The Dust Hypothesis

[szmanta]

Dear All:

I have read several times the hypothesis that the Diadema die-off in
the  Caribbean was somehow caused by African dust.  Can someone explain
to me the logic behind this when the same species of sea urchin is doing
well, and matter of fact, has been a pest because of too high of
population densities on reefs just off the West coast of Africa (much
closer to the dust and potential  pathogen source)?

Happy New Year to all.

Alina Szmant

>===== Original Message From "Precht, Bill" <Bprecht at pbsj.com> =====
>Dear Coral List:
>
>For those following the "dust" for the past few years I thought you might
>find these tidbits of interest.
>
>Have a great holiday!
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
>The Dust Hypothesis
>
>Question:
>
>Why have coral reefs that are bathed in clear oceanic waters throughout
>much of the Caribbean suffered algal infestation, coral diseases, and near
>extinction of herbivorous sea urchins almost simultaneously during the
>1970s, 1980s, and early 1990s? The best known factors detrimental to coral
>reefs include sewage, run-off from land, dredging, UV light, etc. These
>factors do not apply for many affected reefs where human population is low.
>Is there an alternative way to spread nutrients and diseases?
>
>(Contineud)
>
>http://coastal.er.usgs.gov/african_dust/
>
>
>   Online mini-movie
>
>      Watch USGS scientists Ginger Garrison, Gene Shinn, Chuck Holmes, and
>      Dale Griffin in "The Effects of Globally Transported African and
>      Asian Dust on Coral Reef and Human Health"
>
>   http://coastal.er.usgs.gov/african_dust/documentary/
>
>
>   National Public Radio interview
>
>      Project scientists Gene Shinn and Ginger Garrison were interviewed
>      along with geologist/novelist Sarah Andrews on National Public Radio
>      station KQED in San Francisco on the popular morning talk show
>      "Forum" on January 15, 2002. Listen to the interview.
>
>   www.kqed.org/audioarchive/frameset/forum/2002/01/2002-01-15b-forum.html
>
>
>////////////////
>
>
>Mercury From China Rains Down on California
>
>   Environmental News Service (ENS)
>   http://ens-news.com/
>
>   December 20, 2002
>
>SANTA CRUZ, California, - Industrial emissions in Asia are a major source
>of mercury in rainwater that falls along the California coast, a new study
>suggests.
>
>The mercury in rainwater is not in itself a health threat, but mercury
>pollution is a problem in San Francisco Bay and other California waters
>because the toxic element builds up in the food chain. State regulatory
>agencies are looking for ways to reduce the amount of mercury entering the
>state's waters from various sources.
>
>It is not just the mercury itself but a whole cocktail of atmospheric
>pollutants that contribute to the deposition of mercury in rainfall.
>Elemental mercury behaves as a gas in the atmosphere and is not washed out
>in rain until it has been oxidized into a charged ionic form that can be
>captured by water droplets.
>
>Ozone, a major component of urban and industrial smog, plays a key role in
>this oxidation process, said Douglas Steding, lead author of a paper
>published Thursday in the online edition of the "Journal of Geophysical
>Research - Atmospheres." The report by Steding and other researchers from
>the University of California, Santa Cruz (UCSC) will appear in a later
>print edition of the journal.
>
>"There is a relatively large reservoir of mercury in the atmosphere, and
>it's the rate of oxidation that determines how much of it gets deposited in
>rainfall," Steding said.
>
>Mercury is a trace contaminant of most coal, and emissions from coal
>burning power plants are a major source of mercury pollution in many parts
>of the world. In the Pacific Basin, the main source of atmospheric mercury
>is coal combustion in China.
>
>China relies on coal as a fuel and accounts for about 10 percent of the
>total global industrial emissions of mercury.
>
>Air pollution in China also generates ozone, which peaks during the winter
>due to increased fuel consumption for heating. Air loaded with mercury and
>ozone moves off the continent into the Western Pacific, where it is
>incorporated into developing storms.
>
>"The mercury we measured in rainwater results from a combination of mercury
>emissions and ozone production, as well as meteorological factors - the
>storm tracks that transport the pollutants across the Pacific," Steding
>said.
>
>Steding collected rainwater samples at two sites in central California: on
>the coast at UCSC's Long Marine Laboratory and at Moffett Field near San
>Jose, on the inland side of the Santa Cruz Mountains. For each rainfall
>event, the researchers used air mass trajectories calculated by a national
>climate lab to trace the movement of the storms across the Pacific from
>Asia.
>
>Rainwater collected at the coastal site showed the background
>concentrations of mercury in storms as they arrived off the Pacific Ocean.
>Those measurements were about three times higher than estimates of the
>natural, preindustrial level, Steding said.
>
>Rainwater from the inland site showed mercury concentrations 44 percent
>higher than at the coastal site. Steding attributed the difference between
>the two sites to ozone in Bay Area smog, rather than local emissions of
>mercury.
>
>"There is a local influence of urban smog on the mercury oxidation rate. We
>see a background signal of mercury blowing off the Pacific, then a local
>enrichment that's probably due to urban smog," Steding said. "If we want to
>reduce mercury deposition, it's not enough to shut down local emissions of
>mercury, because other pollutants influence how much of the mercury in the
>atmosphere ends up in rainwater."
>
>Steding said people should not worry about health effects from the mercury
>in rainwater, because the concentrations are very low. But the deposition
>in rain does add mercury to surface waters, where the toxin enters the food
>chain and builds up to high levels in certain kinds of fish.
>
>State health officials have issued advisories warning people not to eat
>fish from more than a dozen bodies of water in California, including San
>Francisco Bay.
>
>  #  #  #
>
>http://ens-news.com/ens/dec2002/2002-12-20-09.asp#anchor1
>
>
>///////////////////
>
>
>Steding, Douglas J.; Flegal, A. Russell
>
>Mercury concentrations in coastal California precipitation:
>Evidence of local and trans-Pacific fluxes of mercury to North America
>
>10.1029/2002JD002081
>
>19 December 2002
>
>http://www.agu.org/pubs/toc2002/jd.shtml#dec
>
>
>////////////////
>
>
>Mercury In California Rainwater Traced ...
>
>ScienceDaily News Release
>
>.. Steding emphasized that people should not worry about health effects
>from the mercury in rainwater, because the concentrations are very low.
>
>http://www.sciencedaily.com/releases/2002/12/021220075156.htm
>
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
>*****************************************
>Season's Greetings from NOAA's CHAMP!
>*****************************************
>~~~~~~~
>For directions on subscribing and unsubscribing to coral-list or the
>digests, please see http://www.coral.noaa.gov/lists/coral-list.html .

Alina M. Szmant
UNCW Center for Marine Science
On travel from UNCW

~~~~~~~
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