[Coral-List] Diademia Coral-List Server

Fri Oct 6 15:05:28 EDT 2006

There is such a wealth of information on this topic that it seems  
fruitless to even begin any sort of literature "justification" in  
posts. Workshops, meetings, special issues of journals, reports, and  
more have debated bottom up and top down factors for decades and at  
this point if we do not realize that both, and more, play roles in  
community structuring then we are indeed in trouble. As Martin said,  
the complexity is enormous and, in fact, each reef is different. The  
polarization of views regarding factors contributing to coral reef  
decline or to the reasons for the existence of alternate stable reef  
communities, such as phase shifts, as being due to a single dominant  
ecological, biological, or environmental factor serves to hinder  
understanding unless, of course, that particular reef is strongly  
influenced by one or a few dominant factors.

  But what it comes down to in my mind, at least, is the following?

How then do you explain luxuriant coral growth to the near exclusion  
of macroalgae in nutrient rich lagoons (many examples in the Pacific,  
even with high sedimentation rates from decaying vegetation) but  
macroalgal abundance in remote, offshore nutrient poor and population- 
free areas (e.g Mona Island, Glover's reef)?

Why are algal blooms transient and reef coral-dominated at the Flower  
Garden Banks despite relatively low Diadema densities? Is this a  
bottom-up factor community or is it because there are a lot of  
grazing fish by comparison with other Caribbean reefs?

Historically, I think, it is pretty well demonstrated that the  
Caribbean was out of whack before anyone really started studying it,  
and since then I think it is also pretty well established what a  
critical role Diadema played throughout most of the Caribbean in more  
recent times. There are currently sites with relatively high Diadema  
and relatively low coral cover, and conversely low Diadema and high  
coral cover.  Maybe the the historical grazing factors are forever  
lost, and maybe Diadema is rightly credited for allowing for the  
conditions Martin alludes to in his words and the studies cited (I  
think he is, fwiw), for indeed where there are a lot of Diadema,  
there tends not to be much macroalgae.

Moreover, there are areas with no Diadema having lots of macroalgae   
and areas with Diadema having no macroalgae separated literally by a  
few meters of sand from each other.

As to aquariums, the fact that you can grow corals in closed systems  
with highly elevated nutrient levels without macroalgal dominance in  
the presence of high and diverse numbers of grazers is a certainty,  
as well as the certainty of absolute dominance of algae over corals  
in closed systems that lack any grazers. In the latter case, the  
algae pulls nitrogen and phosphorus to almost unmeasurable levels in  
the water column to the point where other nutrients become limiting  
to further growth. Even corals not eventually overgrown with algae  
eventually die, likely from starvation. Where does this leave us?

Eric

_______________________________
Eric Borneman
Department of Biology and Biochemistry
University of Houston
Science and Research Bldg. II
4800 Calhoun Rd.
Houston, TX 77204-5001

ph: 713-743-2667

On Oct 6, 2006, at 9:23 AM, Martin Moe wrote:

> Hi James,
>
> You make some very good points in your post. I am, of
> course, not unaware of the great stresses we have
> placed on our reefs from anthropogenic release of
> nitrogen and phosphorus, addition of a great variety
> of organic and inorganic pollutants, global warming,
> microorganisms and nutrients from sewerage discharge,
> outfall, and seepage, environmentally unsound and
> unsustainable fishing practices, and just excessive
> human visitation. And these problems must be, and are
> being, addressed. But the biological world is very
> complex and coral reefs are among the most
> ecologically complex ecosystems that exist.
>
> It has been demonstrated that return of Diadema to
> stressed reefs improves coral ecology. For example
> Carpenter and Edmunds (Ecology Letters, (2006) 0:
> 271-280 stated, “Here, we show that dense populations
> of Diadema now occur over a multi-kilometer wide scale
> at six locations scattered along a 4100 km arc across
> the entire Caribbean. In all cases, these dense
> populations are found in shallow water (<6 m depth) on
> outer reef communities and are associated with reduced
> macroalgal cover and enhanced coral recruitment. We
> conclude that grazing by this echinoid is creating
> conditions favoring the recruitment of coral.” And the
> concluding statement in the paper by Precht and
> Aronson, Death and Resurrection of Caribbean Coral
> reefs, a palaeoecological perspective, (November 2005,
> Coral Reef Conservation, Cambridge University Press,
> Zoological Society of London, 2006). “…. recovery of
> the sea urchin D. antillarum is probably the key to
> facilitating coral recovery throughout the region.”
> There are a number of other recent papers as well that
> document and explore the phase shift from algae to
> coral that occurs when Diadema return to the reefs,
> significantly in Jamaica, where the reefs have been
> long studied.
>
> But as I mentioned, coral reefs are a very complex
> ecosystem and “one size does not fit all”. I’m sure
> that there are situations, especially in areas under
> development and near population centers, where the
> effects of herbivory would be greatly overshadowed by
> human influence and effluence. Also the presence or
> absence of complex reef structure influences the
> success of Diadema establishment. Extensive complex
> habitat greatly aids recovery of Diadema. (Habitat
> complexity and consumer-mediated positive feedbacks on
> a Caribbean coral reef Lee, 2006. and Rapid
> Phase-Shift Reversal on a Jamaican Coral Reef. Idjadi,
> Lee, Bruno, Precht, Allen-Requa, and Edmunds, Coral
> Reefs (manuscript submitted Nov. 2005) Reestablishment
> of Diadema populations in isolated areas where there
> is little cover probably depends on the kind of
> massive recruitment that can only occur when dense
> populations are widespread over a great area. However,
> all in all, recovery of Diadema where and when it can
> occur is a very good thing for a coral reef.
>
> However, as you mention there is the specter that the
> forces of development and the political support that
> developers acquire (buy?) can use loss of herbivory
> and the potential to replace herbivory as tools to
> create support for environmentally unsound
> development. As deplorable as this may be, ignoring
> and repressing research on the potential of returning
> hervibory to Atlantic reefs because it may be used as
> a development tool, is, to put it mildly, counter
> productive. Return of herbivory is an important tool
> in coral reef restoration efforts, but by no means the
> only tool.
>
> I hope I have not given the impression that I am
> arguing that there is no validity in the points you
> have raised, this was not my intent for this is not
> true. I know that repair of coral reef ecology is more
> than just restoration of herbivory. My position is
> that there are many stresses on coral reefs,
> especially on our Florida reefs, that can not be
> ignored, and loss of herbivory is one of the greatest
> of them. We should do all that is possible to return
> effective herbivory since that will improve the
> ecology and resilience of the reefs and enhance coral
> growth, settlement, and survival. And this should be
> done in addition to efforts to reduce anthropomorphic
> stress, and not at the expense of these efforts. I
> think concentrating solely on either the “top down” or
> “bottom up” concept of reef restoration would be a
> mistake, because successful coral reef restoration
> will require efforts from both directions. There must
> be cooperation and collaboration in the science to
> save what can be saved of our coral reefs.
>
> Martin
>
>
> --- "Dr. James M Cervino" <cnidaria at earthlink.net>
> wrote:
>
>> Hi Martin,
>>
>> I know you are one of the best coral aquarium
>> specialists on the planet as you truly understand
>> the chemical interactions and mechanisms within a
>> closed system. However, I disagree with a few of
>> the comments that were posted below.  I am not
>> saying that Diademia grazing has no impact of the
>> abundance of macro-algae on a reef flat, however,
>> we must never ignore the more important impacts
>> of Nitrogen and Phosphorous above the thresholds
>> needed in a oligotrophic system such as a coral
>> reef (P. Bell,1992, Eutrophication and coral
>> reefs: some examples in the Great Barrier Reef
>> lagoon, Water Research, 26: 553-568; B. Lapointe,
>> & M. Clark, 1992, Nutrient inputs from the
>> watershed and coastal eutrophication in the
>> Florida Keys, Estuaries, 15: 465-476; B.
>> Lapointe, in press, Eutrophication thresholds for
>> macroalgal overgrowth of coral reefs, in K.
>> Thacker (Ed.) Protecting Jamaica's Coral Reefs:
>> Water quality issues; Goreau. T., 1992c, Coral
>> reef protection and coastal development in
>> Western Jamaica, p. 39-65 in K. Thacker (ed.),
>> Protecting Jamaica's coral reefs: water quality
>> issues, Negril Coral Reef Preservation Society,
>> Negril, Jamaica; Goreau, T., & K. Thacker, 1994,
>> Coral reefs, sewage, and water quality standards,
>> Proceedings of the Caribbean Water & Wastewater
>> Conference, Kingston, Jamaica) and to think that
>> grazing will control the will control the
>> abhorrent concentrations of nutrients that are
>> being released into coastal reef zones is
>> erroneous .
>>
>> When we fail to address "bottom-up" measures to
>> protect the habitat first and foremost,  all the
>> Diademia antiullarun in the Ocean Realm will not
>> be able to control the increasing macro-algae
>> forests that the worlds reefs of the new
>> millennium have evolved into. Myself and a
>> research assistant went to an MPA meeting 8
>> months ago on ManO War Cay (10km from  Guana Cay
>> ) where a few "experts"presented a "Top-Down"
>> action plan that will restore the fish
>> populations within designated locations in the
>> Abacos.  MPA plans, such as the one being
>> proposed in the Bahamas 8 months ago, tend to
>> favor the actions of the developers in Jamaica,
>> Bimini and Guana Cay instead of the protection of
>> the coral reefs from the bottom up in the decades
>> to come.
>>
>> PS: Developers that want to build golf courses
>> will use this the nutrient debate in court as
>> they watch the coral list server and sort of turn
>> to it as a reference point.  Lets not allow
>> developers to think that the nutrient thresholds
>> published by the scientists quoted above can be
>> ignored, as this will give them reason to say
>> that the only reason reefs have shifted from
>> productive Cnidarian reef systems to macro algae
>> dominated habitats is due to the grazer
>> disappearing.
>>
>>   James
>>
>>
>>> I am of course, referring to the restoration of
>>> the keystone herbivore of the southwestern north
>>> Atlantic, the sea urchin Diadema antillarum. It is
>>> well documented that when Diadema return to the
>> reefs
>>> in large numbers, the phase shift from coral to
>> algae
>>> is reversed. There is much we don’t yet understand
>>> about this fundamental ecological balance, but
>>> aggressive research projects aimed at furthering
>> this
>>> understanding and developing the technology and
>>> techniques for restoration of this keystone
>> herbivore
>>> should be pursued.  If we do this now, we can
>> reduce
>>> the rate of coral reef decline and hopefully buy
>> the
>>> time we need to fix the huge problems. OK, so I’m
>> an
>>> optimist.
>>>
>>
>> -- 
>> **************************************************
>> Dr. James M. Cervino, MS, Ph.D.
>> Marine Pathology
>> Department of Biological & Health Sciences
>> Pace University New York NYC
>> Phone: (917) 620-5287
>> Web site: http://www.globalcoral.org
>> ***************************************************
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