Ocean acidification progressing at an alarming rate

SEAFOOD.COM NEWS [BBC] By Matt McGrath – November 15, 2013 -The world’s oceans are becoming acidic at an “unprecedented rate” and may be souring more rapidly than at any time in the past 300 million years.

In their strongest statement yet on this issue, scientists say acidification could increase by 170% by 2100. They say that some 30% of ocean species are unlikely to survive in these conditions.

The researchers conclude that human emissions of CO2 are clearly to blame.

The study will be presented at global climate talks in Poland next week.

In 2012, over 500 of the world’s leading experts on ocean acidification gathered in California.

Led by the International Biosphere-Geosphere Programme, a review of the state of the science has now been published.

This Summary for Policymakers states with “very high confidence” that increasing acidification is caused by human activities which are adding 24 million tonnes of CO2 to oceans every day.

Read the full article here.

Unprecedented Rate and Scale of Ocean Acidification Found in the Arctic

ST. PETERSBURG, Fla. — Acidification of the Arctic Ocean is occurring faster than projected according to new findings published in the journal PLOS ONE.  The increase in rate is being blamed on rapidly melting sea ice, a process that may have important consequences for health of the Arctic ecosystem.

Ocean acidification is the process by which pH levels of seawater decrease due to greater amounts of carbon dioxide being absorbed by the oceans from the atmosphere.  Currently oceans absorb about one-fourth of the greenhouse gas.  Lower pH levels make water more acidic and lab studies have shown that more acidic water decrease calcification rates in many calcifying organisms, reducing their ability to build shells or skeletons.  These changes, in species ranging from corals to shrimp, have the potential to impact species up and down the food web.

The team of federal and university researchers found that the decline of sea ice in the Arctic summer has important consequences for the surface layer of the Arctic Ocean.  As sea ice cover recedes to record lows, as it did late in the summer of 2012, the seawater beneath is exposed to carbon dioxide, which is the main driver of ocean acidification.

In addition, the freshwater melted from sea ice dilutes the seawater, lowering pH levels and reducing the concentrations of calcium and carbonate, which are the constituents, or building blocks, of the mineral aragonite. Aragonite and other carbonate minerals make up the hard part of many marine micro-organisms’ skeletons and shells. The lowering of calcium and carbonate concentrations may impact the growth of organisms that many species rely on for food.

The new research shows that acidification in surface waters of the Arctic Ocean is rapidly expanding into areas that were previously isolated from contact with the atmosphere due to the former widespread ice cover.

“A remarkable 20 percent of the Canadian Basin has become more corrosive to carbonate minerals in an unprecedented short period of time.  Nowhere on Earth have we documented such large scale, rapid ocean acidification” according to lead researcher and ocean acidification project chief, U.S. Geological Survey oceanographer Lisa Robbins.

Globally, Earth’s ocean surface is becoming acidified due to absorption of man-made carbon dioxide. Ocean acidification models show that with increasing atmospheric carbon dioxide, the Arctic Ocean will have crucially low concentrations of dissolved carbonate minerals, such as aragonite, in the next decade.

Read the full article here.

A convenient truth: 90% of the tunas are gone!

Last week, I had the privilege of presiding over the defense of the Ph.D. dissertation of Maria José Juan-Jordá in La Coruña, Spain. Maria José is a bright young researcher and has already published several chapters of her dissertation in the peer-reviewed literature.

The first chapter in her dissertation(1) is the last in a series of peer-reviewed scientific papers that demonstrate that the combined biomass of large oceanic predators (mostly tunas) has not declined by 90% as stated in another scientific paper ten years ago.

The 90% decline figure came from an analysis published in 2003 which concluded that “large predatory fish biomass today is only about 10% of pre-industrial levels” [Myers and Worm, 2003(2)].  Those analyses relied heavily upon catch rates from a single fishing gear type (longline) and aggregated catch across species to estimate trends in “community biomass”. The paper quickly became high-profile in the tuna world. Many environmental groups embraced it as proof that all tunas, not just the bluefins, were in serious trouble. On the other hand, tuna scientists who were actually conducting stock assessments, especially for tropical tunas knew immediately that the 90% number was totally wrong.

Over the next few years, a number of peer reviewed publications(3,4,5,6,7,8) showed that the conclusions in Myers and Worm (2003) were fundamentally flawed. Two of the most important reasons for this are: The aggregation of data, and the use of data from a single fishing method. The end result is that the 90% decline is an overestimate. This process of rebuttal is a natural part of the way science develops. Sometimes scientists reach conclusions that are wrong, for whatever reason, and other scientists discover flaws and point to them. A paper, once published, is not necessarily immortal.

Nevertheless, the notion of 90% global demise of tuna populations is still out there. It is repeated in many consumer guides published by various environmental groups that want to influence market preferences. It also pops up elsewhere: Earlier this year, I visited the web site of a newly-formed commission that aims to improve governance of ocean resources, and I was surprised to see the 90% number mentioned there. A colleague of mine who also noticed it said he was “disappointed that one of the most rebutted fisheries paper of all time continues to raise its head.”

Read the full story here.

Biodiversity Loss in the Ocean: How Bad Is It? [research paper]

photo © 2009 gorfor | more info (via: Wylio)

Science 1 June 2007:
Vol. 316 no. 5829 pp. 1281-1284
DOI: 10.1126/science.316.5829.1281b

The Research Article Impacts of biodiversity loss on ocean ecosystem services By B. Worm et al. (3 Nov. 2006, p. 787) projects that 100 of seafood-producing species stocks will collapse by 2048.

The projection is inaccurate and overly pessimistic.

Worm et al. define collapse as occurring when the current year’s catch is <10 of the highest observed in a stock’s time series. However, fish catch is rarely an adequate proxy for fish abundance, particularly for rebuilding stocks under management. A variety of biological, economic, and social factors and management decisions determine catches; low catches may occur even when stocks are high (e.g., due to low fish prices or the effects of restrictive management practices), and vice versa.

The inadequacy of Worm et al.‘s abundance proxy is illustrated by the time series of data for Georges Bank haddock (Melanogrammus aeglefinus). The highest catch for haddock occurred in 1965 at 150,362 tons (1). This catch occurred during a period of intense domestic and international fishing (1).

In 2003, haddock catch was 12,576 tons, or 8 of the time series maximum. Under the Wormet al. definition, the stock would be categorized as collapsed in 2003. However, stock assessment data (1) estimate the total magnitude of the spawning biomass in 2003 to be 91 of that in 1965. Comparing the estimate of spawning stock biomass in 2003 to the level producing maximum sustainable yield (MSY), the stock was not even being overfished in 2003 (2).

Get the whole report here.

Why do we keep hearing global fisheries are collapsing?

Some marine scientists say many of the world’s fish stocks are nearing collapse…but the data suggest otherwise. So why is the media still reporting that we’re on the verge of a fisheries apocalypse?

Peter Kareiva, Cool Green Science Blog, provides insight into this question, along with an article published in Science Chronicles by world-renown scientist Ray Hilborn.

Hilborn, an aquatic and fishery sciences professor at the University of Washington, writes in his article:

“If you have paid any attention to the conservation literature or science journalism over the last five years, you likely have gotten the impression that our oceans are so poorly managed that they soon will be empty of fish — unless governments order drastic curtailment of current fishing practices, including the establishment of huge no-take zones across great swaths of the oceans.

“To be fair, there are some places where such severe declines may be true. A more balanced diagnosis, however, tells a different story — one that still requires changes in some fishing practices, but that is far from alarmist. But this balanced diagnosis is being almost wholly ignored in favor of an apocalyptic rhetoric that obscures the true issues fisheries face as well as the correct cures for those problems.”

Read both reports here.