Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Program Information
• Funding

See "Related Datasets" and "Supplemental Files" sections for access to related data published as part of these pCO2 flume experiments published in Edmunds et al., (2020, doi:10.1093/icesjms/fsaa015).  

Related metabolism data was published in Edmunds et al. (2024, doi:10.1002/lno.12504).

Fore reef communities were assembled in three outdoor flumes in Mo'orea, which were assigned randomly to a pCO₂ treatment targeting ambient (400 μatm), 700 μatm, and 1300 μatm pCO₂. The elevated pCO₂ treatments approximated atmospheric conditions projected for about the year 2140 under representative concentration pathways (RCP) 2.6, 4.5, and 8.5. Treatments were maintained for one year beginning in late Austral spring (November 2017), and actual pCO₂ treatments over the year differed from target values (described below). In brief, each flume consisted of a working section that was 5.0-m long, 30-cm wide and filled to ~ 30-cm depth with ~ 500 L of seawater. The fixed and unfixed communities within each fume occupied a 4.7 × 0.3 m portion of the floor of the working section of each flume. Seawater was circulated continually through a return section, and was supplied with fresh seawater at ~ 5 L min^-1. Seawater was pumped from Cook’s Bay (14-m depth) and filtered through sand (pore size ~ 450–550 µm) before entering the flumes. With this pore size, small particulates passed through the filter and were added to the flumes where they were available as food for heterotrophic organisms.

Fore reef communities:

The reef communities were assembled to correspond to the mean percent cover of the major benthic space holders recorded in 2006 at 17-m depth on the fore reef of the north shore of Mo'orea. A historic community structure (rather than present day) was used because 2006 represented the long-term community structure on this reef, and it created the capacity to compare aspects of the present experiment with a previous experiment. Based on six sites sampled around Mo'orea in 2006, the community structure in the flumes was targeted to ~ 11% cover of Pocillopora spp., ~ 8% massive Porites spp., 8% Acropora spp., and ~ 53% reef rock. This construct created a community with ~ 27% coral cover, which was slightly lower than the actual mean coral cover in 2006 (32%), because the remaining 14 genera of scleractinians and Millepora contributed 5% coral cover. The Pocillopora conformed to the classic morphology of P. verrucosa, but it is likely that other Pocillopora spp. were present in the flumes. Likewise, Acropora spp. were selected to represent A. hyacinthus and A. retusa, which were common on the fore reef when the experiment was completed, and colonies of these species were scattered haphazardly among the flumes. Given the morphological complexity of Acropora spp., it is possible that other species were placed into the flumes. Pieces of coral rubble (~ 11.5-cm diameter) were added to achieve ~ 29% cover. Coral and rubble were haphazardly scattered along the working section of each flume to approach the targets for percentage cover, and this resulted in portions of the flumes having slightly different covers of coral. This was important for the central 2.4-m portion of the flume, where community members were fixed to allow the community structure to be quantified monthly using planar photographs. In the adjacent portions of the flumes, community members were unfixed (and rested on the floor of the flumes) so that they could be removed monthly for buoyant weighing (described below). 

Corals and rubble were collected from ~ 17-m depth on the north shore fore reef, epoxied (Z-Spar A788, Pettit Marine Paint, Rockaway, NJ, USA) to plastic bases, and placed in a seawater table for at least 2 d before being added to the flumes. This time allowed the epoxy to cure and for the corals to recover from collection. Fore reef communities were assembled in the flumes on 27 October 2017, where they were maintained under ambient seawater conditions until 3 November. At this time, treatment pCO₂ levels were initiated in two flumes (one remained at ambient pCO₂), with pCO₂ gradually increased to target values over 24 h.

Physical and chemical parameters (see "Supplemental Files" for data access):

Seawater was circulated in the flumes at ~ 0.1 m s^-1 using a pump (Wave II 373 J s^-1, W. Lim Co., El Monte, CA, USA), and flow speeds were measured across the working sections using a Nortek Vectrino Acoustic Doppler Velocimeter. This flow speed was ecologically relevant for 15-m depth on the fore reef of Mo’orea (14-y mean = 0.065 m s^-1). The flumes were exposed to natural sunlight that was reduced with a blue filter (LEE #183, Lee Filters, Andover, England) to photon flux densities (PFD) in the range of photosynthetically active radiation (400–700 nm) that approximated those at 17-m depth. Light in the flumes was measured continuously (at 0.0006 Hz) using cosine-corrected sensors (Odyssey, Dataflow Systems Ltd, Christchurch, New Zealand) that recoded PAR. Odyssey sensors were calibrated with a Li-COR meter [LI-1400, Li-COR Biosciences, Lincoln, NE, USA] attached to a 2p sensor [LI 192A]). Temperatures in the flumes were regulated with chillers (heaters were not required) and were maintained close to the mean monthly seawater temperature at 17-m depth on the fore reef.

Seawater carbonate chemistry was uncontrolled in one flume (ambient, ~ 400 μatm pCO₂), and controlled in two others to simulate conditions arising from seawater pCO₂ targeted at 700 μatm and 1300 μatm. Seawater pH was not altered in the ambient flume, but was controlled in the treatment flumes by bubbling CO₂ into the seawater to alter pH relative to a set-point (regulated using an Aquacontroller, Neptune Systems, Morgan Hill, CA, USA) that operated a solenoid supplying pure CO₂ gas to a diffuser stone submerged in each flume. A diurnal upward pH adjustment of ~ 0.1 unit was applied to the two treatment flumes to simulate natural diurnal variation in seawater pCO₂ on the reef of Mo’orea. The ambient flume also maintained a diurnal variation in pCO₂ with a night time pH ~ 0.1 unit lower than in the daytime. Ambient air was bubbled continuously into all flumes. Periodic measurements of pCO₂ in the flumes confirmed that nocturnal pCO₂ met, or exceeded day-time target values (described in results).

Throughout the experiment, logging sensors (described above) recorded PAR, and temperature (Hobo Pro v2 [± 0.2 °C], Onset Computer Corp., Bourne, MA, USA). pH was measured daily on the total hydrogen ion scale (pH_T) using a handheld meter (see below). The values from the temperature and pH measurements were used to adjust the thermostat and pH-set points to achieve target pCO₂ values. Seawater carbonate chemistry (pH and A_T) and salinity were measured during the day (14:00 hrs) and night (20:00 hrs) and were obtained weekly. A bench-top conductivity meter (Thermo Scientific, Orionstar A212, Waltham, MA, USA) was used to measure salinity. The remaining parameters of the seawater carbonate system were calculated from temperature, salinity, pH_T, and A_T, using the R package Seacarb.

pH_T was measured using a DG 115-SC electrode (Mettler Toledo, Columbus, OH, USA) that was calibrated with a TRIS buffer. A_T was measured using open-cell, acidimetric titration using a certified titrant with an automatic titrator (T50, Mettler Toledo) fitted with a DG 115-SC electrode (Mettler Toledo). The accuracy and precision of measurements were determined by processing certified reference materials (CRMs batch numbers 158 and 172; from A. Dickson Laboratory, Scripps Institution of Oceanography, CA, USA), against which measured values of A_T maintained an accuracy of 1.7 ± 0.3 μmol kg^-1 (n = 15) and precision of 1.8 ± 0.1 μmol kg^-1 (n = 475).

Response variables:

See more details about coral weight and Gnet calculation in the related dataset "Edmunds et al. 2020 ICES: pCO2 flume - Coral weight" https://www.bco-dmo.org/dataset/924603.  

Community structure:
* This section describes the methodology of the "percent_area" column in this dataset.
* The images of each flume (1-3) are in the "Supplemental Files" section of this dataset.

The effects of the treatments on the community structure were described using photographs recorded monthly in planar view. The image-based technique strengthened the ability to address the effects of OA on the community ecology of coral reefs, which frequently is recorded using planar photographs (including in Mo'orea). Photographs were recorded in ambient light using a GoPro Hero 4 camera (12 MP, 3-mm focal length) that was fitted to a stand and positioned on the upper edge of the flumes to record the benthic community through the air-water interface. At each sampling, the camera was sequentially moved along the flume to record the community in the middle 2.4 m of the working section using ~ 15 contiguous photographs.

Photographs were analyzed using ImageJ software after they were stitched together to make a single image for each sampling. This image covered the ~ 2.4-m length of the central portion of the flume where the corals were secured to a plastic-coated metal grid with a mesh size of 5 × 5 cm. The stitching of photographs sometimes was imperfect due to parallax errors, and in such cases, separate pictures were evaluated to assess organism size. The planar area of living tissue on corals was quantified by outlining organisms in ImageJ, after scaling the image using the metal grid as a size reference. Organism size (cm²) was expressed as a percentage of the area (7200 cm²) occupied by the fixed portion of the community. The summed area of community members was used to determine cover of the benthic community, and the areas of each organism were used to quantify growth (and shrinkage). Where organisms died, their area was set to zero.

Organism identifiers (Taxon, LifeSciences Identifier (LSID), name as appears in Species column):

Acropora hyacinthus, urn:lsid:marinespecies.org:taxname:207044, A. hyacinthus
Acropora retusa, urn:lsid:marinespecies.org:taxname:430653, A. retusa
Porites, urn:lsid:marinespecies.org:taxname:206485, Massive Porites
Pocillopora damicornis, urn:lsid:marinespecies.org:taxname:206953,
Pocillopora verrucosa, urn:lsid:marinespecies.org:taxname:206954,

SEACARB for the analysis of seawater chemistry: Lavigne, H. and Gattuso, J. P. 2013. Seacarb, seawater carbonate
chemistry with, R. R package version 2.4.10. Available at: http://CRAN.R-project.org/package=seacarb (last accessed 11 July 2014).

* Sheet 2 of submitted file "Areas.xlsx" was imported into the BCO-DMO data system for this dataset. Values "nd" imported as missing data values.  Sheet 1 contained metadata added to Parameters section.
** Missing data values are displayed differently based on the file format you download.  They are blank in csv files, "NaN" in MatLab files, etc.
* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores.  Can not start with a number]
* dataset Lon bounds corrected from deg 149... to -149...
* quote characters removed from some species values so entire column is consistent.
* Year and month reformatted for consistency within the dataset and between related coral weight datast. Variable full month and abbreviated month in month column, and separate column for year converted to one Year_Month column formatted to match related datasets.
* Sheet 2 of "Physical _and_Chemical_conditions.xlsx" exported as a supplemental file. Column names adjusted to BCO-DMO conventions. Column values with micron (greek mu character) changed to -> u replaced in the flume identifier column and – replaced with standard hyphen character -.
* Site list added for LTER sites from the existing table included for datasets "Edmunds et al. 2024 Oecologia..."

While coral reefs have undergone unprecedented changes in community structure in the past 50 y, they now may be exposed to their gravest threat since the Triassic. This threat is increasing atmospheric CO2, which equilibrates with seawater and causes ocean acidification (OA). In the marine environment, the resulting decline in carbonate saturation state (Omega) makes it energetically less feasible for calcifying taxa to mineralize; this is a major concern for coral reefs. It is possible that the scleractinian architects of reefs will cease to exist as a mineralized taxon within a century, and that calcifying algae will be severely impaired. While there is a rush to understand these effects and make recommendations leading to their mitigation, these efforts are influenced strongly by the notion that the impacts of pCO2 (which causes Omega to change) on calcifying taxa, and the mechanisms that drive them, are well-known. The investigators believe that many of the key processes of mineralization on reefs that are potentially affected by OA are only poorly known and that current knowledge is inadequate to support the scaling of OA effects to the community level. It is vital to measure organismal-scale calcification of key taxa, elucidate the mechanistic bases of these responses, evaluate community scale calcification, and finally, to conduct focused experiments to describe the functional relationships between these scales of mineralization.

This project is a 4-y effort focused on the effects of Ocean Acidification (OA) on coral reefs at multiple spatial and functional scales. The project focuses on the corals, calcified algae, and coral reefs of Moorea, French Polynesia, establishes baseline community-wide calcification data for the detection of OA effects on a decadal-scale, and builds on the research context and climate change focus of the Moorea Coral Reef LTER.

This project is a hypothesis-driven approach to compare the effects of OA on reef taxa and coral reefs in Moorea. The PIs will utilize microcosms to address the impacts and mechanisms of OA on biological processes, as well as the ecological processes shaping community structure. Additionally, studies of reef-wide metabolism will be used to evaluate the impacts of OA on intact reef ecosystems, to provide a context within which the experimental investigations can be scaled to the real world, and critically, to provide a much needed reference against which future changes can be gauged.

Datasets listed in the "Dataset Collection" section include references to results journal publications published as part of this project.

NSF Climate Research Investment (CRI) activities that were initiated in 2010 are now included under Science, Engineering and Education for Sustainability NSF-Wide Investment (SEES). SEES is a portfolio of activities that highlights NSF's unique role in helping society address the challenge(s) of achieving sustainability. Detailed information about the SEES program is available from NSF (https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=504707).

In recognition of the need for basic research concerning the nature, extent and impact of ocean acidification on oceanic environments in the past, present and future, the goal of the SEES: OA program is to understand (a) the chemistry and physical chemistry of ocean acidification; (b) how ocean acidification interacts with processes at the organismal level; and (c) how the earth system history informs our understanding of the effects of ocean acidification on the present day and future ocean.

Solicitations issued under this program:
NSF 10-530, FY 2010-FY2011
NSF 12-500, FY 2012
NSF 12-600, FY 2013
NSF 13-586, FY 2014
NSF 13-586 was the final solicitation that will be released for this program.

PI Meetings:
1st U.S. Ocean Acidification PI Meeting(March 22-24, 2011, Woods Hole, MA)
2nd U.S. Ocean Acidification PI Meeting(Sept. 18-20, 2013, Washington, DC)
3rd U.S. Ocean Acidification PI Meeting (June 9-11, 2015, Woods Hole, MA – Tentative)

NSF media releases for the Ocean Acidification Program:

Press Release 10-186 NSF Awards Grants to Study Effects of Ocean Acidification

Discovery Blue Mussels "Hang On" Along Rocky Shores: For How Long?

Discovery nsf.gov - National Science Foundation (NSF) Discoveries - Trouble in Paradise: Ocean Acidification This Way Comes - US National Science Foundation (NSF)

Press Release 12-179 nsf.gov - National Science Foundation (NSF) News - Ocean Acidification: Finding New Answers Through National Science Foundation Research Grants - US National Science Foundation (NSF)

Press Release 13-102 World Oceans Month Brings Mixed News for Oysters

Press Release 13-108 nsf.gov - National Science Foundation (NSF) News - Natural Underwater Springs Show How Coral Reefs Respond to Ocean Acidification - US National Science Foundation (NSF)

Press Release 13-148 Ocean acidification: Making new discoveries through National Science Foundation research grants

Press Release 13-148 - Video nsf.gov - News - Video - NSF Ocean Sciences Division Director David Conover answers questions about ocean acidification. - US National Science Foundation (NSF)

Press Release 14-010 nsf.gov - National Science Foundation (NSF) News - Palau's coral reefs surprisingly resistant to ocean acidification - US National Science Foundation (NSF)

Press Release 14-116 nsf.gov - National Science Foundation (NSF) News - Ocean Acidification: NSF awards $11.4 million in new grants to study effects on marine ecosystems - US National Science Foundation (NSF)