Southern Oscillation (ENSO). The ENSO has worldwide
meteorological effects, including increasing wind shear
in the subtropical Atlantic that is also known to suppress
tropical-cyclone formation.
Effects
Iron and minerals in African dust form reddish-brown
layers in white- to cream-colored carbonate sediments
throughout the rock record in Florida and the Caribbean.
In modern times, Caribbean corals experienced an unusual
onset of disease and demise in the late 1970s that peaked
in 1983–1984. The peak coincided with a major ENSO
and positive NAO coupled with the largest dust flux at
the island of Barbados since monitoring began there in
1965 (Shinn et al., 2000). Significant coral bleaching
began in the Pacific in 1982–1983 (Glynn, 1988),
followed by widespread Atlantic coral bleaching in
1986–1987, both times of high dust flux. The El Niño of
1998 was also a time of increased dust flux to the
Caribbean.
Sporadic fish kills and cases of ciguatera fish poisonings occurred in 1983–1984. Caribbean-wide demise of
the herbivorous black long-spined sea urchin Diadema
antillarum (Lessios et al., 1984) and onset of sea-fan disease caused by the soil fungus Aspergillus sydoweii also
began around that time (Weir-Brush et al., 2004). Aspergillus sydoweii has been cultured from African dust collected in Mali, Africa. Aspergillus sydoweii does not
reproduce in seawater. These Caribbean-wide die-offs
severely impacted reef vitality by allowing algal growth
to go unchecked. Whether diseases and bleaching are
caused by specific elements or microbes carried by
African dust or simple elevation of water temperature is
controversial and not well understood. A major problem
has been separating effects of dust from those of the rising
temperature. Both hypotheses are based mainly on correlation and not on absolute proof, other than the fact that
A. sydoweii is a verified cause of sea-fan disease.
What is known is that viable microbes, bacteria, and
fungi are common dust components (Griffin et al., 2003;
Griffin, 2007). Shielding of ultraviolet radiation by the
dust clouds themselves enables microbes to survive long
journeys through the atmosphere. Hundreds of viable species have been cultured and recognized in dust thus far
(Kellogg and Griffin, 2006). Of those recognized, about
10% are human pathogens and 30% are plant pathogens
(Griffin et al., 2003). Most microbes recovered from dust
have not yet been identified.
In addition to viable microbes, toxic metals including
mercury and arsenic are also components of dust (Holmes
and Miller, 2004; Garrison et al., 2006). Bioassays have
shown that copper in African dust is toxic to phytoplankton in near-surface ocean waters and thus affects primary
productivity as well as the CO 2 budget (Payton et al.,
2009). Human-health effects, first noted by Darwin
(1845) while he was aboard the HMS Beagle, are well
known to Caribbean-island citizens.
Asian dust
Asian and Australian dusts settle on Pacific and Indian
Ocean coral reefs and atolls but effects of those dusts are
less well known. Australian dust contains abundant
microbes (De Deckker, 2008). In addition, red tides
have been reported along the Australian coast following
dust events. Satellite imagery shows that Australian dust
clouds usually move from the west (Outback region)
out over the Great Barrier Reef and eastward toward
New Zealand.
Beginning in April, Asian dust clouds often blanket
Korea, pass over Japan, and then cross the North Pacific.
Iron in Asian dust increases primary productivity in the
open Pacific (Young et al., 1991). Asian dust is also the
source of soils in the Hawaiian Islands (Chadwick et al.,
1999). These dust clouds impact the Western US, Alaska,
and the North Sea where the dust stains sea ice. Asian dust
has at times blocked the sun in Denver, Colorado, and has
been identified, along with African dust, in Alpine snow.
Asian dust is widespread, yet there are few published
accounts of its toxic components, especially microbes.
Clearly, Asian dust transports industrial pollutants as it
passes over Chinese factories and coal-fired power plants.
The full effects of Asian dust on coral reefs in the Pacific
and Indian Oceans are not well known. Investigation of
impacts of various airborne soil dusts on coral reefs and
other marine organisms is in its infancy.
Summary
Dust storms are global events. Dusts from Africa, Asia,
the Americas, the Middle East, and Australia periodically
fill the air with soil particles to which viable microbes,
bacteria, fungi, and toxic chemicals are attached. Dusts
and their exotic components are transported through the
troposphere to be deposited far from their sources. Dusts
cause hazy days and spectacular sunsets, but also pose risk
to human health (e.g., asthma), marine life (e.g., red tides),
and coral reef health (e.g., sea-fan disease). Impacts of airborne dusts on all ecosystems are just beginning to be
recognized.
Bibliography
Darwin, C., 1845. An account of the fine dust which often falls on
vessels in the Atlantic Ocean. Quarterly Journal of the Geological Society of London, 2, 26–30.
Chadwick, O. A., Derry, L. A., Vitousek, P. M., Huebert, B. J., and
Hedin, L. O., 1999. Changing sources of nutrients during
four million years of ecosystem development. Nature, 397,
491–497.
D’Almeida, G. A., 1986. A model for saharan dust transport. Journal of Climatology and Applied Meteorology, 24, 903–916.
De Deckker, P., Abed, R. M. M., de Beer, D., Hinrichs, K-U.,
O’Loingsigh, T., Schefurb, E., Stuut, J-B. W., Tapper, N. J.,
and van der Kaars, S., 2008. Geochemical and microbiogical fingerprinting of airborne dust that fell in Canberra, Australia, in
October 2002. Geochemistry, Geophysics, and Geosystems, 9,
Q12Q10, doi:10.1029/2008GC002091
Garrison, V. H., Foreman, W. T., Genualdi, S., Griffin, D. W.,
Kellogg, C. A., Majewski, M. S., Mohammed A., Ramsubhag,
AIRBORNE DUST IMPACTS
17
meteorological effects, including increasing wind shear
in the subtropical Atlantic that is also known to suppress
tropical-cyclone formation.
Effects
Iron and minerals in African dust form reddish-brown
layers in white- to cream-colored carbonate sediments
throughout the rock record in Florida and the Caribbean.
In modern times, Caribbean corals experienced an unusual
onset of disease and demise in the late 1970s that peaked
in 1983–1984. The peak coincided with a major ENSO
and positive NAO coupled with the largest dust flux at
the island of Barbados since monitoring began there in
1965 (Shinn et al., 2000). Significant coral bleaching
began in the Pacific in 1982–1983 (Glynn, 1988),
followed by widespread Atlantic coral bleaching in
1986–1987, both times of high dust flux. The El Niño of
1998 was also a time of increased dust flux to the
Caribbean.
Sporadic fish kills and cases of ciguatera fish poisonings occurred in 1983–1984. Caribbean-wide demise of
the herbivorous black long-spined sea urchin Diadema
antillarum (Lessios et al., 1984) and onset of sea-fan disease caused by the soil fungus Aspergillus sydoweii also
began around that time (Weir-Brush et al., 2004). Aspergillus sydoweii has been cultured from African dust collected in Mali, Africa. Aspergillus sydoweii does not
reproduce in seawater. These Caribbean-wide die-offs
severely impacted reef vitality by allowing algal growth
to go unchecked. Whether diseases and bleaching are
caused by specific elements or microbes carried by
African dust or simple elevation of water temperature is
controversial and not well understood. A major problem
has been separating effects of dust from those of the rising
temperature. Both hypotheses are based mainly on correlation and not on absolute proof, other than the fact that
A. sydoweii is a verified cause of sea-fan disease.
What is known is that viable microbes, bacteria, and
fungi are common dust components (Griffin et al., 2003;
Griffin, 2007). Shielding of ultraviolet radiation by the
dust clouds themselves enables microbes to survive long
journeys through the atmosphere. Hundreds of viable species have been cultured and recognized in dust thus far
(Kellogg and Griffin, 2006). Of those recognized, about
10% are human pathogens and 30% are plant pathogens
(Griffin et al., 2003). Most microbes recovered from dust
have not yet been identified.
In addition to viable microbes, toxic metals including
mercury and arsenic are also components of dust (Holmes
and Miller, 2004; Garrison et al., 2006). Bioassays have
shown that copper in African dust is toxic to phytoplankton in near-surface ocean waters and thus affects primary
productivity as well as the CO 2 budget (Payton et al.,
2009). Human-health effects, first noted by Darwin
(1845) while he was aboard the HMS Beagle, are well
known to Caribbean-island citizens.
Asian dust
Asian and Australian dusts settle on Pacific and Indian
Ocean coral reefs and atolls but effects of those dusts are
less well known. Australian dust contains abundant
microbes (De Deckker, 2008). In addition, red tides
have been reported along the Australian coast following
dust events. Satellite imagery shows that Australian dust
clouds usually move from the west (Outback region)
out over the Great Barrier Reef and eastward toward
New Zealand.
Beginning in April, Asian dust clouds often blanket
Korea, pass over Japan, and then cross the North Pacific.
Iron in Asian dust increases primary productivity in the
open Pacific (Young et al., 1991). Asian dust is also the
source of soils in the Hawaiian Islands (Chadwick et al.,
1999). These dust clouds impact the Western US, Alaska,
and the North Sea where the dust stains sea ice. Asian dust
has at times blocked the sun in Denver, Colorado, and has
been identified, along with African dust, in Alpine snow.
Asian dust is widespread, yet there are few published
accounts of its toxic components, especially microbes.
Clearly, Asian dust transports industrial pollutants as it
passes over Chinese factories and coal-fired power plants.
The full effects of Asian dust on coral reefs in the Pacific
and Indian Oceans are not well known. Investigation of
impacts of various airborne soil dusts on coral reefs and
other marine organisms is in its infancy.
Summary
Dust storms are global events. Dusts from Africa, Asia,
the Americas, the Middle East, and Australia periodically
fill the air with soil particles to which viable microbes,
bacteria, fungi, and toxic chemicals are attached. Dusts
and their exotic components are transported through the
troposphere to be deposited far from their sources. Dusts
cause hazy days and spectacular sunsets, but also pose risk
to human health (e.g., asthma), marine life (e.g., red tides),
and coral reef health (e.g., sea-fan disease). Impacts of airborne dusts on all ecosystems are just beginning to be
recognized.
Bibliography
Darwin, C., 1845. An account of the fine dust which often falls on
vessels in the Atlantic Ocean. Quarterly Journal of the Geological Society of London, 2, 26–30.
Chadwick, O. A., Derry, L. A., Vitousek, P. M., Huebert, B. J., and
Hedin, L. O., 1999. Changing sources of nutrients during
four million years of ecosystem development. Nature, 397,
491–497.
D’Almeida, G. A., 1986. A model for saharan dust transport. Journal of Climatology and Applied Meteorology, 24, 903–916.
De Deckker, P., Abed, R. M. M., de Beer, D., Hinrichs, K-U.,
O’Loingsigh, T., Schefurb, E., Stuut, J-B. W., Tapper, N. J.,
and van der Kaars, S., 2008. Geochemical and microbiogical fingerprinting of airborne dust that fell in Canberra, Australia, in
October 2002. Geochemistry, Geophysics, and Geosystems, 9,
Q12Q10, doi:10.1029/2008GC002091
Garrison, V. H., Foreman, W. T., Genualdi, S., Griffin, D. W.,
Kellogg, C. A., Majewski, M. S., Mohammed A., Ramsubhag,
AIRBORNE DUST IMPACTS
17