Question

different aquatic animals have different tolerance to ph changes in the water they live in. for example a wood frog will die if the ph of the water falls below 4 while a clam will die if the ph of the water falls below 6. describe how these animals can act as natural indicators for the acidity of in lakes and rivers

Answer 1

Often, in terms of a water body becoming acidified, it depends on the rate of acidification. Fish and other aquatic species, such as invertebrates, are fairly resilient to miniscule changes, but they also have a threshold at which not a lot of them, adapted or no, can survive.

Answer 2

Aquatic animals can act as natural indicators of the acidity in lakes and rivers in the following way-

• Every animal has a certain environment that it is most suited to. For example, polar bears are best adapted to a temperature of -40° F. Similarly, every aquatic species has a distinct pH level of water that it prefers the best.
• However, minor deviations from the pH levels can be tolerated as every aquatic animal has a threshold of adaptation, which is essential for survival.
• However, if the pH level deviates vastly from this preferred threshold, the organism cannot adapt to the environment since such a major change would require major structural changes in the body of the organism that is only possible through evolution, over millions of years. A single organism when faced with such a deviant atmosphere simply cannot survive.
• For instance, just as the question mentions, a wood frog cannot tolerate a pH level that drops below 4. Water with a pH level of less than 4 would be too acidic for them to live in.
• This can be used as a natural indicator of the pH level of the water in an aquatic body. The absence of a particular species from an aquatic body, which is usually found in other aquatic bodies in the specific climate zone and region, indicates that the pH level was less or more than what they could tolerate.
• Hence, for example, if a sea side rock pool does not have any clams in it even though it is supposed to be a habitat for them, it would indicate that the pH level of the water has fallen to acidic levels below pH 6, which is not what a clam can survive.

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