Study: Reefs may “Unglue” in Oceans with High Carbon Dioxide

Cements that bind individual coral skeletons and larger coral reef structures are predominantly absent in waters with naturally high levels of carbon dioxide (CO2), making these reefs highly susceptible to a wearing down of their physical framework, say scientists with NOAA’s Atlantic Oceanographic and Meteorological Laboratory in Miami, Fla. and other institutions.

The study, released in the July 28 issue of the Proceedings of the National Academy of Sciences, found that the coral reefs of the eastern tropical Pacific provide a real-world example of the challenges all coral reefs will face under high-CO2 conditions resulting in ocean acidification.

In a More Acidic Ocean, Coral Reef “Skeletons” May Crumble

Coral reefs can resemble underwater monuments, with strong towers and meandering walls that stand firm against the tides. But a new study says that if global warming causes ocean water to become more acidic those elaborate structures may crumble because the cement-like binding agent that holds the reefs together won’t be able to form in those inhospitable waters.

Pacific Region May Show the Future of Coral Reefs in More Acidic Oceans

The gradual acidification of the oceans through increasing absorption of atmospheric carbon dioxide is thought to be potentially bad news for coral reefs. As seawater pH falls, the saturation level of carbonate ions in the water also declines. Since reefs are made up of calcium carbonate (from coral skeletons and other sources) they should be slower to form and faster to fall apart.

L´Ue fa Epoca per capire l´acidificazione degli oceani (in Italian)

BRUXELLES. A giugno l´Unione europea ha dato il via, con un finanziamento parziale di 6,5 milioni di euro, all´European project of ocean acidification (Epoca), un consorzio che comprende 100 scienziati appartenenti a 27 organizzazioni di 9 paesi diversi. L´obiettivo di Epoca è quello di documentare l´acidificazione dell´oceano e di comprendere il suo impatto sui processi biologici, in seguito il progetto punta a prevedere le sue conseguenze per i prossimi 100 anni e consigliare i responsabili delle politiche su soglie potenziali o punti critici da non oltrepassare.

Coral Reef ‘Glue’ May Not Stick Under Climate Change

The cement that buttresses coral reefs, giving them the strength to withstand crashing waves and other onslaughts, may stop forming as oceans acidify under increased carbon dioxide in the atmosphere.

Researchers have already predicted that a more acidic ocean will make it more difficult for corals to build their calcium carbonate skeletons. The new finding suggests that the reef’s broader structure may also suffer because a lower pH reduces the formation of the reef’s cement binder. The binder is made from calcium carbonate that precipitates out of ocean water when it rushes through the pores of coral skeletons.

Correlations between gastropod shell dissolution and water chemical properties in a tropical estuary

Although poorly reported in the scientific literature, acidic waters characterize many South East Asian estuaries. The observation of shell dissolution in a typically marine gastropod whelk (Thais) prompted investigation into determining relationships between shell properties of this whelk and the water chemistry (including pH) of the Sungai Brunei estuary (Borneo) in which it occurs. Shell weight, shell length and topographical shell features were determined for populations of Thais gradata distributed along a gradient of pH and salinity ranging between 5.78 and 8.3 pH units, and 3.58 and 31.2 psu. Shell weight varied independently of the co-varying acidity, salinity and calcium levels experienced. In contrast, shell length and a semi-quantitative variable based on shell sculpturing (shell erosion rank, SER) were significantly correlated with these water chemistry variables. This study brings attention to the potential use of estuarine organisms and systems in investigating current marine acidification questions.

Study: High CO2 environment damages reefs

Reefs may erode in areas with high carbon dioxide levels because the “glue” binding coral skeletons to larger reef structures is missing, a U.S. study found.

The study found coral reefs in the eastern tropical Pacific Ocean offer a real-world example of the what reef ecosystems will face under high carbon dioxide conditions resulting in ocean acidification, the National Oceanic and Atmospheric Administration said Monday in a release.

In our view: Oceans in Jeopardy

If you cringed reading that the enjoyment and safety of Vancouver Lake is threatened by “an enormous plume of cyanobacteria,” as WSU marine ecologist Gretchen Rollwagen-Bollens put it recently, you should be in red-alert state knowing that corrosive changes in the ocean are threatening marine ecosystems.

A recent study by the National Oceanic and Atmospheric Administration and the National Aeronautics and Space Administration found that the situation facing North America’s West Coast is far worse than scientists had imagined. Ocean acidification, caused by the ocean’s absorption of carbon dioxide, is transforming oceans’ pH level. We’ll bypass the big words and scientific descriptions here, but the changing pH is of concern. The level has dropped and is expected to drop another meaningful chunk by 2100. If that happens, it will seriously damage marine creatures’ ability to grow. If corals, plankton and tiny marine snails can no longer form properly, scientists say the whole food chain could be disrupted, from plankton to shellfish to marine mammals. Salmon, mackerel and whales, watch out. And beware commercial fisheries and communities dependent on maritime resources.

Poorly cemented coral reefs of the eastern tropical Pacific: Possible insights into reef development in a high-CO2 world

Ocean acidification describes the progressive, global reduction in seawater pH that is currently underway because of the accelerating oceanic uptake of atmospheric CO2. Acidification is expected to reduce coral reef calcification and increase reef dissolution. Inorganic cementation in reefs describes the precipitation of CaCO3 that acts to bind framework components and occlude porosity. Little is known about the effects of ocean acidification on reef cementation and whether changes in cementation rates will affect reef resistance to erosion. Coral reefs of the eastern tropical Pacific (ETP) are poorly developed and subject to rapid bioerosion. Upwelling processes mix cool, subthermocline waters with elevated pCO2 (the partial pressure of CO2) and nutrients into the surface layers throughout the ETP. Concerns about ocean acidification have led to the suggestion that this region of naturally low pH waters may serve as a model of coral reef development in a high-CO2 world. We analyzed seawater chemistry and reef framework samples from multiple reef sites in the ETP and found that a low carbonate saturation state (Ω) and trace abundances of cement are characteristic of these reefs. These low cement abundances may be a factor in the high bioerosion rates previously reported for ETP reefs, although elevated nutrients in upwelled waters may also be limiting cementation and/or stimulating bioerosion. ETP reefs represent a real-world example of coral reef growth in low-Ω waters that provide insights into how the biological–geological interface of coral reef ecosystems will change in a high-CO2 world.

In situ ecosystem-based carbon dioxide perturbation experiments: Design and performance evaluation of a mesocosm facility

We describe a mesocosm facility that can be used for in situ CO2 perturbation experiments. The facility consists of a floating raft, nine impermeable cylindrical enclosures (each approximately 2400 L in volume), pCO2 regulation units, and bubble-mediated seawater mixers. Each enclosure is two-thirds filled with the seawater, and the headspace above is filled with air at a target pCO2 concentration. Each enclosure is capped with a transparent dome that transmits incoming radiation. To produce pCO2 levels higher than the ambient concentration, the mass flow controller in the pCO2 regulation unit delivers varying amounts (10-740 mL min-1) of ultra-pure CO2 into the gas mixer where it is rapidly mixed with ambient air (approximately 50 L min-1). To produce pCO2 levels lower than the ambient concentration, CO2-free air and ambient air are mixed in the gas mixer. Prior to daily seawater sampling, approximately 0.5 L min-1 of the target concentration pCO2 air stream is diverted to the seawater mixer for thorough mixing with the seawater in the enclosure, while the major fraction of the target concentration pCO2 air stream continues to flow into the enclosure headspace. A performance evaluation of the mesocosm facility assessed attainment of target pCO2 concentrations in the headspace and enclosure seawater, and the mixing efficiency of the seawater mixer. The results indicate that the facility is suitable for carrying out in situ pCO2 perturbation experiments.