Archive for November, 2011

Calcification rates and the effect of ocean acidification on Mediterranean cold-water corals

Global environmental changes, including ocean acidification, have been identified as a major threat to scleractinian corals. General predictions are that ocean acidification will be detrimental to reef growth and that 40 to more than 80 per cent of present-day reefs will decline during the next 50 years. Cold-water corals (CWCs) are thought to be strongly affected by changes in ocean acidification owing to their distribution in deep and/or cold waters, which naturally exhibit a CaCO3 saturation state lower than in shallow/warm waters. Calcification was measured in three species of Mediterranean cold-water scleractinian corals (Lophelia pertusaMadrepora oculata and Desmophyllum dianthus) on-board research vessels and soon after collection. Incubations were performed in ambient sea water. The species M. oculata was additionally incubated in sea water reduced or enriched in CO2. At ambient conditions, calcification rates ranged between −0.01 and 0.23% d−1. Calcification rates of M. oculata under variable partial pressure of CO2 (pCO2) were the same for ambient and elevated pCO2 (404 and 867 µatm) with 0.06 ± 0.06% d−1, while calcification was 0.12 ± 0.06% d−1 when pCO2 was reduced to its pre-industrial level (285 µatm). This suggests that present-day CWC calcification in the Mediterranean Sea has already drastically declined (by 50%) as a consequence of anthropogenic-induced ocean acidification.

Continue reading ‘Calcification rates and the effect of ocean acidification on Mediterranean cold-water corals’

Ocean acidification in the coastal ocean

The oceans play a crucial role in the global carbon cycle and store about one third of the anthropogenic carbon dioxide (CO2) emissions since 1800. When CO2 dissolves in seawater, it generates a decrease in pH and in the concentration of carbonate (CO32-) ions. Since pre-industrial time, surface ocean pH has declined by 0.1 unit and, according to model projections, a further decrease of 0.2-0.4 unit is anticipated for the end of the century. In the coastal ocean, the few available datasets suggest more complicated pH trends than in the open ocean due to various biogeochemical and hydrological processes. Although the coastal ocean only represents a small portion of the oceanic surface area, it exhibits high biological activities and an important biodiversity that may be affected in the coming decades in response to the ongoing and projected modifi cations of the carbonate chemistry. In this brief article, we present some information on the potential effect of ocean acidifi cation on key coastal organisms and communities, and provide a list of international and national projects looking at coastal ecosystems.

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Virioplankton and bacterioplankton in a shallow CO2-dominated hydrothermal vent (Panarea Island, Tyrrhenian Sea)

Gas hydrothermal vents are used as a natural analogue for studying the effects of CO2 leakage from hypothetical shallow marine storage sites on benthic and pelagic systems. This study investigated the interrelationships between planktonic prokaryotes and viruses in the Panarea Islands hydrothermal system (southern Tyrrhenian Sea, Italy), especially their abundance, distribution and diversity. No difference in prokaryotic abundance was shown between high-CO2 and control sites. The community structure displayed differences between fumarolic field and the control, and between surface and bottom waters, the latter likely due to the presence of different water masses. Bacterial assemblages were qualitatively dominated by chemo- and photoautotrophic organisms, able to utilise both CO2 and H2S for their metabolic requirements. From significantly lower virioplankton abundance in the proximity of the exhalative area together with particularly low Virus-to-Prokaryotes Ratio, we inferred a reduced impact on prokaryotic abundance and proliferation. Even if the fate of viruses in this particular condition remains still unknown, we consider that lower viral abundance could reflect in enhancing the energy flow to higher trophic levels, thus largely influencing the overall functioning of the system. Continue reading ‘Virioplankton and bacterioplankton in a shallow CO2-dominated hydrothermal vent (Panarea Island, Tyrrhenian Sea)’

Submarine springs offer preview of ocean acidification effects on coral reefs

Observations at submarine springs found along the coast of Mexico’s Yucatan Peninsula are giving scientists a preview of the possible fate of coral reef ecosystems in response to ocean acidification.

The naturally low pH (a measure of acidity) in the water around the springs creates conditions similar to those that will result from the widespread acidification of surface waters that scientists expect to occur as the oceans absorb increasing amounts of carbon dioxide from the atmosphere. Ecological surveys around the springs found small, patchily distributed colonies of only a few species of corals, without the structurally complex corals that compose the framework of the nearby Mesoamerican Barrier Reef, one of the Caribbean’s largest coral reef ecosystems.

A team led by scientists at the University of California, Santa Cruz, has been studying the submarine springs at Puerto Morelos near the Mesoamerican reef for the past three years. The researchers reported their findings in a paper published in the journal Coral Reefs (published online Nov. 20).

Continue reading ‘Submarine springs offer preview of ocean acidification effects on coral reefs’

New buoy network could help determine long-term impacts of ocean acidification

A major education effort by scientists and fishermen is leading to the conclusion that if Ocean Acidification is not a problem yet,  it’s about to be.  And a proposal that will likely be before the legislature next session is looking for money to enlarge the state’s Ocean Acidification observation network with new monitoring buoys to provide an early warning system that could help avoid an immediate fishing disaster – and help determine the long-term impacts of acidification.

Here’s the problem with ocean acidification:   When there’s too much Carbon Dioxide – or CO2 — in the air,   too much of it gets into the water.  Then, CO2 increases the acidity of the seawater,  which keeps calcium carbonate from being available.  Calcium Carbonate is what forms the shells of Oysters and Clams – and the skeletons of many other marine organisms. If that layer of the food chain fails,  everything above it will be at risk.

Dr. Jeremy Mathis is an Assistant Professor of Chemical Oceanography at the UAF School of Fisheries and Ocean Sciences.   He says measurements of acid levels are now not much more than a series of snapshots – readings taken when fishermen or university boats sample water from time to time.  That data has shown some alarming trends,  But he says it’s very hard to put those numbers into context.

Continue reading ‘New buoy network could help determine long-term impacts of ocean acidification’

The acid truth about our oceans: experts urge action to limit ocean acidification

Durban, South Africa, 29 November 2011 Ocean acidification can no longer remain on the periphery of the international debates on climate change and the environment and should be addressed by the UN Framework Convention on Climate Change and other global environmental conventions, urges IUCN and the International Ocean Acidification Reference User Group (RUG) at the climate change summit in Durban.

In the run up to the United Nations Conference on Sustainable Development, which will take place in Rio de Janeiro in June next year (Rio+20), world experts from RUG call for decision makers to urgently address the critical issue of ocean acidification.

“The increasing amounts of carbon dioxide that we emit into the atmosphere every day are changing our oceans, steadily increasing their acidity, and dramatically affecting marine life,” says Professor Dan Laffoley Marine Vice Chair of IUCN’s World Commission on Protected Areas and Chair of RUG. “This may also have severe impacts on human life in the future. Only by reducing our CO2 emissions and enhancing the protection of oceans to strengthen their ability to recover, can we effectively address this issue. Policy makers in Durban, and in Rio in June next year, need to recognize this and take appropriate actions.”

Continue reading ‘The acid truth about our oceans: experts urge action to limit ocean acidification’

Triple trouble – Ocean under stress

Scientists concerned how three environmental problems could combine to threaten the ocean, take warnings to the climate change discussion at the United Nations Framework Convention on Climate Change Seventeenth session of the Conference of the Parties (COP17) in Durban, South Africa.

Over the coming decades and centuries, the ocean will become increasingly stressed by at least three interacting factors. Rising seawater temperatures, ocean acidification and ocean deoxygenation will cause substantial changes in marine physics, chemistry and biology. These changes will affect the ocean in ways that we are only beginning to understand; these changes are likely to affect every one of us.

The global ocean covers nearly three quarters of Earth’s surface, contains 96% of its living space, provides around half of the oxygen we breathe and is an increasing source of protein for a rapidly growing world population. However, human activity over the last 200 years is having an impact on this precious resource on local, regional and global scales. It is imperative that international decision-makers understand the enormous role the ocean plays in sustaining life on Earth and the consequences of a high CO2 world for the ocean and society.

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Seminar: Effects of temperature and CO2-induced ocean acidification on calcification and extension rates of the tropical zooxanthellate scleractinian coral Siderastrea siderea

 Wednesday, November 30, 2011

3:00-4:00 p.m.

Venable Hall, Room G201

Anthropogenic elevation of atmospheric carbon dioxide (CO2) has led to an increase in the temperature and acidity of the oceans. Future increases in atmospheric CO2 are predicted to increase seawater temperatures by an additional 2 to 3°C and to reduce seawater pH by 0.3 to 0.4 units over this century. These global scale changes in ocean temperature and chemistry are predicted to have increasingly negative impacts on the health of coral reefs and may lead to increasing rates of coral mortality. We show that over approximately the last three decades on the Mesoamerican Barrier Reef System in the western Caribbean Sea, coral skeletal extension rates within forereef colonies of the reef-building coral Siderastrea siderea declined with increasing seawater temperature, while extension rates of backreef and nearshore colonies were not impacted. In addition, we explored the effects of temperature and CO2-incuded ocean acidification on the calcification of S. siderea reared for 60 days across a range of temperatures and acidities. Our results indicate that although calcification rates of S. siderea coral colonies were suppressed under elevated seawater temperature, these corals are able to calcify at a faster rate under CO2-acidified conditions projected for the next century. These findings reveal how corals have responded thus far to recent anthropogenic warming, offer insights into how they are likely to respond to future warming and acidification, and suggest that rising seawater temperature, rather than ocean acidification, is the more immediate threat to coral reefs.

Continue reading ‘Seminar: Effects of temperature and CO2-induced ocean acidification on calcification and extension rates of the tropical zooxanthellate scleractinian coral Siderastrea siderea’

Amplification of hypoxic and acidic events by La Niña conditions on the continental shelf off California

Low-oxygen and low-pH events are an increasing concern and threat in the Eastern Pacific coastal waters, and can be lethal for benthic and demersal organisms on the continental shelf. The normal seasonal cycle includes uplifting of isopycnals during upwelling in spring, which brings low-oxygen and low-pH water onto the shelf. Five years of continuous observations of subsurface dissolved oxygen off Southern California, reveal large additional oxygen deficiencies relative to the seasonal cycle during the latest La Niña event. While some changes in oxygen related to the isopycnal depression/uplifting during El Niño/La Niña are not unexpected, the observed oxygen changes are 2–3 times larger than what can be explained by cross-shore exchanges. In late summer 2010, oxygen levels at mid-depth of the water column reached values of 2.5 ml/L, which is much lower than normal oxygen levels at this time of the seasons, 4–5 ml/L. The extra uplifting of isopycnals related to the La Niña event can explain oxygen reductions only to roughly 3.5 ml/L. We find that the additional oxygen decrease beyond that is strongly correlated with decreased subsurface primary production and strengthened poleward flows by the California Undercurrent. The combined actions of these three processes created a La Niña-caused oxygen decrease as large and as long as the normal seasonal minimum during upwelling period in spring, but later in the year. With a different timing of a La Niña, the seasonal oxygen minimum and the La Niña anomaly could overlap to potentially create hypoxic events of previously not observed magnitudes.

Continue reading ‘Amplification of hypoxic and acidic events by La Niña conditions on the continental shelf off California’

Featured video: Oyster standoff with ocean acidification

Vodpod videos no longer available.

Biologist Jennifer Ruesink considers UW oyster research and work with the shellfish industry in face of today’s environmental challenges, including ocean acidification. The UW 360 segment also includes Emma Timmins-Schiffman, aquatic and fishery sciences graduate student, and Taylor Shellfish Farms‘ Joth Davis, who is a UW affiliate faculty member.

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Ocean acidification in the IPCC AR5 WG II

OUP book