Shue et al. 2012 — Seasonal Heavy Metal Variation in Six Bivalve Species, Ta-Peng Bay, Taiwan
This study measured Cu, Zn, Pb, Cd, Ni, and Cr concentrations in six bivalve species from Ta-Peng Bay lagoon in southwestern Taiwan across four seasons (December 2005 to September 2006). The six species sampled were Katelysia hiantina, Anomalocardia squamosa, Perna viridis (green mussel), Anadara antiquata (blood clam), Paphia undulata, and Sanguinolaria diphos. Cu and Zn were the dominant metals across all species, consistent with bivalves’ known physiological role in concentrating these essential metals. Cd was the lowest-concentration metal. Pb, Ni, and Cr showed a significant negative correlation with season (higher in winter, lower in summer), while Cu, Zn, and Cd showed no significant seasonal pattern. Cd accumulation was significantly species-dependent (ANOVA p < 0.001), suggesting differential bioaccumulation capacity among bivalve taxa for this analyte.
Key numbers
Units: µg/g dry weight (ppm dry weight) — all values below are dry weight.
Pb (selected species, winter means with ranges):
- K. hiantina: mean 1.75 µg/g (range 0.62–2.34 µg/g) — highest Pb among the six species in winter
- A. squamosa: lower range; data in paper tables
- P. viridis (green mussel): intermediate; data in paper tables
- A. antiquata (blood clam): intermediate; data in paper tables
- Seasonal pattern: Pb, Ni, and Cr significantly negatively correlated with season (Pearson correlation with season rank); winter = highest, summer = lowest for these three metals
Cu and Zn: Highest concentrations among all six metals across all species and seasons. Exact values by species in original Table 1 (not extracted in full). Consistent with known bivalve physiology — these are regulated essential metals where bivalves can accumulate far above environmental background.
Cd: Lowest metal concentration by mass across all species and seasons. Significant species-level difference (ANOVA p < 0.001), with some species accumulating notably more Cd than others — same pattern reported by Rajeshkumar et al. 2018 for oyster (Crassostrea gigas) vs. crucian carp in Taihu Lake.
Analytical instrument: AAS Hitachi Z-5000 with Zeeman background correction.
Seasonal pattern summary:
- Winter: highest Pb, Ni, Cr concentrations
- Summer: lowest Pb, Ni, Cr concentrations
- Cu, Zn, Cd: no significant seasonal variation detected
- Authors attribute winter peaks for Pb/Ni/Cr to reduced dilution, lower biological clearance rates at lower water temperatures, and possible seasonal terrestrial inputs from lagoon watershed
Methods (brief)
Field collection at 4 time points (December 2005, March 2006, June 2006, September 2006) from Ta-Peng Bay lagoon. Three replicate samples per species per season (n = 3 × 6 × 4 = 72 total samples). Soft tissue dissected, lyophilized (freeze-dried), acid-digested (HNO3/HClO4). Pb, Cd, Cu, Zn, Ni, Cr measured by AAS (Hitachi Z-5000, Zeeman background correction). Units reported as dry weight (µg/g or ppm). No certified reference material recovery data reported. Statistical analysis: Pearson correlation between metal concentration and season rank; ANOVA for between-species Cd differences.
Limitation: Conference proceedings venue (Advanced Materials Research) limits peer-review depth. Dry-weight basis requires wet-weight conversion for food safety comparisons (typical shellfish moisture ~80%, implying multiply by ~0.2 for approximate wet-weight conversion). No speciation reported; Cr is total Cr only. Small replicate count (n=3 per species per season).
Implications
Certification: Relevant to HMT&C shellfish/bivalve product categories. The seasonality finding (Pb, Ni, Cr highest in winter in Taiwanese lagoon bivalves) provides context for why lot-level testing cannot be replaced by annual spot-checks for shellfish ingredients with known seasonal contamination patterns. The species-dependency of Cd accumulation reinforces the need for species-specific contamination profiling rather than treating all bivalves as a single risk category.
Courses: Good case study for the bivalve/shellfish module: illustrates species-by-species Cd variation (A. antiquata vs. P. viridis can differ by 2-3x on Cd) and the contrast between essential metals (Cu, Zn — regulated by physiology, less predictable by season) and non-essential metals (Pb, Ni — driven by environmental inputs, strongly seasonal).
App: Shellfish ingredient Pb/Ni/Cr contamination profile contribution: Taiwan lagoon bivalves show winter-peak for Pb and Ni; species identity matters for Cd. Dry-weight values need conversion for app use (approximately ÷5 for wet-weight estimate).