Seawater carbonate chemistry and calcium carbonate of Padina spp., photosynthesis of Padina pavonica in nature CO2 gradients experiment

• Main Authors: Johnson, Vivienne R, Russell, Bayden D, Fabricius, Katharina Elisabeth, Brownlee, Colin, Hall-Spencer, Jason M
• Format: Dataset
• Language: English
• Published: PANGAEA 2012
• Subjects: Abundance; Aeolian_Island_Vulcano; Alkalinity; total; standard deviation; Animalia; Aragonite saturation state; Benthic animals; Benthos; Bicarbonate ion; Biomass/Abundance/Elemental composition; Calcification/Dissolution; Calcite saturation state; Calcium carbonate; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Chlorophyll c per cell; Chromista; CO2 vent; Coast and continental shelf; Coverage; Echinodermata; Electron transport rate; relative; Event label; Field observation; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Identification; In situ sampler; ISS; Length; Macroalgae; Maximal electron transport rate; Maximum photochemical quantum yield of photosystem II; Mediterranean Sea; Mediterranean Sea Acidification in a Changing Climate; MedSeA; OA-ICC; Ocean Acidification International Coordination Centre; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.823111; https://doi.org/10.1594/PANGAEA.823111

Predicting the impacts of ocean acidification on coastal ecosystems requires an understanding of the effects on macroalgae and their grazers, as these underpin the ecology of rocky shores. Whilst calcified coralline algae (Rhodophyta) appear to be especially vulnerable to ocean acidification, there is a lack of information concerning calcified brown algae (Phaeophyta), which are not obligate calcifiers but are still important producers of calcium carbonate and organic matter in shallow coastal waters. Here, we compare ecological shifts in subtidal rocky shore systems along CO2 gradients created by volcanic seeps in the Mediterranean and Papua New Guinea, focussing on abundant macroalgae and grazing sea urchins. In both the temperate and tropical systems the abundances of grazing sea urchins declined dramatically along CO2 gradients. Temperate and tropical species of the calcifying macroalgal genus Padina (Dictyoaceae, Phaeophyta) showed reductions in CaCO3 content with CO2 enrichment. In contrast to other studies of calcified macroalgae, however, we observed an increase in the abundance of Padina spp. in acidified conditions. Reduced sea urchin grazing pressure and significant increases in photosynthetic rates may explain the unexpected success of decalcified Padina spp. at elevated levels of CO2. This is the first study to provide a comparison of ecological changes along CO2 gradients between temperate and tropical rocky shores. The similarities we found in the responses of Padina spp. and sea urchin abundance at several vent systems increases confidence in predictions of the ecological impacts of ocean acidification over a large geographical range.