Algae are a divergent group of aquatic living organisms that are capable of conducting the photosynthesis process. They can produce oxygen and can consume carbon dioxide thus serves as a base for the food chain of aquatic organisms. The algal body posses simple morphology with chlorophyll and the size ranges from microscopic single-celled to macroscopic multi-celled organisms. The mode of nutrition in algae is typically autotrophic,they have the potential to derive the energy from the sunlight ad transfer it to the next level of the food chain. Even though the algae supports the existence of other organisms, the algal bloom or algal toxins are deleterious to the other organisms and the environment.The industry of aquaculture is frequently facing challenges by the presence of harmful algal blooms. An algal bloom is the rapid growth of the algal population in an aquatic environment, it can occur in either fresh or marine water. These algae compete with the
cultured species for nutrients and oxygen Some of the algal blooms occur due to the presence of an excess of nutrients in the culture water and as a result of increased growth of algae causes death to other small organisms in the aquatic system. These dead matters pave the way for more bacteria to flourish in the environment and eventually consume all the dissolved oxygen in the water and make the fishes die in the scarcity of oxygen. In addition to this, some algal blooms can produce neurotoxins and biotoxins, which can cause severe impacts to the native organism of that particular environment.
Generally, algal toxins are organic molecules that are associated with harmful algal blooms, which can cause drastic problems in the aquaculture of both fishes and shellfishes. If the algal toxins produced by the algae are in sufficient quantity and potency, it can kill cultured organisms by decreasing the feeding and growth rate. In total, Being a constant problematic factor in aquaculture, both toxic and non-toxic algal bloom can destroy the cultured organisms, the toxic blooms can produce algal toxins like biotoxin, neurotoxin and non-toxic algal bloom can cause oxygen depletion. The harmful algal is not only a contributing threat to the survival of the cultured species but also cause huge impacts on the health of the consumers. The phycotoxins are the main reason for the adverse effect on the health of the
It is inevitable to control the growth of these algal blooms in aquaculture to maintain a safe and profitable culturing. The algal blooms can be controlled by different ways such as;
By the application of ultrasounds, which have sound waves with a frequency above the human hearing frequency can control excessive algal growth. Usually, during the day time, the algal communities are found at the top surface of the water for carrying out photosynthesis. By applying the ultrasound technique to the water surface, the algal buoyancy gets fluctuated hence sinks to move towards the bottom of the water and fails to carry out the photosynthesis in the absence of light, and ultimately dies. For long term algal control, the frequency of the ultrasound should be adjusted regularly according to the type of algae.
Algal growth can also b
e controlled by treating the culture water with various chemical additives. Alum, lanthanum is usually used in aquaculture to prevent algal growth. Copper based compounds like copper chelate, copper sulphate and chemical endothall in the algaecide are efficient in eradicating algae from the culture. The chemical method is very effective if the whole culture system is uniformly treated with it.
The level of phosphorus and nitrogen are normally controlled by the dissolved oxygen present in the water. The continuous exposure of water with nutrient-rich compounds eventually reduces the oxygen level of the water and promotes the rising of phosphorus and nitrogen. The nutrient content is a major factor that promotes the survival and growth of algae. Through the introduction of aerators to the aquaculture sectors, the algal growth can be reduced due to insufficient phosphorus content. The aerators can be also beneficial for the aerobic bacteria in the water to improve their decomposing ability hence the level of nutrients
van be reduced. The bacteria will compete with the algal community for the nutrients and hence reduces the flourishment of the algal bloom.
The control and prevention of algal growth are adequate for the sustainability of aquaculture. Excessive algal growth can not only able to cause severe problems to the survival of the cultured species it can be very harmful to the health of the consumers. Hence the algal growth can become tremendous destruction to the industry of aquaculture. The threat by the algae is a huge challenge to the growing aquaculture sector, so the need to eradicate it is very essential. Prevention of the growth of algae can ensure safe and sustainable aquaculture.
- Brown, Andrew Ross, et al. “Assessing risks and mitigating impacts of harmful algal blooms on mariculture and marine fisheries.” Reviews in Aquaculture 12.3 (2020): 1663-1688.
- Young, Nick, et al. “Marine harmful algal blooms and human health: A systematic scoping review.” Harmful Algae 98 (2020): 101901.
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