Does Acid Rain Affect the Growth of Aquatic Plants?

Effects on Aquatic Plants

• As acid rain fills lakes and streams, the number of microscopic aquatic plants, including phytoplankton and algae, begin to decline. Once acid levels fall below a pH level of 6, most green algae and other small plant life disappear, according to researchers at Ramapo College in New Jersey. Plus, higher acid levels can change a lake's chemistry, boosting phosphate activity and smothering aquatic plants. However, not all aquatic plant life suffers from higher acid levels. Research from Environment Canada found that more acid in water increases levels of periphytic algae, the slippery, green film that covers rocks, shore plants and other submerged objects. Periphytic algae rises because higher acid levels kill off microscopic herbivores in the water.

Up the Food Chain

• Because microscopic plants such as phytoplankton serve as the aquatic food chain's foundation, a reduction in plant life has wide-ranging consequences for marine ecology. Smaller fish eat phytoplankton. When their food source shrinks, their numbers dwindle, and that in turn means less food for larger fish higher on the food chain. A watershed's underlying bedrock can either perpetuate or reduce the cycle. Limestone and calcite bedrocks have high alkalinity and can neutralize acid in water. Bedrocks made of granite and other nonalkaline foundations cannot counter acid rain's effects.

Acid Rain Levels

• Acid rain doesn't affect all regions equally. A study from the U.S. Environmental Protection Agency found that specific areas were especially susceptible to ecological damage from acid rain. New York's Catskills and Adirondacks mountain ranges have bigger-than-average numbers of lakes poisoned by acid rain, as do the mid-Appalachian Highlands along the East Coast. In the Northeast, where bedrock has little alkalinity, some lakes had a pH level below 5 at the time of publication. With a pH of 4.2, Echo Pond in Franklin, N.Y., is one of America's most acidic lakes, the EPA reported. Acid rain is also a serious problem in Ontario, Canada, where rain laced with emissions from U.S. factories has drifted along the jet stream. Ontario had more than 100 fishless, acidified lakes at the time of publication, according to Ramapo College. Environment Canada estimates that about half of sulphuric acid deposits in eastern Canada come from the United States.

Limiting Acid Rain

• Governments have established programs to reduce acid rain. The EPA's Acid Rain Program has enforced limits on emissions coming from coal-fired power plants on the East Coast and in the Midwest, charging $2,000 at the time of publication for each ton of sulphuric or nitric acid released beyond a plant's allowed annual maximum. Some states have also launched initiatives: New Hampshire, passed a law in 2002 mandating that power plants there cut their sulphuric acid emissions by 70 percent compared with 1999 levels. Regional groups have become involved as well. The Conference of New England Governors and Eastern Canadian Premiers has developed public-education initiatives on the causes of acid rain and created a plan to reduce power-plant sulfur emissions at least 80 percent beyond levels allowed in the U.S. Clean Air Act.