Over the last decade, proliferations of benthic mat-forming Phormidium have been reported with increasing frequency in New Zealand’s cobble-bed rivers. The dominant species within these mats (Phormidium autumnale) commonly produces a range of neurotoxins, collectively known as anatoxins. Ingestion of toxic Phormidium-dominated mats has resulted in the death of an estimated 100 dogs at New Zealand’s rivers since 2005. In September 2014, a 12-week-old border terrier died rapidly after contact with floating ‘algal mats’ at a small farm pond near Kaikoura (South Island, New Zealand). The aim of this study was to establish whether ingestion of the algal mats was the cause of the death and if the dominant species was similar to that found in rivers. Environmental samples from the pond and the dog’s stomach contents contained moderate levels of anatoxin-a (25 µg L⁻¹ and 36 µg kg⁻¹ wet weight, respectively) and high levels of dihydroanatoxin-a (2,118 µg L⁻¹ and 4,437 µg kg⁻¹, respectively). The dominant organism in the environmental sample was cultured and a polyphasic approach used for characterisation. Morphological analysis of environmental samples and six isolates indicated the dominant species was most similar to Ph. autumnale. Further confirmation was provided by 16S ribosomal RNA gene sequences which showed a high percentage identity (≥ 99%) to strains isolated from Phormidium-dominated mats in New Zealand rivers. Identification of anatoxin-a and dihydroanatoxin-a in the stomach contents, environmental samples and isolates, in concert with the rapid dog death provide strong evidence that anatoxin poisoning was the cause of death. To our knowledge this is the first report in New Zealand of a dog death related to ingestion of toxic Phormidium mats from a farm pond. This study highlights the wide diversity of habitats that toxin-producing Phormidium can inhabit, and the need for greater awareness of the risks Phormidium-dominated mats pose to human and animal health.

Over the last decade, proliferations of benthic mat-forming Phormidium have been reported with increasing frequency in New Zealand’s cobble-bed rivers. The dominant species within these mats (Phormidium autumnale) commonly produces a range of neurotoxins, collectively known as anatoxins. Ingestion of toxic Phormidium-dominated mats has resulted in the death of an estimated 100 dogs at New Zealand’s rivers since 2005. In September 2014, a 12-week-old border terrier died rapidly after contact with floating ‘algal mats’ at a small farm pond near Kaikoura (South Island, New Zealand). The aim of this study was to establish whether ingestion of the algal mats was the cause of the death and if the dominant species was similar to that found in rivers. Environmental samples from the pond and the dog’s stomach contents contained moderate levels of anatoxin-a (25 µg L⁻¹ and 36 µg kg⁻¹ wet weight, respectively) and high levels of dihydroanatoxin-a (2,118 µg L⁻¹ and 4,437 µg kg⁻¹, respectively). The dominant organism in the environmental sample was cultured and a polyphasic approach used for characterisation. Morphological analysis of environmental samples and six isolates indicated the dominant species was most similar to Ph. autumnale. Further confirmation was provided by 16S ribosomal RNA gene sequences which showed a high percentage identity (≥ 99%) to strains isolated from Phormidium-dominated mats in New Zealand rivers. Identification of anatoxin-a and dihydroanatoxin-a in the stomach contents, environmental samples and isolates, in concert with the rapid dog death provide strong evidence that anatoxin poisoning was the cause of death. To our knowledge this is the first report in New Zealand of a dog death related to ingestion of toxic Phormidium mats from a farm pond. This study highlights the wide diversity of habitats that toxin-producing Phormidium can inhabit, and the need for greater awareness of the risks Phormidium-dominated mats pose to human and animal health.

The production of valuable metabolites from microalgae represents a potentially sustainable source of a range of products that can be difficult to synthesise directly. Microalgae respond to the dynamic and often subtly shifting growth environment in a complex way. The optimal conditions for growth can be quite different to those needed for optimal product generation, depending on the nature of the biosynthesis of that product. This is especially so for secondary metabolites. A combination of a multi-vessel photobioreactor array, where certain growth conditions can be monitored and controlled precisely together with an experimental design matrix has been used to determine the optimal combination of temperature, irradiance and pH for a group of xanthophylls including fucoxanthin in the algae Tisochrysis lutea in continuous culture. Continuous culture as a mode is more suited for industrial production than batch mode in which the media constituents and algal population change dramatically over time. The central composite design experiment matrix has a range of set values for each parameter being investigated that bracket the optimal conditions. The three parameters investigated in this work (temperature, irradiance and pH) are major factors influencing algal growth. The method can be applied to other parameters that might affect growth or might affect production of a metabolite of interest, such as a nutrient level. The combined approach has been used previously to indicate optimal growth conditions for biomass generation and this work is one of the first to apply it to the generation of an algal product of interest.

The production of valuable metabolites from microalgae represents a potentially sustainable source of a range of products that can be difficult to synthesise directly. Microalgae respond to the dynamic and often subtly shifting growth environment in a complex way. The optimal conditions for growth can be quite different to those needed for optimal product generation, depending on the nature of the biosynthesis of that product. This is especially so for secondary metabolites. A combination of a multi-vessel photobioreactor array, where certain growth conditions can be monitored and controlled precisely together with an experimental design matrix has been used to determine the optimal combination of temperature, irradiance and pH for a group of xanthophylls including fucoxanthin in the algae Tisochrysis lutea in continuous culture. Continuous culture as a mode is more suited for industrial production than batch mode in which the media constituents and algal population change dramatically over time. The central composite design experiment matrix has a range of set values for each parameter being investigated that bracket the optimal conditions. The three parameters investigated in this work (temperature, irradiance and pH) are major factors influencing algal growth. The method can be applied to other parameters that might affect growth or might affect production of a metabolite of interest, such as a nutrient level. The combined approach has been used previously to indicate optimal growth conditions for biomass generation and this work is one of the first to apply it to the generation of an algal product of interest.