The diatom Didymosphenia geminata, which forms nuisance blooms in low nutrient streams worldwide, was documented as an aggressive invader in South America in 2010 from the Futaleufú basin (43.2• S), in Chilean and Argentinean Patagonia. Within 1 year it was confirmed from 20 rivers distributed over 800 km. Driven by perceived economic impacts to tourism and recreation, a strong response ensued, with education, monitoring and nascent biosecurity efforts based on similar measures in New Zealand. Considering the difficulty in containment (potential range on New Zealand's South Island was occupied by D. geminata within 3 years), the much larger potential range, and limited resources or previous experience in managing invaders in continental waters in South America, it is unlikely that current biosecurity measures will produce significant results. Lacking a coordinated strategic approach or conservation priorities, existing efforts may divert resources from alternatives with greater potential for success, while potentially feeding the public perception that the problem is being addressed. We propose a conservation strategy based on best available but incomplete information on habitat requirements, and a conceptual model of invasion vectors to identify defensible conservation zones (islands and hydrographically isolated areas) with greater potential for being maintained invasion-free.

No abstract

Large nuisance blooms of Didymosphenia geminata have become increasingly widespread in Patagonia. Although the first published account for South America was in 1964, reports of large growths in Chile and Argentina commenced around 2010. Since then, these blooms have been observed all along the Andes region to the south of parallel 42 S. General surveys are needed to help provide an explanation. Possibilities include one or more new genetic variants or responses of local populations to global environmental changes. Electron microscopy of material from the Argentinean Patagonia revealed marked differences between regions, though it is unclear how much local factors and/or variations in life cycle contribute. Thus, we are approaching the problem from a molecular perspective, which we hope will help to overcome this limitation. Initial studies showed that D. geminata seems to be highly recalcitrant to DNA extraction, thus hindering the survey of molecular markers. We have now developed an improved DNA extraction technique for Didymosphenia mats, which markedly outperforms other techniques. However, endpoint polymerase chain reaction analyses suggest the persistence of polymerase chain reaction inhibitors in the samples, highlighting the need of further improvements for quantitative studies.