01687naa a2200217 a 450000100080000000500110000800800410001910000110006024501600007126000090023152010250024065300190126565300150128465300310129965300130133065300130134365300270135665300180138365300170140177300510141810861152012-07-19       2012    bl uuuu     u00u1 u    #d1 aEpagri  aSalinity critical threshold values for photosynthesis of two cosmopolitan seaweed speciesbProviding baselines for potential shifts on seaweed assemblages.  c2012  aClimate change has increased precipitation in several South American regions leading to higher freshwater inputs into marine systems with potential to cause salinity declines along the coast. The current salinity profile on the southern coast of Brazil was surveyed during four years providing a baseline of the current salinity pattern in the region. Additionally, the effects of salinity decreases on the photosynthesis of the seaweeds Ulva lactuca and Sargassum stenophyllum were investigated in laboratory. Seaweeds were cultured at salinities 5, 15 and 34 and at the mean winter and summer temperatures. Photosynthetic performance was measured following 24 and 96 h from the beginning of experiment. U. lactuca remained practically unaltered by low salinities while S. stenophyllum presented declines of important photosynthetic parameters. This is due to the different regulation abilities of energy distribution at the PSII of the two species. These differences have potential to lead to seaweed community shifts.  aClimate change  aFreshwater  aPhotosynthetic performance  aRainfall  aSalinity  aSargassum stenophyllum  aSouth America  aUlva lactuca  tMarine Environmental Research, p. 01-05, 2012.