Coral reefs in Norway
Lophelia pertusa
More than 1400 possible Lophelia-reefs mapped
The new research vessel “G.O. Sars” is providing new
possibilities for an effective mapping of coral reefs in Norwegian waters.
This was demonstrated during the recent coral mapping cruise on July 7-23
where two new and advanced multibeam echo sounders were used for the first
time. Ground truthing was performed with the ROV “Aglantha”.
(Click on the images to see a larger version.)
We
surveyed the north of the Træna deep, at the Røst reef, and
the continental break from Bleikdjupet north to Sveinsgrunnen. Steinavær
in Andfjorden was also covered.
Lophelia corals build characteristic mounds on the sea bottom,
and on a multibeam map we can recognise these structures. However, mounds
of stones and till can be misinterpreted as coral mounds, so ground truthing
is necessary. 
In
Træna a 23 x 13 km area was mapped. The multibeam maps have been
interpreted by marine biologists and marine geologists. The results indicate
that there are 1447 possible coral reefs with an average length of 150
m (in red) in this area.
The possible new reefs cover a total area of 3.63 km2. However, it is imperative to perform ground truthing. Wherever we were able to check with the ROV we verified Lophelia corals.
Multibeam
data are read in real time into a mapping and navigational system called
“Olex”. This system makes it possible to navigate the ROV
on the mutlibeam map. Thus the position of the vessel and ROV can be read
accurately on maps in 2D or 3D mode, and makes it possible to follow the
ROV as it travels along the bottom landscape. The figures show large reefs
situated on the continental break off Sveinsgrunnen. The first figure
shows the position of the vessel and the ROV (green). In the 3D insert
the ROV is indicated by a yellow dot. In the other figure the reefs are
seen from the continental shelf towards the deep ocean.
At Steinavær in Andfjorden, 69 14.24 N, 16 39.00 E, we detected the most fantastic reef ever during all our years of coral mapping. The reef grows on each side of an underwater sound. On the northern side of the sound we travelled with the ROV for about 500 m. The bottom was covered with a carpet of coral colonies. We saw cod and red fish on the reef. Here, as in all coral areas, we detected remains of fishing activity such as lost long lines and gillnets.
Scientific content: Jan Helge Fosså. Web design: Yvonne R. Bonète. Webmaster: Bernt Andreas Drange.