The relationship between water convection and dissolved oxygen levels in aquatic bodies: The introduction of an aeration device can effectively regulate dissolved oxygen levels.

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2020-11-12

Although fish floating to the surface can be caused by a variety of factors, in addition to excessive stocking density, overloading the total fish biomass, and poor water quality, the convective properties of water are also a major factor that cannot be overlooked. Simply put, when water temperature is low, its specific gravity (or density) increases, causing it to sink; conversely, when water temperature is high, its specific gravity (or density) decreases, making it float upward. Understanding and mastering the principles of water convection will greatly facilitate the smooth operation of aquaculture. On warm days, after being heated by the sun during the day, the warmer, lighter water tends to stay on top. As the sun sets and the air temperature begins to drop, the upper layer of water cools down, increasing its density, and gradually starts to sink. If the nighttime temperature remains relatively high, the water cools down slowly, and the upper layer won't reach the bottom of the pond until early morning. This is one of the main reasons why oxygen levels tend to drop sharply from late night into early morning on hot days. However, if a heavy rainstorm occurs in the evening, the situation changes dramatically. The cold, heavy rainwater quickly sinks to the bottom of the pond, stirring up sediment, leftover feed, fecal waste, biological residues, and other organic matter from the pond bottom and bringing them into the middle and upper layers of the water. These harmful organic substances rapidly deplete the dissolved oxygen in the water. Before dawn even breaks, the dissolved oxygen in the water may be completely used up, leaving the fish vulnerable to oxygen depletion and causing them to float to the surface—a phenomenon known as "floating and surfacing." Therefore, sudden heavy rainfall in the evening or at night can also lead to oxygen depletion and fish floating to the surface.

Although fish surfacing is caused by a variety of factors, in addition to such reasons as excessive stocking density, overloading the total fish population, and poor water quality, the convective properties of water are also a major factor that cannot be overlooked. Simply put, when water temperature is low, its specific gravity (or density) becomes heavier (higher), causing it to sink; conversely, when water temperature is high, its specific gravity (or density) becomes lighter (lower), causing it to rise. Understanding and mastering the principles of water convection will greatly facilitate the smooth operation of aquaculture.

In warm weather, after the daytime water is heated by the sun, the warmer, lighter water tends to float on top. Once the sun sets and the temperature begins to drop, the upper layer of water cools down, increasing its density and causing it to slowly sink. If the nighttime temperature remains relatively high, the water cools down more slowly, and the upper layer won't reach the bottom of the pond until early morning. This is one of the main reasons why oxygen levels tend to drop during the late night and early morning hours on hot days.

If a heavy downpour occurs in the evening, the situation changes dramatically. The cold, dense rainwater quickly sinks to the bottom of the pond, stirring up sedimented leftover feed, fecal waste, biological debris, and other organic matter from the pond bottom and bringing them together with the bottom-layer water into the middle and upper layers of the pond. These harmful organic substances rapidly deplete the oxygen in the water, and before dawn even breaks, the dissolved oxygen levels in the water may be completely exhausted. As a result, fish are highly likely to exhibit symptoms of oxygen deprivation—such as floating at the surface or "turning over"—leading to mass fish mortality. Therefore, sudden heavy rainfall occurring at night (or in the evening) can also trigger oxygen depletion and fish die-offs.

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The relationship between water convection and dissolved oxygen levels in aquatic bodies: The introduction of an aeration device can effectively regulate dissolved oxygen levels.

Although fish floating to the surface can be caused by a variety of factors, in addition to excessive stocking density, overloading the total fish biomass, and poor water quality, the convective properties of water are also a major factor that cannot be overlooked. Simply put, when water temperature is low, its specific gravity (or density) increases, causing it to sink; conversely, when water temperature is high, its specific gravity (or density) decreases, making it float upward. Understanding and mastering the principles of water convection will greatly facilitate the smooth operation of aquaculture. On warm days, after being heated by the sun during the day, the warmer, lighter water tends to stay on top. As the sun sets and the air temperature begins to drop, the upper layer of water cools down, increasing its density, and gradually starts to sink. If the nighttime temperature remains relatively high, the water cools down slowly, and the upper layer won't reach the bottom of the pond until early morning. This is one of the main reasons why oxygen levels tend to drop sharply from late night into early morning on hot days. However, if a heavy rainstorm occurs in the evening, the situation changes dramatically. The cold, heavy rainwater quickly sinks to the bottom of the pond, stirring up sediment, leftover feed, fecal waste, biological residues, and other organic matter from the pond bottom and bringing them into the middle and upper layers of the water. These harmful organic substances rapidly deplete the dissolved oxygen in the water. Before dawn even breaks, the dissolved oxygen in the water may be completely used up, leaving the fish vulnerable to oxygen depletion and causing them to float to the surface—a phenomenon known as "floating and surfacing." Therefore, sudden heavy rainfall in the evening or at night can also lead to oxygen depletion and fish floating to the surface.

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2020-11-12