Assessing the Toxicity and Mitigating the Impact of Harmful Blooms in Eutrophic Waters of the Norfolk Broads.

is a toxin-producing microalga, which causes harmful algal blooms globally, frequently leading to massive fish kills that have adverse ecological and economic implications for natural waterways and aquaculture alike. The dramatic effects observed on fish are thought to be due to algal polyether toxins, known as the prymnesins, but their lack of environmental detection has resulted in an uncertainty about the true ichthyotoxic agents. Using qPCR, we found elevated levels of and its lytic virus, PpDNAV-BW1, in a fish-killing bloom on the Norfolk Broads, United Kingdom, in March 2015. We also detected, for the first time, the B-type prymnesin toxins in Broads waterway samples and gill tissue isolated from a dead fish taken from the study site. Furthermore, Norfolk Broads isolates unambiguously produced B-type toxins in laboratory-grown cultures. A 2 year longitudinal study of the Broads study site showed blooms to be correlated with increased temperature and that PpDNAV plays a significant role in bloom demise. Finally, we used a field trial to show that treatment with low doses of hydrogen peroxide represents an effective strategy to mitigate blooms of in enclosed water bodies.