Assessment of Water Quality and Response Rate of Zooplankton in a Nebraska “Barrow Pit” After Rotenone Application

Understanding the extent and depth of rotenone impacts on all trophic levels is essential to effective aquatic management. We examined changes in water quality tenets and zooplankton communities following the establishment of 3 ppm rotenone concentration in a Nebraska barrow pit. Dissolved oxygen initially decreased 57% and subsequently increased 298% the week following rotenone application. Turbidity decreased from 25.8 FAU ± 0.80 pre-treatment to 6.6 FAU ± 0.98 one year later. Total zooplankton (0.17/L ± 0.03) were limited prior to rotenone application and absent for the following 3 weeks. One year later the total number of zooplankton increased 1024%, and during the same timeframe both pseudo-control barrow pits remained similar or decreased in total zooplankton present. Rotifers were the first taxon to recover. Copepods and their nauplii were absent for 2 months and recovered to levels greater than pseudo-controls three months after the rotenone treatment. Cladocerans were the slowest to re-establish as they were absent for 3 months and did not match those recorded in pseudo-controls until 7 months later. This research can assist aquatic managers in understanding how water quality and zooplankton communities will change following the application of rotenone in a Nebraska barrow pit