Does Long-Term Macrophyte Management in Lakes Affect Biotic Richness and Diversity?

• Published in: Journal of aquatic plant management 2005-07, Vol.43 (2), p.57-64
• Main Authors: Harman, W N, Hingula, L P, Macnamara, CE
• Format: Article
• Language: English
• Subjects: Elodea canadensis; Freshwater; Myriophyllum spicatum
• ISSN: 0146-6623

We hypothesize that the richness and diversity of the biota in Lake Moraine (42 degree 50'47"N, 75 degree 31'39"W) in New York have been negatively impacted by 60 years of macrophyte and algae management to control Eurasian watermilfoil (Myriophyllum spicatum L.) and associated noxious plants. To test this hypothesis we compare water quality characteristics, richness and selected indicators of plant diversity, zooplankton, benthic macroinvertebrates and fish in Lake Moraine with those in nearby Hatch Lake (42 degree 50'06"N, 75 degree 40'67"W). The latter is of similar size and would be expected to have similar biota, but has not been subjected to management. Measurements of temperature, pH, oxygen, conductivity, Secchi transparency, calcium, total phosphorus and nitrites + nitrates are comparable. Taxa richness and the diversity indices applied to the aquatic macrophytes are similar in both lakes. The greatest disparity is the lack of Eurasian watermilfoil and Canadian waterweed (Elodea canadensis Michx.) in the main basin of Lake Moraine. The elimination of the former was the intent of a 2001 application of fluridone (1-methyl-3phenyl-5(3-(tri-furomethyl)phenyl) -4(1H)-pyridinone[C sub(19)H sub(14)F sub(3)NO]) and the loss of the latter was a related consequence. Zooplankton richness is similar in both lakes. The diversity of benthic macroinvertebrates is similar; however, richness at the genus level is quite different. There is a paucity of species collected in Lake Moraine that are intolerant to winter lowering of water levels. Fish species richness in both lakes is similar, but there are differences in specific taxa and percent abundance directly related to stocking and the balance between forage fish populations and piscivorous fish populations in the two lakes. That phenomenon also appears responsible for some of the variation in the zooplankton communities in both lakes. Overall, taxonomic richness and diversity in Lake Moraine and Hatch Lake are remarkably similar. Annual winter drawdown of water levels is implicated as having greater effect on the biota than long-term herbicide utilization. The hypothesis is rejected.