Mink (Neovison vison) as a natural vector in the dispersal of the diatom Didymosphenia geminata

Abstract

Considerable resources have been invested worldwide in response to the spread of the diatom Didymosphenia geminata in rivers and streams. Considering the very low possibility of elimination of an invasive microbe, management has focused on biosecurity protocols, addressed exclusively toward the human role in dispersal (e.g. ‘check, clean dry’ campaigns and gear-washing stations for recreational users). Natural dispersal by wildlife vectors may also play an important role in the spread of D. geminata and other algal species, potentially limiting or negating the efficacy of biosecurity measures. We investigated the possibility that introduced mink (Neovison vison) may be a potential dispersal agent for D. geminata and other stream diatoms in Chilean Patagonia. Neovison were trapped near a zone of strong and persistent D. geminata blooms in the fifth order Río Simpson, and also in a fourth order upstream tributary, Río Huemules, the latter with smaller, more incipient blooms. Epibiotic D. geminata cells were identified from Neovison at Río Simpson (44% positive, average 791 cells per animal, n=18 animals), and Río Huemules (20% positive, average 40 cells per animal, n=5 animals). Many other species were also observed: 20 genera, 5683 cells per mink in Río Simpson, and 18 genera, 3605 cells per mink in Río Huemules. Navicula, Epithemia, Fragilaria and Placoneis were among the genera most frequently encountered. Neovison are known to prefer the riparian ecotone of streams of all sizes, have the capacity to travel several kilometers upstream and downstream, and possibly as far as 10 km overland to colonize new catchments. Together with an estimated survival time of 60 or more days for D. geminata in a humid environment (e.g. mink fur), Neovison represent a potentially significant factor in the colonization of upstream reaches and adjacent catchments. We comment on the potential for other wildlife vectors in Patagonia, and respective alternative patterns of short- to long-distance dispersal of diatoms in continental waters. Our results suggest that wildlife vectors should be considered in the management of D. geminata, and in the case of Neovison, integrative management of multiple invasive species, and a reassessment of conservation priorities may be necessary.

Keywords:

• diatom dispersal
• wildlife vector
• secondary spread
• epibiotic flora
• biosecurity

Acknowledgements

Ramón Henríquez, Director of the Servicio Agrícola y Ganadero, Aysén Region, supported field work and offered the use of the Laboratorio Regional Pecuario in Coyhaique. Cinco Ríos Lodge provided access to the Río Simpson. Paulina Montero and Carmen Gloria contributed microscopes and materials in the CIEP phycology lab. Research design and analysis was significantly improved with help from undergraduate thesis advisors Luciano Caputo and Jorge Jaramillo of the Universidad Austral de Chile.