Potential disruptive effects of zoosporic parasites on peatland-based organic freshwater aquaculture: Case study from the Republic of Ireland.

Irish freshwater aquaculture holds great potential for aiding food security. However, its necessary expansion has been hampered by the adoption of important environmental EU directives. A novel peatland-based recirculating aquaculture multi-trophic pond system (RAMPS) was developed to assess its potential to assist in the sustainable development of industry whilst remaining aligned with environmental protection by adhering to organic aquaculture practices. Microalgae play a pivotal role in the farms' wastewater bioremediation. However, a collapse of the algal population within the system towards the end of the pilot study was observed. No relationship between physicochemical fluctuations and the collapse were indicated. Further investigations into the potential presence of biological agents were then conducted and fourteen species of zoosporic parasites from five different genera (Labyrinthula, Vampyrella, Amoeboaphelidium, Paraphelidium and Aphelidium) were identified after conducting next-generation sequencing (MinION). The presence of these species indicated the potential cause of algal collapse. Additionally, changes in weather conditions may have also contributed to the issue. Given the lack of data available on zoosporic parasites and their potential impact on organic aquaculture practices, additional research needs to be conducted. Developing a means to monitor and mitigate against these complex zoosporic parasites will inform food security, it will particularly help safeguard "organic" freshwater aquaculture where there is a reliance on using natural-based approaches to address disease mitigation. . This information will in turn inform the replication of this RAMPs system in peatlands internationally creating local employment in green technologies, as communities' transition away from burning peat as fossil fuel. Also, zoosporic parasites may reduce important microalgae in peatland-based culture ponds that serve as exceptional sequesters of carbon. Findings of this study will inform related research that focus on the emergence of microbial pathogens in local aquatic ecosystems brought on by variances in climate.