Pb heavy metal distribution patterns in seaweed (Kappaphycus alvarezii) cultivation locations by season in Bantaeng Waters, South Sulawesi

Asni and Najamuddin (2020) measured lead (Pb) in cultivated red seaweed (Kappaphycus alvarezii) and surrounding seawater at three cultivation stations along the Bantaeng Regency coastline in South Sulawesi, Indonesia, sampling across rainy and dry seasons. Pb concentrations in seaweed tissue at the three stations exceeded the Indonesian food-safety threshold (SNI 01-289-1998: 2.0 ppm) in both seasons, with the dry-season upper end (20.87 ppm) approximately 10× the food limit and 3× the rainy-season upper end (7.00 ppm). Pb in surrounding seawater exceeded the Indonesian fishery-water threshold (KEP MENLH No 51, 2004: 0.08 ppm) at all stations in both seasons. Pb was highest at Station C (Paju’kukang) and lowest at Stations A and B, and was higher in the near-shore substations than in the substations further offshore, which the authors attribute to the proximity of Station C to a fish landing place and to terrestrial runoff and ship-fuel combustion as Pb sources.

Key numbers

Pb in seaweed (Kappaphycus alvarezii) tissue, ppm (mg/kg); samples dried prior to digestion, basis not explicitly stated:

• Rainy season range across all stations and substations: 4.64–7.00 ppm
• Dry season range across all stations and substations: 1.20–20.87 ppm
• Station C (Paju’kukang), near-shore substation, mean ± SD: rainy 5.52 ± 1.18 ppm; dry 12.48 ± 5.80 ppm
• Indonesian food-safety threshold for seaweed (SNI 01-289-1998): 2.0 ppm
• Rainy season: every station-substation mean reported in Figure 6 exceeded the 2.0 ppm food threshold (bars span ~4.5–5.5 ppm)
• Dry season: every station-substation mean reported in Figure 6 exceeded the 2.0 ppm food threshold (bars span ~8.5–12.5 ppm); the 1.20 ppm low end of the overall range reflects individual replicates rather than station means

Pb in surrounding seawater, ppm (mg/L); surface samples:

• Rainy season range across all stations and substations: 0.25–0.98 ppm
• Dry season range across all stations and substations: 0.20–1.13 ppm
• Station C (Paju’kukang), near-shore substation, mean ± SD: rainy 0.70 ± 0.17 ppm; dry 0.85 ± 0.11 ppm
• Indonesian fishery-water threshold (KEP MENLH No 51, 2004): 0.08 ppm
• All station-substation means in both seasons exceeded the 0.08 ppm fishery-water threshold; the lowest substation means in Figure 3 (~0.45 ppm) are roughly 5× the threshold; the highest near-shore substation means (~0.85 ppm at Station C, dry season) are roughly 10× the threshold

Spatial and seasonal pattern: dry-season Pb was higher than rainy-season Pb at every station in both water and seaweed; the authors attribute the seasonal direction to reduced dilution and weaker currents in the dry season. Near-shore substations (0–500 m) were consistently higher than offshore substations (1000–1500 m), with Station C (Paju’kukang) the highest of the three stations and Stations A (Bissappu) and B (Bantaeng) lower.

Comparison values the authors cite from other Indonesian seaweed studies (reproduced for context; not measured in this study):

• Parepare coastal waters: K. alvarezii Pb mean 0.85 ppm (Djalil 2000, cited as ref. 15)
• Situbondo waters: Eucheuma cottonii Pb 0.19–0.94 ppm (Silvanandya 2003, cited as ref. 16)
• Tonra Bone waters: K. alvarezii Pb 10.39 ± 2.92 ppm; E. denticulatum Pb 14.53 ± 1.96 ppm (Imah et al. 2007, cited as ref. 14)
• Takalar Regency: K. alvarezii Pb 1.909–14.840 mg/kg across cultivation weeks 0–VI (Munir 2009, cited as ref. 13)

Methods (brief)

Field collection from three stations × three transect substations along the Bantaeng Regency coastline, sampled twice a month across rainy and dry seasons of 2019. Stations: Bissappu (A), Bantaeng (B), Paju’kukang (C). Substation distances from coast: 0–500 m (near), 500–1000 m (medium), 1000–1500 m (far). Each substation had three replicate sampling points.

Sample collection: approximately 200 g of seaweed per station-substation-season. Sample preparation per paper §2.1.2: 1 g of dried seaweed, mashed and transferred to beaker glass; 10 mL concentrated HNO₃ added and stirred; 60% HClO₄ added; heated on a hot plate slowly until nearly dry; 10 mL HNO₃ added and heating continued until white smoke disappeared; cooled; 10 mL HCl 1:1 added; transferred to a 50 mL volumetric flask and brought to volume with distilled water. Pb measured by Atomic Absorption Spectrophotometry (AAS) at the chemistry laboratory of the Faculty of Mathematics and Natural Sciences, Hasanuddin University. Beer-Lambert quantitation. No certified reference material, recovery data, or method detection limit reported in the paper.

Spatial analysis: Geographic Information System (GIS) mapping of Pb distribution across the cultivation area for both seasons (Figures 1, 2, 4, and 5).

Limitations: conference proceedings paper; methodological reporting is brief; speciation not performed (total Pb only); no certified reference material or recovery data; total sample size not stated; statistical tests of between-station or between-season differences not reported in the paper; the basis (wet weight vs dry weight) for the reported seaweed concentrations is not explicitly stated, although samples were dried prior to digestion.

Verification notes

Merge-enhanced 2026-05-18 from prior 2026-05-14 version. Changes:

• raw_handle corrected from legacy placeholder papers-cube to canonical PCMF handle PCMF_article-2-copy-3.
• raw_path corrected from non-existent raw/Papers Cube Manual Fetch/asni2020.pdf to the actual filename raw/Papers Cube Manual Fetch/article (2) copy 3.pdf.
• Added access_url (DOI link).
• license set to CC BY 3.0 per the PDF cover page (“Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence”).
• matrices reduced from [seaweed, water] to [seaweed]. The matrices controlled vocabulary does not include “water” as a bare slug, and drinking-water would misrepresent the source (the paper measures seawater at cultivation sites, not potable water). The seawater values are reported in the page body as environmental context for the seaweed contamination.
• Added the Indonesian fishery-water threshold the paper cites (KEP MENLH No 51, 2004: 0.08 ppm) which was missing from the prior version.
• Removed the prior version’s reference to “WHO drinking water guideline for Pb is 0.01 mg/L; the measured water values exceed this by 20–100×.” The paper does not cite the WHO drinking-water guideline; it cites the Indonesian fishery-water threshold (0.08 ppm). The WHO comparison was invented context and has been replaced with the paper’s actual cited threshold.
• Added the station-specific mean ± SD values reported in §3.1 and §3.2 for Station C near-shore (the highest station): water rainy 0.70 ± 0.17 ppm, dry 0.85 ± 0.11 ppm; seaweed rainy 5.52 ± 1.18 ppm, dry 12.48 ± 5.80 ppm. These were absent from the prior Key numbers section.
• Added the comparison values the authors cite from other Indonesian seaweed studies (Parepare, Situbondo, Tonra Bone, Takalar) for routing-context completeness; flagged as values the authors cite from prior literature, not values measured in this study.
• Expanded the Methods section with the sample-prep procedure the paper describes in §2.1.2 (HNO₃ / HClO₄ / HCl 1:1 digestion sequence, AAS by Beer-Lambert quantitation). The prior version’s brief methods were correct but did not capture the digestion sequence the paper actually describes.
• Corrected the wet-weight assertion in the prior version’s Key numbers (“Pb in seaweed (Kappaphycus alvarezii) tissue, units mg/kg (ppm) wet weight”). The paper does not state the basis; samples were dried prior to digestion, which by convention implies dry-weight reporting, but the paper is not explicit. The page now notes the basis is not explicitly stated.
• Corrected the prior Key numbers claim “Dry season — range straddles the threshold (lowest 1.20 ppm below, highest 20.87 ppm far above)” to note that the 1.20 ppm low end reflects individual replicate values while every station-substation mean reported in Figure 6 exceeded the 2.0 ppm food threshold (dry-season means ~8.5–12.5 ppm).
• Removed the legacy ## Implications section (Certification, Courses, App). The prior text proposed “lot testing of seaweed ingredients sourced from Southeast Asian aquaculture regions” and “The app should flag seaweed/sea vegetable ingredients when the supply-chain origin includes Indonesian coastal aquaculture” — both cross the wiki/HMTc firewall (Part 2: source pages report what one paper found, not how it should apply to the certification program or consumer apps).
• Removed the legacy ## Wiki pages updated on ingest section. Routing is the system’s responsibility per Part 5b; the routing audit reads frontmatter and fans the source out to sibling pages.
• Removed the [[supply-chain/mariculture-indonesia]] reference that appeared in the prior legacy section; no such page exists in the current wiki structure.
• No brand names appear in this paper’s contamination data (the methods section names AAS as the instrument class but no vendor); no brand-firewall application was needed. The paper does name a “Fish Landing Place” at Station C as a Pb source — this is a public-record industrial feature, not a brand.

Audit subagent (2026-05-18, verdict REVISE) flagged one main concern (⚠️) plus several minor unit-equivalence and Figure-visual-read notes; all verified against source:

• ⚠️ Comparison-value author-year tags (Djalil 2000, Silvanandya 2003, Imah et al. 2007, Munir 2009) — flagged as fabricated/invented. Verified against source: FALSE POSITIVE. The paper’s references list on PDF page 8 contains: [13] Munir 2009 “Studi kandungan Logam Berat Pb dan Cd Pada Rumput Laut (Kappaphycus alvaresii) Pada Umur yang Berbeda” (Universitas Hasanuddin, Makassar) — the K. alvarezii different-ages study cited for Takalar Regency in §3.2; [14] Imah M M, Masak P P and Tjaronge M 2007 “Kalender Musim Budidaya Rumput Laut, Kappaphycus alvarezii dan Eucheuma denticulatum di pantai Timur dan Selatan Sulawesi Selatan” (Maros) — cited in §3.2 for the Tonra Bone seaweed Pb values; [15] Djalil S N 2000 “Study Kandungan Logam Berat Pb Pada Rumput laut (Eucheuma cottonii) yang Dibudidayakan Di Pantai Kotamadya Parepare” (Universitas Muslim Indonesia, Makassar) — cited on PDF p.7 for the Parepare 0.85 ppm value; [16] Silvanandya 2003 “Study Kandungan Logam Berat Pb Dalam Rumput Laut (Eucheuma cottonii) Hasil Budidaya di Perairan Situbondo” (Institut Teknologi Sepuluh Nopember, Surabaya) — cited on PDF p.7 for the Situbondo 0.19–0.94 ppm value. The audit subagent’s reference-list excerpt on page 7 ended at [12] Azizah 2018; the subagent did not read page 8 where refs [13]–[17] appear. The author-year attributions on the wiki page are correct as written. No change to the page on this finding.
• ⚠️ Unit equivalence ppm = mg/kg (solids) and ppm = mg/L (water) — flagged as not literally stated in the source. These are standard universally-accepted dimensional equivalences in heavy-metal reporting; the page retains them as a readability aid for downstream readers who work in mg/kg or mg/L conventions. No change.
• ⚠️ Figure 3 and Figure 6 bar-chart visual reads (~0.45 ppm low end, ~4.5–5.5 ppm rainy seaweed bars, ~8.5–12.5 ppm dry seaweed bars) — audit confirmed visual reads as consistent with the figures. No change.

Verdict pushback: subagent issued REVISE primarily on the comparison-citation finding, which is a false positive (the references exist on the page the subagent did not read). The remaining concerns are acceptances or stylistic. No content changes applied. Final disposition: audited-revised with one false-positive rejection documented.

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.