[Coral-List] Worthing, Barbados
Risk, Michael
riskmj at mcmaster.ca
Sat Aug 3 20:05:07 UTC 2019
Amelia asked me for some information on Worthing, and I realized that
although I have mentioned this several times, there is not a lot
available that can be easily accessed. Because it seems to represent
significant findings for the Caribbean, allow me to present an outline
here.
15-odd years ago, I begin working on a variety of Barbados projects
with Baird Engineering, a Canadian firm of coastal engineers. My
interaction with them produced what I think are some good pieces of
science (Risk et al. 2009, Tracking the record of sewage off Jeddah,
Saudi Arabia: MEPS 397: 219-226; Risk et al. 2010, Trace elements in
bivalve shells: Aq. Biol. 10: 85-97).
Some time in 2004, I ran some surveys on the south coast of Barbados.
At Worthing (between Oistins in the east and Bridgetown to the west)
there is a large, dynamic beach called, in an excess of originality,
Sandy Beach. There are large offshore bars at the site, covered with
dead Acropora palmata debris.
Late in the previous century and early in this one, the beach on the
west accreted seaward until it met the offshore bar, cutting off the
channel that had separated the beach from the bar and creating a small
lagoon with restricted circulation. My surveys in that lagoon in early
2004 showed evidence of recent environmental deterioration:
recently-dead coral colonies, Diadema so freshly dead that the spines
were still attached, etc. Surveys indicated that the water quality had
decreased recently, due to lack of flushing.
Hurricane Ivan hit in Sep 2004, and blew the west end of the lagoon
open. The benthic habitat there was newly-exposed to relatively fresh
seawater. I say "relatively", because that water would have travelled
at least 5km along the south coast of Barbados, an island which could
be characterized as an outhouse built on a karst outcrop. Nonetheless,
an improvement on the previous situation. This seemed an opportunity to
study the response of the biota to an improvement in WQ.
We installed racks of settling plates in the lagoon, and commenced
benthic surveys: this work was mostly done by personnel of the Coastal
Zone Management Unit and UWI. Gorgonians from the offshore bar recorded
a drop in delta-15N from 6.5 per mille to below 4, coinciding with the
increased flushing following Ivan. Surveys on a small rubble reef in
the middle of the lagoon between Mar 2005 and Sept 2005 showed a 5-fold
increase in numbers of Diadema (and an increase in urchins in general),
a modest increase in fish species and an explosion of coral recruits.
Coral-associated molluscs such as Tritons and juvenile Strombus began
to appear. Coral spat were found on our settling plates, mostly
sediment-resistant species such as Siderastrea. Spat were identified by
Judith Mendes and Paul Sammarco.
We viewed this as a convincing demonstration of the value of improving water
quality. I published an Abstract (in 30th Congress of the International
Association of Theoretical and Applied Limnology. Montreal, Canada, 2007) so
that there would be something citable while I worked up the paper.
Senior management at Baird changed, and I resigned from the Barbados project.
(Those wishing details may contact me personally.) It is doubtful I will ever
have the opportunity to write this up for a full journal paper. We have to
dance with who brung us here.
The Worthing example is encouraging, but limited in scope. There will never
be a flourishing reef at Worthing, because of the high sedimentation loading.
As well...the beach is starting to accrete again, there is discharge from the
Graeme Hall Swamp...this little experiment may already have ended. The
conclusions remain.
Mike
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