Algae bloom in Hawaii
howzit at turtles.org
Sat Jun 23 01:57:38 EDT 2001
>The report of algae on coral reefs in Hawaii was interesting..especially
>the comment by Windy Wiltse (EPA) in one of the newspaper website articles.
>"But that doesn't fit with what's being seen this year, so apparently it's
>not related to rainfall and runoff." So runoff and rain the ruling
>paradigms were not the cause?
"natural" Great word. It means humans don't have to do anything about a
bloom because "natural" is beyond control.
Only yesterday I made a cartoon about "natural".
Yes, I checked out the dust cloud from China. Thank you. I did some
further reading and discovered that:
"Wind erosion can be especially severe in China 5,000 km distant,
scientists at the Mauna Loa observatory in Hawaii can detect the onset of
the Chinese spring-plowing season by the increase in atmospheric dust
fallout. Zhenda and Tao (1993) used aerial photos, Thematic Mapper
satellite images, and field studies to conclude that sandy desertified
lands increased by an average of 2,100 km2 annually between 1975 and 1987.
The authors believe that anthropogenic causes of desertification are
paramount, as the figure below illustrates.
Interestingly this report goes on to say "Causes of sandy desertification
in north China: Natural causes aeolian sand dune encroachment explain
just 5.5% of desertification processes. Data source: Zhenda and Tao (1993)."
This would suggest these ever increasing China-originating dust clouds
aren't "natural" --but rather human-induced.
"So is it possible that this algal event is the result of increasing
desertification and ever larger dust storms that start in China?"
Sure it's possible. But that prompts other mysteries.
Like why (given that these dust clouds drift across the Hawaiian
archipelago) is Maui the only Hawaiian island to be affected by these
Cladophora blooms? And why, given the huge Maui shoreline, has our dive
site been involved in every single reported Maui bloom --AND experienced
three consecutive major blooms no one but us knew anything about?
"Nutrients and iron in dust can stimulate phytoplankton growth"
Nutrients and iron also stimulate Lyngbya blooms --which are annual events
for us. Now sure this iron could come from China...
But the red iron-rich soils of West Maui are increasingly blown away by
winds and settle all over and inside the condo we stay at. Last summer was
especially bad. Soil blows down from the pineapple fields up in the
mountains. In fact I think they stopped growing pineapples up there and
now the fields just lay empty.
On windy days when we're underwater, we can look up and even see the soil
particles on the surface drifting down!
I suppose some would call that kind of erosion "natural" also. But I wouldn't.
Last I just want to point out we dive at a place called
Honokowai. "Honokowai" means "place of fresh water." There's sufficient
differences in salinity from beach to 30 feet to suggest there is
groundwater seepage there. Next, the area had two temporary streams
--had-- now they're concrete drainage ditches. To the south within easy
walking distance (and 600 meters from shore) is the local sewage treatment
plant. It uses injection wells that pump over 11 million liters per day of
effluent containing high loads of phosphates and nitrates into the ground.
Every single day.
More and more of the shoreline has been developed --even just in the last
five years. Beachfront hotels/time shares just down the road. Further
back, fields that used to have "wasteland" meadows and grass have been
converted to houses, roads, a large shopping complex and Star Market. More
concrete and asphalt all the time.
Now I'm no scientist. But prudence and all would suggest that watershed
managers would discount "suspicious" factors close to home before declaring
an algae bloom "natural" --no matter how much we'd want it to be.
Either way I'm encouraged. This time 'round they got good people from the
University of Hawaii checking things out.
All the best and thank you again for the ideas you raised re: dust
clouds. As fascinating as they are worrisome.
> Did anyone out there notice the three huge Asian dust events that passe
>over the area in late April and May?. The dust storms crossed the Pacific
>and one blocked out the sun in Denver and then passed on out into the
>Atlantic. It is known that Asian dust nurishes the Hawaian rainforest
>(Chadwick, O. A., Derry, L. A., Vitousek, P. M., Huebert, B. J., and Hedin,
>L. O., Changing sources of nutrients during four million years of ecosystem
>development. Nature, 397, 491-497, 1999) If Asian dust brings nutrients to
>Hawian rainforests could it also stimulate marine algae growth..Nutrients
>and iron in dust can stimulate phytoplankton growth..a la Martin etc.
> So is it possible that this algal event is the result of increasing
>desertification and ever larger dust storms that start in China? Gene
>for more see http://www.gsfc.nasa.gov/GSFC/EARTH/Toms/microbespics.htm and
>other nasa websites that track dust.
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