23.4 The importance of the hydrosphere (ESAHT)

It is so easy sometimes to take our hydrosphere for granted and we seldom take the time to really think about the role that this part of the planet plays in keeping us alive. Below are just some of the important functions of water in the hydrosphere:

• Water is a part of living cells Each cell in a living organism is made up of almost \(\text{75}\%\) water, and this allows the cell to function normally. In fact, most of the chemical reactions that occur in life, involve substances that are dissolved in water. Without water, cells would not be able to carry out their normal functions and life could not exist.

• Water provides a habitat The hydrosphere provides an important place for many animals and plants to live. Many gases (e.g. \(\text{CO}_{2}\), \(\text{O}_{2}\)), nutrients e.g. nitrate (\(\text{NO}_{3}^{-}\)), nitrite (\(\text{NO}_{2}^{-}\)) and ammonium (\(\text{NH}_{4}^{+}\)) ions, as well as other ions (e.g. \(\text{Mg}^{2+}\) and \(\text{Ca}^{2+}\)) are dissolved in water. The presence of these substances is critical for life to exist in water.

• Regulating climate One of water's unique characteristics is its high specific heat. This means that water takes a long time to heat up and also a long time to cool down. This is important in helping to regulate temperatures on earth so that they stay within a range that is acceptable for life to exist. Ocean currents also help to disperse heat.

• Human needs Humans use water in a number of ways. Drinking water is obviously very important, but water is also used domestically (e.g. washing and cleaning) and in industry. Water can also be used to generate electricity through hydropower.

These are just a few of the functions that water plays on our planet. Many of the functions of water relate to its chemistry and to the way in which it is able to dissolve substances in it.