Samplings
Sampling was performed biweekly during the experiment by collecting 11-L water from the bottom to surface with repeated deployment of a 2.2-L tube sampler. Duplicate water samples were taken in each treatment (section) of the two ponds, and used for measuring water chemistry and abundance of phytoplankton and small zooplankton (copepod nauplii and rotifers). Besides these samples, crustacean plankton were collected by filtering a total of ca. 30-L of vertically integrated water from three different sites in each section with a 100 μm mesh net, and fixed with 99% ethanol for enumeration. During sampling, we measured vertical profiles of water temperature, dissolved oxygen (DO) concentration, conductivity and pH using a multiparameter probe (600XLM, YSI) at each section of both ponds. We also measured photosynthetic active radiation (PAR) using a spherical quantum sensor (LI-193; LiCor, Inc.) at 10-cm intervals from the surface to bottom and calculated extinction coefficients of PAR in the water.