Glacier melt adds ancient edibles to marine buffet

Dec 23, 2009
Researchers measured the nutrient content of subglacial outflow from the Mendenhall Glacier near Juneau, Alaska, seen here. Credit: Eran Hood

Glaciers along the Gulf of Alaska are enriching stream and near shore marine ecosystems from a surprising source - ancient carbon contained in glacial runoff, researchers from four universities and the U.S. Forest Service report in the December 24, 2009, issue of the journal Nature.

In spring 2008, Eran Hood, associate professor of hydrology with the Environmental Science Program at the University of Alaska Southeast, set out to measure the nutrients that reach the gulf from five glaciated watersheds he can drive to from his Juneau office. "We don't currently have much information about how runoff from glaciers may be contributing to productivity in downstream . This is a particularly critical question given the rate at which glaciers along the Gulf of Alaska are thinning and receding" said Hood.

A glacier river plume enters the marine environment in Berner's Bay near Juneau, Alaska. Credit: Eran Hood

Hood then asked former graduate school colleague Durelle Scott, now an assistant professor of biological systems engineering at Virginia Tech, to help analyze the organic matter and nutrient (nitrogen and phosphorus) loads being exported from the Juneau-area study watersheds. "Because there are few reports of nutrient yields from glacial watersheds, Eran and I decided to compare the result from a non-glacial watershed with those of a watershed partially covered by a glacier and a watershed fully covered by a glacier," said Scott.

Hood and Scott's initial findings, reported in the September 2008 issue of the journal Nature Geoscience, presented something of a mystery. As might be expected, there is more organic matter from a forested watershed than from a fully or partially glacier-covered watershed. With soil development, organic matter is transported from the landscape during runoff events. However, there was still a considerable amount of exported from the glaciated landscape.

How can a glacier be a source of the organic carbon? His curiosity piqued, in spring 2009, Hood's Ph.D. student, Jason Fellman, collected samples from 11 watersheds along the Gulf of Alaska from Juneau to the Kenai Peninsula. The samples were analyzed to determine the age, source, and biodegradability of organic matter derived from glacier inputs.

"We found that the more glacier there is in the watershed, the more carbon is bioavailable. And the higher the percentage of glacier coverage, the older the organic material is - up to 4,000 years old," said Scott.

Hood and Scott hypothesize that forests that lived along the Gulf of Alaska between 2,500 to 7,000 years ago were covered by glaciers, and this organic matter is now coming out. "The organic matter in heavily glaciated watersheds is labile, like sugar. Microorganisms appear to be metabolizing ancient carbon and as the microorganisms die and decompose, biodegradable dissolved organic carbon is being flushed out with the glacier melt," said Scott.

How much? "Our findings suggest that runoff from may be a quantitatively important source of bioavailable for coastal ecosystems in the Gulf of Alaska and, as a result, future changes in glacier extent may impact the food webs in this region that support some of the most productive fisheries in the United States," said Hood.

Explore further: NASA sees Tropical Depression Polo winding down

More information: "Glaciers as a source of ancient, labile organic matter to the marine environment," December 24, 2009 issue of the journal Nature.

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User comments : 11

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physpuppy
3 / 5 (1) Dec 23, 2009
Hope there aren't any nasty viruses or bacteria that survive the freeze/thaw as well as time that will end up back into the ecosystem.

Food for thought (ouch)
Velanarris
2.7 / 5 (6) Dec 23, 2009
Very interesting article. As for archaeo-viruses and bacteria, I doubt we'll see anything remarkably dangerous, but there is potential for it.
Sanescience
1.5 / 5 (4) Dec 23, 2009
What about seeds, maybe some lost plant species will be recovered.
HealingMindN
4 / 5 (1) Dec 23, 2009
What's going on with you worry warts? There are all kinds of critters shaken loose from glaciers everyday. Physorg reports it. Now, you feel like nature is "out to get you?" What about humanity's creation of the North Pacific Trash Gyre? I'd say that's a little more something to worry about.
Velanarris
1 / 5 (3) Dec 24, 2009
What's going on with you worry warts? There are all kinds of critters shaken loose from glaciers everyday. Physorg reports it. Now, you feel like nature is "out to get you?" What about humanity's creation of the North Pacific Trash Gyre? I'd say that's a little more something to worry about.

Then get in a trawler and netdrag it out of there.
danman5000
not rated yet Dec 24, 2009
What's going on with you worry warts? There are all kinds of critters shaken loose from glaciers everyday. Physorg reports it. Now, you feel like nature is "out to get you?" What about humanity's creation of the North Pacific Trash Gyre? I'd say that's a little more something to worry about.

Then get in a trawler and netdrag it out of there.

It's not really that simple. It's not a bunch of milk jugs floating around that you can just pick up: its a huge area of microscopic plastic fragments, much of which is suspended in the water well below surface level.
danman5000
not rated yet Dec 24, 2009
Sorry, went past the editing time - I should have said "near microscopic" pieces, as the majority of debris consists of tiny but still visibile pieces (like glitter).
toyo
1 / 5 (1) Dec 28, 2009
Sorry to change the subject, but the quote of : "forests that lived along the Gulf of Alaska between 2,500 to 7,000 years ago " caught my eye.
This is one more nail in the coffin of the 'Global warming is caused by human CO2' debate, IMHO.
operator
1 / 5 (1) Dec 28, 2009
toyo- sorry to say but your understanding of climate science, paleo-ecology and earth sciences in general is quite simplistic, the complex science has been presented as simply as possible so obviously people like yourself can understand the general thrust of it, but the science, the data, the paleo-historic records are far more complex then you suggest. you assumptions and connections are simply unfounded
toyo
1 / 5 (2) Dec 29, 2009
Operator - your pithy attempt to dismiss my argument, by attacking me personally but providing no argument of your own, shows you up as a 'believer'.
I don't 'believe', I want to 'understand'.
Accordingly, I have read the various IPCC reports and I stand by the statement I made above.
If you want to make a statement that is credible, if you understand more than I do, please explain away my statement, don't use personal attacks, they will not work.
And if you can't explain why forests lived in the Gulf of Alaska when anthropogenic CO2 could not have been blamed for global warming, show me the 'model' from the IPCC that explains that one away.
If you can't even do THAT, then please go play with your bible or chant with your other credulous, sneering friends, because you're not adding to the debate, just demeaning it and yourself.
crackerhead
not rated yet Dec 29, 2009
was the forest any thing like the plants under the glacier that were not decomposed ? any relation other than time frame ? WHY was the glaciers growing at that time ? how fast did they encompass that forest ?