Scientists and artists need to know what the water is like to create an accurate picture of an ecosystem. All water ecosystems are not the same. The most apparent example is the difference between saltwater and freshwater, but there are many other characteristics that determine what kind of life might be found in a certain body of water. Would the same animals living in a warm tropical environment be found in a frozen one? It would be unlikely. Humans seem to be about the only animals that can survive in any climate, and we need a lot of extra gear to do that!
By testing the water, scientists can also learn about the health and cleanliness of the water and the ecosystem. A few of the things that can be tested are listed below. Also, be sure to go into the Sea Center where you can perform some of these tests yourself.
Salinity – The amount of salt in the water is called salinity. The ocean has a lot of salinity, averaging from 32 to 37 parts salt per thousand. Freshwater ranges from about 0 to 4 ppt. Tap water and bottled water are usually limited to about .5 ppt. Some animals can live in both salt and fresh water, but most can only survive in one or the other.
Turbidity – If you’re describing water and using words like “brown, mucky, or murky”, you are looking at turbid water. Turbid is the opposite of clear and means the water is full of floating particles such as dirt, debris, or even algae. Turbidity can be one factor in determining if water is polluted. The sediment can clog fish gills, cover laid eggs on the bottom (can be a positive or negative action), or stop sunlight from reaching aquatic plants. Turbid water can also be caused by an overgrowth of plankton that uses up all the oxygen in the water when the plankton dies and decomposes. Some bodies of water, however, are naturally turbid and promote healthy ecosystems. Animals that live in these types of water can have adaptations that help them to thrive under turbid conditions.
pH – pH measures the “base” or “acidity” of water on a 0-to-14 range. The lower the pH number, the more acidic the water is. Most living things can’t survive in water that is tooacidic or too basic. Healthy freshwater has a pH of about 6. Healthy ocean water has a pH of about 8. Most fish and invertebrates live within a pH range of 6 to 9.