Key Concerns
Mercury is toxic to aquatic organisms (WHO 1989). A 28d-EC50 for vegetation damage to the Canadian pondweed (Elodea Canadensis) exposed to mercuric chloride was 7.4 mg/l, with a 50% inhibition of photosynthesis reported following exposure to 0.8 mg/l for 24 hours (Brown and Rattigan 1979). A 14d-EC50 for vegetation damage to duckweed (Lemna minor) was 1.0 mg/l (Brown and Rattigan 1979).
The freshwater invertebrates which are most sensitive to mercury are daphnids (WHO 1989), with acute LC50 values for inorganic mercury ranging from 0.0018 to 4.89 mg/l (Biesinger and Christensen 1972; Baudouin and Scoppa 1974; Canton and Adema 1978; Khangarot and Ray 1987). Acute LC50 values for other freshwater invertebrates range from 0.02 to 7.39 mg/l (WHO 1989).
The fish species most sensitive to mercury was rainbow trout (Oncorhynchus mykiss) with 96h-LC50 values ranging from 0.033 to 0.28 mg/l (MacLeod and Pessah 1973; Hale 1977). Acute LC50 values for other freshwater fish exposed to inorganic mercury ranged from 0.075 to 2 mg/l (WHO 1989). Corresponding LC50 values for fish exposed to organic mercury ranged from 0.004 to 0.123 mg/l (Alabaster 1969; MacLeod and Pessah 1973; Roales and Perlmutter 1974; Wobeser 1975; McKim et al. 1976).
Additional Comments
Mercury normally binds to soil particles, reducing its availability to plants (WHO 1989). Plants are generally insensitive to the effects of mercury compounds. Methyl mercury is more toxic to terrestrial organisms than aryl or inorganic mercury.
| Habitat/ Ecosystem Type | Critical Load/ Level | Status | Reliability | Indication of exceedance | Reference |
|---|---|---|---|---|---|
| Freshwaters |
1 µg/l |
Environmental Quality Standard (Statutory) | quite reliable i.e. the results of some studies are comparable |
Total soluble and insoluble mercury and its compounds, annual mean in inland waters. |
1150 |