Reef Science: Development Highlights
Effects of irradiance, flow, and colony
pigmentation on the temperature microenvironment around corals:
Implications for coral bleaching? Fabricius, Katharina E.
Limnol. Oceanogr., 51(1), 2006, 30-37.
Experiments were conducted to determine
the effects of colony pigmentation, irradiance, and flow on
the temperature microenvironment that corals experience in
shallow water. The warming of colony surfaces increased with
increasing colony pigmentation (darker surfaces) and at high
irradiance but was alleviated by higher water flow. Dark colonies
were up to 1.5°C warmer than ambient seawater at high
irradiance and slow flow. In contrast, very light colonies
were similar in temperature to ambient water at all levels
of flow and irradiance. The darkness of corals progressively
increased along a gradient of decreasing water clarity from
oligotrophic offshore reefs toward turbid high-nutrient reefs
near the coast. The surface temperature of these darkly pigmented
turbid-water corals was significantly greater than that of
the paler corals in the clear-water environments at comparable
seawater temperatures, light, and current conditions. The
surface warming of darkly pigmented colonies in coastal environments
is sufficiently high to exceed their bleaching threshold during
warm, calm, and clear seawater conditions.
The above article suggests that darker-colored (brownish)
corals might be susceptible to bleaching at a lower temperature
than the more colorful (less brownish) corals. The explanation
is that the darker corals absorb more heat (in the form of
light) and get warmer compared to more colorful corals. It
also suggests that water flow aids in lowering the temperature
of the dark colored corals more towards the ambient water
temperature. This is not surprising since a higher flow rate
will facilitate a faster removal of heat.
Contribution of phytoplankton and bacterial cells to the
measured alkalinity of seawater. Kim, Hyun-Cheol, Kitack Lee,
and Wonyong Choi. Limnol. Oceanogr., 51(1), 2006, 331-338.
We report the first direct measurements of the contribution
of phytoplankton and bacterial cells to the measured alkalinity
of unfiltered seawater. Phytoplankton and bacterial cells
suspended in seawater make a significant contribution to the
measured alkalinity of unfiltered seawater; their contribution
is probably next to that of borate ion in most seawater samples.
This non-negligible contribution of particulate organic matter
to the measured alkalinity is due largely to the presence
of negatively charged surface groups on the phytoplankton
and bacterial cells that react with protons during titration
with hydrochloric acid. The contribution of organic particles
to the measured alkalinity of unfiltered seawater could potentially
be an important factor when evaluating the accuracy of presently
available carbonate thermodynamic models using at-sea carbon
system parameters that include measured alkalinity.
Sometimes hobbyists measure a high alkalinity when they start
to cycle their tank with plenty of live rock. Often, that
is not all true alkalinity but a significant part is caused
by the presence of other things such as organics and bacteria
blooms formed by the die-off and cycling processes. Just like
the true alkalinity causing carbonate and bicarbonate, these
organics can also neutralize acids.
Since alkalinity is measured by the amount of acid needed
to more or less neutralize the previously mentioned compounds,
these organics will show up as alkalinity in a test. This
condition is known in aquarium situations and now scientists
have demonstrated that even in often much cleaner natural
seawater the floating bacteria and phytoplankton can show
up as alkalinity because their outside surfaces can consume
Allelopathy and Our Tanks:
While this is not a review of an article this month, a recent
short thread developed on coral-list which is quoted below.
I have edited the names of some for assumed anonymity and
corrected a few typos in the post responses.
This is a picture of a coral a dog ate that developed progressive
neurologic signs about two hours after the ingestion. The
dog was ultimately euthanized because it was not breathing
on its own, and the owners could not afford emergency care.
I found some literature about corals that can have neurotoxins,
specifically lophotoxins, and was wondering if it is possible
that this could be one of those corals.
This particular coral was found on the beach in Jamaica and
apparently is a leather consistency. Any ideas about what
it might be would be helpful, and if it is possible, whether
it could be a species that could be toxic as well as any information
about coral toxins that you may have would be useful. Please
feel free to forward the picture on if you know someone who
might also be of assistance.<<
Date: January 30, 2006 12:28:55 PM CST
Subject: [Coral-List] Toxic coral and a dog
Hi Coral listers,
Can anyone help determine the species of coral and whether
it is toxic please? There is a link to the photo here: http://www.bren.ucsb.edu/~hcoleman/coral.htm
Date: January 30, 2006 6:43:40 PM CST
Subject: Re: [Coral-List] Toxic coral and a dog
Dear Annie and Caroline: It is Briareum asbestinum,
as Julian identified. We worked on the chemistry with Bill
Fenical for many years, and it is not surprising that it is
toxic enough to kill a dog. It's more surprising that the
dog ate enough of what must have tasted very horrible to get
a lethal dose. This species has high levels of chlorinated
diterpenes, in addition to unidentified small proteins that
might be in it. This species also has compounds in it that
can trigger contact dermatitis and even respiratory issues
for people who work with chemical extracts and dried samples
of it regularly.
Below are some of our papers with Briareum; the most
recent of these are available on my website.
Harvell, C. D., W. Fenical, V. Roussis, J. L. Ruesink, C.
C. Griggs, C. H. Greene. 1993. Local and geographic variation
in the defensive chemistry of a West Indian gorgonian coral
(Briareum asbestinum). Marine Ecology Progress Series
Harvell C. D., J. West, and C. C. Griggs. 1997. Chemical
defense of embryos and larvae of a West Indian gorgonian coral,
Briareum asbestinum. Invertebrate Reproduction and
Jensen, P. R., C. D. Harvell, K. Wirtz, and W. Fenical. 1996.
The incidence of anti-microbial activity among Caribbean gorgonians.
Marine Biology 125:411-420.
Kim, K., P. D. Kim, A. P. Alker and C. D. Harvell. 2000.
Antifungal properties of gorgonian corals. Marine Biology
Julian Sprung quickly responded with the identity of the
coral. While Drew cited her works, there are others on the
toxicity of this species, too. Recently, an aquarist asked
me why he didn't see the effects of allelopathy in his tanks,
and I responded that the effects might be subtle to severe
and variable. This example is not unusual. The triple palytoxin
poisoning of Anthony Calfo while propagating corals, the sensitization
of people working with Goniopora, polychaete worms
and zoanthids, all fit this pattern. I have written and repeatedly
discussed during presentations regarding the potential seriousness
of the toxins produced by most of the inhabitants in our tanks.
My hands and arms bear dark spots of healing stings from working
in my tanks on a nearly continuous basis. I preach to people
to propagate soft corals outside their tank to avoid poisoning
other things in the tank. The poisoning of the dog is a good
example of the care that must be taken when dealing with the
many species in our tanks - if not for our own safety, for
those of children and pets who tend to put things in their
I thought the comment that Drew was surprised about a dog
eating the gorgonian was odd. As dog owners can relate, I
have seen them eat my cats' hairballs, feces, and all manner
of what certainly cannot taste good. Cats find antifreeze
palatable and are frequently poisoned by it. The toxicity
of some of the novel compounds found in marine species can
be among the most toxic on earth, lethal even in minute doses.
So, I offer this story and warning to those who remove corals
from their tanks, who leave corals on countertops while propagating
them, who frequently handle marine livestock, and who have
pets and children who could inadvertently become sick, or
worse, from our own negligence and the nature of the species
we take for granted in our tanks.