Wednesday, June 12, 2013
Hawaiian petrels are eating far lower on the food chain, and a new study blames that on industrial fishing.
The takeaway from that is that the entire Pacific food web may be changing as a result of human activities.
(Image, a Hawaiian petrel or `a`o. Credit Brenda Zaun, USFWS.)
Says the study: “Because variation in the diet of generalist predators can reflect changing availability of their prey, a foraging shift in wide-ranging Hawaiian petrel populations suggests a relatively rapid change in the composition of oceanic food webs in the Northeast Pacific.”
The petrels, known in Hawaiian as `a`o, are endangered seabirds that, like the Newell’s shearwaters, nest in mountain burrows in the Hawaiian Islands.
The study is fascinating. Researchers went back through fossil bird bones dating to as far as 4,000 years ago. They looked at isotopes in the bones, and were able to make conclusions about what the birds were eating.
“Here, we use stable carbon and nitrogen isotopes to study the foraging history of a generalist, oceanic predator, the Hawaiian petrel (Pterodroma sandwichensis), which ranges broadly in the Pacific from the equator to near the Aleutian Islands,” the authors wrote.
The research shows that up until about 100 years ago, the diet of the birds was the same for centuries. And then it changed significantly. The changes in isotopes suggest a switch from larger fish to smaller ones, from higher on the food chain to lower.
Which in turn suggests there weren’t as many bigger fish around for the petrels to eat. It’s clear that the diet change occurred. Precisely how is not so clear.
Say the authors: “The nitrogen isotope ratio declined in the petrel following the onset of large-scale industrial fishing, which could have affected the petrel diet through several mechanisms.
"Many seabirds such as the Hawaiian Petrel forage in association with schools of large predatory fish, such as tuna and billfish that drive prey to the ocean surface. Depleted numbers of these schools, therefore, may reduce the availability of prey for the petrel. Additionally, it is possible that that petrel prey species have been depleted by direct harvest or bycatch in fisheries.”
The study is Millennial-scale isotope records from a wide-ranging predator show evidence of recent human impact to oceanic food webs, in PNAS, the Proceedings of the National Academy of Sciences. Authors include Anne E. Wiley. Peggy H. Ostrom, Andreanna J. Welch, Robert C. Fleischer, Hasand Gandhi, John R. Southon, Thomas W. Stafford, Jr., Jay F. Penniman, Darcy Hu, Fern P. Duvall, and Helen F. James.
Several of them are with Hawai`i research organizations, including Pacific Cooperative Studies Unit, University of Hawaii; National Park Service in Honolulu, and the Hawai`i Department of Land and Natural Resources.
More on Hawaiian petrels at this Fish and Wildlife Service website.
© Jan TenBruggencate 2013
A lot of the planet’s carbon, which scientists assume is in the soil, is actually flowing into the water.
And in some ways—from a climate change perspective—that could be a good thing, according to a team of researchers that includes University of Hawai`i oceanographer Fred Mackenzie.
Okay, your eyes are going to glaze over when you read this, but a quick takeaway is this: New research is constantly improving, clarifying and tightening estimates of what’s likely to happen in our climate future.
(Image: An aerial of sediment flowing from the land into the aquatic environment. Credit: Pierre Regnier, Copyright ESA 2003)
When carbon is washed into the rivers, lakes and oceans, a lot of it can be stored there in the form of sediment. And that sediment is far less likely to release the carbon back into the atmosphere. That is because in a warming climate, soil will release carbon before underwater sediment will.
That’s one point made by Mackenzie and a large team of researchers in their paper, Anthropogenic perturbation of the carbon fluxes from land to ocean, in the journal Nature Geoscience. An abstract is available here.
This is complex stuff, but essentially it means the models of climate change will get a little more accurate, presuming that folks developing global warming estimates adjust their assumptions, the authors say: “So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times.”
In fact, the carbon transport to aquatic bodies has not been stable. It has increased over time, the authors say. And what that means is that there’s a lot of carbon hidden in sediments that haven’t been included in global carbon calculations.
Says a press release on the study: “increased leaching of carbon from soil, mainly due to deforestation, sewage inputs and increased weathering, has resulted in less carbon being stored on land and more stored in rivers, streams, lakes, reservoirs, estuaries and coastal zones – environments that are together known as the ‘land-ocean aquatic continuum’.”
“The budget of anthropogenic CO2 reported by the Intergovernmental Panel on Climate Change (IPCC) currently does not take into account the carbon leaking from terrestrial ecosystems to rivers, estuaries and coastal regions. As a result of this leakage, the actual storage by terrestrial ecosystems is about 40% lower than the current estimates by the IPCC,” said co-author Pierre Regnier from Université Libre de Bruxelles.
An interesting note from the study: not all that much of the carbon, only about 10 percent, ends up in the oceans.
© Jan TenBruggencate 2013
Saturday, June 8, 2013
As many as one in five of the most energetic objects of the early universe were black holes—those fascinating deep space vacuum cleaners whose gravity is so immense that even light can’t escape.
An astronomical team that included University of Hawai`i’s Guenther Hasinger reported in The Astrophysical Journal that black holes formed early and often in the young universe.
(Image: Background radiation from when the universe was only a few hundred years old can provide hints of its structure. More detail on hthis image is here. Credits: Illustration by Karen Teramura, UHIfA. Credits for inserted images: cosmic microwave background (left): NASA WMAP Science Team; black hole blow up, AGN (center, top): NASA/JPL-Caltech; first stars blow up (center, bottom): NASA/JPL-Caltech, A. Kashlinsky (GSFC); Hubble Ultra Deep Field (right): NASA/ESA, S. Beckwith(STScI) and the HUDF Team.)
Hasinger, the Director of the university’s Institute for Astronomy, was part of a team that compared background infrared and x-ray signals dating back to the early universe. They used two NASA observatories, the Chandra X-ray Observatory and Spitzer Space Telescope
By comparing the results of the x-ray and infrared, they were able to determine that there were fluctuations in energy that were consistent in both forms of radiation, and that there was information in those fluctuations.
"This measurement took us some five years to complete and the results came as a great surprise to us," said Nico Cappelluti, an astronomer with the National Institute of Astrophysics in Bologna, Italy, and the University of Maryland, Baltimore County, in Baltimore.
In complex calculations, the scientists removed from the data the known star and galaxy sources of energy, and were left with a remainder they could study. And since black holes are particularly intense, energetic energy sources, the astronomers believed they could identify black hole signatures in the remnant radiation maps.
"Our results indicate black holes are responsible for at least 20 percent of the cosmic infrared background, which indicates intense activity from black holes feeding on gas during the epoch of the first stars," said Alexander Kashlinsky, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
All of that leads us into a detour into the insane world of black holes.
The density of the interior of black holes is so immense that nothing gets out. But like a stealthy beast that only makes a lot of noise when it’s eating, black holes are detectable because of the big energy signature of matter being sucked into them.
Around many black holes are accretion disks, where matter is being sucked toward oblivion. And where this final sucking occurs is called the “event horizon.” The matter spinning toward the event horizon lights up and sends out a kind of final radiation distress signal before it is gone. Like a cry of help from someone being drawn into a whirlpool.
Today, there are not nearly as many black hole signatures as there were in the early universe. Hasinger said that many of the universe’s black holes have gone silent. They have sucked all the matter in their regions of space, so there’s nothing left to eat—no accretion disks, so no radiation.
“Today only about 1% of all of these black holes are actively eating and radiating, while in the early universe probably all of them were active,” Hasinger said.
Today, astronomical research indicates every galaxy has a supermassive black hole at its center, and the larger galaxies have larger supermassive black holes. Supermassive black holes have masses ranging from a million to several billion solar masses.
For more information, visit: http://www.ifa.hawaii.edu/info/press-releases/blackholes2013/
© Jan TenBruggencate 2013