Physicochemical paramaters and epiphytic algae in Hydrilla verticillata associated with seasonal occurrences of avian vacuolar myelinopathy

Abstract

Avian vacuolar myelinopathy (AVM) is an avian disease affecting primarily American coots (Fulica americana) and bald eagles (Halieetus leucocephalus) in impoundments across the Southeast. The disease is transferred up trophic levels from aquatic vegetation and associated algal epiphytes to herbivorous waterbirds to avian predators. An association between AVM outbreaks and a novel cyanobacterial species in the order Stigonematales has been described. The epiphytic cyanobacterium is found primarily on the leaves of Hydrilla verticillata We found a significant relationship between disease observations in birds and the breakdown of thermal strata in a Southeastern reservoir. We found denser colonies of the associated cyanobacterium in interior sub-canopy habitats created by dense hydrilla beds. The results can guide reservoir managers as they allocate limited resources to assessing the effects of AVM. Searches for affected birds should be conducted after destratification and plant samples should be taken from the interior sub-canopy regions of dense hydrilla.