Primary production rate
In each section of the Pond 217 and 218, we routinely measured
photosynthetic and community respiration rate by measuring changes in
O2 concentration rate in light and dark bottles (Wetzel
and Likens 2010). Then, net-photosynthetic rate – irradiance curve (P-I
curve) was estimated for each section of the both ponds. Using the P-I
curve, extinction coefficient and daily changes in photosynthetically
available radiation (PAR) in the water column, we estimated specific
production rate (\(\mu\): μg O2chl-a -1 d-1). To minimize
specificity in light conditions at measured date, we calculated μ using
temporal profile of PAR for three days before each sampling date. Then
average value for these three days was used in analysis. Details of the
method estimating primary production rate were described in supplemental
methods.