Mobilization of aluminium and deposition on fish gills during sea salt episodes ? catchment liming as countermeasure

Abstract

Episodic events may be critical with respect to aluminium (Al) toxicity in moderately acidified salmon rivers. The present work demonstrates that sea salt episodes enhance the toxicity of Al in acidic rivers. The documented sea salt episode (300 [micro sign]M Cl) mobilized positively charged Al species (0.4 to 1.1 [micro sign]M Al(i)), enhanced the Al accumulation on fish gills (0.9 to 10 [micro sign]mol g(-1) dw) and caused increased stress responses (6 to15 mM blood glucose) in fish. Accumulated Al on gills remained high several days after the episode. The presented results are based on a six-week field study in two tributary rivers on the west coast of Norway. Changes in the river water qualities and Al speciation were followed using in situ fractionation techniques. Al accumulation on gills and stress responses were followed for Atlantic salmon (Salmo salar) kept in tanks continually exposed to the changing water quality. The potential mobilization of Al from the two catchments was studied by extracting soils with diluted seawater (salinity of 3). To counteract Al toxicity, one of the tributary catchments has been limed. The potential mobility of Al by sea salt was lower in limed soils compared to acid soils, and the Al deposition on fish gills (<3.5 [micro sign]mol g(-1) dw) and associated stress responses stayed low during the sea salt episode in the river draining the limed catchment. Thus, for acid river systems in coastal areas, catchment liming should be considered as a useful countermeasure for Al toxicity.

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

“…Both in situ bioassays and field surveys suggest that acid episodes are harmful to fish (Barlaup andÅtland, 1996;Hindar et al, 2004;Magee et al, 2003;Teien et al, 2004bTeien et al, , 2005a. In short-term exposures, fish can be exposed to controlled levels of water quality constituents mimicking elements of a natural episode, but is at the same time a poor representation of the complex variation in water chemistry the wild and native fish populations are exposed to prior to, during and following an episode.…”

“…Field bioassays have the capacity to document both mortality rates and sub-lethal responses in fish, and link these to the intensity and duration of an acid/Al episode (Barlaup andÅtland, 1996;Lacroix and Korman, 1996;Magee et al, 2003;Teien et al, 2004bTeien et al, , 2005a. The effects of an episode can be simulated in short-term experiments where the toxic components and the toxicity moderating variables can be controlled and varied (data included here).…”

“…An acidification episode has a short duration where the pH depression most often is related to sulfate and possible nitrate pulses, snowmelt, heavy rainfall and sea salt deposition. During an episode, chemical elements such as H + , Al, Ca and organic carbon will be continuously changing in response to dilution, mobilization and transformation processes (Evans et al, 2001;Henriksen et al, 1984;Hindar et al, 2004;Teien et al, 2004bTeien et al, , 2005a. While severe acidification (both chronic and episodic) can cause population extinction, the biological response to a more moderate episode depends not only on the increase in H + and Al concentrations, but also on exposure duration and timing and on changes in other water quality relevant elements.…”

The suitability of gallium as a substitute for aluminum in tracing experiments

“…Studies in carp indicate that Ga is toxic and accumulates on the gill surface (Yang and Chen 2003), as does Al in salmon Teien et al 2004) and crayfish (Ward et al 2006). However, other metals such as copper (Karan et al 1996) and cadmium (Wong and Wong 2000) also accumulate here, causing similar damage and immune response, with a majority of effects being extracellular.…”

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

“…An acidification episode has a short duration where the pH depression most often is related to sulfate and possible nitrate pulses, snowmelt, heavy rainfall and sea salt deposition. During an episode, chemical elements such as H + , Al, Ca and organic carbon will be continuously changing in response to dilution, mobilization and transformation processes (Evans et al, 2001;Henriksen et al, 1984; Teien et al, 2004bTeien et al, , 2005a. While severe acidification (both chronic and episodic) can cause population extinction, the biological response to a more moderate episode depends not only on the increase in H + and Al concentrations, but also on exposure duration and timing and on changes in other water quality relevant elements.…”