Event Title

Do Brine Shrimp Bioaccumulate Methylmercury From the Deep Brine Layer of the Great Salt Lake

Presenter Information

Erin Fleming

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

3-29-2011 11:40 AM

End Date

3-29-2011 12:00 PM

Description

A railroad causeway separating the north and south halves of the Great Salt Lake has led to the formation of a density stratified deep brine layer in the South Arm of the lake. Anoxic, sulfur-rich conditions in the deep brine layer facilitate the formation of methylmercury, which is a toxin of concern in local waterfowl. Brine shrimp (Artemia franciscana), which are known to be a significant part of the duck's diet, may accumulate methylmercury by feeding at the interface of the deep brine layer and the upper mixed layer. We designed an experiment to test the hypothesis that brine shrimp accumulate methylmercury from the interface of the deep brine layer. We added brine shrimp nauplii to 1.5-m tall columns filled with lake water from 3 m (mixed layer) and 7 m (deep brine layer) for 14 days. Aquaria filled with 0, 10, and 25% deep brine layer to mixed layer water were used to understand the possible importance of occasional mixing events. In the field and at the end of the experiment, we collected water and Artemia samples for 13C, 15N and mercury content. We found field methylmercury concentrations below 6 meters to be 28 ng/L and total mercury 48 ng/L, compared to 2 ng/L in the mixed layer of the lake. Particulate N was nearly 10 times higher in the field deep brine layer samples, potentially providing an abundant, albeit toxic food source. Artemia concentrated at the bottom of the mixed layer in the columns. However, for both the column and aquaria experiments, total mercury concentrations in Artemia were lower in mixed layer treatments compared to deep brine layer treatments. Isotopic analysis of the 13C and 15N values of the seston and Artemia indicated no difference in feeding between treatments. Our results that Artemia do not feed on the deep brine layer, but the collected data add to the general understanding of the lake.

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Mar 29th, 11:40 AM Mar 29th, 12:00 PM

Do Brine Shrimp Bioaccumulate Methylmercury From the Deep Brine Layer of the Great Salt Lake

Eccles Conference Center

A railroad causeway separating the north and south halves of the Great Salt Lake has led to the formation of a density stratified deep brine layer in the South Arm of the lake. Anoxic, sulfur-rich conditions in the deep brine layer facilitate the formation of methylmercury, which is a toxin of concern in local waterfowl. Brine shrimp (Artemia franciscana), which are known to be a significant part of the duck's diet, may accumulate methylmercury by feeding at the interface of the deep brine layer and the upper mixed layer. We designed an experiment to test the hypothesis that brine shrimp accumulate methylmercury from the interface of the deep brine layer. We added brine shrimp nauplii to 1.5-m tall columns filled with lake water from 3 m (mixed layer) and 7 m (deep brine layer) for 14 days. Aquaria filled with 0, 10, and 25% deep brine layer to mixed layer water were used to understand the possible importance of occasional mixing events. In the field and at the end of the experiment, we collected water and Artemia samples for 13C, 15N and mercury content. We found field methylmercury concentrations below 6 meters to be 28 ng/L and total mercury 48 ng/L, compared to 2 ng/L in the mixed layer of the lake. Particulate N was nearly 10 times higher in the field deep brine layer samples, potentially providing an abundant, albeit toxic food source. Artemia concentrated at the bottom of the mixed layer in the columns. However, for both the column and aquaria experiments, total mercury concentrations in Artemia were lower in mixed layer treatments compared to deep brine layer treatments. Isotopic analysis of the 13C and 15N values of the seston and Artemia indicated no difference in feeding between treatments. Our results that Artemia do not feed on the deep brine layer, but the collected data add to the general understanding of the lake.

https://digitalcommons.usu.edu/runoff/2011/AllAbstracts/3