Determination of planktonic metabolism and trophic status in Texas shallow ponds
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Potential daily aerial rates of plankton production and respiration for twenty-seven shallow ponds within the Bullhide Creek watershed between January and March 2013 were determined. Photosynthetic parameters were estimated using the oxygen change method in closed biochemical oxygen demand bottles (BOD). Daily potential planktonic production and respiration were estimated using the Walsby method and incident solar radiation data for a cloudless day during the survey period. Results contrasted original predictions with plankton communities being autotrophic on average (P:R = 1.39). Although recent research has concluded that most surface waters are heterotrophic, we found eight ponds were strongly heterotrophic (P:R < 0.7) nine were strongly autotrophic (P:R > 1.3) and ten in approximate balance (P:R 0.7-1.3). Plankton photosynthesis and P:R ratios were not affected by the abundance of submerged aquatic vegetation (SAV), (p=.87). Average P:R ratio for ponds without SAV averaged 1.61, with intermediate and abundant SAV averaging 1.14 and 1.79 respectively.