A study published in the journal “Microbiology Open” ensures that the impact of hyper densification in fish cages can contribute to the increase of organic matter in marine ecosystems.
In the aquaculture industry, the Atlantic salmon (Salmo salar), present in most of the farming centers in our country, releases different types of organic matter during its life cycle, which is integrated into the nutrient cycle in the water column.
Unconsumed food, excretion and fecal pellets released by fish affect the microbial communities present in the water and sea floor. However, a recent investigation also determined the impact of the epithelial mucus of S. salar in these ecosystems.
“The mucus that is constantly generated in the salmon’s epithelium is consumed by bacteria and ectoparasites such as Caligus, which is one of the problems of the salmon industry. It must be understood that this fluid is an anti-stress mechanism, therefore, the greater the number of stressors there is an increase in the release of this organic matter,” explained Dr. Camila Fernández, an academic at the CNRS (France,) from the Department of Oceanography of the University of Concepción (UdeC) and researcher at the Center for Dynamic Research of High Latitude Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh), co-author of the study.
After tests carried out on 18 specimens of S. salar, the mucus generates ammonia only by being released into seawater, which is consumed by bacteria and converted into other nutrients such as nitrate. “The impact this has on the marine microbiome is that it will favor some groups of microbiotas and that modifies the ability to recycle nutrients within the cage, an ecosystem different from what one can find outside these crops,” she said.
Dr. Fernández explained that hyper densification in salmon cages would favor stress conditions for this species, which could eventually, and on a large scale, modify the trophic state of the ecosystems in which the industry develops, as there are too many nutrients for the microbiota to take care of.
“We see the cage as a permanent source of organic material. This eventually must be taken into account to see, for example, the carrying capacity of an ecosystem. We are not necessarily going to have eutrophication episodes, but it is a parameter to take into account,” commented the researcher, who also works for the Interdisciplinary Aquaculture Research Center (Incar), the Copas Sur-Austral Oceanographic Research Center and the Associate International Laboratory Mast/Morfun.
The work, which took three years of research, was published in the scientific journal “Microbiology Open.” The next studies will be focused on determining the relationship between the epithelial mucus of the Atlantic salmon and Harmful Algal Blooms (HABs,) commented Dr. Fernández.