No abstract

Transgenic strains of the nematode Caenorhabditiselegans, which carry stress-inducible lacZ reporter genes, aremeasurably stressed by exposure to heavy metals in aqueous solution. Thisstress response can be quantified, using enzymatic assays for the reportergene-product (Escherichia coli beta-galactosidase), or estimatedapproximately by in situ staining for beta-galactosidase in exposedworms. Stress responses to heavy metals have been demonstrated both inlaboratory tests using Cd2+ or Hg2+, and also in watersamples taken from a metal-polluted river system in southwest England. TheRiver Carnon flows through an area with an ancient mining history,principally for Sn, but also for Cu and other metals; As, Cd, Al, Mn, and Zn,as well as large amounts of Fe, are all present in these ore bodies. Foursites in the Carnon river basin were compared with respect to theirmacroinvertebrate diversity, physical and chemical characteristics (includingthe concentrations of As, Cd, Al, Cu, Mn, Zn, and Fe). Transgenic worms wereexposed to water samples from these four sites, and also to a 0.33%(v/v) dilution of metal-laden minewater from the principal local mine (WhealJane). Transgene expression was induced in all five cases, though markedlyless so for the least polluted of the sites (which also supported a richermacroinvertebrate fauna). Two different transgenic strains were tested inthis study; strain PC72 (using a homologous hsp16 promoter) isslightly more sensitive to most metal-containing water samples than strainCB4027 (using a heterologous Drosophila hsp70 promoter). Bothtransgenic strains and two different assay methods gave essentially similarresults. These findings demonstrate that transgenic nematodes could provide arapid and simple assessment of aquatic pollution, in that the transgeneresponse is inducible by mixtures of dissolved metals at concentrationsactually encountered in metal-polluted watercourses.

No abstract

Freshly fertilized ova, eyed ova and yolk-sac fry of brown trout, Salmo truifa L., were exposed to each of four trace metals (aluminium: 6000 nmol I -I ; copper: 80 nmol I-'; lead: 50 nmol I-'; zinc: 300 nmol I-I) while held in flowing artificial soft-water media maintained at pH 4.5 or 5.6 and [Ca] 20 or 200 pmol I-'. In continuous exposure from fertilization, survival of ova was severely affected at pH 4.5 and [Ca] 20 pmol I -I , regardless of the presence of Cu, Pb or Zn; A1 reduced embryonic mortality and improved hatching success. High ambient [Ca] at pH 4.5 increased egg survival. At ' swim-up ', surviving fry exposed to A1 or Pb had lower whole body Ca, Na and K content, irrespective ofpH or ambient [Ca]. Cu reduced whole body Ca and K content at pH 5.6 and [Ca] 200 pmol-I, and whole body Ca, Na and K content in the other media. Zn reduced whole body mineral content at pH 5.6 and [Ca] 20 pmol I-'. Whole body Mg content was reduced by all trace metals at pH 5.6 and [Ca] 20 pmol I-', and by Cu at pH 5.6 and [Ca] 200 p o l I-I. Al and Cu impaired skeletal calcification at pH 5.6 at both ambient [Ca]; Pb only at [Ca] 20 pmol I-'. Zn enhanced calcification at pH 4.5 and [Ca] 200 pmol I-'. In the absence of trace metals, low pH reduced body Ca, Na, Kcontent and skeletalcalcificationat [Ca] 200 pmol I-'. The uptake ofCa, Na and K, measured at regular intervals from hatching was impaired to the same extent by all treatments at pH 4.5, irrespective ofambient [Ca] or trace metal presence. At pH 5.6, irrespective of ambient [Ca], Al, Cu and Pb impaired Ca and K uptake. The rate of Na uptake was reduced by A1 and Cu. Al-treated yolk-sac fry, exposed to low ambient [Ca] from 200-300"days post-hatch, suffered high mortalities regardless of pH. Ca, Na and K uptake was impaired by all treatments at pH 4.5, and by A1 and Cu at pH 5.6 in a similar exposure period. The development of the early stages of brown trout in the presence of trace metals is discussed in relation to recruitment failure in areas of soft. acid water.

In 30‐day exposures in artificial soft water medium, survival of brown trout alevins was not affected by low pH (4.5,4.8, 5.4), by low calcium concentration (10.25 μmol l−1) or by manganese (≤20 μmol l−1), but was impaired by aluminium (6–8 μmol l−1) at low calcium concentration (10 μmol l−1) irrespective of pH (4.5 or 5.4). Manganese (6.6, 20 μmol l−1) impaired net calcium uptake and calcium deposition in the skeleton at low calcium concentration (25 μmol l−1) irrespective of pH. Aluminium (2–8 μmol l−1) impaired gross development, net uptake of calcium, potassium and sodium, and calcium deposition in the skeleton, and slightly increased the net loss of magnesium, some of these effects being more severe at calcium concentration 10 μmol l−1 than 50 μmol l−1, and some more severe at pH 5.4 than pH 4.5. Net uptake of calcium and sodium were impaired at low pH (4.5, 4.8), and skeletal calcium deposition was impaired at low calcium concentration (10 μmol l−1), but these effects of low pH and low calcium concentration were slight compared with those of the trace metals. The possible role of trace metals in reports of the deleterious effects on fish of low pH levels is discussed.