[L&O Featured Article] L&O Featured Article, Vol. 54 (2) March 2009

[L&O Feature Articles Announcements]

The Featured Article for the March 2009 issue of L&O is:

 

Davies, Andrew J., Gerard Duineveld, Marc Lavaleye, Magda J. Bergman, Hans
van Haren, and J. Murray Roberts. 2009. Downwelling and deep-water bottom
currents as food supply mechanisms to the cold-water coral Lophelia pertusa
(Scleractinia) at the Mingulay Reef Complex. Limnol. Oceanogr. 54(2):
620-629.

 

This article can be read online at:

 

http://www.aslo.org/lo/toc/vol_54/issue_2/0620.pdf

 

Introductory Comments by Anthony Larkum (L&O Associate Editor)

 

Warm-water coral reefs are so eye-catching and visible-the Great Barrier
Reef is said to be the only organic structure on the planet that can be seen
from outer space-that we tend to forget that there are coral reefs of a very
different kind in deeper and colder waters. The featured paper in this issue
of L&O draws our attention to these structures and presents vital clues as
to how the many mouths of a deep-water coral community in the North Atlantic
Ocean, dominated by the colonial scleractinian Lophelia pertusa, are
maintained and fed.

            

Deep water coral reefs are found on continental shelves and slopes at depths
below 100m, where there is not enough light to sustain algal symbionts, as
is the case in tropical and subtropical coral reefs.  Yet deep-water corals
thrive: many reefs have been in existence over geological time-scales and
have laid down carbonate mounds several hundreds of meters in thickness. An
important question has been just how these deep-water corals obtain food.
This is not an easy question to answer because their inaccessibility and the
exposed nature of such sites has made direct observation for periods long
enough to yield answers difficult.

            

Davies et al. used current meters and sensors on landers and moorings to
obtain vital clues that address this question. Over two years, they studied
currents, temperature, turbidity, and fluorescence at Mingulay Reef at a
depth of 140 m in a relatively shallow strait between the Outer Hebridean
Island chain and the Scottish mainland. This enabled them to determine
particle supply to the coral community. They found that there are two major
mechanisms for supplying organic particles to the hungry coral mouths.  The
first consists of a tidally-driven process that sucks surface water down to
the coral community within an hour at the onset of ebb and flood tides. The
second is the upwelling of deeper water, bringing with it a high load of
suspended organic matter. These processes combine, usually at peak tides, to
deliver particles to the reefs.

            

Deep-water reefs exist on canyons, slopes, and seamounts and in much deeper
waters than this one.  This study provides, for the first time, important
clues as to how such communities depend strongly on the interplay between
water flow and bottom topography to supply the food particles and larvae on
which these communities depend.

            

 

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