| Summary: | Purpose The aim of this study was to test the hypothesis that increased pCO2 would increase photosynthetic and growth rates to various extents between seagrass species. This dataset consists of one data file (spreadsheet) from a 2 week aquarium experiment manipulating pH (pCO2) changes and measuring photosynthetic and growth responses of three tropical seagrass species (Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii). The aim of this study was to test the hypothesis that increased pCO2 would increase photosynthetic and growth rates to various extents between seagrass species. Method: This experiment exposed three seagrass species, Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii, to four pCO2 treatments (440, 700, 890, 1204 µatm) for two weeks to investigate the effects of acidification on their physiology. These treatments were chosen to bracket the range of atmospheric CO2 levels predicted for different end-of-century emission scenarios in the near-future (2100). Each treatment was replicated across four aquaria, each with 2 duplicate pots per species. C. serrulata and H. uninervis were collected from the intertidal meadow at Cockle Bay, Magnetic Island, Great Barrier Reef (19°10.88’S, 146°50.63’E) in late March 2013. T. hemprichii was collected from Green Island in the Northern Great Barrier Reef (16°45.37’S, 145°58.19’E) in early April 2013. H. uninervis and sediment was collected as intact plugs. C. serrulata and T. hemprichii were collected by excavating intact shoots with connected horizontal rhizomes from the sediment. The experiment started two to four weeks after the collection. Photosynthetic rates and respiration of the second youngest leaf of a haphazardly chosen shoot from each pot were measured using optical oxygen sensors. Photosynthetic rates were measured over a series of light steps (10, 30, 70, 110, 220, 400, 510 µmol m-2 s-1), with each light step lasting 20 minutes. Rates were normalised to the dry weight of the leaf, after drying leaves at 60°C for 48 ...
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