Invisible plastics problem in intensive aquaculture: The case of polyvinylpyrrolidone

For over 70 years, aquaculture practices have relied on the same methods for biosecurity, however epidemics remain a primary limitation of global aquaculture yields with billions in revenue being lost every year due to disease. The intense nature of fish and shellfish farming necessitates the regular use of synthetic chemicals as both preventive and treatment measures, covering broodstocks to hatching and continuing through all stages of rearing. This practice, however, results in the contamination of rearing environments with persistent xenobiotics. A specific drawback in this foundational strategy for aquaculture biosecurity is highlighted in the current review: the consistent use of a water-soluble polymer polyvinylpyrrolidone (PVP) across most, if not all, stages of rearing aquacultural livestock. PVP is used intensively within aquaculture practices as it is a ubiquitous additive within commercially available germicidal, prophylactic, and therapeutic products applied to control and prevent disease outbreaks within aquacultural farms. As a polymer, PVP is synthetic and biodegradation-resistant, and has recently been described as an emerging contaminant of freshwater ecosystems. It is well documented that other persistent, synthetic polymer pollutants such as microplastics, reduce the fecundity, growth, and significantly deplete immune function in commercially important aquatic species. Despite this, intentionally added persistent soluble polymers, such as PVP, have not been considered in the context of aquaculture productivity. This review explores the potential impact of PVP on fish and shellfish highlighting the need for aquaculture to adopt sustainable chemical practices, drawing inspiration from advancements in nanotechnology applied within human medicines to address biosecurity protocol deficiencies.