Water quality limits for Atlantic salmon (<i>Salmo salar</i> L.) exposed to short term reductions in pH and increased aluminum simulating episodes

International audienceAcidification has caused the loss or reduction of numerous Atlantic salmon (Salmo salar L.) populations on both sides of the North Atlantic. Acid deposition peaked in the 1980's and resulted in both chronically and episodically acidified rivers. At present, water quality is improving in all affected rivers due to reduced acid deposition. However, spring snow melt, heavy rainfall and sea salt episodes can still cause short term drops in pH and elevated concentrations of bioavailable aluminum. Technical malfunction in lime dozers will cause short termed episodic spates in the limed rivers. The current situation has prompted a need for dose-response relationships based on short term exposures of Atlantic salmon to assess the potential population effects of episodic acidification. Water quality guidelines for salmon have been lacking, despite a large number of experiments, all demonstrating dose-response relationships between water chemistry and fish health. We have summarized results from 347 short-term (+ and Al) and as Carlin-tagged smolt releases after preexposure to moderately acidic waters. The results from the various bioassays are compared to water quality limits proposed on basis of the relationship between water quality and population status/health in Norwegian rivers. The focus of this article is placed on chemical-biological interactions that can be drawn across experiments and exposure protocols. We propose dose-response relationships for acid neutralizing capacity (ANC), pH, cationic Al and gill accumulated Al, versus mortality in freshwater, effects on hypo-osmoregulatory capacity in seawater challenge tests and on smolt to adult survival in release experiments. The "no effect" dose depends on the life history stage tested and on the sensitivity of the biomarkers. Parr are more tolerant than smolt. Concentrations of Al that have no significant impact on freshwater life history stages can still have major population effects if they occur prior to smolt migration. While smolt can survive in freshwater for a prolonged period of time (>10 days) at an Al dose resulting in a gill Al concentration of up to 300 µg Alg?1 dw, a 3 day exposure resulting in a gill Al accumulation in the range of 25 to 60 µg Alg?1 dw reduces smolt to adult survival in a dose related manner by 20 to 50%. For smolt to adult survival, the biological significant response is delayed relative to the dose and occurs first after the fish enters the marine environment. In addition to exposure intensity and timing, exposure duration is important for the setting of critical limits

CONFIDENCE overview of improvements in radioecological human food chain models and future needs

Radioecological models used to make predictions of the radionuclide activity concentrations in human foodstuffs must be sufficiently robust and fit for purpose with uncertainties reduced where practicable. The CONFIDENCE project had a work package with the objective to improve the capabilities of radioecological models and this paper presents the key findings of this work. Recommendations for future radioecological studies/model developments are made based on the findings of the work conducted and consultations with end-users

Påvirkes laksesmolt av aluminium i brakkvann? Storelva i Holt, Aust-Agder og Audna, Vest-Agder, 2006

Fangst av laks i Storelva, Aust-Agder har ikke økt som forventet etter kalking. Dette kan skyldes en rekke faktorer, deriblant vannkvalitet. I prosjektet er vannkvalitet og dens effekt på smoltkvalitet undersøkt i Storelva, samt i Sandnesfjorden. Hypotesene er at smolt belastes av aluminium som følge av utilstrekkelig kalking av Storelva, og/eller at postsmolt skades som følge av at aluminium remobiliseres på en giftig form i brakkvannet i Sandnesfjorden. Vannkvaliteten i Storelva og i de utenforliggende fjordene var bedre i 2006 enn i tidligere år. Dette skyldes mest sannsynlig at vannføringen var høy under smoltutvandringen, noe som medførte lav salinitet i Songevatn og Nævestadfjorden, mens det mer saltrike vannet ble presset utover mot Sandnesfjorden. En tilsvarende undersøkelse utført i Audna påviste heller ikke tilstedeværelse av estuarine blandsoner i Sniksfjorden dette året

Bystander Effects Induced by Exposure to Sublethal Radiation and Heavy Metals in Atlantic Salmon

These experiments were designed to identify cellular effects in 3 key organs in Atlantic Salmon (Salmo salar, L.) after exposure in vivo to very low doses of radiation, and subtoxic levels of aluminum (Al) and cadmium (Cd) or copper (Cu) alone or in combination. The salmon (approx. 35g) were exposed to doses of 4, 18 and 75 mGy doses of gamma radiation, respectively, administered over 5 hrs in untreated lake water or with Cd, Al or Cd+Al added to lake water. Six fish per group were sacrificed after exposure and the head kidney, fin and gill were dissected and sent for tissue culture. The Al and Cd speciation in the water and the levels in fish gills were measured as well as physiological parameters associated with stress. Small explants of each tissue were set up as tissue cultures using RPMI 1640 medium supplemented with serum, insulin, hydrocortisone and antibiotics. After 2 days, the culture medium was harvested and filtered then placed on a reporter cell line for determination of stress signal activity (bystander effects). Radiation doses as low as 4 mGy alone or in combination with Cd and / or Al, caused bystander signals to be produced in tissues harvested from in vivo exposed salmon. The effects vary between different organs and are not consistently additive or synergistic for a given treatment. Individual results were recorded for each individual fish. Some individual fish were consistently more sensitive to the stressors. Tissue type also appears to be critical, with gill cells showing high degrees of synergism between radiation and metal exposure. Most data for Cd suggests that lower toxicity is found when the metal is used in combination with radiation exposure. This may be due to competition between calcium and Cd since calcium is a key component in the signal transduction pathway being followed. The results indicate that this stress signal response will be a useful indicator of combined environmental stress in species inhabiting aquatic ecosystems

Developing biotic ligand models for uranium: research within the STAR EU Network of Excellence

Uranium is a radioactive contaminant of concern for the aquatic environment, with potentially deleterious releases to freshwaters due to mining, processing and waste disposal. As a metallic element forming cations in aqueous solution, with a chemotoxic mode of action, uranyl is in principle suitable for the development of Biotic Ligand Models to describe the influence of chemistry on its toxicity. Although past research has demonstrated relationships between uranyl (U(VI)) toxicity and key freshwater quality parameters such as dissolved organic carbon concentration, no biotic ligand model has so far been developed for this metal. Ongoing research within the EU Network of Excellence STAR (STrategy for Allied Radioecology) aims to generate uranyl toxicity data for freshwater species suitable for development of Biotic Ligand Models. The species under study are Atlantic salmon (Salmo salar), common duckweed (Lemna minor) and water flea (Daphnia magna). For each species, toxic responses across relevant ranges of water chemistry variations (e.g. pH, Na, Mg, K, Ca concentrations) have been measured. Chemical speciation in exposure waters will be computed using the WHAM7 model, following review and updating of the uranyl binding constants. We will present a selection of experimental results to show the key water quality parameters influencing uranyl toxicity to each organism, and will also show how the results will be used to develop Biotic Ligand Models for each organism to allow the effects of water chemistry on uranyl toxicity to be predicted