Mercury and Toxics Contaminates Everglades

Mercury and Toxics Contaminates Everglades

2007 September -   The U.S. Environmental 
Protection Agency has released a report on the ecological condition of the 
entire 2,063 square-mile freshwater portion of the publicly owned part of 
the Everglades. 
The report documents the third phase of an 11 year study of the Everglades 
marshes, which determined that mercury in prey fish is declining, but 
still elevated, while phosphorous contamination of soil has increased. 
"The goals of EPA's Everglades Ecosystem Assessment Program are to first 
describe, then diagnose, and finally predict the status of ecosystem 
conditions," said EPA Region 4 Administrator Jimmy Palmer. "The report 
describes the study area and will ultimately inform future decisions to 
restore and manage this unique environment." 
Mercury contamination was a major focus of the study, and the results are 
mixed. 
Although the concentration of mercury in mosquitofish, a key prey fish for 
Everglades game fish and wading birds, dropped significantly since 1995, 
fish in about 65 percent of the marsh were found to exceed the contaminant 
threshold. 
This poses a potential threat to fish-eating wildlife and to human health 
through fish consumption. 
Mercury in fish was not found to be related to concentrations of mercury 
in surface water, but rather declined with increased carbon and sulfur in 
the water. 
There was a slight decrease of methylmercury, a neurotoxin and the form of 
mercury that is most easily concentrated in organisms, in surface water as 
compared to 10 years ago. But the total mercury concentration, which 
includes both methylmercury and atmospherically deposited mercury, 
increased slightly in surface water. 
Total mercury concentration in surface water has been below the level 
established to protect human health throughout the study. Changes observed 
in surface water mercury and other contaminants are subtle, near the 
limits of laboratory instruments' ability to distinguish differences and 
are being studied further to see how they vary with rainfall the report 
says. 
Phosphorous was studied because it is a common constituent of agricultural 
fertilizers which are discharged along with stormwater into surface water 
during periods of heavy rain. 
In the Everglades, this nutrient has allowed cattails to flourish and 
crowd out native saw grass, wading birds and fish. 
There was a slight decline in surface water phosphorous as compared to 10 
years ago. But phosphorous in soil exceeded Florida's impact threshold in 
24 percent, and the restoration goal in 49 percent, of the Everglades - 
both higher percentages than in 1995. 
Sulfate contamination was also studied and, although the effects of 
sulfate on ecosystem health are not well understood, the U.S. Geological 
Survey has documented links between sulfate and high levels of 
methylmercury. 
Sulfate contamination may also be contributing to declines in native 
plants by altering chemical conditions in the sediments. More than half, 
or 57 percent, of the Everglades marsh had surface water sulfate 
concentrations exceeding the restoration goal, as compared to 66 percent 
in 1995. 
Ecological stressors on the Everglades such as poor water management, soil 
loss, water quality degradation and mercury contamination, among other 
issues, are often interrelated. 
The EPA recommends that efforts to manage water quality and pollutants 
such as mercury, phosphorous and sulfur be integrated to prevent further 
degradation. 
The study is part of the Everglades Ecosystem Assessment Program, an 
innovative, long-term research, monitoring and assessment effort. Since 
1993, three phases of marsh sampling and one phase of canal sampling have 
been conducted throughout the Everglades at over 1,000 different 
locations. Its goal is to provide critical, timely, scientific information 
needed for management decisions on the Everglades ecosystem and its 
restoration. 

---


More Aging Earth Headlines >> 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 - 26 - 27 - Aging Earth Home

AGING EARTH HOME

---

© 2009; Aging Earth .com
Powered by WorldsLargestNetwork.com