Sublethal effects in avocet and stilt hatchlings from selenium-contaminated sites

Area of Science:

• Environmental Toxicology
• Avian Ecology
• Biochemistry

Background:

• Excess selenium (Se) in aquatic ecosystems poses risks to waterbirds.
• Selenium bioaccumulation in the food chain can lead to embryotoxicity and teratogenicity.
• Avocets and stilts are susceptible to selenium-induced adverse effects.

Purpose of the Study:

• To investigate the effects of varying selenium concentrations on avocet and stilt embryos and hatchlings.
• To assess selenium levels in eggs and their correlation with hatching success and physical development.
• To evaluate biochemical markers of oxidative stress in hatchlings exposed to different selenium levels.

Main Methods:

• Collection of American avocet and black-necked stilt eggs from three sites with differing water selenium concentrations (2.5, 8.6, and 190 ppb).
• Laboratory hatching of eggs and measurement of egg selenium concentrations.
• Assessment of hatching success, malformations, body weights, bone lengths, liver weights, and hepatic biochemical markers (GSH peroxidase, G6PDH, GSSG).

Main Results:

• Egg selenium concentrations varied significantly across sites, highest at Westfarmers (WF).
• Avocet hatchlings from the high-selenium WF site showed reduced yolk sac-free hatching weights and bone lengths, but increased liver weights.
• Increased oxidative stress markers (elevated GSH peroxidase, decreased G6PDH, increased GSSG/GSH ratio) were observed in WF avocet hatchlings.

Conclusions:

• Selenium exposure impairs embryo growth and causes hepatotoxicity in avocet hatchlings.
• Oxidative stress in hatchlings is linked to selenium exposure and may indicate future functional impairments.
• Selenium levels in aquatic food chains require careful monitoring to protect waterbird populations.