[Coral-List] An ecological disaster

Martin Moe martin_moe at yahoo.com
Tue Oct 2 10:05:57 EDT 2007

Is it an ecological disaster if an entire class of
organisms, containing a number of keystone species, is
destroyed over an area of 1000 square miles, and few
people know about it, or seem to care? Sure it is,
look at the results of the Diadema plague in the early
1980s, but in this case it is the large sponges,
almost every species in the class Demospongea, in
Florida Bay and along the nearshore waters of the
Upper Florida Keys that have suffered decimation this
summer. The loss of benthic structure alone that these
organisms provided to the biology of these shallow
areas will affect the ecology and productivity of
these waters for years to come.  The cause of this
ecological disaster was a bloom of Synechococcus sp
blue-green algae. The bloom reached densities of
around 2 billion cells per liter in some areas with
visibility near the bottom measured in inches and the
water appearing as green and dense as the proverbial
pea soup. This alga, a common element of the
phytoplantkton in these waters, can form a dense and
very persistent bloom when the right amounts of macro
and trace nutrients are present, and the ability of
the blue-green algae (cyanobacteria) to sequester and
recycle iron and other essential trace metal nutrients
greatly enhances the persistence of the bloom. 

Observations by Ken Nedimyer, a marine biologist and
marinelife collector in this area graphically describe
the ecological devastation that this bloom has

“I don't know whether you saw the letter Skip wrote a
week or so ago about the algae bloom related sponge
die off around Lower Matecumbe, but I want to confirm
his observations and add that it's much bigger and
more extensive than anything I've ever seen.  I did
some snorkeling on Old Dan Bank behind Long Key today,
and except for one type of sponge, there appears to be
a 100% die off of all sponges in every type of
habitat.  I was mostly on top of the grass bank, and
it was ghastly looking.  Sponges of all types used to
be all over the flat, from the deeper areas on both
sides of the flat to the very shallow areas on top of
the flat, but they are all dead now. Sponges were the
very fabric that held the dead porites clomps
together, forming part of the structure of the flat,
but the sponge is all dead now and the only thing left
is the loose porites, the grasses, and the macro
algae.  The whole nature of that grass flat system has
just radically changed.  

The shallow hard bottom habitats on the bayside of
Long Key and Lower Matecumbe that used to be dominated
by sponges are now devoid of all live sponge, and in
many cases there is nothing at all left on those
bottoms other than halimida and some stray octocorals.
I also took a dive in Channel Two and another one on
an oceanside patch reef off Lower Matecumbe, and it
was pretty much the same story there, although there
were a few more surviving sponges in both of those
habitats.  I could estimate the loss on live sponge
material in Channel Two at around 90%, and on the
offshore patch reef around 80%, but those are just
estimates. Channel Two is now a Channel of Death with
dead sponge material littering the bottom and a
ghastly look everywhere.  It's almost as if you went
into a lush hardwood hammock and cleared all the
underbrush away from the trees and just left the trees
standing.  It's empty looking.  All those little
clumps of sponge that used to dot the bottom and fill
in niches in the coral habitat are all gone, leaving
an empty reef.  I don't know how this is going to
affect the fish and invertebrate populations in that
channel, but anything that depends on sponge for food
or habitat will starve to death until more sponge
grows back.  Like the grass flat at Old Dan, in many
cases the sponge is the glue that held some of these
coral structures together, and now that it's all died
off, many of the structures are going to fall apart
and the habitat is going to seriously degrade.” Ken

Part of the Algal Bloom Status Report of August 2007
by the South Florida Natural Resources Center states: 

•	Based on chlorophyll a mapping from NOAA and
satellite imagery (Figure 1), it appears the bloom
originated sometime in May in the central part of the
Bay, and it has spread to at least over half the
central part of the Bay by this time.  Chlorophyll a
is the primary photosynthetic pigment used by algae
and an indicator of phytoplankton blooms.  

•	Potential collateral impacts from the bloom:
1.	Low night-time dissolved oxygen, especially since
water temperatures are very high (in the 90’s)
2.	Benthic community impacts from DO declines:
3.	fish kills
4.	invertebrate kills (i.e. sponges)
5.	seagrass die-off
6.	SAV impacts from light attenuation (defoliation
and/or die-off)

So what can we do about these persistent algae blooms,
well, nothing
. and everything. Algae blooms are
created by nutrients, some natural, and mostly
because we, in some way, added these nutrients to the
nearshore waters. It may be from inadequate treatment
of sewage, excess nitrogen and phosphate from runoff
and river deposition, road construction, removal of
natural nutrient sinks (marshland and mangroves),
injection of water from offshore upwellings, and many
other sources, some remote and some local. What must
be done is to correct the abuses we have heaped on our
ecosystem, a huge task, but we can do it.

The answer is to clean up our near shore waters and to
"Get the Water Right" in the vast Everglades water
system. Anything less will not cure the present and
future ecological disasters that befall us. Make no
mistake, the total loss of a major component, the
sponges, of the Florida Bay ecosystem is an ecological
disaster, even if it is not patently obvious to us as
we speed over these devastated algae bottoms and sea
grass beds in our go-fast boats. 

Martin Moe

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