Aluminum toxicity to fish

Baker, J. P. and C. L. Schofield. 1982. Aluminum toxicity to fish in acidic waters. Water Air Soil Pollut. 18 289-309. 

In aquatic systems dissolved aluminum species are toxic to fish. There exists a vast number of aluminum species, ranging from inorganic monomeric to complex colloidal. polymeric and organic complexes. A major problem, when studying aluminum species in water is that the species quickly convert one into the other (Fairman and Sanz-Medel 1995). 

Effects of aluminum in low pH solutions on aquatic biota, especially fish, and on land plants growing in acidic soil have been studied by various investigators (35-38). Although much of the work has assigned the observed toxicity to monomeric dissolved forms of Al, the behavior of polymeric species in biochemical systems is probably in need of more careful study than it has so far received. Schindler (39) in a review of the topic of environmental impacts of acid rain noted that aluminum is highly toxic to fish and quoted literature references to the effect that polymeric and colloidal aluminum hydroxide species may physically obstruct gill membranes and cause asphyxiation. The maximal pH range for this effect was reported as 5.2 to 5.4. 

Acid rain is changing the pH of many lakes and streams in parts of the United States and Europe. When the pH of a lake falls below 4.5-5, most fish and plant life cannot survive. As the soil near a lake becomes more acidic, aluminum becomes more soluble. Increased levels of aluminum ion in lakes are toxic to fish and other water animals. 

At the pH levels now being recorded in some Canadian and American bodies of water, aluminum has been found to be toxic to fish and other aquatic organisms. Perhaps the next generation of chemists, with the same investigative and enterprising spirit demonstrated by Charles and Julia Hall and Paul Heroult, will find a answer for some of these problems. 

The death of fish is the most highly publicized effect of acid rain, yet even the loss of fish is due not just to the direct action of acidity itself but also to more subtle changes in the chemistry of lakes brought about by acid rain. It is now known, for example, that acid rain dissolves aluminum — one of the most abundant elements in the soil — and carries it into lakes and streams at levels toxic to fish. Aluminum interferes with salt balance, and produces a clogging of the gUls that causes fish to literally suffocate to death. 

As discussed in Chapter 1, fish have been lost from several hundred acidified lakes and streams in the Adirondacks, Ontario and Nova Scotia, as well as in Scandinavia. The death of fish illustrates a particularly insidious aspect of acid rain the effects of acidity can be synergistic. For example, acidity can kill fish by interfering with the fish s salt balance by causing reproductive abnormalities by leaching aluminum into the lake at levels toxic to fish gills, so that the fish literally suffocate and by kUling the organisms on which fish feed. The combined effect of these stresses can wipe out a fish population. 

The low pH of acid precipitation can destroy forests and kill fish. Some lakes and streams lie in soil that has the natural ability to buffer the increased acidity of acid rain, usually because the soil contains a high amount of lime. Other lakes and streams, however, have no such buffering capacity. The pH of the water is not the main problem—at least not directly. The problem lies in the amount of aluminum compounds that are leached out of the soil surrounding the lake or stream at lower pHs. Aluminum is toxic to many aquatic species. 

That Al3+ is the main toxic agent in many acidified lakes is supported by observations of improved fish survival rates when the silica content of the water is increased, as dissolved silica can form either soluble or insoluble aluminosilicates (see Section 7.6). Mobilized aluminum has also been linked to forest damage, since, in sufficient concentration, it is directly toxic to roots of spruce trees and many other plants. 

Sparling DW, Lowe TP, Campbell PGC. 1997. Ecotoxicology of aluminum to fish and wildlife. In Yokel RA, Golub MS, eds. Research issues in aluminum toxicity. Washington, DC Taylor Francis, 47-68. 

Sanders et al. (1983) have also shown that the effects of Cu(II) on the growth of crab larvae and on their metallothionein with copper chelate buffer systems must be interpreted on the basis of free Cu ion activity. The data obtained reveal predictable relations between [Cu ] in seawater and processes at the cellular and organismic levels. Similarly, the uptake of metal ions by plants (e.g., of aluminum) is usually related to free metal-ion activity. Others have shown that the chelation of a variety of metals reduces the toxicity of metals to organisms for example, a reduction in the uptake of mercury by fish in the presence of EDTA and cysteine a reduction in copper and/or zinc toxicity to... 

Under most circumstances, exposure to aquatic organisms would be unlikely due to the limited use pattern of aluminum phosphide in terrestrial environments. Two studies of aquatic toxicity are available in the literature. Both studies are acute tests with fish, the snakehead catfish and the rainbow trout. The reported values of LC50 are 0.10 and 0.0041 mg 1 for the snakehead catfish and rainbow trout, respectively. These results indicate that phosphine is highly toxic to these fish species. 

Effect of fluoride complexation on aluminum toxicity towards juvenile Atlantic salmon (Salmo salar). Can J Fish Aquat Sci 47 1446-1452. WHO (1998) Guidelines for drinking-water quality, 2nd edn. Addendum to Volume 1 Recommendations. 

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