Abundance of Submerged Vascular Vegetation in the Rhode River from 1966 to 1973

Abstract

Surveys on the distribution and abundance of submerged vascular plants in the Rhode River showed that there was an irregular decline in the amount of vegetation from 1966 to 1973, along with significant changes in species dominance. In 1966, redheadgrass (Potamogeton perfoliatus) and Eurasian watermilfoil (Myriophyllum spicatum) were both very abundant with lesser amounts of widgeongrass (Ruppia maritima), horned pondweed (Zannichellia palustris), sago pondweed (Potamogeton pectinatus), and elodea (Elodea canadensis). In 1967, all of these species declined substantially, and elodea disappeared entirely. In 1968, redhead-grass and horned pondweed returned in substantial abundance, but they again declined in 1969 and virtually all submerged aquatics disappeared in 1970. In 1972, horned pondweed and sago pondweed reached an eight-year peak, but other species remained at very low levels. In 1973, all species were low, and a prominent lack of vegatation similar to 1967, 1970, and 1971 occurred again. Elodea has not been seen in the Rhode River since 1966. We believe these changes represent a decline in environmental quality in the Rhode River that may have serious longrange implications.