Abstract
Estuaries worldwide have been severely degraded and become reservoirs for many types of pollutants, such as heavy metals. This study investigated the levels of Cd, Cu, Mn, Ni, Pb, and Zn in water and whole fish. We sampled 40 juvenile silversides Odontesthes regia and 41 juvenile puye Galaxias maculatus from the Valdivia River estuary, adjacent to the urban area in southern South America (Chile). Samples were analyzed using a flame atomic absorption spectrophotometer. In water samples, metals except Zn were mostly below the detection limits and all metals were below the maximum levels established by local guidelines in this estuary. In whole fish samples, concentrations of Cu, Zn, Pb, Mn, and Cd were significantly higher in puyes than in silversides. Additionally, Zn, Pb, and Mn were correlated to body length and weight in puyes, whereas Cd was correlated to body length in silversides. The mean concentration of heavy metals in silverside and puyes were higher than those reported in the literature. In silversides, all heavy metal levels were below the limits permitted by current legislation (FAO), whereas in puyes Pb and Cd levels were above the recommended maximum level established by international guidelines, therefore putting the human population at risk.
Highlights
Estuaries are highly productive systems that support commercially important organisms and are a refuge for many species during spawning
In puyes (G. maculatus), we found significant negative correlations between Zn and Mn and body length, whereas Pb was significantly correlated with increased body weight (Table 3)
Our measurements show heavy metal concentrations in the Valdivia River basin are currently below the recommended values permitted by the current legislation, indicating a low risk of heavy metal contamination to the aquatic environment
Summary
Estuaries are highly productive systems that support commercially important organisms and are a refuge for many species during spawning. Heavy metals are one of the main groups of these pollutants and are present in the aquatic environment at elevated levels because of human activity [3]. Heavy metals can be dissolved or suspended in water and are absorbed by aquatic organisms and accumulate in various organs. They are transferred to food webs and create a risk to human health if concentrations reach high levels [4,5]. Silversides are considered juvenile until they are approximately 14 cm long, and adults can be up to 22 cm long. Adults and juveniles are found in estuary banks, coexisting with O. regia. A puye is considered juvenile until it is approximately 5.8 cm long, whereas adults can be up to 14 cm long. O. regia and G. maculatus form part of the diet of birds, mammals, and fish and are captured by artisanal fishermen, who make up a significant part of the fishing economy in southern Chile [11]
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