How can a shift in environmental pH affect aquatic ecosystems? What protects these ecosystems in some regions?

Question

What will be an ideal response?

Answer 1

"The pH of an environment is extremely critical, because it affects the function of virtually all enzymes, hormones, and other proteins in the bodies of all organisms living in that environment. Ordinarily, organisms are able to regulate their internal pH within the narrow limits necessary to function properly. A consistently low environmental pH, however, often overwhelms the regulatory mechanisms in many life-forms, thus weakening or killing them. Most freshwater lakes, ponds, and streams have a natural pH in the range from 6 to 8, and organisms are adapted accordingly. Most are severely stressed, and many die, if the environmental pH shifts as little as one unit from the optimum. As aquatic ecosystems become acidified (pH 5 and below), more organisms die off, either because the acidified water kills them or because it keeps them from reproducing."
"From the Green Mountains of Vermont to the San Bernardino Mountains of California, the die-off of forests trees in the 1980s caused great concern. Red spruce forests are especially vulnerable. In New England, 1.3 million acres of high-elevation forests were devastated. Commonly, the damaged trees lost needles as acidic water drew calcium from them, rendering them more susceptible to winter freezing. Sugar maples, important tress in the Northeast, have shown extensive mortality, ranging from 20–80% of all trees in some forests. Much of the damage from acid precipitation to forests is due to chemical interactions within the forests soils. Sustained acid precipitation at first adds nitrogen and sulfur to the soils, which stimulate tree growth. In time, though, these chemicals leach out large quantities of the buffering chemicals (usually calcium and magnesium salts). When these buffering salts no longer neutralize the acid rain, aluminum ions, which are toxic, are dissolved from minerals in the soil. The combination of aluminum and the increasing scarcity of calcium, which is essential to plant growth, leads to reduced tree growth."