Just last week, it was reported that the shores of Quintana Beach County Park, near Freeport, Texas, were covered with dead fish caused by low dissolved oxygen levels in the water, likely because of a recent temperature rise within the area. We have discussed the impact our weather, in general, has on the aqua life, but this incident gives us a full-blown picture of what our reality will look like if we do not take adequate and immediate action, after all, Texas waters are not the only waters across the world that have fish. The fish are reported to have essentially suffocated. The question we should be asking ourselves should be how large water bodies can lose oxygen and have such effects:

a) Biological Oxygen Demand (BOD) is the amount of oxygen consumed by microorganisms during the decomposition of organic matter. When excessive amounts of organic material, such as dead plants or algae, enter a body of water, bacteria and other microorganisms consume oxygen as they break down the organic matter. This process depletes the dissolved oxygen levels in the water.

b) In large bodies of water, temperature variations can cause stratification, where the water column separates into distinct layers. The surface layer called the epilimnion, receives sunlight and oxygen, while the deeper layer, called the hypolimnion, is colder and receives less oxygen. In some cases, the lower layer can become isolated from the surface, leading to a lack of oxygen replenishment. Over time, oxygen levels in the hypolimnion may decrease, and certain oxygen-dependent organisms may die or migrate to other areas.

c) Decreased water flow and mixing also impact oxygen levels. Water movement and circulation play a vital role in oxygen distribution. If there is a reduction in water flow or mixing, such as in stagnant or poorly circulated areas, oxygen exchange between the atmosphere and water may be limited. This reduced exchange can contribute to oxygen depletion in these areas.

It’s important to note that human activities, such as pollution and climate change, can exacerbate these natural processes and accelerate oxygen depletion in water bodies. While the dead fish on the Texan shore has not been credited to any human activities, given the world’s largest liquefied natural gas facility sits nearby. We cannot ignore the role we play in our surroundings as a whole. High levels of pollution, particularly from industrial discharges or untreated sewage, can introduce additional organic matter and nutrients, intensifying oxygen consumption by microorganisms. Climate change can also impact oxygen levels through its effects on water temperature, precipitation patterns, and ecosystem dynamics, further influencing oxygen availability in large bodies of water.

“If you try to drown a fish, the ocean will laugh at you.”

– Matshona Dhliwayo