Effects of environmental water salinity on blood acid-base status in juvenile turbot ( Scophthalmus maximus L.)

Abstract

The time courses of extracellular ionic and acid-base adjustments were studied in juvenile turbot ( Scophthalmus maximus) following a decrease of water salinity, either abruptly from 32 to 10%. or after a first step (4 weeks) in 19%. salinity followed by a direct transfer to 10%. brackish water (BW). Net exchanges of acid-base equivalents with the external water were also determined after transfer from 32%. SW to 10%. BW. Direct transfer from seawater (SW) to 10%. BW induced a transient decrease in plasma osmolarity, plasma sodium and chloride concentrations, associated with a marked and transient metabolic alkalosis in the blood. A significant net outflux of acidic equivalents was also measured only during the first day in BW. Four weeks preadaptation in 19%. BW reduced the intensity of the osmotic disturbances elicited by a subsequent abrupt transfer to 10%. BW. These ionic readjustments were also coupled with minimal acid-base changes, of lesser magnitude than those described after directly from SW to 10%. BW.