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.”

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.

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.

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.

Mike Hale, The Grub Hunter: Don’t slam the sardine

Smaller fish such as sardines and herring are less vulnerable to pollutants. (Bob Fila — Chicago Tribune file)

By Mike Hale, Monterey Herald

I live for Sardine Tuesdays, those rare occasions when Local Catch Monterey Bay offends some of its members by highlighting those small, oily “trash” fish that belong on the end of a hook — not in a fry pan fouling the air within two square blocks.

The sign-out sheet at my pickup location always includes more than a few persuasive scribbles from disappointed members urging someone — anyone — to take their share.

I always oblige. Then I tote home my double dose of sardines — meeting the cold glare of my fish-phobe wife and the delirious purr of our rotund Sopa, who creates a happy tangle of orange fur around my ankles.

Sardines and other small fish at the bottom of the food chain (herring, mackerel, smelt, anchovies) often end up in pet food, but in the right hands they are a tasty, healthful addition to the human diet (a fact ridiculously obvious anywhere outside our Fast Food Nation).

When Local Catch offers the smaller-sized sardines as it did last week, I prepare my home for a massive fish fry by opening my kitchen windows. It’s a simple process: I liberally season the cleaned, headless sardines before dredging them in flour and frying them in vegetable oil. After a spritzing of lemon juice, I hold these crispy beauties by the tail and eat them whole (the tiny bones practically dissolve upon cooking).

If that seems like a lot of trouble, order them out. Oddly enough, the former Sardine Capital of the World has traditionally boasted very few restaurants that serve these undervalued and underutilized fish (and believe it or not, the Sardine Factory has never served sardines).

But the tide is turning. Heading to Fisherman’s Wharf provides options: Domenico’s offers a fried anchovy appetizer and olive-oil marinated, grilled local sardines served with a Sicilian salsa; Abalonetti Bar & Grill grills its local sardines, topped with a spicy marinara. Off the pier: Crystal Fish in Monterey serves a fine sardine sushi; Lokal in Carmel Valley often adds to its menu tasty sardine sandwiches called bocadillos, slathering the bread with a pungent mojito aioli; jeninni kitchen + wine bar in Pacific Grove rolls out bruschetta with anchovies; and Mundaka in Carmel right now offers Spanish mackerel escabeche, a method where the fish is cooked before pickled.

Boats are pulling Spanish mackerel out of the bay now, and Mundaka chef Brandon Miller seasons them with fennel, black pepper and cumin before roasting. He then sautés vegetables, adding water and vinegar to create a pickling liquid he pours over the fish.

When smelt are running in San Francisco Bay, Miller will source them from his hometown and serve what he calls “fries with eyes.” He dredges the whole smelt in flour and deep-fries until crispy, serving them with a side of squid ink aioli.

“You can’t just eat all the big fish, because there is only so many of them in the ocean,” he said. “I like to target these little fish. They are delicious and really good for you.”

Cardiologists light up at the subject. Sardines and their brethren are full of heart-healthy omega-3s, and not full of toxins (such as mercury) that can build up in large fish such as tuna. They are also chock-full of fat-fighting compounds that help stabilize blood sugar, and rich in coenzyme Q10, vitamin B12, selenium, calcium, phosphorus and vitamin D.

Without a doubt, sardines are stinky, slimy, slippery and seemingly indigestible. But look closer, climb down the food chain and give them a try anyway. Open the windows, put on a pot of boiling vinegar and cause a stink.

Read the original post MontereyHerald.com.

Pink sea slugs swarming northwards as ocean temperatures rise

The bright pink sea slugs are typically found in Southern California, but have been found moving farther and farther north as ocean temperatures increase, possible due to global warming.

Central and Northern California are beginning to take on a pink hue as Hopkins’ rose sea slugs take over — something that scientists say may be due to global warming.

The increasing global temperatures have caused an explosion in the population of the Hopkins’ rose nudibranch beyond Southern California, where it is typically found. Usually, it is extremely uncommon north of San Francisco, but scientists are spotting them in tide pools far north of that, according to a Santa Cruz Sentinel report.

Rare wind patterns that scientists have yet to explain have caused temperatures in West Coast oceans to rise, which has lured the sea slug far best its typical range.

And it’s not the only unusual visitor to the area, with fisherman in San Francisco capturing a sea turtle back in September that in the past would have only been found off the coast of Mexico or the Galapagos far to the south. Meanwhile, humpback whales and dolphins are being spotted on a regular basis in the Monterey Bay, according to the report.

Scientists say the waters off the coast are about 5 degrees higher than they normally are for most of 2014, and it has just been increasing in warmth, according to Logan Johnson, a National Weather Service forecaster in Monterey, who was quoted in the report.

Currently, waters in the Monterey Bay are running in the high 50s, and it’s staying there.

Typically, such temperatures would suggest that El Nino is on its way. The current warming is being created by what is known as upwelling, which is when Northwesterly winds blow away water at the surface, causing colder waters farther down to replace it — but scientists haven’t spotted those winds.

John Pearse, an ecology and evolutionary biology professor at the University of California Santa Cruz, said another warm phase is beginning, although scientists have no way of know if this is part of normal oscillation or if it’s global warming, according to the report.

Colder currents could be causing the sea slug’s range to shrink because their prey — rose-colored encrusting bryozoan, a moss-like life form — can be found up and down the Pacific Coast as far north as British Columbia. Now that northward currents are carrying the species larvae to tide pools, upwelling isn’t washing them away.

Read original post: ScienceRecorder.com