Archive for August, 2014

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In our view: acidification harms oceans

Published 23 August 2014 Media coverage Closed

When it comes to ocean acidification, the state of Washington is in damage-control mode. There is little doubt such acidification has — and will — take a toll on the state’s economy; the question is, at what cost?

At stake is the state’s $270 million shellfish industry — along with Alaska’s $100 million king crab fishery, other Washington fisheries, and the economies of all states that are reliant upon the ocean for sustenance. Because of that, U.S. Sens. Maria Cantwell, D-Wash., and Mark Begich, D-Alaska, visited the Puget Sound region last week to talk about ocean acidification and legislation they are preparing in order to mitigate its impact. The plan would provide funding for the National Oceanic and Atmospheric Administration to expand a network of high-tech buoys and sensors that monitor ocean conditions.

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Autonomous in situ measurements of seawater alkalinity

Published 22 August 2014 Science Closed
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Total alkalinity (AT) is an important parameter for describing the marine inorganic carbon system and understanding the effects of atmospheric CO2 on the oceans. Measurements of AT are limited, however, because of the laborious process of collecting and analyzing samples. In this work we evaluate the performance of an autonomous instrument for high temporal resolution measurements of seawater AT. The Submersible Autonomous Moored Instrument for alkalinity (SAMI-alk) uses a novel tracer monitored titration method where a colorimetric pH indicator quantifies both pH and relative volumes of sample and titrant, circumventing the need for gravimetric or volumetric measurements. The SAMI-alk performance was validated in the laboratory and in situ during two field studies. Overall in situ accuracy was −2.2 ± 13.1 μmol kg–1 (n = 86), on the basis of comparison to discrete samples. Precision on duplicate analyses of a carbonate standard was ±4.7 μmol kg–1 (n = 22). This prototype instrument can measure in situ AT hourly for one month, limited by consumption of reagent and standard solutions.

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Ocean acidification wrecks sharks’ smellovision

Published 22 August 2014 Web sites and blogs Closed
Picture by brandXpictures

Picture by brandXpictures

Scarier than any movie shark that can smell a drop of blood miles away (they can’t, by the way) is this week’s news about sharks’ sense of smell. A team of Australian and American scientists has just shown that smooth dogfishes (also called dusky smooth-hound sharks) can’t smell food as well after living in ocean acidification conditions expected for the year 2100. These “future” sharks could correctly track food smells only 15% of the time, compared to a 60% accuracy rate for unexposed sharks. In fact, the acidification-exposed sharks even avoided food smells!

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Acid–base physiology response to ocean acidification of two ecologically and economically important holothuroids from contrasting habitats, Holothuria scabra and Holothuria parva

Published 21 August 2014 Science Closed
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Sea cucumbers are dominant invertebrates in several ecosystems such as coral reefs, seagrass meadows and mangroves. As bioturbators, they have an important ecological role in making available calcium carbonate and nutrients to the rest of the community. However, due to their commercial value, they face overexploitation in the natural environment. On top of that, occurring ocean acidification could impact these organisms, considered sensitive as echinoderms are osmoconformers, high-magnesium calcite producers and have a low metabolism. As a first investigation of the impact of ocean acidification on sea cucumbers, we tested the impact of short-term (6 to 12 days) exposure to ocean acidification (seawater pH 7.7 and 7.4) on two sea cucumbers collected in SW Madagascar, Holothuria scabra, a high commercial value species living in the seagrass meadows, and H. parva, inhabiting the mangroves. The former lives in a habitat with moderate fluctuations of seawater chemistry (driven by day–night differences) while the second lives in a highly variable intertidal environment. In both species, pH of the coelomic fluid was significantly negatively affected by reduced seawater pH, with a pronounced extracellular acidosis in individuals maintained at pH 7.7 and 7.4. This acidosis was due to an increased dissolved inorganic carbon content and pCO2 of the coelomic fluid, indicating a limited diffusion of the CO2 towards the external medium. However, respiration and ammonium excretion rates were not affected. No evidence of accumulation of bicarbonate was observed to buffer the coelomic fluid pH. If this acidosis stays uncompensated for when facing long-term exposure, other processes could be affected in both species, eventually leading to impacts on their ecological role.

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Faster recovery of a diatom from UV damage under ocean acidification

Published 21 August 2014 Science Closed
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Diatoms are the most important group of primary producers in marine ecosystems. As oceanic pH declines and increased stratification leads to the upper mixing layer becoming shallower, diatoms are interactively affected by both lower pH and higher average exposures to solar ultraviolet radiation. The photochemical yields of a model diatom, Phaeodactylum tricornutum, were inhibited by ultraviolet radiation under both growth and excess light levels, while the functional absorbance cross sections of the remaining Photosystem II increased. Cells grown under ocean acidification (OA) were less affected during UV exposure. The recovery of PSII under low photosynthetically active radiation was much faster than in the dark, indicating that photosynthetic processes were essential for the full recovery of Photosystem II. This light dependent recovery required de novo synthesized protein. Cells grown under ocean acidification recovered faster, possibly attributable to higher CO2 availability for the Calvin cycle producing more resources for repair. The lower UV inhibition combined with higher recovery rate under ocean acidification could benefit species such as Phaeodactylum tricornutum, and change their competitiveness in the future ocean.

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A seawater filtration method suitable for total dissolved inorganic carbon and pH analyses

Published 21 August 2014 Science Closed
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High biomass and heavy particle loads may interfere with carbonate chemistry analyses of samples from experimental aquaria and cultures used to investigate the impact of ocean acidification on organisms, as well as from biologically productive coastal regions. For such samples, a filtration method is needed that does not change the dissolved CO2 content, and consequently does not alter the total dissolved inorganic carbon and pH of the sample. Here, a filtration method is presented in which the sample seawater is pumped by a peristaltic pump through a replaceable 0.45 mu m filter in a 50 mm polycarbonate filter holder and then into the sample bottle. Seawater samples of known carbonate composition were filtered to confirm that the filtration method did not alter the CO2 content, and compromise the subsequent sample analysis and data usefulness. Seawater samples with added phytoplankton concentrations in the range of 1-5 x 10(5) cells mL(-1) were also filtered successfully. Finally, seawater with added biogenic CaCO3 was tested to prove that the method could successfully filter out such particles and produce dependable results. This approach will help to ensure more consistent and reliable carbonate chemistry measurements in coastal environments and from ocean acidification aquaria and cultures, by providing a well-tested method for sample filtration.

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Effect on pCO2 by phytoplankton uptake of dissolved organic nutrients in the Central and Northern Baltic Sea, a model study

Published 21 August 2014 Science Closed
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Dissolved organic matter (DOM) has been added to an existing biogeochemical model and the phytoplankton were allowed to utilize the dissolved organic nutrients for primary production. The results show typical vertical structures for dissolved organic carbon (DOC), and improved or maintained model skill for both mean vertical profiles and mean seasonal variation of biogeochemical variables, evaluated by objective skill metrics. Due to scarce DOM measurements in the Baltic Sea it was hard to validate the new variables, but the model can recreate the general magnitude and distribution of terrestrial and in situ produced DOC, DON, and DOP, as far as we know them. The improvements are especially clear for the total nutrient levels and in recreating the biological drawdown of CO2 in the Eastern Gotland basin. Without phytoplankton uptake of dissolved organic nitrogen and phosphate, CO2 assimilation is lower during the summer months and the partial pressure of CO2 increases by about 200 μatm in the Eastern Gotland Basin, while in the Bothnian Bay, both the duration and magnitude of CO2 assimilation are halved. Thus the phytoplankton uptake of dissolved organic nutrients lowers pCO2 in both basins. Variations in the river transported DOM concentration mainly affect the magnitude of the summer cyanobacteria bloom.

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Falling ocean pH levels means rising threats for coral reefs

Published 20 August 2014 Press releases Closed

The rate of acidification in coral reef ecosystems is more than three times faster than in the open ocean, say a team of Southern Cross University biogeochemists.

Led by recent graduate Dr Tyler Cyronak, the results highlight how coral reefs may be acidifying faster than expected.

The University’s Centre for Coastal Biogeochemistry Research has published its results, ‘Enhanced coral reef acidification driven by regional biogeochemical feedbacks’ by Dr Tyler Cyronak, Associate Professor Isaac Santos, Associate Professor Kai Schulz, and Professor Bradley Eyre, in the latest edition of the Geophysical Research Letters journal.

Ocean acidification, or the lowering of the ocean pH due to anthropogenic inputs of carbon dioxide, has been well documented in the open ocean. However, this research looked back at studies done in coral reefs since the 1960s and found that the rate of acidification in coral reef ecosystems was more than three faster than in the open ocean.
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Alaska: Ocean acidification puts livelihoods at risk

Published 20 August 2014 Media coverage Closed

Ocean acidification will endanger the livelihoods of communities located in southeast and southwest Alaska, according to new NOAA-led study published in Progress in Oceanography.

This interdisciplinary study, entitled ‘Ocean acidification risk assessment for Alaska’s fishery sector,’ shows that many of Alaska’s marine fisheries are located in waters that are already experiencing ocean acidification.

Ocean acidification is the lowering of ocean pH due to increasing levels of CO2 in the atmosphere. Since pre-industrial times, the surface ocean pH has reportedly fallen by 0.1 pH units. This change represents approximately a 30 percent increase in acidity. Future predictions indicate that the oceans will continue to absorb carbon dioxide and as a result will become even more acidic.

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Scientists, White House say ocean acidification is well under way

Published 20 August 2014 Science Closed

The oceans aren’t vast enough to absorb growing amounts of carbon dioxide without ill effects to marine life and to the 1 billion people who make their living on the seas. Longer heat waves, drought, rising sea levels, more intense storms—these are some of the better-known impacts of climate change. Less familiar is the acidification of the oceans, which is well under way and will continue as the amount of atmospheric carbon dioxide rises.

The oceans absorb about one-quarter of the CO2 emitted from fossil-fuel combustion, about the same proportion taken up by land. The rest remains in the atmosphere, where its concentration steadily increases. The rate at which the oceans are acidifying, through chemical reactions with the CO2, is faster than has occurred in at least 65 million years and possibly 300 million years, according to Ove Hoegh-Guldberg of the University of Queensland. Marine organisms that require carbonate ions to build their shells likely won’t have sufficient time to adapt to the changing pH. “We’re taking life outside the conditions that it actually evolved for,” Hoegh-Guldberg said at the Our Ocean Conference, sponsored by the US Department of State and held 16–17 June in Washington, DC.

A much slower acidification event that occurred 55 million years ago (the Paleocene–Eocene Thermal Maximum) caused a mass extinction of deep-sea plankton and a collapse of coral reefs, according to research published in May’s Paleoceanography.

Since the Industrial Revolution, the acidity of the oceans has jumped 25%, from a pH of 8.2 to 8.1, according to the US Global Change Research Program’s 2014 National Climate Assessment. If current trends in CO2 emissions continue unchecked, acidity will increase by 100–150% from preindustrial levels by the end of the century, said Carol Turley of the Plymouth Marine Laboratory in the UK. “It is happening now, it’s happening rapidly, and it’s happening at a speed we haven’t seen for millions of years,” said Turley at the State Department conference.

The physical chemistry of ocean acidification caused by increased atmospheric CO2 is straightforward: Some of the dissolved gas reacts with water to form carbonic acid, H2CO3. However, “it gets much more complicated in coastal waters, around a coral reef or shellfish beds and estuaries, because there’s other processes besides invasion of fossil-fuel CO2,” says Scott Doney of the Woods Hole Oceanographic Institution (WHOI). “Coastal waters can be affected by a variety of biological processes, by chemicals, and by materials from the land,” he says. “In some places, fossil-fuel carbon may not even be the biggest contributor.”

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Low calcium carbonate saturation state in an Arctic inland sea having large and varying fluvial inputs: The Hudson Bay system

Published 19 August 2014 Science Closed
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The Hudson Bay system (HBS) is a shallow inland sea in the Arctic, composed of Hudson Strait, Foxe Basin/Channel, James Bay and Hudson Bay. Dissolved inorganic carbon (DIC) and total alkalinity (TA) measurements were used to investigate the state of ocean acidification, specifically calcium carbonate saturation states (Ω) and pH. The freshwater sources were identified from the relationship between oxygen isotope composition (δ18O) and salinity to understand the role of freshwater in ocean acidification.

The saturation state of seawater with respect to calcium carbonate (Ω) in surface water (<10m) of the HBS was strongly influenced by river runoff. Aragonite under-saturation (Ωarg10%). The watershed characteristics, however, influenced the alkalinity of river runoff in different parts of Hudson Bay, which contributed to Ω variation in the coastal region. In southwestern Hudson Bay where the watershed is dominated by limestone, Ω was higher compared to eastern Hudson Bay, where the watershed consists of an igneous rock formation. In deeper waters, low Ω is caused by remineralisation of organic matter. The highest DIC concentrations (>2300 µmol/kg) were observed in the depths of central Hudson Bay with a pHtotal of 7.49 and Ωarg of 0.37. Over 67% and 22% of the bottom water of Hudson Bay was undersaturated with respect to aragonite and calcite respectively, despite Hudson Bay being very shallow (less than 250m deep). The aragonite saturation horizon in the central Hudson Bay was around 50m.

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Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas (update)

Published 19 August 2014 Science Closed
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Four carbonate system variables were measured in surface waters during a cruise aimed at investigating ocean acidification impacts traversing northwestern European shelf seas in the summer of 2011. High-resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pH using the total pH scale (pHT), in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom), which allowed us to evaluate the level of agreement between the variables on a cruise whose main aim was not intercomparison, and thus where conditions were more representative of normal working conditions. Calculations of carbonate system variables from other measurements generally compared well with direct observations of the same variables (Pearson’s correlation coefficient always greater than or equal to 0.94; mean residuals were similar to the respective accuracies of the measurements). We therefore conclude that four of the independent data sets of carbonate chemistry variables were of high quality. A diurnal cycle with a maximum amplitude of 41 μatm was observed in the difference between the pCO2 values obtained by the two independent analytical pCO2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on future research cruises.

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Lucrative crab industry in danger

Published 19 August 2014 Media coverage , Web sites and blogs Closed

DUTCH HARBOR, Alaska — For decades, the crab piled up in fishing boats like gold coins hauled from a rich and fertile sea.

But the very ocean that nursed these creatures may prove to be this industry’s undoing.

New research earlier this year shows that Bristol Bay red king crab — the supersized monster that has come to symbolize the fortunes of Alaska’s crab fleet — could fall victim to the changing chemistry of the oceans.

Barring a hasty reduction in carbon-dioxide emissions — or evidence that the creatures could acclimate to changing sea conditions — a team of scientists fears Alaska’s $100 million red king crab fishery could crash in decades to come.

That grim possibility also raises alarm about the crab fleet’s other major moneymaker, snow crab.

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Scientists warn of dangers from ocean acidification

Published 18 August 2014 Media coverage Closed

Ten scientists addressed the different factors causing ocean acidification and how it affects marine ecosystems during the morning session of the meeting. If left unchecked, ocean acidification could cause major losses to shellfisheries like clams, oysters, lobsters, shrimp and sea urchins and put at risk thousands of jobs and billions of dollars to the state’s economy.

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Nutrient availability affects the response of juvenile corals and the endosymbionts to ocean acidification

Published 18 August 2014 Science Closed
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The interactive effects of nutrient availability and ocean acidification on coral calcification were investigated using post-settlement juvenile corals of Acropora digitifera cultured in nutrient-sufficient or nutrient-depleted seawater for 4 d and then exposed to seawater with different partial pressure of carbon dioxide () conditions (38.8 or 92.5 Pa) for 10 d. After the nutrient pretreatment, corals in the high nutrient condition (HN corals) had a significantly higher abundance of endosymbiotic algae than did those in the low nutrient condition (LN corals). The high abundance of endosymbionts in HN corals was reduced as a result of subsequent seawater acidification, and the chlorophyll a per algal cell increased. The photosynthetic oxygen production rate by endosymbionts was enhanced by the acidified seawater regardless of the nutrient treatment, indicating that the reduction in endosymbiont density in HN corals due to acidification was compensated for by the increase in chlorophyll a per cell. Though the photosynthetic rate increased in the acidified conditions for both LN and HN corals, the calcification rate significantly decreased for LN corals but not for HN corals. The acquisition of nutrients from seawater, rather than the increase in alkalinity caused by photosynthesis, might effectively alleviate the negative response of coral calcification to seawater acidification, suggesting that the response of corals and their endosymbionts to ocean acidification can be influenced by nutrient conditions.

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Sharks won’t hunt as well in acidifying oceans

Published 18 August 2014 Media coverage Closed

The world’s oceans are a sink for carbon dioxide, absorbing about 25 percent of all the additional CO2. With rising levels of greenhouse gases, oceans have experienced an average 0.1-unit reduction in pH since preindustrial times. Sharks have such a superior sense of smell — they’ve been called “swimming noses” — but changes in seawater chemistry projected for the end of this century could affect their feeding, according to findings published in Global Change Biology this week.

To find prey in the expansive ocean, large predators rely on odor tracking; chemical signals can be transported much farther in the marine environment than visual, mechanical, or electrical signals. According to a “business as usual” scenario, projected CO2 levels for the year 2100 are expected to exceed 900 ppm, while the pH of ocean waters will drop an additional 0.3 to 0.4 units.

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Odor tracking in sharks is reduced under future ocean acidification conditions

Published 18 August 2014 Science Closed
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Recent studies show that ocean acidification impairs sensory functions and alters the behavior of teleost fishes. If sharks and other elasmobranchs are similarly affected, this could have significant consequences for marine ecosystems globally. Here, we show that projected future CO2 levels impair odor tracking behavior of the smooth dogfish (Mustelus canis). Adult M. canis were held for 5 days in a current-day control (405 ± 26 μatm) and mid (741 ± 22 μatm) or high CO2 (1064 ± 17 μatm) treatments consistent with the projections for the year 2100 on a ‘business as usual’ scenario. Both control and mid CO2-treated individuals maintained normal odor tracking behavior, whereas high CO2-treated sharks significantly avoided the odor cues indicative of food. Control sharks spent >60% of their time in the water stream containing the food stimulus, but this value fell below 15% in high CO2-treated sharks. In addition, sharks treated under mid and high CO2 conditions reduced attack behavior compared to the control individuals. Our findings show that shark feeding could be affected by changes in seawater chemistry projected for the end of this century. Understanding the effects of ocean acidification on critical behaviors, such as prey tracking in large predators, can help determine the potential impacts of future ocean acidification on ecosystem function.

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Time to take ocean acidification seriously

Published 17 August 2014 Media coverage Closed

U.S. senators Maria Cantwell, D-Wash., and Mark Begich, D-Alaska, are preparing legislation calling for a national strategy to combat ocean acidification.

And well they should: The two states they represent have much at stake in this attempt to get a grip on a devastating environmental problem.

As early as 2005, oyster larvae in the marine waters of the Pacific Northwest began experiencing a massive die-off. Two years ago scientists conclusively linked it to decreasing pH levels in ocean water caused by mass loading of carbon dioxide from power plants, cars and other human sources. About 25 percent of all carbon dioxide released into the air settles in the ocean.

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Ocean’s rising acidification eating away at shellfish that coastal tribes depend on

Published 16 August 2014 Media coverage Closed

The ancestral connections of tribal coastal communities to the ocean’s natural resources stretch back thousands of years. But growing acidification is changing oceanic conditions, putting the cultural and economic reliance of coastal tribes—a critical definition of who they are—at risk.

It’s a big challenge to tribes in the Pacific Northwest, said Billy Frank Jr. (Suquamish) back in 2010, addressing the 20 tribes that make up the Northwest Indian Fisheries Commission.

“It’s scary,” he said in a video posted at the fisheries commission website. “The State of Washington hasn’t been managing it. The federal government hasn’t been managing it. We’ve got to bring the science people in to tell them what we’re talking about.”

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Ocean acidification accelerates dissolution of experimental coral reef communities

Published 15 August 2014 Science Closed
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Ocean acidification (OA) poses a severe threat to tropical coral reefs, yet much of what is know about these effects comes from individual corals and algae incubated in isolation under high pCO2. Studies of similar effects on coral reef communities are scarce. To investigate the response of coral reef communities to OA, we used large outdoor flumes in which communities composed of calcified algae, corals, and sediment were combined to match the percentage cover of benthic communities in the shallow back reef of Moorea, French Polynesia. Reef communities in the flumes were exposed to ambient (~400 μatm) and high pCO2 (~1300 μatm) for 8 weeks, and calcification rates measured for the constructed communities including the sediments. Community calcification was depressed 59% under high pCO2, with sediment dissolution explaining ~50% of this decrease; net calcification of corals and calcified algae remained positive, but was reduced 29% under elevated pCO2. These results show that despite the capacity of coral reef calcifiers to maintain positive net accretion of calcium carbonate under OA conditions, reef communities might switch to net dissolution as pCO2 increases, particularly at night, due to enhanced sediment dissolution.

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