Increase of heart rate without elevation of cardiac output in adult Atlantic salmon (Salmo salar) exposed to acidic water and aluminium

Abstract

Adult Atlantic salmon (Salmo salar) were exposed for 48 h to water from acidified (pH 5.2) Fossbekk River (Norway), with and without 94 µg aluminium (Al)/L added as AlCl3, and to water from circumneutral (pH 6.7) Ims River (Norway) (controls). Cardiac output, heart rate, and stroke volume were monitored throughout the exposure period with Doppler flow probes placed around the ventral aorta of the fish. Fish exposed to Fossbekk River water without added Al showed few physiological disturbances. When 94 µg Al/L was added to Fossbekk River water, most of the fish died before the end of the 48-h exposure period, and a large elevation in heart rate was observed together with a decrease in plasma chloride concentrations and an increase in haematocrit, plasma glucose and plasma cortisol levels. Cardiac output was maintained at basal levels during the first 24 h of exposure because the tachycardia was accompanied by a concomitant reduction of stroke volume. Signs of arrhythmia appeared after 32 h of exposure and were associated with a further decrease in stroke volume that caused cardiac output to decrease below basal levels. The incapacity of the tachycardia to elevate cardiac output and the subsequent death of the fish suggest that this response to low pH and Al is more of a maladaptation reaction than a compensatory or adaptative reaction.

Cortisol and glucose responses in juvenile brown trout subjected to a fluctuating flow regime in an artificial stream

“…The lack of elevated glucose corresponds with observations made by Einarsdó ttir & Nilssen (1996) and Brodeur et al (1999). The present results confirm that care has to be taken when using blood glucose as the sole stress indictor in fishes, as emphasized by Mommsen et al (1999).…”

Effects of soft-water acclimation on the physiology, swimming performance, and cardiac parameters of the rainbow trout, Oncorhynchus mykiss

“…Hence, cardiac output was measured during acclimation, while Fish Physiol Biochem (2008) 34:313-322 319 fish were swimming at a speed of 0.35 m s -1 . Indeed, resting f H values of rainbow trout at similar water temperatures are, as expected, typically lower (e.g., 43.6 ± 14.1 beats min -1 (Dussault et al 2001); 50 beats min -1 (Brodeur et al 1999)). In fact, the f H of soft-water-acclimated fish was already significantly higher than that of hard-water-acclimated fish during acclimation (97 ± 1.9 vs. 86 ± 2.6 beats min -1 ; P = 0.04).…”

The Bioavailability and Toxicity of Aluminum in Aquatic Environments

“…Exposure to the river water alone for 48 h caused few hematological changes in the fish, even though the water contained a total of about 240 µg · L -1 Al, of which 33 µg · L -1 was in the inorganic monomeric fraction (pH 5.2, 27 µM Ca; Brodeur et al, 1999). The absence of Al toxicity was likely related to the high color of the water (33 mg Pt/L), indicating that enough DOM was available to complex the Al in mostly nontoxic forms.…”

“…Cardiac output in the fish was measured using Doppler flow probes implanted around the ventral aorta, and the Al-exposed fish showed tachycardia (increased heart rate) and a proportionally greater decrease in stroke volume, together leading to decreased cardiac output, and the fish showed pronounced cardiac arrhythmia before death. The tachycardia was seen as maladaptive, because heart stroke volume could not keep up as cardiac filling time decreased, and the tachycardia was probably a result of increased adrenergic stimulation of the heart (Brodeur et al, 1999). Presumably, the changes in cardiac function were a result of the hemoconcentration experienced by the fish exposed to the Fossbekk River water supplemented with Al.…”