Mercury :: freshwater ecosystems

Ecosystems: 

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.

Environmental limit: 

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

References: 

Baudouin, M. F.; Scoppa, P 1974 Acute toxicity of various metals to freshwater zooplankton Bulletin of Environmental Contamination and Toxicology 745-751
Biesinger, K. E.; Christensen, G. M. 1972 Effects of various metals on survival, growth, reporduction, and metabolism of Daphnia magna Journal of the Fisheries Research Board of Canada 1691-1700
Brown, B. T.; Rattigan, B. M. 1979 Toxicity of soluble copper and other metal ions to Elodea canadensis. Environmental Pollution 303-314
Hale, J. G. 1977 Toxicity of metal mining wastes Bulletin of Environmental Contamination and Toxicology 66-73
Khangarot, B. S.; Ray, P. K. 1987 Sensitivity of toad tadpoles, Bufo melanostictus (Schneider), to heavy metals Bulletin of Environmental Contamination and Toxicology 523-527
MacLeod, J. C.; Pessah, E 1973 Temperature effects on mercury accumulation, toxicity and metabolism rate in rainbow trout Journal of the Fisheries Research Board of Canada 485-492
McKim, J. M.; Olson, G. F.; Holcombe, G. W.; Hunt, C. P. 1976 Long term effects of methylmercuric chloride on three generations of brook trout (Salvelinus fontinalis): toxicity, accumulation, distribution and elimination Journal of the Fisheries Research Board of Canada 2726-2739