These photosyntheis data from the Duplin River and Doboy Sound were collected by Evelyn Sherr and David Whitney. Photosynthesis was measured by the 14-C method with in-situ incubations. Chlorophyll a determined by the HPLC method of Jacobsen (Jacobsen, T. R. 1978. A quantitative method for the separation of chlorophylls a and b from phytoplankton pigments by high pressure liquid chromatography. Marine Science Communications 4: 33-47). Light intensity measured with a Li-Cor quantum meter. Locations are as follows: R1 Upper Duplin River above Moses Hammock. 31° 28.6'N 81° 16.4'W R2 Duplin River at Lumber Landing 31° 27.6'N 81° 17.0'W R3 Marsh Landing dock 31° 28.6'N 81° 16.4'W S1 Head of Doboy Sound at Hudson Creek 31° 27.5'N 81° 20.4'W S2 Doboy Sound at Teakettle Creek 31° 25.6'N 81° 19.0'W S3 Doboy Sound off Sapelo lighthouse 31° 23.4'N 81° 17.8'W