STOMATAL CONDUCTANCE AND GAS-EXCHANGE IN 4 SPECIES OF CARIBBEAN MANGROVES EXPOSED TO AMBIENT AND INCREASED CO2

Stomatal conductance and gas exchange rates in sun leaves were measure d in multiple individuals of four species of Caribbean mangroves commo n to south Florida, USA. Under ambient CO2 levels (340-360 ppm), stoma tal conductance (mol m(-2) s(-1)), net primary productivity (g CO2 m(- 2) min(-1)), transpiration (g H2O m(-2) s(-1)), and instantaneous tran spiration efficiency, ITE, (mu mol CO2/mmol H2O) were not significantl y different among the four species: Rhizophora mangle (Rm), Avicennia germinans (Ag), Laguncularia racemosa (Lr), and Conocarpus erectus (Ce ). Under exposure to increased CO2 (361-485 ppm) there were highly sig nificant (P < 0.001) decreases in stomatal conductance and transpirati on, and a highly significant increase in ITE in all four species. Howe ver, there was no significant change in net primary productivity in Rm , Ag and Ce, whereas there was a significant decrease (P < 0.01) in ne t primary productivity in Lr.