Lake characteristics influence recovery of microplankton in arctic LTER lakes following experimental fertilization

Lakes N-1 and N-2 at the Arctic Long Term Ecological Research site at Tooli k Lake, Alaska, U.S.A. were fertilized with nitrogen and phosphorus for 5 a nd 6 years, respectively. The response and recovery of the microplankton co mmunity (protozoans, rotifers and crustacean nauplii) differed in the two l akes. Microplankton biomass in Lake N-1 increased five-fold while that in L ake-N-2 only doubled, despite larger nutrient additions to N-2. Microplankt on community structure in Lake N-1 shifted toward dominance by few taxa, wh ile the community in Lake N-2 maintained diversity. Finally, the recovery o f Lake N-1 to near prefertilization microplankton biomass levels was rapid, while Lake N-2 showed at least a 1-year lag in recovery. These differences appear to be related to differences in the structure of lake sediments.