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Effect of Mercury on Aquatic Ecosystems: National Assessment of Mercury in Aquatic Ecosystems

Reflooded post-harvest rice straw.
After harvest, wetlands are reflooded to decay residual rice straw. The decaying organic material can fuel the bacteria that create methylmercury, even during the colder months. Photo credit: M. Marvin-DiPasquale, USGS.

Areal photograph of lakes in Voyageurs National Park, Minnesota.
Voyageurs National Park (VNP), a pristine setting with abundant lakes, wetlands, and streams situated on granitic bedrock, is located near northern Minnesota's border with Canada. Long-term studies at VNP have revealed trends in mercury concentration in precipitation, surface water, and fish. Photo credit: David P. Krabbenhoft, USGS.

Mound Spring, Sentinel Meadows, Yellowstone National Park, Wyo.
USGS scientists have detected naturally occurring methylmercury in many of the Yellowstone National Park's hot springs, such as Mound Spring, Sentinel Meadows, Wyoming.

USGS scientist collecting samples of aquatic species from the Pike River, Wis.
USGS scientist collecting samples of aquatic species from the Pike River, Wisconsin, for later analysis of mercury contamination.

A map of states with mercury fish consumption advisories.
States with mercury fish consumption advisories (EPA, 2008). Every state has at least one advisory.

Graph, sampling depth in meters on left, oxygen concentration in micromoles per kilogram on right.
The location of the maximum methylmercury concentration at depth in the Pacific Ocean was the first evidence noted by the researchers pointing to the new methylation cycle. The graphic shows sampling depth on the left (in meters), and oxygen concentration on the right (in micromoles per kilogram of seawater [µmol/kg]) along a north-south latitudinal transect in the eastern North Pacific Ocean. The specific depth of maximal methylmercury concentration was consistently found at the ocean depth where the most rapid loss of oxygen was also observed. The process linking these two observations is microbial decomposition of "ocean rain", which is settling algae produced near the surface of the ocean. The decomposition process consumes oxygen from the water, but also leads to unintended methylmercury production.

Scientists prepare to lower a rosette of 12 Niskin bottles.
Scientists prepare to lower a rosette of 12 Niskin bottles on the vessel R/V Thomas G. Thompson. The device enables the collection of samples in the ocean via remote triggering of each bottle at different depths. Extreme care was taken to ensure that the rosette does not contaminate the samples. Photo courtesy of William Landing, Florida State University.

A scientist is applying a solution of water and a isotope of mercury on the shores of a lake.
Applying a solution of water and a stable isotope of mercury (202Hg) on the shores of a lake in the Experimental Lake Area (ELA) in Ontario, Canada. An international team of scientists tracked the applied mercury isotope to study the movement of mercury from the watershed into the lake and fish.

An allegator in the Florida Everglades.
Does mercury affect aquatic life in the Florida Everglades?. USGS scientists are studying the fate and transport of mercury to find the answer to the question.

USGS scientists using ultra-clean techniques to collect a water sample.
USGS scientists using ultra-clean techniques to collect water samples for the analysis of trace levels of mercury and methylmercury.

Sampling for mercury in high altitude (approximately 10,000 feet) lakes in the Rocky Mountains.
USGS scientists collecting water samples for analysis of mercury in high altitude (approximately 10,000 feet) lakes in the Rocky Mountains.

Sampling lakes in the Rocky Mountains for mercury and methylmercury.
USGS scientists sampled lakes in the Rocky Mountains for mercury and methylmercury.

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Page Last Modified: Friday, 11-Jul-2014 20:14:33 EDT