Seawater carbonate chemistry and kelp forest community structure,net community calcification

• Main Authors: Donham, E M, Hamilton, Scott L, Price, Nichole N, Kram, Susan, Kelly, Emily, Johnson, Maggie Dorothy, Neu, Alexander T, Smith, Jennifer E
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2021
• Subjects: Behaviour; Benthos; Calcification/Dissolution; Coast and continental shelf; Community composition and diversity; Entire community; Laboratory experiment; Mesocosm or benthocosm; North Pacific; Other; Rocky-shore community; Temperate; Type; Identification; Treatment; Individuals; Dry mass; Calcification rate; Grazing rate; Coverage; pH; Partial pressure of carbon dioxide water at sea surface temperature wet air; Bicarbonate ion; Carbonate ion; Carbon dioxide; Calcite saturation state; Aragonite saturation state; Temperature, water; Salinity; Alkalinity, total; Carbonate system computation flag; Fugacity of carbon dioxide water at sea surface temperature wet air; Carbon, inorganic, dissolved; Experiment; Potentiometric; Calculated using CO2SYS; Potentiometric titration; Calculated using seacarb after Nisumaa et al. 2010; Ocean Acidification International Coordination Centre OA-ICC; Pacific; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.934044; https://doi.pangaea.de/10.1594/PANGAEA.934044

Ocean acidification (OA) is likely to differentially affect the biology and physiology of calcifying and non-calcifying taxa, thereby potentially altering key ecological interactions (e.g., facilitation, competition, predation) in ways that are difficult to predict from single-species experiments. We used a two-factor experimental design to investigate how multispecies benthic assemblages in southern California kelp forests respond to OA and grazing by the purple sea urchin, Strongylocentrotus purpuratus. Settlement tiles accrued natural mixed assemblages of algae and invertebrates in a kelp forest off San Diego, CA for one year before being exposed to OA and grazing in a laboratory experiment for two months. Space occupying organisms were identified and pooled into six functional groups: calcified invertebrates, non-calcified invertebrates, calcified algae, fleshy algae, sediment, and bare space for subsequent analyses of community structure. Interestingly, communities that developed on separate tile racks were unique, despite being deployed close in space, and further changes in community structure in response to OA and grazing depended on this initial community state. On Rack 1, we found significant effects of both pCO2 and grazing with elevated pCO2 increasing cover of fleshy algae, but sea urchin grazers decreasing cover of fleshy algae. On Rack 2, we found a 35% higher percent cover of sediment on tiles reared in ambient pCO2 but observed 27% higher cover of bare space in the high pCO2 conditions. On Rack 3, we found an average of 45% lower percent cover of calcified sessile invertebrates at ambient pCO2 than in high pCO2 treatments on Rack 3. Net community calcification was 137% lower in elevated pCO2 treatments. Kelp sporophyte densities on tiles without urchins were 74% higher than on tiles with urchins and kelp densities were highest in the elevated pCO2 treatment. Urchin growth and grazing rates were 49% and 126% higher under ambient than high pCO2 conditions. This study highlights consistent negative impacts of OA on community processes such as calcification and grazing rates, even though impacts on community structure were highly context-dependent. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2021) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2021-07-26.