Sunday, February 28, 2010

Pacific Garbage Patch is Hawai'i-bound

When anything slips out of the Great Pacific Garbage Patch, say hello. Because chances are it ends up on a Hawaii beach.

Teams of researchers have been working on the fate of marine debris in both the Atlantic and Pacific.

(Image: This Laysan albatross chick died with its belly full of plastic, some of which may have been picked up by its parents in the Great Pacific Garbage Patch. A lesson about controlling the flow of plastic debris into the marine environment.)

“In the North Pacific, Hawai'i is the final destination of marine debris,” said Nikolai Maximenko, a senior researcher with the International Pacific Research Center, and the University of Hawai'i's School of Ocean and Earth Science and Technology.

He reported last week from the American Geophysical Union 2010 Ocean Sciences Meeting in Portland, Oregon.

As we understand it, when trash gets lost or dumped off fishing boats, falls off big ships or washes into the ocean from the shore in the North Pacific, it begins a nearly endless transit around the ocean on a vast current system.

A large amount of that trash slowly moves toward the interior of the the North Pacific Current, and eventually gets trapped in the immense field of garbage in the eastern North Pacific, between Hawai'i and California.

And when currents and winds drive anything out of that system, it tends to get swept south and westward. The only thing in its way at that point is the 1,400-mile-long Hawaiian archipelago.

So our Hawaiian reefs and beaches get trashed with tangles of rope and net, plastic tubes from Japanese oyster farms, bottles, multicolored cigarette lighters, and endless fields of tiny bits of unidentifiable plastic.

A research program in the Atlantic, involving thousands of graduate students, reported on 6,100 plankton net tows in that ocean. They found that 62 percent of the nets contained plastic—64,000 pieces of plastic. Most of it, 83 percent, was found in the central latitudes, between 22 and 38 degrees north, said Kara Lavender Law, Oceanography Faculty Scientist of the Sea Education Association at Woods Hole, Massachusetts.

Another Woods Hole faculty scientist, Giora Proskurowski, said that while researchers have towed nets through the water for hundreds of miles, no one knows just how much of that stuff is out there, in part because any amount of wind or wave causes much of the debris to mix deep into the upper layers of the ocean. There, it doesn't show up in surface-towed plankton nets.

If you do a tow on a dead calm day, the stuff floats to the surface and you get a lot. If you tow when there's any kind of weather, the results under-represent reality, he said.

Law said that the majority of the smaller bits of plastic are not identifiable as to their source, unless they are bits of fishing line or industrial plastic pellets. Some plastic debris is denser that seawater and sinks to the bottom, where its impacts have not been well studied.

© Jan TenBruggencate 2010

Wednesday, February 17, 2010

Marine protected areas do protect corals

Hawai'i has a range of marine protected areas, with varying kinds and degrees of protection—from no fishing to virtually no human activity at all--but do they work?

That's been an assumption—but there is new evidence that, for corals and perhaps for fisheries as well, they do.

In the February 2010 issue of the online scientific journal PloS One, University of North Carolina researchers Elizabeth Selig and John Bruno published the paper, “A Global Analysis of the Effectiveness of Marine Protected Areas in Preventing Coral Loss.”

Corals are particularly important, because, the authors write, “Coral loss has cascading effects throughout reef ecosystems leading to subsequent changes in the population dynamics of reef inhabitants.”

They reviewed more than 8,000 coral surveys from more than 4,000 reefs around the globe, and their conclusions were favorable for marine protected areas (MPAs).

They found that coral cover remained stable in protected areas, but declined on unprotected reefs. And they found, as might be expected, that longer protection was more effective than shorter.

“These findings suggest that MPAs can be a useful tool not only for fisheries management, but also for maintaining coral cover,” the paper said.

In an email to colleagues, co-author Bruno wrote:

“Our results also suggest that older MPAs were generally more effective in preventing coral loss. Initially, coral cover continued to decrease after MPA establishment. Several years later, however, rates of coral cover decline slowed and then ceased. The analysis was based on a global database of 8534 reef surveys from 1969-2006. We used this long-term record of reef communities to compare changes in coral cover inside 310 MPAs to that on over 4000 unprotected reefs in 83 countries.”

© Jan TenBruggencate 2010

Tuesday, February 16, 2010

Upper half mile of ocean increasingly acidic

The scary underbelly of the whole climate change scenario is that the oceans are being changed fundamentally.

As carbon dioxide builds up in the air, some of it mixes with water and becomes acid. The increasing acidity of the oceans has been reported before, but the latest data, representing the first broad survey of the Pacific basin, is compelling.

Direct observations of basin-wide acidification of the North Pacific Ocean” is reported in the journal Geophysical Research Letters by Robert H. Byrne and Xuewu Liu of the College of Marine Science, University of South Florida, Sabine Mecking of the Applied Physics Laboratory, University of Washington. Richard A. Feely, of the Pacific Marine Environmental Laboratory, NOAA.

They took 2,100 samples, from the surface to the ocean floor, during cruises between O'ahu and Kodiak, Alaska—obtaining a unique cross-sectional slice of the Pacific Ocean. Cruises took place in 1991 and again in 2006.

They found that in those 15 years, there had been a marked increase in acidity in the upper half-mile of the ocean, which in some places is more than 3 miles deep.

Previous studies have found similar results in single locations. What this study does is “confirm on a large scale what has been observed at three time-series points in the north Atlantic and Pacific — significant upper ocean acidification, roughly keeping pace with rising atmospheric carbon dioxide.

“It appears that future acidification of the ocean's mixed layer can be expected to occur at rates that closely mirror changes in atmospheric CO2...

“If atmospheric CO2 continues to rise at an accelerating rate, ocean pH can be expected to fall at an accelerating rate.”

What does that mean? It most likely means bad news for corals, shellfish, plankton and all kinds of other marine life that depend on no rapid changes in the oceans' acidity-alkalinity balance.

And it is perhaps the most unassailable argument for reducing our production of carbon dioxide.

© Jan TenBruggencate 2010

Monday, February 8, 2010

They may be charismatic, but megafauna often get wrongly blamed for poor fishing

Hawai'i's humpback whales are being blamed for the low herring count in Prince William Sound, just as the depleted Atlantic bluefin tuna are being blamed for low sardine counts off Europe.

Even Hawaiian monk seals are blamed for declines in human nearshore fishing success.

It's a bizarre phenomenon. Among the folks pointing fingers are anglers, chafing under fishing restrictions, are finding culprits to blame, and doing it largely on purely anecdotal evidence.

In the case of the Alaskan herring, researchers concede that the Exxon Valdez oil spill, which dumped 11 million gallons into the sound 21 years ago, crashed the herring population. The spill occurred just during the spawning season, and the next year's herring take was down 75 percent.

Since then, the little fish haven't recovered. Meanwhile, as Hawai'i residents know, Humpback whale populations have roughly doubled. The whales winter in tropical waters, like those in Hawai'i, and summer in the resource-rich feeding grounds off Alaska and other northern waters.

Anglers and others say that just like Hawai'i, they're seeing more Humpbacks around Alaska. And some of the big whales seem to be staying the entire winter, passing up their winter migration.

Researchers concede they are considering other factors, like other fish having moved into the traditional herring spot on the food chain, climate change, toxins, and a rampant disease, Icthyophonus, which is attacking young herring. Oh, and maybe residual impacts from the oil spill have some role.

But clearly humpback whales do eat herring, and always did. So do seals, porpoise, birds, and other fish. Other species of fish also feed on the herring eggs.

The research is concluding that, with regard to humpbacks, yep, whales are big animals and they eat a lot of herring.

It seems inescapable, though, that generally, if you crash a prey population and the feeding pressure from all kinds of predators remains strong, you'll have a delayed recovery.

Here's a page on the biology of Atlantic herring.

And while we're in the Atlantic, there's a related story about the prime sashimi fish, bluefin tuna. It eats sardines. Also herring, mackerel, anchovy, flying fish (malolo), squid, eels and various crustaceans.

The bluefin has been overfished to the point of near collapse, according to the best fisheries scientists. They're arguing for a complete ban on fishing for bluefin, to save the species.

Many fishing industries understandably don't want a ban—even a temporary ban to let the species recover.

Among the arguments: even this depleted bluefin population is responsible for herring decline.

Seems to be a pattern.

In Hawai'i, endangered Hawaiian monk seals have sometimes been blamed by anglers for low fish numbers—but when someone actually went and did the science, they found that humans and seals generally eat different fish

The aggressive digging and rock-flipping behavior of seals tends to favor seafloor species that are not preferred by human fish-hunters. And the feeding often occurs in deeper water than most coastal anglers use for fishing.

© Jan TenBruggencate 2010