Reef Science: Development Highlights
Lesser Michael P., Mazel Charles H.,
Gorbunov Maxim Y., and Falkowski Paul G. 2004. Discovery of symbiotic nitrogen-fixing cyanobacteria
in corals. Science 305: 997-1000.
Colonies of the Caribbean coral Montastraea
cavernosa exhibit a solar stimulated orange-red fluorescence
that is spectrally similar to a variety of fluorescent proteins
expressed by corals. The source of this fluorescence is phycoerythrin
in unicellular, nonheterocystis, symbiotic cyanobacteria within
the host cells of the coral. The cyanobacteria coexist with
the symbiotic dinoflagellates (zooxanthellae) of the coral
and express the nitrogen-fixing enzyme nitrogenase. The presence
of this prokaryotic symbiont in a nitrogen-limited zooxanthellate
coral suggests that nitrogen fixation may be an important
source of this limiting element for the symbiotic association.
For many years, the presence of orange
fluorescent morphs of M. cavernosa has interested divers
and researchers alike. The colonies are generally found in
moderate depth water, and they are fluorescent orange during
the day. Similarly, a number of Indo-Pacific corals are fluorescent
orange by day, such as various fungiids like some Diaseris
and Cycloseris, and these too are often found in deeper
water. At least in M. cavernosa, the fluorescence is
not due to the fluorescing proteins that are responsible for
most bright coloration in zooxanthellate corals, nor are they
due to the golden brown zooxanthellae. Instead, these colonies
harbor other intracellular symbionts besides zooxanthellae,
and they are cyanobacteria. Cyanobacteria are able to fix
nitrogen, generally considered to be a limiting nutrient for
both corals and zooxanthellae and present at very low levels
in seawater. Nitrogen needs of corals, required for tissue
growth, reproduction, and protein synthesis, are often acquired
largely by feeding on particulate material and zooplankton.
A primary question will be why these morphs harbor high densities
of cyanobacteria while others do not, or perhaps host lower
numbers that do not result in the orange fluorescence. Another
question will be how widespread this type of symbiosis might
be in other species. The presence of symbiotic bacteria, algae,
and now cyanobacteria highlights the importance of such associations
in species diverse coral reefs and adds another level of complexity
to the ecology and biology of corals.
The Tenth International Coral Reef Symposium,
Okinawa, Japan - June 28-July 2, 2004
The coral reef conference of the International
Coral Reef Society, the largest of its kind, is held every
four years. For those who have ever attended, it is a wealth
of information and a very exciting event to learn the most
recent research and thoughts regarding all aspects of coral
reefs. This year, the abstracts for the conference presentation
are available, so I need not summarize the event. They are
available for download as a .pdf file at http://www.plando.co.jp/icrs2004/
There were several major areas that represented
a great number of topics. There was a great deal of research
on the symbiosis between corals and their diverse zooxanthellae,
and many on the roles of restoration, disease and global warming/global
change on coral reefs. I was, unfortunately, unable to attend
as many interesting topics as I would have liked, as I was
extremely busy during this conference in various sessions.
This year, I chaired a mini-symposium.
"Coral Reef Aquarium Husbandry: A Tool for Science,"
and co-chaired a mini-symposium with Andy Bruckner, "Aquarium
Trade Issues: Addressing Sustainability of the Ornamental
Coral Reef Species Trade through Improved Management of Wild
Harvest and Environmentally-Friendly Coral Farming and Aquaculture
Approaches." Dana Riddle was scheduled to present a topic
on coral farming during the latter symposium, but apparently
was unable to attend. I had looked forward to seeing another
person with ties to the reef aquarium hobby at the conference.
I will be discussing aspects of these symposia in upcoming
articles for Reefkeeping Magazine. I also presented
the following five topics in various sessions:
"Reproduction in Aquarium Corals," in which
I summarized the novel and known asexual and sexual reproductive
events known from corals in aquaria.
"Apoptosis in Diseased Reef Corals: A First Look,"
in which I described the presence of apoptosis as a mode
of cell death in corals with white band disease and shut-down
reaction, and the ability to trigger apoptosis with known
"Pathologies Affecting Reef Corals at the Flower
Garden Banks, Northwest Gulf of Mexico," in which I
described disease incidence and several new pathologies,
based on work I have done on these reefs over the past two
"Pathologies Affecting Reef Corals in Captivity,"
in which I described diseases that occur in coral in aquaria,
"Coral Reef Guinea Pigs: Culture of Research Clonal
Lines for the Coral Disease and Health Consortium,"
in which I presented the status of the coral culture facility
in which clonal lines are being developed for disease researchers.
The conference proceedings will not be
available for quite some time, but should be more affordable
to interested persons than in years past as there will be
a CD version. I will announce to members of Reef Central when
they become available.
L. Shimek, Ph. D.
K. B. Heidelberg, K. B., K. P. Sebens
and J. E. Purcell. 2004. Composition and sources of near reef
zooplankton on a Jamaican forereef along with implications
for coral feeding. Coral Reefs (2004) 23: 263-276.
Nocturnal near-reef zooplankton from the
forereef of Discovery Bay, Jamaica, were sampled during winter
and summer 1994 using a diver-operated plankton pump with
an intake head positioned within centimeters of benthic zooplanktivores.
The pump collected zooplankton not effectively sampled by
conventional net tows or demersal traps. We found consistently
greater densities of zooplankton than did earlier studies
that used other sampling methods in similar locations. There
was no significant difference between winter (3491 ±
578 per m3) and summer (2853
± 293 per m3) zooplankton
densities. Both oceanic- and reef-associated forms were found
at temporal and spatial scales relevant to benthic suspension
feeders. Copepods were always the most abundant group, averaging
89% of the total zooplankton, and most were not of demersal
origin. The cyclopoids, Oithona spp., were the numerically
dominant organisms, with an average density of 1684 ±
260 per m3. Other zooplankton
(e.g., shrimp larvae, crab larvae, polychaetes, chaetognaths,
amphipods, and isopods) were highly variable and much less
abundant. Near-reef zooplankton abundances were high throughout
the night sampling period, not just after sunset and before
sunrise as previously described. Mean biomass was 4.5 mg C
per m3, with values ranging
from 1.0 to 15.6 mg C per m3.
This work has important implications for evaluating which
zooplankton types are available to benthic suspension feeders,
One more of a series of papers showing
how numerous available zooplankton are for coral consumption
and how important it is that the corals have this food available
to them. The reader is referred to Eric Borneman's series
on feeding the reef in Reefkeeping.com in 2002 and 2003 for
some earlier data about feeding.