Question

Helicopters have been used to move young salmon from lake to lake for purposes of aquaculture in remote areas such as Alaska. From the viewpoint of the behavior of dissolved gases, why is it important for helicopters used in this wany to stay at very low altitudes? (Hint: After fish were transported at altitudes where the total ambient presesure was $0.9$ atm, high percentages suffered disease or death because of gas bubble formation in various tisstaes.)

Short answer

Helicopters used for moving young salmon through altitudes must maintain at lower altitudes to avoid rapid decreases in pressure. High-altitude travel decreases the pressure quickly, which reduces the solubility of gases present in the fish's tissues, leading to the formation of gas bubbles. Such changes harm the fish, causing disease or death. Therefore, operating at lower altitudes ensures the pressure stays relatively constant and promotes the healthy transportation of the fish.

Step-by-step solution

Gas Solubility Understanding

It is crucial to understand the connection between gas solubility, pressure, and temperature. At a given temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. This is known as Henry's Law.

Effects of Pressure Changes on Aquatic Life

Gas bubble formation in various tissues causes decompression sickness or 'the bends'. When fish are in water at certain depth, they assort to a certain pressure and certain amount of gas is dissolved in their tissues. If the pressure decreases too quickly, the dissolved gas in fish tissue can form bubbles as it will not be able to diffuse out of the tissues quickly enough. These bubbles can cause damage to tissues and organs and lead to disease or death.

Implications of Pressure Changes during Transportation of Fish

From the above understanding, by transporting fish at high altitudes where the pressure is lower (0.9 atm), gas solubility decreases which might result in the formation of gas bubbles in the tissues of the fish, leading to disease or death. Thus, it's crucial for helicopters transporting fish to maintain low altitudes where the pressure variances are slight to facilitate the fish's survival.

Key concepts

Henry's Law

Henry's Law is a fundamental principle that plays a crucial role in understanding how gases behave when dissolved in liquids, an essential aspect of aquatic animal physiology. According to Henry's Law, at a constant temperature, the concentration of a gas dissolved in a liquid is directly proportional to the partial pressure of that gas in contact with the liquid.

In mathematical terms, the law is expressed as: $C=kP$, where $C$ represents the concentration of the gas dissolved, $P$ is the partial pressure of the gas, and $k$ is Henry's Law constant, which varies for different solute-solvent combinations.

This concept is critical when considering the transport of aquatic life, such as fish, because any change in atmospheric pressure can alter the gas concentrations within their bodies. For example, if the pressure is reduced during transportation by helicopter, as in the exercise, the gas concentration in the fish's bloodstream could drop, leading to potential health issues.

Decompression Sickness in Fish

Decompression sickness, commonly known as 'the bends', is a condition usually associated with divers but can also affect aquatic animals like fish. The condition occurs when nitrogen gas, which is normally dissolved in the bloodstream and tissues under high pressure, forms bubbles as the pressure decreases. These nitrogen bubbles can cause various physiological problems.

For fish, rapid changes in pressure, such as when they are quickly brought to the surface from deep water or transported at high altitudes, can be deadly. The bubbles formed by rapid decompression can obstruct blood vessels, damage tissues, and even cause death. It's crucial for transport methods, like helicopters, to maintain altitudes that do not significantly decrease pressure in order to prevent this condition in fish.

Gas Solubility and Pressure

The relationship between gas solubility and pressure is at the heart of understanding the risks associated with transporting fish by air. Gas solubility in a liquid increases as the pressure increases and decreases as the pressure decreases, given the temperature remains constant. This is why deep-sea fish contain more dissolved gases in their bodies since the pressure is greater.

When transporting fish between places at different altitudes, the change in pressure can lead to a reduction in solubility, potentially resulting in gas coming out of solution and forming harmful bubbles. To prevent this, transport methods must minimize the pressure changes by staying at low altitudes, ensuring the overall ambient pressure does not drop too significantly and the gas remains dissolved in the fish's tissues.