lipid-soluble arsenicals, arsenate, DMA, and unidentified species must remain separate. For occurrence pooling, downstream work should prefer the primary papers behind the review and use this page as context unless a later extraction pass explicitly models Table 2’s semi-quantitative species symbols.

Related evidence

• Seaweed/kelp foods (nori, wakame, kombu, dulse — as food products)
• Ingredient class — algae/seaweed-based
• Seaweed
• Arsenic, Total
• Arsenic, Inorganic

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.