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Studies of aquatic plants of eastern Pennsylvania lakes were continued with quantitative inventories of 6 lakes and qualitative surveys of 6 additional lakes. The surveys resulted in 14 new records of PNHP-Iisted species and updates of 6 previously known occurrences. Accumulated information on species abundance resulted in one recommendation to delist and 2 recommendations for changes in status at the annual Rare Plant Forum. A study of 8 Pennsylvania populations of Myriophyllum heterophyllum, carried out by our intern, failed to find any evidence of hybridization that might help to explain the aggressive growth of this species in northeastern counties.
Analysis of occurrence patterns of non-native aquatic species revealed differences between low alkalinity, mesotrophic lakes and highly eutrophic lakes. Although curly pondweed (Potamogeton crispus) is present in both types of lakes, only in highly eutrophic situations (high alkalinity, phosphorus and nitrogen) is it abundant. On the other hand, long-leaved waterwort (Elatine triandra), shows the opposite pattern; it is abundant in low phosphorus, low alkalinity lakes. Additional lake quality data are needed to allow for further analyses of the influence of water chemistry on plant occurrence. 2
Date Posted: 26 September 2018