Mountain streams often contain fewer living things than equivalent streams at sea level. Give one reason why this might be true in terms of oxygen solubilities at different pressures.

When exploring the factors affecting how gases like oxygen dissolve in water, we refer to Henry's Law. It plays a pivotal role in understanding the solubility of gases and states that at a constant temperature, the concentration of a gas in a liquid is directly proportional to the pressure of that gas above the liquid. In other words, more gas will dissolve in water if the pressure above the water is increased, given the temperature remains unchanged. So, when we're looking at mountain streams versus those at sea level, Henry's Law gives us a fundamental basis for why we might observe different amounts of dissolved oxygen.

This law is not only critical in environmental studies but also widely applied in the beverage industry for carbonating drinks, in medicine for administering anesthetic gases, and even in engineering fields such as chemical processing.

Altitude plays a key role in determining atmospheric pressure, which in turn affects the solubility of gases in water. As we climb higher above sea level, the atmospheric pressure drops, resulting in what we call a lower barometric pressure. This decline in pressure with altitude is due to the thinning of the air – the higher you go, the less air there is pressing down from above.

This phenomenon is familiar to anyone who has experienced the popping of ears when ascending in an airplane or driving up a mountain. For aquatic life, however, this change in pressure with altitude has serious implications as it correlates with the amount of oxygen that can be dissolved in water, a vital factor for their survival.

The availability of dissolved oxygen in water is crucial for the survival of aquatic life. Fish, amphibians, and numerous invertebrates rely on oxygen dissolved in water to breathe. As established by Henry's Law, the lower atmospheric pressure at higher altitudes means that there is less oxygen dissolved in mountain streams. This limited oxygen availability can restrict the types of organisms that can thrive in these conditions, often leading to less biodiversity in high-altitude aquatic ecosystems.

The intricate balance of the ecosystem is highly sensitive to the levels of dissolved oxygen. Even small changes can impact species health and behavior, leading to reduced populations or the necessity for certain species to evolve special adaptations to survive in these oxygen-sparse conditions.

The solubility of gases in water is greatly influenced by atmospheric pressure. When we discuss solubility, we often consider factors like temperature and the nature of the solvent and solute. However, for gases, atmospheric pressure is a significant driver. At higher atmospheric pressures, more gas molecules are forced into solution. Conversely, when the atmospheric pressure is lower, such as in high-altitude environments, fewer gas molecules dissolve.

This relationship has practical implications beyond aquatic ecosystems. It affects how we design equipment for divers, how we understand and predict the weather, and it's even crucial for understanding how humans and animals adapt to high altitudes. For example, humans may experience altitude sickness in part due to the lower oxygen levels in the blood, a direct result of decreased gas solubility at lower atmospheric pressure.