Responses of three tropical seagrass species to CO2 enrichment

• Main Authors: Ow, Yan X, Collier, C J, Uthicke, Sven
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: Alkalinity; total; standard error; Ammonium; Aragonite saturation state; Benthos; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using CO2calc; Calculated using seacarb after Nisumaa et al. (2010); Carbohydrates; non structural; solube; in tissue; Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Charophyta; Chlorophyll a; Chlorophyll b; Coast and continental shelf; Cockle_Bay; Colorimetric; Cymodocea serrulata; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross photosynthesis/respiration ratio; Growth/Morphology; Growth rate; Halodule uninervis; Identification; Irradiance; Laboratory experiment; Light saturation; Maximum potential capacity of photosynthesis; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.859062; https://doi.org/10.1594/PANGAEA.859062

Increased atmospheric carbon dioxide leads to ocean acidification and carbon dioxide (CO2) enrichment of seawater. Given the important ecological functions of seagrass meadows, understanding their responses to CO2 will be critical for the management of coastal ecosystems. This study examined the physiological responses of three tropical seagrasses to a range of seawater pCO2 levels in a laboratory. Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii were exposed to four different pCO2 treatments (442-1204 µatm) for 2 weeks, approximating the range of end-of-century emission scenarios. Photosynthetic responses were quantified using optode-based oxygen flux measurements. Across all three species, net productivity and energetic surplus (PG:R) significantly increased with a rise in pCO2 (linear models, P < 0.05). Photosynthesis-irradiance curve-derived photosynthetic parameters-maximum photosynthetic rates (P max) and efficiency (alpha) also increased as pCO2 increased (linear models, P < 0.05). The response for productivity measures was similar across species, i.e. similar slopes in linear models. A decrease in compensation light requirement (Ec) with increasing pCO2 was evident in C. serrulata and H. uninervis, but not in T. hemprichii. Despite higher productivity with pCO2 enrichment, leaf growth rates in C. serrulata did not increase, while those in H. uninervis and T. hemprichii significantly increased with increasing pCO2 levels. While seagrasses can be carbon-limited and productivity can respond positively to CO2 enrichment, varying carbon allocation strategies amongst species suggest differential growth response between species. Thus, future increase in seawater CO2 concentration may lead to an overall increase in seagrass biomass and productivity, as well as community changes in seagrass meadows.