[Coral-List] Parrotfish (and Urchin Introductions)

Martin Moe martin_moe at yahoo.com
Thu Aug 7 13:20:30 EDT 2014



This seems like a good place to bring this up. In my work
with culture of Diadema I have encountered problems in larval development,
attainment of competency, settlement, metamorphosis, and early juvenile survival
that were not present in a recent successful rearing of Tripneustes. Diadema,
however, have a greater susceptibility to environmental pollution than other
urchins. Now, there are many potential causes for these problems, especially in
a small, very limited wet lab, but I have come to wonder about, and suspect,
that the variable presence of endocrine disruptors may be one of the problems. The
water I am using comes from Florida Bay, but a location very near to the large
tidal exchanges with oceanic water through the Channel 5 and Channel 2 inlets.
Florida Bay is a sink for nutrients from South Florida and from run off in Gulf
rivers from the Mississippi to the Shark River out of the Everglades. And there
is a “dead zone” the size of Connecticut offshore of the Mississippi River,
which is a good indication that more than just nutrients flow into the Gulf in this
watershed from the central US. I do clean the water with chlorination and heavy carbon filtration but more intensive filtration of raw water is not available to me.

 
From my limited academic perspective, I think that there are
two significant unknowns when it comes to “pollution” that affects tropical
western Atlantic coral reefs. 1. Are endocrine disrupting chemicals present,
perhaps variable and of course depending on location, in waters and sediments on
these reefs in concentrations that can affect larval invertebrate development?
2. And if so, what are they, when are they, in what concentrations, and what effects on
various larvae might they have? I realize that answers to these questions
entails a very great expenditure of time, money, and science; and I know that such answers will not be soon available. But I hope that these difficulties will not
cause them to be ignored and swept under the rugs of
politics and funding difficulties.
 
Quite some time ago I gave up writing peer reviewed
scientific papers. The reasons were that I no longer had employment with a research
institution, it was quite expensive to publish as an individual in journals, and writing for magazines and self published books resulted in income
rather than outgo. Selfish, true, but necessary, and I have continued to use
the “grey literature” to report my work. There are two articles I recently published
in CORAL magazine that may be of interest and helpful to some on the coral list.
 
Endocrine disruptors: On finding invisible pollution in my
backyard: CORAL, 2012, January/February, Volume 9, No. 1, pp 30 - 40; and Breeding the West Indian Sea Egg:
Tripneustes ventricosus: CORAL, 2014, July/August, Volume 11, No. 4,  2014, pp 80 - 94.

 
I would be glad to send a PDF of each or either to anyone
that requests at this email address, keysmmoe at gmail.com.

Martin Moe



On Tuesday, August 5, 2014 3:50 PM, John McManus <jmcmanus at rsmas.miami.edu> wrote:
 


Clearly I should do more deep night diving. I stand corrected on the Diadema
depths. This is another example of the general literature being misleading.
Agassiz went a little overboard in saying one should "study nature, not
books",
 but he had a good point. And, even studying hundreds of reefs in
daylight does not tell one everything important  about reefs at night.  

For the Keys, the nutrient question has been studied quite well, and there
are strong indications that nutrient loading from land is not the main
issue. In some other reef areas, the impacts of nutrient loading are quite
clear. One can sometimes trace algal abundances, especially as epiphytes on
seagrass, easily back to sources such as groundwater outflows, pipes,
streams, or golf courses. Broader inflows from agriculture are often
 harder
to distinguish, as they often co-occur with overfishing. 

I don't put much faith in basing nutrient loading decisions only on water
quality measurements except in unusually strong cases. Nutrients may enter
the reef, especially during storms, and immediately become incorporated into
algal tissue. Only total nutrient budgeting, experimental growth studies
(such as rates of growth on slides) and time series are likely to be
reliable in the average case. 

Speaking of perspective, it is
 important as well that everyone stays
cognizant of the potential differences between Caribbean and
Indo-Pacific-Red Sea reefs. Most of the world's reefs are not
 Caribbean
reefs, and are much different. Some of the differences are nicely summarized
in:

Roff G, Mumby PJ (2012) Global disparity in the resilience of coral reefs.
Trends in Ecology and Evolution 27:404-413.

Despite this, the general objectives of reef management remain the same --
minimize overfishing, pollution, sedimentation, direct damage from boats,
etc. Where possible, one should thoroughly investigate to identify how much
each stressor is a problem locally.  Unfortunately, for
 hundreds of
thousands of reefs and coral patches, that is unlikely to ever be the case.
Most reef management must be based on broad area trends, minimal
observations, and clear thinking. 

Cheers!

John 














-----Original Message-----
From: Szmant, Alina [mailto:szmanta at uncw.edu] 
Sent: Tuesday, August 05, 2014 1:38 PM
To: John McManus; coral-list at coral.aoml.noaa.gov
Subject: RE: [Coral-List] Parrotfish (and Urchin Introductions)

Hi John:

The concept that Diadema were only abundant in shallow reef waters is
incorrect, and due to few people having done night dives at depth on
Caribbean reefs before the die-off.  My observations at the 70-90 ft depths
at night
 were that the reef looked like a pin cushion with Diadema coming
out from the deeper ledges where they sheltered in the daytime.

In the FL Keys, the corals went downhill starting in 1987 with the onset of
almost annual bleaching events, in the presence of many, many grazers (Mark
Hay documented some of the highest grazing fish bite rates in Keys).
Diadema was already gone, but Keys have always had plenty of herbivorous
fishes.  Nutrients in the keys reefs are not the cause of any algal blooms
(see Szmant and Forrester 1996 for a comprehensive study of water column and
sediment nutrients).  Later work funded by COP again showed Keys reef
 waters
to be very low in both nutrients and Chla.  Nutrient enrichment experiment
have shown that the common/dominant reef algae such as Halimeda and Dictyota
actually do poorly with nutrient enrichment.  So at least in the case of the
FL Keys, to me it is clear that global warming has been THE cause of coral
loss leading to too much open substrate for algal colonization.  As Williams
and Polunin (2001) showed, fishes can only eat so much even when there are
plenty of them.

Alina



"Great minds discuss
 ideas; average minds discuss events; small minds
discuss people." Eleanor Roosevelt

"The time is always right to do what is right"  Martin Luther King

*************************************************************************
Dr. Alina M. Szmant
Professor of Marine Biology
AAUS Scientific Diving Lifetime Achievement Awardee Center for Marine
Science University of North Carolina Wilmington
5600 Marvin Moss Ln
Wilmington NC 28409 USA
tel:  910-962-2362  fax: 910-962-2410  cell: 910-200-3913
http://people.uncw.edu/szmanta
*******************************************************


-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of John McManus
Sent: Tuesday, August 05, 2014 12:40 PM
To: coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Parrotfish (and Urchin Introductions)

Thanks for pointing out the that Diadema involves both pros and cons. Of
course, we also must keep in mind that Diadema tends to be depth
 limited --
being normally abundant in the Caribbean in the top 10-15 meters. 

I want to urge everyone to actually read the whole report. Parrotfish come
across from the summaries and news articles as the new 'pandas'. Actually,
the report covers lots of herbivores, including Diadema, and various
acanthurids (surgeonfish and doctorfish). It also covers sedimentation and
nutrient loading. The evidence presented does tend to warrant some extra
attention for maintaining parrotfish populations, but clearly a holistic
approach is needed.  

If we assume, as some recent evidence indicates, that pristine reefs
generally had inverted biomass pyramids (more biomass in predators than
herbivores), then what we usually see now has passed from inverted pyramids
to upright pyramids to fleshy algal dominance. The latter state tends to be
self-perpetuating, due to high recruitment and growth rates, exclusion of
settling spaces for other organisms, overgrowth of living corals in some
areas, and exclusion of critical habitat features for herbivorous fish. In
cases where nutrient loads
 have been partly at fault, these will often have
to be reduced as a precondition to recovery. Then fleshy algal dominance
must be overcome by perturbations such as storm waves combined with
unusually high abundances of herbivores.  The reef communities must be reset
and put on new pathways. If there is any hope of returning some reefs closer
to near pristine states, they must first pass through the high herbivory
stage, even amid some negative impacts. 

Of course, bleaching, diseases, and ultimately acidification can be expected
to
 make fleshy algal dominance more and more likely to occur. However, we
cannot blame these things for the current state of many reefs until the
obvious steps of decreasing nutrients and increasing herbivory have been
taken. We have to stop kicking the patients. 

Cheers!

John    



-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Szmant, Alina
Sent: Tuesday, August 05, 2014 11:11 AM
To: David Fisk; coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Parrotfish (and Urchin Introductions)

Thanks Dave.  I have photos from the 1970s and pre-1982 Caribbean that show
exactly that...Diadema grazing scars on the corals, over-grazing of the
substrate by the sea urchins.  And I am guessing the low rates of coral
recruitment in the few pre-1983 studies (before bleaching started affecting
the corals, and there was 60+ % coral cover, but before we figured out the
coral spawning cycles) was due to over-grazing by too high densities of
Diadema.. We hated Diadema back then and did not hesitate to bludgeon a few
to clear a path
 to the substrate, much to the delight of the wrasses!

There is no magic bullet to fix what is wrong with Caribbean reefs.  Healthy
fish grazer communities are just as important
 as healthy (not too many, not
too few) Diadema populations, but even more critical is environmental
conditions the corals can tolerate (i.e. not too hot in the summer as has
been experienced since the late 1980s).  



"Great minds discuss ideas; average minds discuss events; small minds
discuss people." Eleanor Roosevelt

"The time is always right to do what is right"  Martin Luther King

*************************************************************************
Dr. Alina M. Szmant
Professor of Marine Biology
AAUS Scientific Diving Lifetime Achievement Awardee Center for Marine
Science University of North Carolina Wilmington
5600 Marvin Moss Ln
Wilmington NC 28409 USA
tel:  910-962-2362  fax: 910-962-2410  cell: 910-200-3913
http://people.uncw.edu/szmanta
*******************************************************

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of David Fisk
Sent: Monday, August 04, 2014 11:53 PM
To: coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Parrotfish (and Urchin Introductions)

If it only was so simple to "put more effort and resources towards
reestablishing this keystone invertebrate herbivore", ie, in this case,
urchins. In itself, this most likely will not fix the issue for the obvious
reason that there needs to be natural controls on the urchin population.

Without a check on numbers by urchin predators, the reefs will
 be overgrazed
like many in the Pacific where the carbonate base and fabric of some reefs
are diminishing because of large populations of urchins. Urchin overgrazing
results in algal free substrates but there is no new coral recruitment
happening either, and the remaining live corals are undercut and eventually
carried away by waves and storms.. Eventually, increased exposure of adjacent
coastal areas to storm waves
 are one consequence of this situation. I have
seen reefs in the Pacific where it appears that up to 30-40cm of limestone
pavement has been eroded away by urchins, judging by the age and size of the
remaining few large live corals, which were probably less than 50 years old.

There is plenty of evidence in the literature indicating that too little or
too much grazing pressure will lead to different but equally undesirable
outcomes. Furthermore, a single beneficial grazing level and density of
grazers (fish or invertebrate) that will enhance natural coral recruitment
will not necessarily be the same for all locations.

It might be worth trying a small trial study for urchin introductions, but
such an intervention would clearly have to have a longer term management and
monitoring component to head off further problems, bearing in mind the known
consequences of getting it wrong, as well as allowing for the risk of some
unknown detrimental factor coming into play.

Cheers, Dave Fisk
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