Question

How can a shift in environmental \(\mathrm{pH}\) affect aquatic ecosystems? What protects these ecosystems in some regions?

Short answer

Changes in environmental pH can cause stress to aquatic life, even leading to death and lowering biodiversity in extreme cases, by affecting the solubility and availability of chemicals in the water. However, some regions can resist these changes with their buffering capacity. This capacity, often due to substances such as limestone, neutralizes added acids or bases, thus protecting the aquatic ecosystems.

Step-by-step solution

Understanding pH and aquatic life

The pH of a body of water is very important as it affects the solubility and biological availability of all chemical constituents in the water such as nutrients and heavy metals. Most aquatic organisms thrive at a pH level between 6 (slightly acidic), and 9 (slightly alkaline). An undue shift either way can cause distress to the organisms, leading to death in extreme cases.

Describing the effects of pH shifts

A significant pH alteration in the water makes it less habitable. Acidic conditions can make the water corrosive and toxic to aquatic life by leaching high levels of metals from the surrounding rock. Further, it may also lower the biodiversity as only a few species can tolerate such harsh conditions. Alkaline conditions, on the other hand, can make the water uninhabitable by causing ammonia toxicity and hindering the nutrient uptake by plankton and other aquatic plants.

Explaining the concept of buffering capacity

However, some regions have a natural defense system, referred to as 'buffering capacity'. Buffering capacity is the ability of a body of water to resist changes in pH despite the addition of acidic or basic substances. This is often due to presence of materials like limestone and other alkaline substances in the surrounding land which neutralize the added acids or bases.