Posts Tagged ocean acidification

Jan 12 2017

Ocean acidification to hit West Coast Dungeness crab fishery, new assessment shows

The acidification of the ocean expected as seawater absorbs increasing amounts of carbon dioxide from the atmosphere will reverberate through the West Coast’s marine food web, but not necessarily in the ways you might expect, new research shows.

Dungeness crabs, for example, will likely suffer as their food sources decline. Dungeness crab fisheries valued at about $220 million annually may face a strong downturn over the next 50 years, according to the research published Jan. 12 in the journal Global Change Biology. But pteropods and copepods, tiny marine organisms with shells that are vulnerable to acidification, will likely experience only a slight overall decline because they are prolific enough to offset much of the impact, the study found.

Dungeness crab.jkirkhart35/Flickr

Marine mammals and seabirds are less likely to be affected by ocean acidification, the study found.

“What stands out is that some groups you’d expect to do poorly don’t necessarily do so badly – that’s probably the most important takeaway here,” saidKristin Marshall, lead author of the study who pursued the research as a postdoctoral researcher at the University of Washington and NOAA Fisheries’ Northwest Fisheries Science Center. “This is a testament in part to the system’s resilience to these projected impacts. That’s sort of the silver lining of what we found.”

While previous studies have examined the vulnerability of particular species to acidification in laboratories, this is among the first to model the effects across an entire ecosystem and estimate the impacts on commercial fisheries.

“The real challenge is to go from experiments on what happens to individual animals in the lab over a matter of weeks, to try to capture the effects on the whole population and understand how vulnerable it really is,” said Isaac Kaplan, a research scientist at NOAA Fisheries’ Northwest Fisheries Science Center in Seattle.

The research used sophisticated models of the California Current ecosystem off the Pacific Coast to assess the impacts of a projected 0.2 unit decline in the pH of seawater in the next 50 years, which equates to a 55 percent increase in acidity. The California Current is considered especially vulnerable to acidification because the upwelling of deep, nutrient-rich water low in pH already influences the West Coast through certain parts of the year.

The ocean absorbs about one-third of carbon dioxide released into the atmosphere from the burning of fossil fuels, which has led to a 0.1 unit drop in pH since the mid-1700s.

The research built on an earlier effort by NOAA scientists Shallin Busch and Paul McElhanythat quantified the sensitivity of various species to acidification, as originally reported in 393 separate papers. In a novel approach, Busch and McElhany weighed the evidence for each species based on its reported sensitivity in the laboratory, relevance to the California Current and agreement between studies.

This synthesis by Busch and McElhany identified 10 groups of species with highest vulnerability to acidification. Marshall and colleagues incorporated this into the ecosystem model to examine how acidification will play out in nature. The study particularly examined the effects on commercially important species including Dungeness crab; groundfish such as rockfish, sole and hake; and coastal pelagic fish such as sardines and anchovy over the period from 2013 to 2063.

graphic showing changes based on new study
The study modeled the potential risks of ocean acidification (under a future decrease in pH) on the West Coast marine food web and fisheries over 50 years, from 2013 to 2063. NOAA Fisheries

“This was basically a vulnerability assessment to sharpen our view of where the effects are likely to be the greatest and what we should be most concerned about in terms of how the system will respond,” said Tim Essington, a UW professor of aquatic and fishery sciences and a co-author of the research.

The study provides a foundation for further research into the most affected species, he said.

Although earlier studies have shown that Dungeness crab larvae is vulnerable to acidification, the assessment found that the species declined largely in response to declines in its prey – including bivalves such as clams and other bottom-dwelling invertebrate species.

Since Dungeness crab is one of the most valuable fisheries on the West Coast, its decline would have some of the most severe economic effects, according to the research. Groundfish such as petrale sole, Dover sole and deep-dwelling rockfish are also expected to decline due to acidification, according to the assessment. However, fisheries for those species are much less valuable so the economic impact would not be as large.

Coastal pelagic fish were only slightly affected.

“Dungeness crab is a bigger economic story than groundfish,” Kaplan said. “There are winners and losers, but the magnitude of the impact depends on how important the species is economically.”

The research was funded by the NOAA Ocean Acidification Program and the National Centers for Coastal Ocean Science. Marshall was supported by a National Research Council fellowship.

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For more information, contact Marshall at kmarsh2@uw.edu and Kaplan atisaac.kaplan@noaa.gov 206-302-2446.

This piece was adapted from a Northwest Fisheries Science Center news release.

 

Nov 9 2016

Sea Snails on Acid

Twice a day the rocky Pacific coast traps seawater in pools as the tide rolls in and out. Compared to the ocean, the puddles are so small and innocuous that it seems nothing momentous could possibly be happening there, but there is. It turns out tiny black turban snails may be getting a buzz from the changing levels of acidity caused by ocean acidification. The scientists at Bodega Marine Lab looked closely at sea stars and snails to find out.

The underside of the purple sea star is covered in tiny delicate suction cups that make one wonder how it moves fast enough to be a voracious hunter, but it is. It’s the bully on the playground, a merciless predator. It can pry open mussel shells, turn its stomach inside out and wrap it around large prey, and digest its meal before even swallowing. It’s no wonder that when black turban snails sense the purple star’s arrival, they all flee to safety, crawling quickly up the side of a tide pool until the enemy leaves the water. Quickly for snails, that is.

Black turban snail, upper right, with its nemesis the purple sea star in the foreground. Credit: Gabriel Ng

 

Snails have always been good at running away from their primary predator – the purple sea star – until now. Brittany Jellison, a graduate student at University of California Davis, has found in a recent study that the snail’s dramatic response might be slowing down because of ocean acidification. Jellison modified tide pools to mimic ocean acidification conditions. Then she observed the snail’s response by measuring the path they took to safety. What she found when watching the snail was a trippy set of behaviors.

“Elevated carbon dioxide is a foreign substance in seawater, and snails are taking that foreign substance into their body, so yes, they in essence are on drugs,” said Brian Gaylord, a professor at UC Davis Bodega Marine Lab, where Jellison discovered that under ocean acidification conditions, snails didn’t immediately flee the pool to safety.

Ocean acidification occurs when the ocean absorbs excess carbon dioxide from the atmosphere.  While most scientists studying the phenomenon are trying to understand how it effects a single species in a lab, Jellison’s work explores how ocean acidification effects multiple species interactions.

Brittany Jellison collecting black turban snails for lab studies. Credit: Gabriel Ng

 

“I think what’s really important here is that she is moving beyond thinking about an individual species, and instead thinking about how the direct effects on individuals scale up when they are in nature and interacting with other species. That is the important part of it,” said Kristy Kroeker, Assistant Professor at the Department of Ecology and Evolutionary Biology at University of California Santa Cruz.

Professor Philip Munday of James Cook University agrees. He studies how ocean acidification effects reef fish and their ability to adapt to a changing environment.

“Ecosystems are a whole combination of interactive species,” said Munday. “If we want to understand how ocean acidification is going to impact marine ecosystems we need to understand how it will impact with the really critical ecological interactions, such as predatory-prey interactions. That’s one of the really exciting things about Jellison’s work.”

Tide pools on the Pacific coast have natural fluctuations in acidity, and the black turban snail and other animals that live there have adapted to that. Jellison wondered if the snails would be tolerant to ocean acidification conditions as well, or if they would reach their tipping point, and no longer able to tolerate the changes.

To find out, Jellison made model tide pools in aquariums. So that the snails would feel most at home, she simulated the conditions of natural tide pools, with one exception. Jellison changed the levels of acidification in some of the pools to mimic the levels that are expected for rock pools under ocean acidification by the year 2100. Having some tide pools with normal conditions and some with future acidic conditions allowed her to compare the behavior of sober snails with snails on acid.

With the arena built, let the show begin. Clutching her camera, Jellison carefully lowered black turban snails into the tank. One by one the snails reacted to a chemical cue produced by the predator sea star. Jellison took photos every two minutes for a half hour, then analyzed them for the distance the snails traveled, where they moved, and most importantly, if they left the water and escaped to safety. In total, Jellison did two 5-day trials, created 32 aquariums, tested 32 snails, and took photos every two minutes for 28 minutes per snail.

Under normal conditions, the snails will run away and exit the water, a flight response that keeps them safe. Jellison found that in water with higher acidity the snails started to run away, but instead of moving to dry ground, they seemed to get confused, haphazardly meandering around the pool.

Ocean acidification’s ability to change the interactions between predators and prey can have far reaching consequences. Jellison and her team aren’t yet sure exactly why the snails act confused. They think it’s related to changes in the brain as the animal tries to maintain balanced brain chemistry, which is something they would like to understand further.

“I really love research and I especially love working with marine animals,” said Jellison, “but when I think about what my work is saying about the future it can be a little bit hard to take in. Most of the things we are finding is that the world is going to look very different form what we see today.”

In the meantime, Jellison continues this research out in the field, in a creative study that has her waking up at all hours to hike to the tide pools and observe snails – all to understand the cascading effects of ocean acidification on the ecosystem. “I have a lot of hope that we will move forward as a society and try to come up with solutions and actually make changes. It is having hope that is important,” said Jellison.

Ocean acidification may cross national boundaries, and reach all corners of the earth, but a glimpse into a puddle of seawater reveals an elaborate community, a tiny snail, and a big message.


Read the original post: https://blogs.scientificamerican.com/guest-blog/sea-snails-on-acid/

Jun 29 2016

Ocean Acidification Affects Predator-Prey Response Acidic Waters Dull Snails’ Ability to Escape from Predatory Sea Stars

starfish

Black turban snails escape predation by sea stars by crawling out of tide pools. Experiments at UC Davis’ Bodega Marine Laboratory show that the snails lose this escape response as waters become more acidic, a consequence of climate change. Photo: Brittany Jellison

Ocean Acidification Affects Predator-Prey Response | UC Davis

 

Quick Summary

  • Sea snails in more acidic sea water did not show escape response
  • Atmospheric carbon dioxide affects ocean chemistry, may impact ocean life
  • Changes in tide pools now foreshadow future changes in the open ocean

Ocean acidification makes it harder for sea snails to escape from their sea star predators, according to a study from the University of California, Davis.

The findings, published in the journal Proceedings of The Royal Society B, suggest that by disturbing predator-prey interactions, ocean acidification could spur cascading consequences for food web systems in shoreline ecosystems.

For instance, black turban snails graze on algae. If more snails are eaten by predators, algae densities could increase.

“Ocean acidification can affect individual marine organisms along the Pacific coast, by changing the chemistry of the seawater,” said lead author Brittany Jellison, a Ph.D. student studying marine ecology at the UC Davis Bodega Marine Laboratory.

“But it can also alter how species interact, such as by impairing the ability of prey to avoid predators,” she said.

Sea star and snail interactions under ocean acidification

Jellison and colleagues from the UC Davis Bodega Marine Laboratory collected ochre sea stars and black turban snails — two common species along the Pacific coastline — from tide pools on the Bodega Marine Reserve. In lab tanks, they explored interactions between the sea stars and snails under 16 different levels of seawater pH, or acidity, ranging from present levels to those expected for rocky intertidal pools by the year 2100.

The scientists found that lower pH levels, which indicate higher acidity, did not slow the snails’ movements or reduce their ability to sense the predatory sea stars. However, the more acidic waters did impair the snails’ escape response.

Tipping point

Usually, when a black turban snail senses an ochre sea star, it quickly crawls up and out of the tide pool to avoid it, as sea stars rarely leave the water to eat. But when pH levels fell to 7.1 or below, the snails failed to fully implement their escape response. Neither did the snails recover their escape response when the water’s acidity fluctuated between normal and more acidic levels.

The pH levels that spur these behavioral changes already occur in tide pools and are expected to become more frequent in coming decades.

More research is needed to understand why the snails show a degraded escape response, or if they may adapt to more acidic ocean conditions in the future.

More CO2, more ocean acidification

One-third of carbon dioxide emitted by humans enters the oceans, making seawater more acidic, the study noted.

Rocky tide pools may operate as an indicator for future ocean conditions. They experience pH levels that are predicted for the open ocean later. Models project a 0.3-0.4 drop in the global average of ocean pH by 2100.

“Dozens of West Coast species display escape responses to sea stars,” said senior author Brian Gaylord, a professor of evolution and ecology at the UC Davis Bodega Marine Laboratory and Jellison’s faculty adviser. “We don’t yet know the extent to which ocean acidification could alter these additional predator-prey interactions, but there is clear potential for broader disruption of links within shoreline food webs.”

The study’s co-authors, all affiliated with the UC Davis Bodega Marine Laboratory, include graduate student Aaron Ninokawa, Professor Tessa Hill of the Department of Earth and Planetary Sciences and Coastal Marine Science Institute, and professors Eric Sanford and Brian Gaylord of the Department of Evolution and Ecology.

The study was funded by grants from the National Science Foundation, California Sea Grant and UC Davis Bodega Marine Laboratory.

Media contact(s)

Andy Fell, News and Media Relations, UC Davis, 530-752-4533, ahfell@ucdavis.edu

Brian Gaylord, Bodega Marine Laboratory, 707-875-1940, bpgaylord@ucdavis.edu

Brittany Jellison, Evolution and Ecology, 805-338-6610, bmjellison@ucdavis.edu

Apr 25 2016

Ocean souring on climate change

climate

“This upwelling is both a blessing and a curse,” Chan said. “The upwelling injects nutrients that make our ocean so productive. That’s why Steinbeck wrote ‘Cannery Row.’ We live in a very special ocean. But the curse is that this upwelling creates low oxygen and low pH. So we’re much closer to any tipping points that could push us past a threshold.”

Although the causes and effects of ocean acidification and low oxygen are global, the panel found hopeful news about the potential to deal with it locally.

Seagrass beds and kelp forests are more productive than tropical forests, capturing more carbon than other systems on the planet. By restoring marine vegetation, scientists hope to raise pH and oxygen levels in key areas.

Curbing marine pollution can also improve ocean chemistry, scientists said. Runoff from farms and lawns, such as nitrogen and phosphorus, feed algal blooms that dump carbon and deplete oxygen from local waters. Cutting back on those pollutants can “put off a potential evil hour when carbon dioxide are so high” that they cause irreparable damage to marine life, Dickson said.

Efforts to battle ocean acidification and low oxygen on the West Coast will be test cases for dealing with the problem elsewhere, scientists said

“The West Coast will be a harbinger for the types of ocean acidification impacts that will be widely felt across coastal North America in the coming decades,” the report states.

Despite the gloomy news, Chan said he’s hopeful that a solution is at hand, noting that bills pending in the California Legislature — Assembly Bill 2139 and Senate Bill 1363 — would study ocean acidity and promote eelgrass restoration.

“I’m leaving with an optimistic note, which I tend not to as a scientist, but I think the people who make decisions get it, and are ready to do something,” he said.


Read the original post: http://www.sandiegouniontribune.com/

Mar 20 2016

Ocean acidification takes a toll on California’s tide pools at nighttime

A new study, based on the most extensive set of measurements ever made in tide pools, suggests that ocean acidification will increasingly put many marine organisms at risk by exacerbating normal changes in ocean chemistry that occur overnight. Conducted along California’s rocky coastline, the study shows that the most vulnerable organisms are likely to be those with calcium carbonate shells or skeletons.

Ocean acidification is occurring as the oceans absorb increasing amounts of carbon dioxide from the atmosphere, where carbon dioxide concentrations are steadily rising due to emissions from the burning of fossil fuels. Absorption of carbon dioxide changes seawater chemistry, pushing it toward the lower, acidic end of the pH scale, although it remains slightly alkaline. A small decrease in pH affects the chemical equilibrium of ocean water, reducing the availability of carbonate ions needed by a wide range of organisms to build and maintain structures of calcium carbonate, such as the shells of mussels and oysters.

Kristy Kroeker, assistant professor of ecology and evolutionary biology at UC Santa Cruz, is a coauthor of the new study, published March 18 in Scientific Reports. “There is a lot of concern about how ocean acidification is going to affect marine species in the future, but most of our understanding comes from laboratory studies where a single organism is exposed to acidified seawater under very controlled conditions for a short period of time,” Kroeker explained. “In reality, every organism is embedded in a complex community that experiences dynamic environmental conditions that will gradually change over time.”

researchers-400.jpg
 
Researchers studied changes in tide pools near the Bodega Marine Laboratory. (Photos by Ken Caldeira/Carnegie)

tide-pool-400.jpg

An extensive set of measurements recorded daily swings in the chemistry of seawater in tide pools.

Calcifying organisms

In the new study, researchers closely monitored conditions in tide pools along California’s rocky coast, which are isolated from the open ocean during low tides. During the daytime, photosynthesis—the mechanism by which plants use the sun’s energy to convert carbon dioxide and water into sugar, giving off oxygen in the process—takes up carbon dioxide from the seawater and acts to reverse ocean acidification’s effects. At night, however, photosynthesis stops, while the respiration of plants and animals takes up oxygen and releases carbon dioxide. This adds carbon dioxide to the seawater and exacerbates the effects of ocean acidification, increasing the risk to calcifying organisms.

“Tide pools are home to lots of different species that regularly experience daily swings in chemistry,” Kroeker said. “Tide pools can experience particularly corrosive seawater during nighttime low tides, when all of the animals are ‘exhaling’ carbon dioxide into the water that has been cut off from the ocean.”

The research team, led by scientists at the Carnegie Institution of Science, used these natural nighttime spikes in corrosive conditions to examine how entire communities of marine species respond to natural acidification. Observing a variety of California’s natural rocky tide pools near the Bodega Marine Laboratory, they found that the rate of shell and skeletal growth was not greatly affected by seawater chemistry in the daytime. However, during low tide at night, water in the tide pools became corrosive to calcium carbonate shells and skeletons. The study found evidence that the rate at which these shells and skeletons dissolved during these nighttime periods was greatly affected by seawater chemistry.

“Unless carbon dioxide emissions are rapidly curtailed, we expect ocean acidification to continue to lower the pH of seawater,” said lead author Lester Kwiatkowski of the Carnegie Institution of Science. “This work highlights that even in today’s temperate coastal oceans, calcifying species, such as mussels and coralline algae, can dissolve during the night due to the more acidic conditions caused by community respiration.”

These results highlight the vulnerability of marine species in even the most dynamic conditions to the global process of ocean acidification, Kroeker said.

According to coauther Ken Caldeira of the Carnegie Institution, “If what we see happening along California’s coast today is indicative of what will continue in the coming decades, by the year 2050 there will likely be twice as much nighttime dissolution as there is today. Nobody really knows how our coastal ecosystems will respond to these corrosive waters, but it certainly won’t be well.”

The study was a collaborative effort by the Carnegie Institution for Science, UC Davis, and UC Santa Cruz. This work was funded by the Carnegie Institution for Science, UC Multi-campus Research Initiatives and Programs, and the National Science Foundation.


Read the original post: http://news.ucsc.edu/

Jan 12 2016

Dual Impact of Ocean Acidification and Low-Oxygen on West Coast Foretells Future for World Oceans

— Posted with permission of SEAFOODNEWS.COM. Please do not republish without their permission. —

Copyright © 2016 Seafoodnews.com

Seafood News


SEAFOODNEWS.COM [UW Today] By Michelle Ma – January 12, 2016

The Pacific Ocean along the West Coast serves as a model for how other areas of the ocean could respond in coming decades as the climate warms and emission of greenhouse gases like carbon dioxide increases. This region — the coastal ocean stretching from British Columbia to Mexico — provides an early warning signal of what to expect as ocean acidification continues and as low-oxygen zones expand.

Now, a panel of scientists from California, Oregon and Washington has examined the dual impacts of ocean acidification and low-oxygen conditions, or hypoxia, on the physiology of fish and invertebrates. The study, published in the January edition of the journal BioScience, takes an in-depth look at how the effects of these stressors can impact organisms such as shellfish and their larvae, as well as organisms that have received less attention so far, including commercially valuable fish and squid.

The results show that ocean acidification and hypoxia combine with other factors, such as rising ocean temperatures, to create serious challenges for marine life. These multiple-stressor effects will likely only increase as ocean conditions worldwide begin resembling those off the West Coast, which naturally expose marine life to stronger low-oxygen and acidification stressors than most other regions of the seas.

“Our research recognizes that these climate change stressors will co-occur, essentially piling on top of one another,” said co-author Terrie Klinger, professor and director of the University of Washington’s School of Marine and Environmental Affairs.

“We know that along the West Coast temperature and acidity are increasing, and at the same time, hypoxia is spreading. Many organisms will be challenged to tolerate these simultaneous stressors, even though they might be able to tolerate individual stressors when they occur on their own.”

Oceans around the world are increasing in acidity as they absorb about a quarter of the carbon dioxide released into the atmosphere each year. This changes the chemistry of the seawater and causes physiological stress to organisms, especially those with calcium carbonate shells or skeletons, such as oysters, mussels and corals.

Hypoxia, on the other hand, is a condition in which ocean waters have very low oxygen levels. At the extreme, hypoxia can result in “dead zones” where mass die-offs of fish and shellfish occur. The waters along the West Coast sometimes experience both ocean acidification and hypoxia simultaneously.

“Along this coast, we have relatively intensified conditions of ocean acidification compared with other places. And at the same time we have hypoxic events that can further stress marine organisms,” Klinger said. “Conditions observed along our coast now are forecast for the global ocean decades in the future. Along the West Coast, it’s as if the future is here now.”

Klinger is co-director of the Washington Ocean Acidification Center based at the UW and served on the West Coast Ocean Acidification and Hypoxia Science Panel, which was convened two years ago to promote coast-wide collaboration and cooperation on science and policy related to these issues.

For this paper, the authors examined dozens of scientific publications that reported physiological responses among marine animals exposed to lower oxygen levels, elevated acidity and other stressors. The studies revealed how physiological changes in marine organisms can lead to changes in animal behavior, biogeography and ecosystem structure, all of which can contribute to broader-scale effects on the marine environment.

The tri-state panel has completed this phase of its work and will wrap things up in the coming months. Among the products already published or planned are a number of scientific publications — including this synthesis piece — as well as resources for policymakers and the general public describing ocean research priorities, monitoring needs and management strategies to sustain marine ecosystems in the face of ocean acidification and hypoxia.

The group’s other papers and findings related to ocean acidification and hypoxia will soon be available on its website.

Co-authors of this paper include George Somero, Jody Beers and Steve Litvin at Stanford University’s Hopkins Marine Station; Francis Chan of Oregon State University; and Tessa Hill of the University of California, Davis.

The research was funded by the California Ocean Protection Council, the California Ocean Science Trust, the Institute for Natural Resources at Oregon State University and the National Science Foundation.


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Oct 14 2015

New research maps areas most vulnerable to ocean acidification

 

New NOAA-led research maps the distribution of aragonite saturation state in both surface and subsurface waters of the global ocean and provides further evidence that ocean acidification is happening on a global scale. The study identifies the Arctic and Antarctic oceans, and the upwelling ocean waters off the west coasts of North America, South America and Africa as regions that are especially vulnerable to ocean acidification.

“These findings will help us better understand and develop strategies to adapt to the severity of ocean acidification in different marine ecosystems around the world,” said Richard A. Feely, a NOAA oceanographer and co-author of the study, which has been accepted for publication and can be read online in the American Geophysical Union journal Global Biogeochemical Cycles.

Ocean acidification is caused by humankind’s release of carbon dioxide emissions to the atmosphere. Excess carbon dioxide enters the ocean, reacts with water, decreases ocean pH and lowers carbonate ion concentrations, making waters more corrosive to marine species that need carbonate ions and dissolved calcium to build and maintain healthy shells and skeletons. The saturation state of seawater for a mineral such as aragonite is a measure of the potential for the mineral to form or to dissolve.

In the new study, scientists determined the saturation state of aragonite in order to map regions that are vulnerable to ocean acidification. Waters with higher aragonite saturation state tend to be better able to support shellfish, coral and other species that use this mineral to build and maintain their shells and other hard parts.

This study shows that aragonite saturation state in waters shallower than 328 feet or 100 meters depth decreased by an average of 0.4 percent per year from the decade spanning 1989-1998 to the decade spanning 1998-2010. “A decline in the saturation state of carbonate minerals, especially aragonite, is a good indicator of a rise in ocean acidification,” said Li-Qing Jiang, an oceanographer with NOAA’s Cooperative Institute for Climate and Satellites at the University of Maryland and lead author.

The most vulnerable areas of the global ocean are being hit with a double whammy of sorts. In these areas, deep ocean waters that are naturally rich in carbon dioxide are upwelling and mixing with surface waters that are absorbing carbon dioxide from the atmosphere. The carbon dioxide from the atmosphere is coming primarily from human-caused fossil fuel emissions.

“When oyster larvae are born they must draw on the energy in their yolk to build their aragonite shells to protect themselves from predators and grow into healthy adults,” said Feely. In waters depleted of carbonate ions, young oysters must expend more energy to build their shell and may not survive. This has significant consequences for the seafood industry.”


Read the original post: http://www.eurekalert.org/

Sep 2 2015

Climate change will irreversibly force key ocean bacteria into overdrive

 Scientists demonstrate that a key organism in the ocean’s food web will start reproducing at high speed as carbon dioxide levels rise, with no way to stop when nutrients become scarce
Trichodesmium thiebautii is a cyanobacterium, or blue-green alga, that forms colonies of cells.
Trichodesmium is one of the few organisms in the ocean that can “fix” atmospheric nitrogen gas. (Photo/Fish and Wildlife Research Institute)

Imagine being in a car with the gas pedal stuck to the floor, heading toward a cliff’s edge. Metaphorically speaking, that’s what climate change will do to the key group of ocean bacteria known as Trichodesmium, scientists have discovered.

Trichodesmium (called “Tricho” for short by researchers) is one of the few organisms in the ocean that can “fix” atmospheric nitrogen gas, making it available to other organisms. It is crucial because all life — from algae to whales — needs nitrogen to grow.

A new study from USC and the Massachusetts-based Woods Hole Oceanographic Institution (WHOI) shows that changing conditions due to climate change could send Tricho into overdrive with no way to stop — reproducing faster and generating lots more nitrogen. Without the ability to slow down, however, Tricho has the potential to gobble up all its available resources, which could trigger die-offs of the microorganism and the higher organisms that depend on it.

Amped-up bacteria

By breeding hundreds of generations of the bacteria over the course of nearly five years in high-carbon dioxide ocean conditions predicted for the year 2100, researchers found that increased ocean acidification evolved Tricho to work harder, producing 50 percent more nitrogen, and grow faster.

The problem is that these amped-up bacteria can’t turn it off even when they are placed in conditions with less carbon dioxide. Further, the adaptation can’t be reversed over time — something not seen before by evolutionary biologists, and worrisome to marine biologists, according to David Hutchins, lead author of the study.

“Losing the ability to regulate your growth rate is not a healthy thing,” said Hutchins, professor at the USC Dornsife College of Letters, Arts and Sciences. “The last thing you want is to be stuck with these high growth rates when there aren’t enough nutrients to go around. It’s a losing strategy in the struggle to survive.”

Tricho needs phosphorous and iron, which also exist in the ocean in limited supply. With no way to regulate its growth, the turbo-boosted Tricho could burn through all of its available nutrients too quickly and abruptly die off, which would be catastrophic for all other life forms in the ocean that need the nitrogen it would have produced to survive.

Some models predict that increasing ocean acidification will exacerbate the problem of nutrient scarcity by increasing stratification of the ocean — locking key nutrients away from the organisms that need them to survive.

What the future may hold

Hutchins is collaborating with Eric bbb of USC Dornsife and Mak Saito of WHOI to gain a better understanding of what the future ocean will look like, as it continues to be shaped by climate change. They were shocked by the discovery of an evolutionary change that appears to be permanent — something Hutchins described as “unprecedented.”

Tricho has been studied for ages. Nobody expected that it could do something so bizarre,” he said. “The evolutionary biologists are interested in it just to study this as a basic evolutionary principle.”

The team is now studying the DNA of Tricho to try to find out how and why the irreversible evolution occurs. Earlier this year, research led by Webb found that the organism’s DNA inexplicably contains elements that are usually only seen in higher life forms.

“Our results in this and the aforementioned study are truly surprising. Furthermore, they are giving us an improved view of how global climate change will impact Trichodesmium and the vital supplies of new nitrogen it provides to the rest of the marine food web in the future.” Webb said.

The research appears in Nature Communications on Sept. 1.

Hutchins, Webb and Saito collaborated with Nathan Walworth, Jasmine Gale and Fei-Xue Fu of USC; and Dawn Moran and Matthew McIlvin of WHOI. The work was funded by the National Science Foundation (grants OCE 1260490, OCE 1143760, OCE 1260233 and OCE OA 1220484); and the G.B. Moore Foundation (grants 3782 and 3934).


Read the original post: http://news.usc.edu

Aug 21 2015

Researchers Say Ocean Acidification Poses Legitimate Extinction Threat to West Coast Shellfish

— Posted with permission of SEAFOODNEWS.COM. Please do not republish without their permission. —

SEAFOODNEWS.COM [San Francisco Chronicle] by Lizzie Johnson – August 21, 2015

Long before scientists and shellfish companies were aware of what was happening, a silent killer began devastating California’s oyster industry.

About 10 years ago, baby oysters, or spat, began to die at an alarming rate. Farms along the West Coast lost more than half of their bivalves before they reached maturity, creating a shortage of seed. That deficit hit Hog Island Oyster Co. in Marshall especially hard.

So owners Terry Sawyer and John Finger began collaborating with UC Davis’ Bodega Marine Laboratory to figure out what was plaguing the water in Tomales Bay, their backyard.

After more than two years of tests, they have a better understanding of the condition afflicting West Coast oysters, mussels and clams. But there is trouble ahead for California’s shellfish industry as it faces the threat of species extinction.

“We are talking about something that’s going to happen in my lifetime and my children’s lifetime,” said Tessa Hill, an associate professor of geology at UC Davis. “We are going to see dramatic changes in terms of what animals can be successful on the California coast because of ocean acidification.”

That culprit, ocean acidification, is the caustic cousin of climate change, and it shifts the chemistry of ocean water, making it harder for oysters to grow. That’s because about 30 percent of the carbon dioxide released into the atmosphere is absorbed by the ocean, causing pH levels to plummet and making the water more acidic. The more pollution in the air, the more carbon dioxide the ocean absorbs.

Larval stage stunted

The hostile conditions stunt the growth of oysters in the larval stage, making it difficult to build their fragile calcium carbonate shells. If acidification doesn’t kill them outright, an increased susceptibility to disease and predators often will. The stress also weakens many small oysters, so it takes them longer to reach reproductive age.

“It’s definitely scary,” said Zane Finger, who runs the Marshall oyster farm for his father, John. “If you’re doing any kind of job that depends on the environment, whether it’s farming on land or farming in the water, it can be uncertain. Things are changing, and it makes me nervous about the future of this business.”

Oyster growers in Oregon were the first to sound the alarm 10 years ago on ocean acidification. Whiskey Creek Shellfish Hatchery, based in Oregon’s Netarts Bay, and Oregon State University were among the first to work together and publish research on the phenomenon. They established the link between acidification and the collapse of oyster seed production.

Dire prediction

“It was one of the first times that we have been able to show how ocean acidification affects oyster larval development at a critical life stage,” OSU chemical oceanographer Burke Hales said in a statement. He was a co-author on one of the first studies in Oregon. “The predicted rise of atmospheric carbon dioxide in the next two to three decades may push oyster larval growth past the break-even point in terms of production.”

And in 2010, a mix of scientists and industry partners formed the California Current Acidification Network (C-CAN), which works for more research on acidification. UC Davis and Hog Island, both members, have helped expand research along the coast. The relationship has helped Hog Island prepare for future water conditions and allowed the university to conduct research on the link between climate change and acidification.

For the first two years of the company’s collaboration with Hill, data were collected only once a month from a buoy in the estuary. Then the federal Central and Northern California Ocean Observing System (which goes by the mile-long acronym of CeNCOOS), offered to upgrade the system.

Now, it’s a round-the-clock operation that gives minute-by-minute data on water conditions. Hill runs a small lab tucked in the back of a shed at Hog Island’s Marshall oyster farm. The structure is damp and filled with loudly whining equipment. Tubes pump seawater directly in from the bay so the team can closely monitor changes in acidity, salinity, temperature and oxygen.

‘Stressful for oysters’

“You can get up in the morning and look at the charts and say, ‘Oh, the water is stressful for the oysters today,’” Hill said, pointing to a zigzagging line on the computer screen. “It gives them real-time information and a big picture of what’s happening in the bay.”

They’ve learned that the high acidity in the water is related to seasonal upwelling, or when the wind pushes surface water offshore, allowing the deeper, more acidic water to rise up. For now, hatcheries can grow spat during spring and summer, considered the off seasons. But by 2030, upwellings are expected to last longer, and by 2050, they could occur year-round, Hill said.

“The rate of change is something that we have never seen before as a planet,” Sawyer said. “And it’s measurable; you can’t argue with that. We have the data. We should pay attention to it now, immediately, and not later.”

High mortality rate

The mortality rate for baby oysters is still high — anywhere from 50 to 100 percent. But oyster companies have learned to compensate for it by growing more spat in different locations. They’ve also put a quota on the amount of shellfish customers can buy. Diversifying will hopefully prevent another shortage like the one that hit from 2007 to 2010.

Sawyer and John Finger are planning to expand the company’s aquaculture operation. Within the next two years, they will open a $1.5 million oyster hatchery in Humboldt Bay. It will provide seeds to grow in Tomales Bay and, eventually, harvest some of its own oysters as well. Permits have been approved, and cultivation will start later this year.

A day on the farm

For now, operations at Hog Island Oyster Co.’s Marshall farm remain the same. Most mornings, workers slide on their rubber waders and guide a flat-bottomed boat onto the water. Then they slosh to the oyster racks nestled on the muddy floor, dragging them to the surface with long hooks. The smell of musty water and saltwater fills the air as they work.

Soon — and Sawyer hopes for a long time — those oysters will make their way to someone’s plate.

“I care about this on so many levels,” he said. “From a farming point of view, from business, from caring about my kids and the future generations who will have to deal with this. We live in a pretty amazing world, and I would like to preserve that as much as possible.”


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Feb 5 2015

Chemical clues in fossil shells may help us understand today’s ocean acidification

By: Brendan Bane

As atmospheric CO2 levels rise, so too do those in the sea, leading to ocean acidification that outpaces that of any other time in tens of millions of years. Some effects of ocean acidification are imminent, like the fact that calcified organisms such as corals and shellfish will have access to less and less of the chemical components they need to build their shells and skeletons. Other outcomes are less clear, and scientists wanting to predict what may come of our quickly acidifying waters are looking to past climatic events that were similar to our own.

One such event, the Paleo-Eocene Thermal Maximum (PETM), which occurred 56 million years ago, is likely our closest analog to modern ocean acidification. Researchers who refer to the PETM as a case study have long suspected that ancient waters acidified then, but until recently, they never had physical evidence of it actually happening. Then just this past year, researchers uncovered the PETM’s chemical chronology encrypted in the shells of fossilized plankton, called foraminifera, and learned that the two timelines aren’t entirely similar; today’s surface ocean is acidifying ten times faster than it did during the PETM. Their findings were published in Paleoceanography in June, 2014.

Penman (the lead author) offered this image of himself (center), Richard Norris (Scripps) and Pincelli Hull (Yale) inspecting sediment cores from the PETM while aboard a scientific drilling vessel.
Penman (the lead author) offered this image of himself (center), Richard Norris (Scripps) and Pincelli Hull (Yale) inspecting sediment cores from the PETM while aboard a scientific drilling vessel. Photo credit Donald Penman.
“While foraminifera are alive, they incorporate the chemistry of the water into their shells,” said Bärbel Hönisch, associate professor of earth and environmental sciences at Columbia University and coauthor of the study. “When they die, they take that information with them into the sediment.”

Hönisch and several other scientists analyzed the chemical composition of fossilized foraminifera embedded in “nannofossil ooze,” a section of rock particularly rich with tiny fossilized organisms, which they drilled out of sub-ocean sediment near Japan.

Foraminifera, like coral and shellfish, pull carbonate ions from the surrounding seawater to build their shells. In a way, the chemical composition of these shells acts as a snapshot of the chemical composition of the water the foraminifer lived in. When water grows increasingly acidic, foraminifera replace whole carbonate molecules with borate molecules. When the scientists of this study inspected the boron composition of shells from plankton that died during the PETM, they learned not only how acidic the ocean was at the time, but also how quickly its chemistry shifted and how long it stayed that way.

“Acidification during the PETM was relatively rapid,” said oceanographer Richard Zeebe of the University of Hawaii at Manoa, another coauthor of the study, “but it was also sustained. The whole event took a very long time.” A massive surge in atmospheric carbon, its cause still unknown, warmed the globe by four to eight degrees and dropped the ocean’s pH by about 100 percent. Conditions remained that way for approximately 70,000 years. These environmental changes triggered many biological ones. Seafloor-dwelling foraminifera suffered mass extinction while another type of tiny aquatic organism, dinoflagellates, thrived and expanded.

Foraminifera like the one pictured above record their environment’s chemistry in calcium carbonate shells, essentially leaving a trail of chemical breadcrumbs for future investigators. Photo by Howard Spero.
Foraminifera like the one pictured above record their environment’s chemistry in calcium carbonate shells, essentially leaving a trail of chemical breadcrumbs for future investigators. Photo by Howard Spero.
Although the PETM ocean did acidify quickly, it happened ten times slower than what’s happening today. Our ocean’s pH has dropped from 8.2 to 8.1 in the last 150 years, an amount that took a few thousand years in the PETM. Scientists predict the drop will only continue, with the seas reaching a pH of 7.8 to 7.9 by 2100. That change was and continues to be fueled by manmade carbon being pumped into the atmosphere and subsequently absorbed by the ocean.

In understanding how to compare the two events and what outcomes will emerge from modern acidification, rate is key.

“In any aspect of environmental change, particularly global change, rate matters” said lead author Donald Penman of the University of California Santa Cruz. Natural buffers like deep seawater mixing likely mitigated acidification during the PETM. But those same buffers will surely be outpaced by today’s heightened rate. “If you put carbon dioxide into the ocean faster than its natural processes can deal with it,” Penman said, “then they don’t do you any good.”

Marine animals will also be challenged by the speed at which their environment is changing. “We know that organisms and ecosystems can adapt and evolve to slow changes as they have throughout earth’s history,” Penman said. “However, when you invoke the same change over a shorter time, then you can outstrip organisms’ ability to evolve with that change. Species go extinct, and marine ecosystems change dramatically, perhaps irrecoverably.”

The researchers noticed that extinctions occurred during the PETM even at a pH change rate of 0.1 per thousands of years – which may not bode well for today’s foraminifera.

“The fact that some organisms went extinct during the PETM puts our current activities in perspective,” said Hönisch. “If the organisms died then, it is even more likely that some organisms will die now.”

With a clearer picture of the PETM painted, researchers can begin to draw more detailed analogies between the two events, and hopefully catch any drastic environmental changes before they surprise us.

“Now that we have [ocean acidification during PETM] quantified,” Penman said, “we can begin to make calculations of how much and how quickly carbon was emitted during the PETM. This will help us disentangle what sources of carbon and feedbacks were in operation during the PETM, and whether or not they are something we need to worry about in the future.”

0106_brendan_1Penman (the lead author) offered this image of himself (center), Richard Norris (Scripps) and Pincelli Hull (Yale) inspecting sediment cores from the PETM while aboard a scientific drilling vessel. Photo credit Donald Penman.

0106_brendan_3_360Foraminifera like the one pictured above record their environment’s chemistry in calcium carbonate shells, essentially leaving a trail of chemical breadcrumbs for future investigators. Photo by Howard Spero.

Citations:
Penman, D. E., Hönisch, B., Zeebe, R. E., Thomas, E., & Zachos, J. C. (2014). Rapid and sustained surface ocean acidification during the Paleocene‐Eocene Thermal Maximum. Paleoceanography.
Hönisch, B., Ridgwell, A., Schmidt, D. N., Thomas, E., Gibbs, S. J., Sluijs, A., … & Williams, B. (2012). The geological record of ocean acidification. science, 335(6072), 1058-1063.


Read the original post Mongabay.com.