Egg Monitoring:
Selenium Program

Summary of Utah Division of Water Quality 2010 Great Salt Lake Shorebird Egg Monitoring: Selenium Concentrations and Embryo Abnormalities

In March 2010, the Division of Water Quality (DWQ) contracted with Dr. John Cavitt, from the Avian Ecology Laboratory at Weber State University, to collect and analyze shorebird eggs for selenium. The eggs were collected as part of DWQ’s routine monitoring for Great Salt Lake. DWQ received results in the middle of February 2011 after sample processing was delayed due to laboratory and contracting issues.

The plan was for samples to be collected from two sites: the Ogden Bay Waterfowl Management Area, and Saltair. However, nesting sites in Ogden Bay were flooded in June; no active nests were located when researchers returned in July after the water had receded. As a result, egg tissue analyses were restricted to eleven avocet and stilt eggs collected from near Saltair in June 2010. The eggs were analyzed for selenium concentrations and the presence of abnormalities. Read Dr. Cavitt’s complete report.

Selenium Concentrations

The average (geometric mean) selenium concentration for the eggs from Saltair was 4.32 mg/kg dry weight, which is below the selenium water quality standard of 12 mg/kg. Selenium concentrations were relatively consistent, ranging from 4 to 6 mg/kg and similar to the concentrations in eggs previously collected near Saltair. The standard also establishes incremental management responses at interim thresholds. At the observed concentration of 4.32 mg/kg, the action outlined in the standard is to continue routine monitoring.


Two developmental abnormalities were observed in the 11 eggs: a malformation (an embryo had only one eye) and another embryo was malpositioned (abnormally positioned inside the egg). Only limited conclusions regarding bird populations at Saltair can be made with 11 samples, but two abnormalities in 11 eggs is concerning. This rate is higher than previously observed at Great Salt Lake and in other studies.

The cause of the abnormalities is unknown. Selenium causes developmental abnormalities, but at concentrations much higher than the levels found in these eggs. Additionally, no abnormalities were associated with the similar selenium concentrations previously measured in Great Salt Lake eggs as part of the GSL selenium standard studies. In these studies, 72 gull eggs and 100 chicks were observed without any deformities. Nor were any abnormalities observed in 79 eggs from avocets and stilts. The 79 eggs include 7 collected from Saltair that had a higher mean concentration of selenium at 4.73 mg/kg and a higher maximum of 8.2 mg/kg when compared to the results of the current study. This information suggests a higher incidence of deformities than previously observed, but that selenium is not the likely cause.

DWQ staff consulted with avian experts from the Division of Wildlife Resources (DWR) and United States Fish and Wildlife Service (FWS) about the developmental abnormalities and potential causes. These experts share DWQ’s concerns regarding the observed abnormalities, but the existing data is inadequate to suggest the likely cause(s).

Actions in 2011

DWQ remains committed to ensure that water quality is sufficient to protect the biological integrity of Gilbert Bay. However, given that water quality is not the only factor that can cause egg embryo malformations, DWQ needs to collaborate with sister State and federal entities to investigate the cause of these malformations. Other entities, such as the FWS and DWR, are charged with the protection of wildlife. As a result, they are better equipped to address broad concerns about the health of Great Salt Lake birds. DWQ looks forward to continued collaboration to ensure GSL water quality protects the shorebirds. The specifics of any additional investigations are currently being explored in preparation for the spring nesting season. At minimum, DWQ will continue routine egg monitoring in 2011 in accordance with the selenium water quality standard triggers.