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Risks of Using Antifouling Biocides in Aquaculture

Published by International Journal of Molecular Sciences.
By Francisco Antonio Guardiola et al.

The use of biocides in the aquatic environment … has proved to be harmful as it has toxic effects on the marine environment.

Organic booster biocides were recently introduced as alternatives to the organotin compounds found in antifouling products after restrictions were imposed on the use of tributyltin (TBT). The replacement products are generally based on copper metal oxides and organic biocides. The biocides that are most commonly used in antifouling paints include chlorothalonil, dichlofluanid, DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, Sea-nine 211®), Diuron, Irgarol 1051, TCMS pyridine (2,3,3,6-tetrachloro-4-methylsulfonyl pyridine), zinc pyrithione and Zineb.

There are two types of risks associated with the use of biocides in aquaculture: (i) predators and humans may ingest the fish and shellfish that have accumulated in these contaminants and (ii) the development of antibiotic resistance in bacteria. This paper provides an overview of the effects of antifouling (AF) biocides on aquatic organisms. It also provides some insights into the effects and risks of these compounds on non-target organisms.”

“Copper is an essential metal. However, although it is an effective biocide, it may also affect nontarget organisms and cause environmental concerns. The toxicity of copper in water is greatly affected by the chemical form or speciation of the copper and to what degree it is bound to various ligands that may be in the water, making the copper unavailable to organisms. The speciation is essential for understanding the copper’s bioavailability and subsequent toxicity to aquatic organisms.

Copper oxide leaches from the boat surfaces and enters the water as a free copper ion (Cu+ ), which is immediately oxidised to Cu2+ and forms complexes with inorganic and organic ligands.

Copper is a trace element needed at miniscule levels for the proper functioning of all organisms. However, it can be toxic at higher concentrations [85]. Copper is generally toxic to aquatic organisms”

(Other biocides discussed: Diuron, Irgarol, TCMS Pyridine, Zinc Pyrithione, Zineb, Capsaicin, Econea and Medetomidine)

“Biocides are used as components in paints to coat the structures of vessels, as a means of disinfecting aquaculture facilities and cages, as well as in controlling the biofouling phenomenon (antifouling). The use of biocides is not as well-regulated as drug use in aquaculture because the information available on the effects of these agents to the marine ecosystems is still limited. Hence, it is important to know the risks associated with the existence of those biocides in the marine environment. It is also important to evaluate the effects of these compounds through the continuous monitoring of biocide concentration profiles in water, sediment and biota to provide information that could lead to concerted action to ban or regulate their use.”

)Download the full paper here)

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