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Coral
Ecotoxicology: Anti-foulant paints and Irgarol 1051 Boats, ships and other structures that exist in
marine or aquatic environments often become “fouled” by a
biological film consisting of bacteria, algae, and invertebrates, like ba=
rnacles.
To prevent this fouling, marine and freshwater vessels need to be coated =
with
an anti-foulant paint. In the past, anti-foulant paints predominantly
contained a very noxious chemical called tributyl tin (TBT). Its use
has been significantly curtailed as a result of international and national
regulations. Cuprous oxide (a copper oxide) has been phased in as a
substitute for TBT. Cuprous oxide is seen as being less effective than TB=
T as
an antifoulant, so paint formulation using cuprous oxide can be supplemen=
ted
with “booster biocides”. Some of these booster biocides=
are
pesticides or antibacterials, while others are herbicides. A common
herbicidal booster biocide is the chemical, Irgarol 1051 Irgarol 1051 is a s – triazine
herbicide (N’-tert-butyl-N-cyclopropyl-6-(methylthio)=
-1,3,5-triazine-2,4-diamine),
and it is used because as one of its toxic modes of action, it is a very
effective inhibitor of photosynthesis. It is much more water soluble
that its cousin compounds, hence its effectives as a marine/aquatic
anti-foulant. Concentrations of Irgarol 1051, as reported in the literatu=
re,
are typically between “not detectable and 0.7 μg L-1,
(although values in the range 1.7 - 4 μg L-1 have been
occasionally reported in areas of high boating activity (Readman et al, 1=
993,
Basheer et al 2002, Hall et al, 2004). Recently a number of studies have shown that Irg=
arol
1051 inhibits photosynthesis of both isolated endosymbiotic algae (i.e.
zooxanthellae in vitro) and the intact symbiosis (i.e. whole coral=
in
vivo) in a number of coral species. Irgarol 1051 was observed to exhi=
bit
comparatively higher toxicity in comparison with other triazine and non
triazine herbicides (e.g. atrazine, simazine and diuron). Acute
photosynthetic inhibition was observed at low concentrations of this
antifoulant (≥ 0.05μg L-1). The presence of Irgarol
1051 in tropical marine ecosystems is a serious concern, since its mode of
toxicity can also potentially affect the major keystone species of tropic=
al
marine systems: sea grasses, mangroves, and corals. While the impacts on coral photosynthesis of acu=
te
low level exposure to Irgarol 1051 have been shown, other potential toxic=
ity
mechanisms associated with exposure to this antifoulant in corals or coral
reef organisms (invertebrates, fish) have not been investigated. To
investigate other mechanisms of toxicity associated Irgarol 1051, we
initiated a pilot study at the Bermuda Biological Station for Research.&n=
bsp;
Results of this pilot study are now published in a peer-reviewed scientif=
ic journal
and the galley proof can be viewed here (XXX). In collaboration with
several laboratories at the University of Hawaii, Tel Aviv University, and
the Aqaba Marine Science Station, we are continuing this research for the
toxicity of Irgarol 1051, its risk to coral reefs, and potential manageme=
nt
options to reduce any adverse impact Irgarol 1051 may have on coral reefs
around the world. |
Healthy
coral of Madracis mirabilis
Coral
exposed to 0.01 µg L-1 Irgaro 1051 for 24 |
|
Canonical centroid plot of
cnidarian xenobiotic response biomarkers. Original variates were biomarker
levels expressed as a percentage of the control value in each treatment. =
Circles
show the 95% confidence intervals around the distribution centroid of each
stressor. Biplot rays radiating from the grand mean show directions of
original biomarker responses in canonical space. Overlapping centroids
indicates that those populations are not significantly different from one
another, while non-overlapping centroids indicate a difference. |
![3D"http://haereticus-lab.org/Control%20Irgarol%20Coral.jpg"](3D"CoralEcotoxicolog1_files/image002.jpg")
![3D"http://haereticus-lab.org/24%20Irgarol%20coral.jpg"](3D"CoralEcotoxicolog1_files/image003.jpg")
![3D"http://haereticus-lab.org/Coral%201.jpg"](3D"CoralEcotoxicolog1_files/image005.jpg")