Zooplankton changes over the past 40 years in ponds located near to Barrow, Alaska

Arctic aquatic ecosystems are very sensitive to changes in the environment, yet they are poorly understood.  The Arctic tundra is characterized by many ponds and lakes with low levels of production and biodiversity. Recently, with the warmer temperatures, we noticed increases in the biomass of  phytoplankton in Arctic ponds first sampled 40 years ago near Barrow, AK. We hypothesized that the temperature and resource changes over the past 40 years will also affect the aquatic biodiversity and abundance of zooplankton. Preliminary results from 2 ponds sampled over 5 years, indicate drastic changes in species composition. Species such as Diaptomus sp. and Polyartemiella hazeni have virtually disappeared from the ponds, while the predaceous copepod Heterocope septentrionalis has increased substantially in numbers. Nauplii, which are likely the young of H. septentrionalis, were also more abundant in more recent samples and probably serve as a food source for some other organisms. Daphnia middendorffiana tended to appear in high densities in 1972 and 2011, but not 2010. This may reflect differences in predation or spring temperatures. In 2011, Daphnia abundances peaked 2-3 weeks earlier than in the 1970s, perhaps reflecting a longer growing season and warmer spring. Zooplankton abundances will be related to environmental variables to determine the impact of environmental change on secondary production.