For decades, researchers have studied the influences of atmospheric deposition (sometimes referred to as "acid rain") on both plants and animals in Great Smoky Mountains National Park. Laboratory analysis by scientists at the University of Tennessee has revealed that trout living in certain high-elevation streams in the park show traces of aluminum deposits gathering in their bone structure that is believed to be linked to atmospheric deposition.
Water samples collected during the past 20-years indicate an increase in aluminum deposits in Smokies streams. Scientists have sought to determine whether the increased aluminum found in the water samples of high elevation streams is being absorbed into the tissue of fish. They have discovered that aluminum can be found in the otolith, or "ear bone," of trout. Otolith ring structure is similar to rings on a tree trunk, and can be used to determine age. They also hold a permanent record of various trace elements the fish has been exposed to during its life in the stream.