Otoliths as indicators of trace element exposure in freshwater fish: a mesocosm experiment with manganese and an examination of hydro-impoundment on otolith trace element signatures

Abstract

Through biomonitoring, organisms are measured to determine levels of contamination or exposure. In freshwater, biota like fish are used to represent whole communities due to their ecological/commercial relevance. In fish, soft tissues are typically used for trace element analyses although their potential for depuration, transformation, and contaminant re-compartmentalization makes them applicable for only short-term biomonitoring. Alternatively, metabolically inert calcified tissues (e.g., otoliths) have been found useful in long-term trace element biomonitoring. Biomonitor utility was demonstrated through two studies. The first being a mesocosm study on baitfish species exposed to MnSO4 in which otolith chemical signatures were compared with the ambient mesocosm environment. Under study conditions, fish otolith biomonitors were ineffective at detecting manganese. The second study utilized fish otoliths to measure the effect of impoundment by comparing water and otolith trace element concentrations between impounded and non-impounded waterbodies. Otolith signatures successfully discriminated based on impoundment status and species.