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.

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.

Squid boats dot Malibu coast: Roughly 40,157 tons of squid caught this season

Squid boats are seen from Malibu’s Zuma Beach on a recent January evening. Suzanne Guldimann/22nd Century Media

Almost every night this winter, bright lights have appeared off the coast of Malibu.

It’s an eerie sight on a foggy evening, suggesting something unearthly or supernatural, but the only thing these ghostly lights portend is the presence of Doryteuthis opalescens, the common market squid.

It’s a good omen for California’s seafood industry. Market squid is one of California’s largest commercial fisheries, and tons of frozen California calamari are shipped all over the world each year. However, the species had almost entirely disappeared from Southern California waters last year. The absence of squid is being blamed on El Niño.

California Department of Fish and Wildlife environmental scientist Laura Ryley studies squid.

“Market squid was very limited in Southern California last year,” she told The Malibu Surfside News. 

Ryley explained that the squid are thought to react to the warmer water generated by El Niño, migrating further north in search of the right water temperature and conditions for spawning.

“The commercial fishery was landing squid in Eureka and off the coast of Oregon last year,” Ryley said.

She added that the management plan for the species implemented in 2005 provides an opportunity for scientists to gather data on the size, sex and abundance of the species. That data show that market squid generally have the ability to recover swiftly after an El Niño event.

“The patterns in the past show the squid are still able to reproduce and that they bounce back quickly,” she said.

While concerns are being raised over the potential impact of prolonged ocean warming on the species, the return of more normal temperature conditions in the Pacific this winter appears to have signaled the return of the squid. 

An abundance of cephalopods isn’t just an auspicious sign for the fishing industry. It may mean fewer problems for local sea lion and elephant seal populations, which have experienced mass stranding events blamed in part on the same warm water that impacted the squid and other key prey species like Pacific sardines and mackerel.

“I’ve heard that market squid isn’t the sea lion’s favorite, but they will eat it,” Ryley said. “It’s an important food for other species as well. Salmonids eat them. So do sea birds.”

The California Department of Fish and Wildlife’s management plan for the market squid fishery limits the seasonal catch to 118,000 tons per season. The season opens April 1 each year, and runs until the limit is met or until March 31, whichever comes first.

This season got off to a slow start but is accelerating. As of Dec. 30, 2016, the total landings of market squid were 40,157.6 tons.

That’s in sharp contrast to 2013, the last big year for squid, when the quota for the season was reached by early November, according to NOAA Fisheries data, but a major increase from 2014 and 2015, when the numbers plummeted in Southern California.

In the Malibu area, autumn and winter are the peak time for commercial squid fishing. The shallow waters along the Malibu coast are usually a prime location for squid, which migrate to the shallow, sandy, near-shore area in the fall to spawn.

Special light boats equipped with high wattage bulbs attract the squid, which are caught using either seine or scoop nets. The lights are supposed to be shielded to reduce the impact on migratory birds and coastal residents, but compliance isn’t 100 percent yet.

The Monterey Bay Aquarium’s Seafood Watch program rates market squid as a “good alternative” for sustainability, but most of the California catch is frozen and shipped to Asia. 

“The American market prefers squid with a thicker mantle,” Ryley said. 

Market squid rarely grow to be more than 10 inches in length. They are short-lived; 9-10 months is usually the maximum life span, and they spawn just once, at the end of their lives.

Squid can only be caught on weekdays from the U.S.-Mexico border to the California-Oregon border. From noon Friday to noon Sunday the squid are given a “break.”

“The thinking behind that is to give them a time for uninterrupted spawning,” Ryley explained.

Squid fishing is permitted all along the Malibu coast, even within the boundaries of the Point Dume State Marine Conservation Area, located off the coast of Zuma and Lechuza beaches. Only Point Dume State Marine Reserve (Paradise Cove to Westward Beach) is off limits.

With more than half the season’s limit still swimming around in the Pacific, it’s a safe bet that the unearthly green and pink glow of the squid boats will continue to light up Malibu’s coast, drawing the curiosity of more than just squid.

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Scientists: Global Ocean Circulation Could Be More Vulnerable to Shutdown Than We Thought

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

Copyright © 2017 Seafoodnews.com

SEAFOODNEWS.COM [The Washington Post] by Chelsea Harvey – January 5, 2017

Intense future climate change could have a far different impact on the world than current models predict, suggests a thought-provoking new study just out in the journal Science Advances. If atmospheric carbon dioxide concentrations were to double in the future, it finds, a major ocean current — one that helps regulate climate and weather patterns all over the world — could collapse. And that could paint a very different picture of the future than what we’ve assumed so far.

The Atlantic meridional overturning circulation, or AMOC, is often described as a large oceanic conveyor belt. It’s a system of water currents that transports warm water northward from the Atlantic toward the Arctic, contributing to the mild climate conditions found in places like Western Europe. In the Northern Atlantic, the northward flowing surface water eventually cools and sinks down toward the bottom of the ocean, and another current brings that cooler water back down south again. The whole process is part of a much larger system of overturning currents that circulates all over the world, from pole to pole.

But some scientists have begun to worry that the AMOC isn’t accurately represented in current climate models. They say that many models portray the current as being more stable than real-life observations suggest it actually is. Recent studies have suggested that the AMOC is weakening, although there’s some scientific debate about how much of this has been caused by human activities and how much by natural variations.

Nevertheless, the authors of the new study point out, many climate models assume a fairly stable AMOC — and that could be affecting the predictions they make for how the ocean will change under future climate change. And because overturning circulation patterns have such a significant effect on climate and weather all over the world, this could have big implications for all kinds of other climate-related projections as well.

“This is a very common and well-known issue in climate models,” said the new study’s lead author, Wei Liu, a postdoctoral associate at Yale University, who conducted the work while at the University of California at San Diego. “I wanted to see, if I use a corrected model, how this will affect the future climate change.”

Liu and colleagues from the UC-San Diego and the University of Wisconsin at Madison took a commonly used climate model and corrected for what they considered to be the AMOC stability bias. Then they ran an experiment to see how the correction would affect the model’s projections under future climate change. They instantaneously doubled the atmospheric carbon dioxide concentration from present-day levels in both the corrected and uncorrected models, and then they let both models run for hundreds of simulated years.

The differences were striking. In the uncorrected climate model, the AMOC weakens for a while, but eventually recovers. In the corrected model, however, the AMOC continues to weaken and after 300 years, it collapses altogether.

In a commentary also published today in RealClimate, Stefan Rahmstorf, an oceans physics expert at the Potsdam Institute for Climate Impact Research, explained how such a collapse could occur when the AMOC gets too weak.

“Freshwater continually flows into the northern Atlantic through precipitation, rivers and ice-melting,” he wrote. “But supply of salty waters from the south, through the Gulf Stream System, balances this. If however the current slows, there is less salt supply, and the surface ocean gets less salty.”

Because freshwater is less dense than salty water, this process can lead to a kind of stratification, in which the lighter freshwater gets stuck on the surface of the ocean and can’t sink to the bottom when it reaches the cooler north. When this happens, the overturning process that drives the current back down south again can’t occur.

“There is a critical point when this becomes an unstoppable vicious circle,” Rahmstorf wrote. “This is one of the classic tipping points in the climate system.”

The resulting climate consequences, compared to the uncorrected model, are also dramatic. Without the usual transport of warm water into the north, the corrected model predicts a marked cooling over the northern Atlantic, including in the United Kingdom, Iceland and northwestern Europe, as well as in the Arctic, where sea ice begins to expand.

Because the AMOC is part of a larger global conveyor system, which ferries warm and cold currents between the equator and both poles, the model predicts disruptions in other parts of the world as well. Without cold water moving back down south again, the corrected model indicates a stronger warming pattern south of the equator than what’s predicted by the uncorrected model, causing a polarization in precipitation patterns over the Americas — more rain for places like northeastern Brazil and less rain for Central America. The model also predicts a greater reduction in sea ice for the Antarctic.

All this doesn’t necessarily mean that everything we thought we knew about the future climate is wrong. For one thing, most modern climate projections focus on the next few decades or so, noted Thomas Haine, an expert on ocean circulation at Johns Hopkins University. And within 50 years or so, both the uncorrected and corrected models in the new study produce similar results. It is only after that, under extreme warming, that the current shifts.

Liu also cautioned that certain aspects of the experiment can’t exactly be considered realistic — for instance, instantaneously doubling the atmospheric carbon dioxide concentration. Current climate efforts are aimed at keeping us from ever getting to such a point — but even if we did, the process would happen gradually, not overnight. So the model’s outcome might have been different if the researchers had adopted a more realistic scenario.

Haine also suggested that the correction in the new study may have actually been a bit too strong, compared to actual observations — in other words, the modeled AMOC is “probably more unstable than the real system,” he said.

Rahmstorf also pointed out this issue in his commentary — but he added that the climate model used also did not account for an influx of meltwater from Greenland under future climate change, an event that recent research suggests could substantially speed the AMOC’s weakening.

“With unmitigated emissions . . . the Gulf Stream System weakens on average by 37 percent by the year 2300 without Greenland melt,” he notes. “With Greenland meltwater this doubles to 74 percent. And a few months ago, a study with a high-resolution ocean model appeared, suggesting that the meltwater from Greenland is likely to weaken the AMOC considerably within a few decades.”

The fact that current models don’t take this melting into account is further support for the idea that scientists have been underestimating the risk of a future AMOC collapse, he suggested.

According to Liu, the new study serves to make a point about the dramatic effects that can occur when corrections are made in climate models, as well as the AMOC’s major role in the global climate. By tweaking a climate model to make it more consistent with real-life observations, very different outcomes may be observed, Liu noted.

“I would say that it is reasonably well-accepted that a current generation of climate models [is] missing the essential physics in representing the AMOC,” said Haine. And he added that the new study “points to the need to fix these biases in the climate models.”

Peggy Parker, Science and Sustainability Editor
SeafoodNews.com 1-781-861-1441
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Reporter’s Email: peggyparker@seafood.com

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