Coral Reefs Will Transition to Net Dissolving Before End of Century

Ocean acidification refers to the lowering of the ocean’s pH due to the uptake of anthropogenic CO2 from the atmosphere. Coral reef calcification is expected to decrease as the oceans become more acidic. Dissolving calcium carbonate (CaCO3) sands could greatly exacerbate reef loss associated with reduced calcification but is presently poorly constrained. Here we show that CaCO3 dissolution in reef sediments across five globally distributed sites is negatively correlated with the aragonite saturation state (Ωar) of overlying seawater and that CaCO3 sediment dissolution is 10-fold more sensitive to ocean acidification than coral calcification. Consequently, reef sediments globally will transition from net precipitation to net dissolution when seawater Ωar reaches 2.92 ± 0.16 (expected circa 2050 CE). Notably, some reefs are already experiencing net sediment dissolution

Comparison of CO2 dynamics and air-sea exchange in differing tropical reef environments

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Aquatic Geochemistry 19 (2013): 371-397, doi:10.1007/s10498-013-9214-7.Note from corresponding author: authors Feely and Shamberger were added after the initial submission, but before the final submission.An array of MAPCO2 buoys, CRIMP-2, Ala Wai, and Kilo Nalu, deployed in the coastal waters of Hawaii have produced multiyear high temporal resolution CO2 records in three different coral reef environments off the island of Oahu, Hawaii. This study, which includes data from June 2008-December 2011, is part of an integrated effort to understand the factors that influence the dynamics of CO2-carbonic acid system parameters in waters surrounding Pacific high island coral reef ecosystems and subject to differing natural and anthropogenic stresses. The MAPCO2 buoys are located on the Kaneohe Bay backreef, and fringing reef sites on the south shore of O’ahu, Hawai’i. The buoys measure CO2 and O2 in seawater and in the atmosphere at 3-hour intervals, as well as other physical and biogeochemical parameters (CTD, chlorophyll-a, turbidity). The buoy records, combined with data from synoptic spatial sampling, have allowed us to examine the interplay between biological cycles of productivity/respiration and calcification/dissolution and biogeochemical and physical forcings on hourly to inter-annual time scales. Air-sea CO2 gas exchange was also calculated to determine if the locations were sources or sinks of CO2 over seasonal, annual, and interannual time periods. Net annualized fluxes for CRIMP-2, Ala Wai, and Kilo Nalu over the entire study period were 1.15 mol C m-2 yr-1, 0.045 mol C m-2 yr-1, and -0.0056 mol C m-2 yr-1, respectively, where positive values indicate a source or a CO2 flux from the water to the atmosphere, and negative values indicate a sink or flux of CO2 from the atmosphere into the water. These values are of similar magnitude to previous estimates in Kaneohe Bay as well as those reported from other tropical reef environments. Total alkalinity (AT) was measured in conjunction with pCO2 and the carbonic acid system was calculated to compare with other reef systems and open ocean values around Hawaii. These findings emphasize the need for high-resolution data of multiple parameters when attempting to characterize the carbonic-acid system in locations of highly variable physical, chemical, and biological parameters (e.g. coastal systems, reefs).This work was supported in part by a grant/cooperative agreement from the National Oceanic and Atmospheric Administration, Project R/IR-3, which is sponsored by the University of Hawaii Sea Grant College Program, SOEST, under Institutional Grant No. NA09OAR4170060 from NOAA Office of Sea Grant, Department of Commerce.2014-11-0

Hawaii coastal seawater CO2 network: A statistical evaluation of a decade of observations on tropical coral reefs.

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Terlouw, G. J., Knor, L. A. C. M., De Carlo, E. H., Drupp, P. S., Mackenzie, F. T., Li, Y. H., Sutton, A. J., Plueddemann, A. J., & Sabine, C. L. Hawaii coastal seawater CO2 network: A statistical evaluation of a decade of observations on tropical coral reefs. Frontiers in Marine Science, 6, (2019):226, doi:10.3389/fmars.2019.00226.A statistical evaluation of nearly 10 years of high-resolution surface seawater carbon dioxide partial pressure (pCO2) time-series data collected from coastal moorings around O’ahu, Hawai’i suggest that these coral reef ecosystems were largely a net source of CO2 to the atmosphere between 2008 and 2016. The largest air-sea flux (1.24 ± 0.33 mol m−2 yr−1) and the largest variability in seawater pCO2 (950 μatm overall range or 8x the open ocean range) were observed at the CRIMP-2 site, near a shallow barrier coral reef system in Kaneohe Bay O’ahu. Two south shore sites, Kilo Nalu and Ala Wai, also exhibited about twice the surface water pCO2 variability of the open ocean, but had net fluxes that were much closer to the open ocean than the strongly calcifying system at CRIMP-2. All mooring sites showed the opposite seasonal cycle from the atmosphere, with the highest values in the summer and lower values in the winter. Average coastal diurnal variabilities ranged from a high of 192 μatm/day to a low of 32 μatm/day at the CRIMP-2 and Kilo Nalu sites, respectively, which is one to two orders of magnitude greater than observed at the open ocean site. Here we examine the modes and drivers of variability at the different coastal sites. Although daily to seasonal variations in pCO2 and air-sea CO2 fluxes are strongly affected by localized processes, basin-scale climate oscillations also affect the variability on interannual time scales.We acknowledge with gratitude the financial support of our research provided in part by a grant/cooperative agreement from the National Oceanic and Atmospheric Administration, Project R/IR-27, which is sponsored by the University of Hawaii Sea Grant College Program, SOEST, under Institutional Grant No. NA14OAR4170071 from NOAA Office of Sea Grant, Department of Commerce. Additional support was granted by the NOAA/Ocean Acidification Program (to EDC and AS) and the NOAA/Climate Program Office (AP), and the NOAA Ocean Observing and Monitoring Division, Climate Program Office (FundRef number 100007298) through agreement NA14OAR4320158 of the NOAA Cooperative Institute for the North Atlantic Region (AP). The views expressed herein are those of the author(s) and do not necessarily reflect the views of NOAA or any of its subagencies. This is SOEST contribution number 10684, PMEL contribution number 4845, and Hawai’i Sea Grant contribution UNIHI-SEAGRANT-JC-15-30

Addressing climate change with behavioral science: a global intervention tournament in 63 countries

Effectively reducing climate change requires marked, global behavior change. However, it is unclear which strategies are most likely to motivate people to change their climate beliefs and behaviors. Here, we tested 11 expert-crowdsourced interventions on four climate mitigation outcomes: beliefs, policy support, information sharing intention, and an effortful tree-planting behavioral task. Across 59,440 participants from 63 countries, the interventions’ effectiveness was small, largely limited to nonclimate skeptics, and differed across outcomes: Beliefs were strengthened mostly by decreasing psychological distance (by 2.3%), policy support by writing a letter to a future-generation member (2.6%), information sharing by negative emotion induction (12.1%), and no intervention increased the more effortful behavior—several interventions even reduced tree planting. Last, the effects of each intervention differed depending on people’s initial climate beliefs. These findings suggest that the impact of behavioral climate interventions varies across audiences and target behaviors

Observations and Modeling of the CO2-Carbonic Acid System on Hawaiian Coral Reefs: Implications of Future Ocean Acidification and Climate Change

Ph.D. University of Hawaii at Manoa 2015.Includes bibliographical references.The CO2-carbonic acid system of nearshore and coral reef ecosystems is highly variable, and often poorly constrained. In addition to the natural processes altering the carbon system of coral reefs, increased atmospheric and seawater carbon dioxide (CO2) concentrations, from the anthropogenic burning of fossil fuels and land use changes, have the potential to alter the fragile biogeochemical balance of these ecosystems. Autonomous seawater CO2 monitoring buoys are becoming an increasingly utilized method for studying the CO2 chemistry of coastal waters, and these systems provide accurate, high-resolution CO2 data that were previously unobtainable a decade ago. This research presents the results of the longest running, continuous CO2 time-series for a coral reef environment in the world. A network of three monitoring buoys was established in 2008 around Oahu, Hawai‘i, providing high-resolution data. Net annualized air-sea CO2 gas exchange was calculated at each study location and was comparable to estimates at other reef locations around the world. An in-situ study of the permeable carbonate sediment-porewater system at two locations showed that porewater carbon biogeochemistry in permeable reef sediments is strongly controlled by microbial respiration of organic matter. The short residence time of the porewater, due to increased advection, is another major control on the biogeochemical parameters such as total alkalinity and pH. Finally, the data collected by the observing buoys, along with the in-situ porewater data and previous data collected in Kaneohe Bay, were used to create a carbon biogeochemical box model, the Coral Reef and Sediment Carbonate Model (CRESCAM), for the Kaneohe Bay barrier reef flat. The model was forced using the Representative Concentration Pathway CO2 emissions scenarios from the 2013 Intergovernmental Panel on Climate Change 5th Assessment Report. Several case studies were conducted to determine important parameters and to identify possible future conditions on the barrier reef under increasing ocean acidification, rising temperature, and land use changes. Model runs predicted that the barrier reef flat could experience a 20% decrease in coral calcification, by 2100. Although carbonate dissolution is expected to increase in the sediments, dissolution will not provide a sufficient buffer to mitigate any decreases in surface water pH

Dissolution of Coral Reef CaCO3 Sediments: Overlooked and Forgotten in Ocean Acidification Research

Ocean acidification (OA) is expected to have drastic effects on the future of coral reefs, mainly through the reduced formation of calcium carbonate (CaCO3). However, the dissolution of stored CaCO3 has largely been overlooked in the OA community. CaCO3 sediments represent the largest reservoir of carbonate minerals in coral reefs and result from the accumulation and storage of CaCO3 material over thousands of years. This presentation will demonstrate the in situ drivers of dissolution in coral reef carbonate sands and how they will respond increasing average pCO2 (ocean acidification). Results from in situ benthic incubations at coral reefs around the world demonstrated that benthic metabolism and porewater exchange are important controls on CaCO3 sediment dissolution, and this dissolution is enhanced when the water column pCO2 is raised. The rate at which sediments are predicted to dissolve by the year 2100 has important implications to the biogeochemistry of coral reefs and their future survival. We propose that quantifying the global dissolution kinetics of CaCO3 sediments may be just as important as estimating calcification rates when predicting how OA will impact coral reef ecosystems

Carbonate Chemistry and Air-Sea CO2 Flux in a NW Mediterranean Bay Over a Four-Year Period: 2007-2011

The Service d'Observation de la Rade de Villefranche-sur-Mer is designed to study the temporal variability of hydrological conditions as well as the abundance and composition of holo- and meroplankton at a fixed station in this bay of the northwest Mediterranean. The weekly data collected at this site, designated as ``Point B'' since 1957, represent a long-term time series of hydrological conditions in a coastal environment. Since 2007, the historical measurements of hydrological and biological conditions have been complemented by measurements of the CO2-carbonic acid system parameters. In this contribution, CO2-carbonic acid system parameters and ancillary data are presented for the period 2007-2011. The data are evaluated in the context of the physical and biogeochemical processes that contribute to variations in CO2 in the water column and exchange of this gas between the ocean and atmosphere. Seasonal cycles of the partial pressure of CO2 in seawater (pCO(2)) are controlled principally by variations in temperature, showing maxima in the summer and minima during the winter. Normalization of pCO(2) to the mean seawater temperature (18.5 degrees C), however, reveals an apparent reversal of the seasonal cycle with maxima observed in the winter and minima in the summer, consistent with a biogeochemical control of pCO(2) by primary production. Calculations of fluxes of CO2 show this area to be a weak source of CO2 to the atmosphere during the summer and a weak sink during the winter but near neutral overall (range -0.3 to +0.3 mmol CO2 m(-2) h(-1), average 0.02 mmol CO2 m(-2) h(-1)). We also provide an assessment of errors incurred from the estimation of annual fluxes of CO2 as a function of sampling frequency (3-hourly, daily, weekly), using data obtained at the Hawaii Kilo Nalu coastal time-series station, which shows similar behavior to the Point B location despite significant differences in climate and hydrological conditions and the proximity of a coral reef ecosystem

Global Response of Coral Reef Benthic Calcium Carbonate Dissolution to Ocean Acidification

Ocean acidification (OA) is predicted to have a significant impact on the future of coral reefs, mainly through the reduced formation of calcium carbonate (CaCO3). However, the dissolution of stored CaCO3 has largely been overlooked in the OA community. CaCO3 sediments represent the largest reservoir of carbonate minerals in coral reefs and result from the accumulation and storage of CaCO3 material over thousands of years. This presentation will demonstrate the in situ drivers of dissolution in coral reef carbonate sands and how they will respond to increasing average pCO2 (ocean acidification). In situ benthic incubations at coral reefs around the world show that aragonite saturation in the overlying water is a strong predictor of CaCO3 sediment dissolution and most reefs show a similar response to increasing average pCO2 (OA). However, every reef shows a different net sediment dissolution starting condition and the effect of end of century OA conditions on net sediment dissolution is different for every reef. The rate at which sediments are predicted to dissolve by the year 2100 has important implications on the net accretion of coral reefs and their future survival. Quantifying the global dissolution kinetics of CaCO3 sediments is clearly just as important as estimating calcification rates when predicting how OA will impact coral reef ecosystems