Environmental Factors Influencing Blooms of a Neurotoxic Stigonematalan Cyanobacterium Responsible for Avian Vacuolar Myelinopathy

Managers of southeastern reservoirs have been challenged by the introduction of nonnative aquatic plants and subsequent ecological consequences. The authors of this technical note have linked avian vacuolar myelinopathy (AVM), a disease killing waterbirds and raptors, to an epiphytic cyanobacterium which grows primarily on nonindigenous submerged aquatic vegetation (SAV). Waterbirds, especially American coots and herbivorous waterfowl populations, increase on reservoirs with abundant invasive aquatic plants. Once they consume the epiphytic cyanobacteria growing on SAV and become neurologically impaired, birds of prey (especially eagles) readily consume the sick and dead birds. Research studies have suggested that the causative agent is a neurotoxin produced by a previously undescribed Stigonematalean cyanobacterium (UCB) that grows epiphytically on submerged, primarily non-native, aquatic plants. Plant collections from Texas to North Carolina indicate that the range of the suspect cyanobacterium is expanding as invasive aquatic plants colonize new systems, especially those in close proximity to AVM sites. The authors research seeks to guide management of AVM reservoirs by investigating relationships between environmental factors and the presence of the cyanobacterium. Field surveys conducted from 2001-2010 documented the geographic distribution of the Stigonematalan species and confirmed that invasive aquatic plants supported dense colonies of this species. The authors then created a generalized linear model using temperature, oxygen, turbidity, and previous colonization data to explain site-specific variation of Stigonematales densities in an AVM positive site. These field surveys and preliminary models provide insights into predicting the seasonal prevalence of Stigonematales in reservoirs. The original document contains color images.