Evaluation of a Myriophyllum Spicatum Decline in Reservoirs of the Tennessee andCumberland Rivers

摘要

From 1989 through 1991, Myriophyllum spicatum (Eurasian watermilfoil) and othersubmersed macrophyte species declined markedly in many locations within reservoirs of the Tennessee and Cumberland rivers. Environmental characteristics and vegetation cover histories were compared for locations in which plants declined, declined and then recovered, or remained stable. Sediment samples from these locations were planted with M. spicatum, and plants were grown under standard conditions. Sediments from decline and nondecline areas did not differ significantly in their ability to support M. spicatum growth. Of the environmental and sediment characteristics measured, only light availability (calculated as Secchi depth/water depth) differed significantly between decline and nondecline sites. Recovery of M. spicatum populations by 1993 in many decline sites suggests that these declines were short-term phenomena, probably resulting from climatic conditions during 1989-1991. If declines resulting from sediment-related mechanisms occur, they are likely to be long lasting and localized.