Publication Date:
2024-05-24
Description:
Ocean acidification may benefit algae that are able to capitalize on increased carbon availability for photosynthesis, but it is expected to have adverse effects on calcified algae through dissolution. Shifts in dominance between primary producers will have knock-on effects on marine ecosystems and will likely vary regionally, depending on factors such as irradiance (light vs. shade) and nutrient levels (oligotrophic vs. eutrophic). Thus experiments are needed to evaluate interactive effects of combined stressors in the field. In this study, we investigated the physiological responses of macroalgae near a CO2 seep in oligotrophic waters off Vulcano (Italy). The algae were incubated in situ at 0.2 m depth using a combination of three mean CO2 levels (500, 700-800 and 1200 µatm CO2), two light levels (100 and 70% of surface irradiance) and two nutrient levels of N, P, and K (enriched vs. non-enriched treatments) in the non-calcified macroalga Cystoseira compressa (Phaeophyceae, Fucales) and calcified Padina pavonica (Phaeophyceae, Dictyotales). A suite of biochemical assays and in vivo chlorophyll a fluorescence parameters showed that elevated CO2 levels benefitted both of these algae, although their responses varied depending on light and nutrient availability. In C. compressa, elevated CO2 treatments resulted in higher carbon content and antioxidant activity in shaded conditions both with and without nutrient enrichment--they had more Chla, phenols and fucoxanthin with nutrient enrichment and higher quantum yield (Fv/Fm) and photosynthetic efficiency (alpha ETR) without nutrient enrichment. In P. pavonica, elevated CO2 treatments had higher carbon content, Fv/Fm, alpha ETR, and Chla regardless of nutrient levels--they had higher concentrations of phenolic compounds in nutrient enriched, fully-lit conditions and more antioxidants in shaded, nutrient enriched conditions. Nitrogen content increased significantly in fertilized treatments, confirming that these algae were nutrient limited in this oligotrophic part of the Mediterranean. Our findings strengthen evidence that brown algae can be expected to proliferate as the oceans acidify where physicochemical conditions, such as nutrient levels and light, permit.
Keywords:
Alkalinity, total; Alkalinity, total, standard error; Antioxidant activity; Antioxidant activity, standard error; Aragonite saturation state; Aragonite saturation state, standard error; Benthos; Bicarbonate ion; Bicarbonate ion, standard error; Biomass/Abundance/Elemental composition; Calcite saturation state; Calcite saturation state, standard error; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, per dry mass; Carbon/Nitrogen ratio; Carbon/Nitrogen ratio, standard error; Carbonate ion; Carbonate ion, standard error; Carbonate system computation flag; Carbon content, per dry mass, standard error; Carbon dioxide; Carbon dioxide, standard error; Chlorophyll a; Chlorophyll a, standard error; Chlorophyll c; Chlorophyll c, standard error; Chromista; CO2 vent; Coast and continental shelf; Cystoseira compressa; Electron transport rate; Electron transport rate, standard error; Field experiment; Fucoxanthin; Fucoxanthin, standard error; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Light saturation point; Light saturation point, standard error; Macroalgae; Macro-nutrients; Maximum photochemical quantum yield of photosystem II; Maximum photochemical quantum yield of photosystem II, standard error; Mediterranean Sea; Nitrogen, per dry mass; Nitrogen content, per dry mass, standard error; Non photochemical quenching; Non photochemical quenching, standard error; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Padina pavonica; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; pH; pH, standard error; Phenolics, all; Phenolics, all, standard error; Photosynthetic efficiency; Photosynthetic efficiency, standard error; Potentiometric; Potentiometric titration; Primary production/Photosynthesis; Salinity; Salinity, standard error; Single species; Species; Temperate; Temperature; Temperature, water; Temperature, water, standard error; Treatment; Violaxanthin; Violaxanthin, standard error
Type:
Dataset
Format:
text/tab-separated-values, 1470 data points
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