Reefs At Risk
Steneck at maine.maine.edu
Wed Jun 24 22:37:04 EDT 1998
Dear Les et al.,
Although the decline of Acropora is wide-spread in the tropical west
Atlantic, based on my observations it is more abundant in the Florda Keys
than in many regions of the Caribbean where I've worked over the past
several decades (e.g., Bahamas, Jamaica, St. Croix, St. Kits, Bonaire,
Honduras, and Yucatan coast of Mexico). What I observed several weeks
ago during the field trip in the Florida Keys with the Atlantic and Gulf
Reef Assessment workshop was a fair amount of Acropora palmata (although
some was diseased), evidence of high rates of fish grazing (abundant bite
marks), low macroalgal biomass, and high coralline abundance. Bob
Ginsburg reported on his rapid assessment of patch reefs of the Keys and
the mound corals at least appear to have low rates of mortality.
I was not shocked to read Jack Sobel's report on Reefs at Risk. Many
reefs I've studied, even in rather remote regions of the Caribbean are in
poorer condition than those I've seen in the Florida Keys. However,
before we all run off to conduct remedial action, it might be a good idea
to objectively determine the patterns of reef decline. Are we faced with
a decline in all species or are we primarily reacting to the decline of
Acroporids (due to white band disease)? Are patterns of macroalgae
resulting from changes in the reef's trophic structure (i.e., loss of
grazers) or due to eutrophication or both?
Because the answer to these questions were unclear to me, I felt it
worthwhile to encourage the development of a comensurable Rapid
Assessment Protocol (RAP) that can be used throughout the Atlantic and
Gulf reefs of the Americas. The recent AGRA RAP workshop developed just
such a protocol and 20 groups have agreed to apply it to their reefs.
Plans are being made to reconvene another meeting to consider those
assessments and with it perhaps a clearer understanding of the patterns
and processes will emerge. I suspect we will find that one size does not
fit all. But we should be able to suggest which processes are likely to
produce the warning signs you and others know all too well.
Finally, the Belize shift from Acroporids to Agaricia tenuifolia is
interesting (e.g., Aronson and Precht 1997) but not very many kilometers
to the north on the Yucatan barrier reef the abundance of A. tenuifolia
is no where near as abundant as was the Acropora once was (as evident
from the standing dead A. palmata). So I'm not sure the functional
replacement is widespread or at least it has not happened there yet. For
me, the bigger take-home message from Aronson and Prect's story for
Belize and their subsequent observations is that the natural regenerative
capacity of the reef (i.e., the coral recruitment potential) remained
high because herbivory remained high presumably keeping macroalgal
abundance low. Chuck Birkeland made the same point that algal biomass
interferes with coral recruitment in his classic 1977 ICRS paper.
It seems to me, understanding the patterns of coral reef condition
sufficiently so that plausible forcing-function processes can be
identified should be a priority action item for our coral reef research
community. I think we do need to collectively consider which reefs are
at risk, but we should also identify which reefs are seriously degraded
and which ones are relatively pristine. With such information we should
be better able to apply our remedial actions intelligently and surgically.
Les Kaufman Wrote:
Dear Steve and Phil and everybody,
Reef decline appears to have been widespread in the tropical west Atlantic
over the past two decades. Most prominent is the reduction in prevalence
of acroporid corals, and increase, in many places, of macrophytes. Belize
was unusual in that when the acroporids began to vanish, there was an
endemic agariciid (absent elsewhere in the region) that could serve as a
partial functional replacement, and it did.
Since the original high-coral coverage condition is more highly valued
what we are seeing more of today, it would undoubtedly be most productive
1. appreciate natural trends toward regeneration, and their
2. judge whether natural regeneration is satisfactory
3. develop interventions that facilitate and accelerate
on the largest spatial and smallest temporal scales
Let us presume that Step 2, the regeneration rate concommitant with the
passive approach to reef conservation, is not sufficient to offset rates
degradation in Florida. Note that whether this is or isn't the periphery
of reef growth doesn't matter. All that matters is that reefs can grow
here and it is worth some effort to see that they do. Then we must move
to Step 3.
Step 3 implies aggressive perturbation (some would call it "restoration")
experiments. Looking about, I dont' see a great many such experiments in
progress. Kudos to Richmond and Mueller and their people. What are we
doing to adapt and expand their methodologies? What capabilities do we
need at our disposal?
A. ability to upregulate grazing pressure
B. ability to downregulate nutrient inputs
C. ability to force-recruit corals on a large scale
My own guess is that grazing pressure in Florida is pretty high (though
perhaps the ability to force-recruit Diadema would be helpful on a local
basis); and that if nutrients are a major issue, we are already doing what
we can to reduce the inputs. That means, shouldn't we be looking harder
and more seriously than we are at option "C?" This option offers a
wonderful probe of the resiliency of the system....if healthy live corals
appear on the reef but do not survive, then something probably must be
with A or B, or there is a food web problem with coral predators,
give up on reefs altogether for now because it's a large-scale
environmental health issue that must be addressed first.
Since acroporids and agariciids are the principal corals with response
times and growth rates commensurate with human intervention, should they
not be the principal focus of efforts toward C?
It would be really helpful if we could reach some consensus on this. No
one strategy is sufficient to conserve Florida's reefs, but we should be
coming up with a clear and articulate definition of the top-priority
conservation science and methodologies needed to do the job...and we
aren't, unless I've missed something.
Monitoring IS important, but only in the context of adaptive management.
What are our goals? What shall our complete litany of interventions be?
What room have we left ourselves for trial and error? Are the
experiments well designed and sufficiently powerful to serve our needs?
The alternative is to reduce human impacts as much as possible, and then
watch and wait.
These are two very different, complementary strategies.
What combination of these do we, as a community, advocate?
Robert S. Steneck
Professor, School of Marine Sciences
University of Maine
Darling Marine Center
Walpole, ME 04573
207 - 563 - 3146
e-mail: Steneck at Maine.Maine.EDU
The School of Marine Sciences Web site:
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