We studied seasonal fluctuations in the rates o( photosynthesis, transpiration, PAR, and stomatal conductance for 16 species of true mangroves from the Sundarbans region of West Bengal. Soil salinity and pH were also measured. Leaf temperatures were almost always higher than the ambient temperature. We observed considerable seasonal (summer vs winter) as well as interspecific variations in photosynthesis, with the highest rates occurring in Heritiera fomes (13.21 $mu$mol m$^{-2}$ s$^{-1}$ ) and Avicennia marina (11.8 $mu$mol m$^{-2}$ s$^{-1}$ ), and the lowest in Nypa fruticans (1.56 $mu$mol $^{-2}$ s$^{-1}$ ) and Ceriops decandra (2.32 $mu$mol m$^{-2}$ s$^{-1}$ ). In many species, an abrupt rise in leaf temperature retarded the photosynthetic process. In winter, the rate of transpiration and stomatal conductance reached their maxima in A. marina (4.83 mmol $^{-2}$ s$^{-1}$ and 124.23 mmol m$^{-2}$ s$^{-1}$ , respectively) and their mimima in Excoecaria agallocha (1.85 mmol m$^{-2}$ s$^{-1}$ and 49.19 mmol m$^{-2}$ s$^{-1}$ , respectively). In contrast, the maximum summer readings were recorded in E. agallocha (6.07mmol m$^{-2}$ s$^{-1}$ ) and 192.74 mmol m$^{-2}$ s$^{-1}$ respectively).