Publication Date:
2024-03-15
Description:
1. Biological interactions can alter predictions that are based on single-species physiological response. It is known that leaf segments of the seagrass Posidonia oceanica will increase photosynthesis with lowered pH, but it is not clear whether the outcome will be altered when the whole plant and its epiphyte community, with different respiratory and photosynthetic demands, are included. In addition, the effects on the Posidonia epiphyte community have rarely been tested under controlled conditions, at near-future pH levels.
2. In order to better evaluate the effects of pH levels as projected for the upcoming decades on seagrass meadows, shoots of P. oceanica with their associated epiphytes were exposed in the laboratory to three pH levels (ambient: 8.1, 7.7 and 7.3, on the total scale) for 4 weeks. Net productivity, respiration, net calcification and leaf fluorescence were measured on several occasions. At the end of the study, epiphyte community abundance and composition, calcareous mass and crustose coralline algae growth were determined. Finally, photosynthesis vs. irradiance curves (PE) was produced from segments of secondary leaves cleaned of epiphytes and pigments extracted.
3. Posidonia leaf fluorescence and chlorophyll concentrations did not differ between pH treatments. Net productivity of entire shoots and epiphyte-free secondary leaves increased significantly at the lowest pH level yet limited or no stimulation in productivity was observed at the intermediate pH treatment. Under both pH treatments, significant decreases in epiphytic cover were observed, mostly due to the reduction of crustose coralline algae. The loss of the dominant epiphyte producer yet similar photosynthetic response for epiphyte-free secondary leaves and shoots suggests a minimal contribution of epiphytes to shoot productivity under experimental conditions.
4. Synthesis. Observed responses indicate that under future ocean acidification conditions foreseen in the next century an increase in Posidonia productivity is not likely despite the partial loss of epiphytic coralline algae which are competitors for light. A decline in epiphytic cover could, however, reduce the feeding capacity of the meadow for invertebrates. In situ long-term experiments that consider both acidification and warming scenarios are needed to improve ecosystem-level predictions.
Keywords:
Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Aragonite saturation state, standard deviation; Benthos; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcification/Dissolution; Calcite saturation state; Calcite saturation state, standard deviation; Calculated using seacarb; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Community composition and diversity; Counts; Counts, standard deviation; Coverage; Description; Effective quantum yield; Effective quantum yield, standard error; Electron transport rate, relative; Electron transport rate, relative, standard error; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Group; Infrared gas analyzer; Irradiance; Irradiance, standard error; Laboratory experiment; Leaf net production, oxygen; Leaf net production, oxygen, standard error; Light saturation point; Light saturation point, standard error; Macroalgae; Maximal electron transport rate, relative; Maximal electron transport rate, relative, standard error; Maximum potential capacity of photosynthesis, oxygen; Maximum potential capacity of photosynthesis, oxygen , standard error; Mediterranean Sea; Net calcification rate of calcium carbonate; Net calcification rate of calcium carbonate, standard error; Net primary production of oxygen; Net primary production of oxygen, standard error; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide, standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; pH, standard deviation; Photosynthetic quantum efficiency; Photosynthetic quantum efficiency, standard error; Plantae; Posidonia oceanica; Potentiometric; Potentiometric titration; Primary production/Photosynthesis; Ratio; Registration number of species; Replicates; Respiration; Respiration rate, oxygen; Respiration rate, oxygen, standard error; Salinity; Saturation light intensity; Saturation light intensity, standard error; Single species; Species; Taxon/taxa; Temperate; Temperature, water; Temperature, water, standard deviation; Time point, descriptive; Tracheophyta; Treatment; Type; Uniform resource locator/link to reference; Villefranche_OA
Type:
Dataset
Format:
text/tab-separated-values, 13278 data points
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