[Coral-List] Coral nutrition (Andrew Trevor-Jones)

Fri Jun 2 21:41:46 EDT 2006

G'day Folks,

I'm new to the list but I do seem some very familiar names.  My name is 
Andrew Trevor-Jones.  I'm predominately an aquarist, but have a degree in 
marine biology.  Unfortunately, when I graduated in 1982 there were very 
few jobs in the marine biology in Australia, so it is more of a hobby.

I take a more complete view of nutrition, and include N, P and other 
elements/compounds, rather than just C.  While organic carbon is very 
important to the survival of corals, they also need N and P.  Yonge and 
Nicholls (1931) demonstrated the need for more than just carbon.

It is my understanding that corals (on their own) are not able to convert 
inorganic carbon to organic carbon and so their only sources of organic 
carbon are from the zooxanthellae or prey capture (including "capture" of 
bacteria).  The organic carbon is their main source of energy other than 
digesting their own tissues.  The zooxanthellae rely on their host for N 
and P, but that is more a statement on the availability of inorganic N and 
P in the water column.  The main source of N and P for the corals is 
likely to be prey capture, although Hoegh-Gulberg and Williamson (1999) 
demonstrated that at least one species of coral can take up and utilise 
inorganic nitrogen.  Other studies have shown how prey capture by the 
corals can increase growth rates in both the coral and the zooxanthellae. 
The energy required for prey capture comes from the organic carbon so even 
if there isn't much prey around, the products of the zooxanthellae provide 
the energy for the coral to keep trying.

I try to feed all the corals in my aquaria (which in itself is a lot of 
fun: http://www.petsforum.com/personal/Trevor-Jones/coralfeedingiii.html ) 
but I do know that many aquarists don't believe they need to or just 
couldn't be bothered.  As Charles suggests, I think the survival of corals 
in aquaria without direct feeding is more due to the higher level of 
dissolved N and P coupled with the good lighting.

Bleached corals are doubly disadvantaged.  Not only are they missing the 
energy provided by the zooxanthellae that have left, but they have less 
energy they can use for prey capture.  When they starve, it will not only 
be because of lack of organic carbon, but also the lack of N and P.  Even 
if there was sufficient inorganic N and P in the water column, without 
organic carbon, the corals won't have the energy to utilise the N and P.

This is just some of my thoughts on the subject.

Andrew.

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Today's Topics:

   1. Re: [SPAM] Re:  coral bleaching: response to Goreau
      (Charles Delbeek)
   2. starvation? (Andrew Baird)
   3. coral feeding questions (Zac Forsman)

----- Message from Charles Delbeek <delbeek at waquarium.org> on Thu, 01 Jun 
2006 11:07:53 -1000 -----
To:
coral-list at coral.aoml.noaa.gov
Subject:
Re: [Coral-List] [SPAM] Re: coral bleaching: response to Goreau

There are a couple of points in this discussion that I feel the need 
to address:

1) Shops selling phytoplankton as coral food - most research that I 
have read involving feeding in stony corals deals mainly with the 
ingestion of ZOOplankton. Soft corals, particularly azooxanthellate 
ones such as Dendronephthya have been shown to feed on phytoplankton. 
This makes sense to me since most of these corals lack nematocysts 
and their polyp structures appear to be more suited for sieving food 
from passing water than stinging and capturing it as can be seen in 
stony corals which all seem to have nematocysts ... why sting a 
phytoplankton cell to capture it which is basically a passive entity 
unlike a struggling copepod?

I have a pet theory that people who report responses from corals when 
fed phytoplankton could be seeing the result of any number of factors 
such as the addition of nutrients, the decay of phytoplankton leading 
to increased nitrogen and phosphorous levels, to the increase in 
filter feeders and hence, an increase in reproduction of these i.e. 
more zooplankton being generated.

2) Feeding vs. non-feeding of corals in captivity - yes corals will 
feed on zooplankton and more meaty food in the case of corals with 
polyps large enough to take them. No one disputes this. What is in 
question is do corals in captivity need this? Given that nitrogen, 
phosphorous and organic nutrient levels are generally several times 
that found on natural reefs is this enough to keep the corals 
"happy"? The success of aquarists in Europe with stony and soft 
corals in the 1970s and 1980s, without any feeding, would tend to 
support this idea.

3) The role of dissolved nutrients - The Waikiki Aquarium has been 
keeping, propagating and spawning stony corals, mainly Acropora, 
Montipora etc since the late 1970s. We have never added any sort of 
zooplankton or phytoplankton to our systems. We use a saltwater well 
as a water source for the majority of our exhibit and they are 
semi-open systems. The well is 80ft down in coral rock, the chemistry 
of this water has been discussed in Atkinson et al. 1995, there is no 
zooplankton or phytoplankton in this water. That is not to say that 
there isn't any bacteria in the water, or that there could be 
plankton being generated in the systems themselves. All I can say 
with absolute certainty is that WE do not feed the corals. Yet, we 
have observed the release of eggs, sperm and egg/sperm bundles in 
corals such as Acropora, Sandalolitha, Montipora, Euphyllia and 
Goniopora. What our water IS rich in is nitrogen, phoshporous, iron, 
managense,  carbon dioxide etc. ... so my feeling is that the 
zooxanthellae and perhaps the coral tissue itself, is getting more 
than enough of what they need from the water.

4) Increasing contact with the aquarium community - there is an 
annual conference in North America called The Marine Aquarium 
Conference of North America (MACNA), this year it will be held the 
weekend of Sept 23rd in Houston, Texas. This annual conference is the 
best place to meet with and observe what hobbyists are doing. There 
have been several marine scientists who have spoken at this 
conference such as Giselle Mueller-Parker, Daphne Fautin, Marlin 
Atkinson, Charlie Veron, Robert Myers, Bob Richmond, Cindy Hunter ... 
to name just a few. While there is some contact with hobbyists by the 
scientific community there is certainly room for much more. I think 
this sort of interaction will only increase for the simple fact that 
many of the up and coming marine scientists today have started off by 
keeping reef tanks as a hobby, and I am in fact seeing this already. 
There are of course other such conferences in Europe held in Germany, 
France, Belgium and The Netherlands. Next April there will be a 
conference in The Netherlands dealing specifically with the captive 
husbandry of corals in public aquariums, of which I am a member of 
the steering committee ... we would dearly love to have a strong 
representation from the scientific community especially in the field 
of coral nutrition, effects of UV, coral colouration, coral 
reproduction, etc etc. The days of marine scientists claiming it was 
impossible to keep live coral while hobbyists in Europe and elsewhere 
were already doing so, are thankfully behind us for the most part.

Finally, I think one needs to be cautious about making sweeping 
generalizations about what corals need or don't need in terms of 
feeding when it is becoming increasingly obvious that the corals have 
various abilities to gather, use and process sources of nutrition 
spread across the genera.

Aloha!

J. Charles Delbeek M.Sc.

Aquarium Biologist III
Waikiki Aquarium,
University of Hawaii
2777 Kalakaua Ave.
Honolulu, HI, USA 96815
www.waquarium.org

808-923-9741 ext. 0 VOICE
808-923-1771 FAX

----- Message from Andrew Baird <andrew.baird at jcu.edu.au> on Fri, 02 Jun 
2006 10:04:46 -----
To:
coral-list at coral.aoml.noaa.gov
Subject:
[Coral-List] starvation?

Dear Corallist

The following reference has some of the only data on species level rates 
of
mortality on the GBR. Some die fast, some slow, possibly related to
differing levels of heterotrophy and there was considerable variation
between individuals in rates of recovery.

Baird AH, Marshall PA (2002) Mortality, growth and reproduction in
scleractinian corals following bleaching on the Great Barrier Reef. Mar
Ecol Prog Ser 237: 133-141

ABSTRACT: Despite extensive research into the coral bleaching phenomena
there are very few data which examine the population biology of affected
species. These data are required in order to predict the capacity of 
corals
to respond to environmental change. We monitored individual colonies of
4common coral species for 8 mo following historically high sea-surface
temperatures on the Great Barrier Reef in 1998 to compare their response
to, and recovery from, thermal stress and to examine the effect of
bleaching on growth and reproduction in 2 Acropora species. Platygyra
daedalea and Porites lobata colonies took longer to bleach, longer to
recover and longer to die. In contrast, Acropora hyacinthus and A.
millepora colonies bleached quickly and most had either recovered, or 
died,
within14 wk of the initial reports of bleaching. Whole colony mortality 
was
high in A. hyacinthus (88%) and A. millepora (32%) and partial mortality
rare. In contrast, most colonies of P. daedalea and P. lobata lost some
tissue and few whole colonies died. The mean proportion of tissue lost per
colony was 43 ± 6.6 % and 11 ± 1.1 % respectively. Consequently, observed
hierarchies of species susceptibility will depend critically on the time
since the onset of stress and must consider both whole and partial colony
mortality. Colony mortality was highly dependent on visual estimates of 
the
severity of bleaching but independent of size. Growth rates of Acropora
colonies were highly variable and largely independent of the severity of
bleaching. A. hyacinthus was more susceptible to bleaching than A.
millepora with 45% of surviving colonies gravid compared to 88%. High
whole-colony mortality combined with a reduction in the reproductive 
output
of surviving Acropora suggests that recovery to former levels of abundance
is likely to be slow.
Dr Andrew H. Baird, Senior Research Fellow ARC Centre of Excellence for
Coral Reef Studies, Department of Marine Biology, James Cook University,
Townsville, Qld, 4811, Australia. Tel + 617 47814857, Fax:  + 617 
47251570,
email: andrew.baird at jcu.edu.au 

http://www.coralcoe.org.au/research/baird.html

----- Message from Zac Forsman <zforsman2001 at yahoo.com.au> on Fri, 2 Jun 
2006 01:13:37 -0700 (PDT) -----
To:
coral-list at coral.aoml.noaa.gov
cc:
grottoli.1 at osu.edu
Subject:
[Coral-List] coral feeding questions

Great comments Charles!

  -I have one question though: the tanks at the
Waikiki Aquarium all have live rock/sand/gravel. 
Might these serve as refugia for populations of all
kinds of micro organisms that the corals could feed
on?  Increased nutrients might be used by the coral..
but they could also cause a bottom up trophic cascade
that benefit the coral.  Might also increase the
detritus or 'marine snow' in the tank.

I have one other question for Andrea:

   For the studies you mentioned that looked at
zooplankton, did they arrive at those conclusions by
looking at gut contents?  Would that bias the counts
towards critters with a hard carapace?

Is anyone aware of any other controlled feeding
studies out there?

-Just curious,  Zac

Zac Forsman, Ph.D.
Postdoctoral Fellow
Department of Biology
2450 Campus Rd.
Honolulu HI, 96822
http://www2.hawaii.edu/~zac/

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