Decay of Bloom-Forming Algae and the Affects on Dissolved Oxygen

 By: Andrea R. Ortiz 

The figure above is from Wang et. al., 2021. It indicates the algae strains a. A. catenella , b. P. donghaiense , c. S. costatum treatments and their results for 1. cell density, 2. dissolved oxygen concentration, and 3. Ammonia nitrogen concentration at each level surface = black, middle = red, and bottom = blue. 

 

Eutrophication is a process when an excess of minerals and nutrients occurs within a body of water. This sounds like a positive occurrence in theory; however the result of this process welcomes harmful algae blooms and a reduction of dissolved oxygen. The consequences of these overly enriched aquatic environments include destruction of ecosystems and massive loss of various aquatic species. 

In a 2020 study by Wang and colleagues, samples of Chinese costal water were used in order to evaluate the decay of bloom-forming algae and how it affects the reduction of dissolved oxygen (DO). 

Algae strains of A. catenella , P. donghaiense , S. costatum were cultured in a seawater medium under 24 day treatment involving stable temperature at 20 degrees Celsius and no light during incubation.

Interestingly enough the result of this investigation was that density and DO concentration of the algae decreased from each level formed in the tubes while ammonia nitrogen increased. This indicates that massive decay of harmful bloom-forming algae could cause increasing consumption of DO and over production of toxic ammonia nitrogen. Ultimately, it is imperative to further conduct future studies such as this in order prevent detrimental impacts to the world's various aquatic environments. 

Reference: 

Wang, Q., Li, X., Yan, T., Song, J., Yu, R., & Zhou, M. (2020). Laboratory simulation of dissolved oxygen reduction and ammonia nitrogen generation in the decay stage of harmful algae bloom. 

Journal of Oceanology and Limnology, 39(2), 500–507. https://doi.org/10.1007/s00343-020-9295-2