Deadly algae kill 4,000 tonnes of Salmon in Chile

Deadly algae have killed more than 4,000 tonnes of Salmon in Chile. The algal bloom in the water reduced the amount of oxygen suffocating the salmon fishes.

Impacts

More than eighteen salmon fish farms that produce 26% of world salmon have been affected.

What are the reasons for the death of the Salmons?

The presence of urea and ammonia in the salmon farms led to the algal bloom. Three different types of harmful algae were detected in eighteen farms.

Salmon Production in Chile

Chile is the second largest producer of Salmon in the world after Norway. It exported more than 4.4 billion USD of fish in 2020. Chile produces more than 26% of world Salmon.

What is Algal Bloom?

Algal Bloom is rapid increase of algal population in marine water or fresh water. It occurs due to the nutrients from phosphorous or nitrogen fertilizer run off. They create harmful effects such as blocking of sunlight. This causes depletion of oxygen level in water.

Oxygen in Water

The Dissolved oxygen in water is the most important water quality factor. A pond supporting an aquatic ecosystem will have more than 10 ppm oxygen dissolved in it. On the other hand, atmosphere has 200,000 ppm of oxygen. The oxygen concentrations below 3 ppm will stress the species of fish in the water. The oxygen concentrations below 2 ppm will kill the fishes.

Oxygen dissolves in water in two ways. One is through atmospheric contact that happens at the surface. The other primary source of dissolved oxygen is from algae. The algae add dissolved oxygen to the water by photosynthesis, thereby supporting lives in the water system. In that case, how did the algal bloom in Chile kill thousands of fishes?

How does Algal Bloom kill fishes?

During day, the algae produce oxygen through photosynthesis. While at night, in the absence of sunlight, it stops photosynthesis and starts respiring just like other organisms in the water system. Respiration is taking in Oxygen and releasing carbon dioxide. Thus, during night the dissolved oxygen drops too low suffocating the fish in the water system.

Also, as the algal bloom increases, it forms thick blanket over the water surface. This prevents sunlight from penetrating the water. Thus, the second source of oxygen where the oxygen dissolves in water at the surface contacts is blocked.

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