Cold-Water Corals. Distribution of fauna and ... - Jacobs University

Abstract
Over the last decade, the importance of Cold-Water Coral (CWC) reefs as hotspots of
elevated biodiversity on the European continental margin has become firmly established in
scientific literature. Reefs are formed predominantly by the calcium carbonate skeletons of
successive generations of Scleractinian corals such as Lophelia pertusa (Linnaeus, 1758).
This skeletal structure often forms complex 3D structures which can provide a host of habitat
niches for other fauna. Advances in remote sensing techniques has led to the location of a
large number of reef structures, commonly in regions with elevated flow or productivity, such
as on the Norwegian margin. Often these reefs are associated with high commercial fish
stocks, and structural damage to reef ecosystems from fishing activity has led to
progressively more CWC reefs being closed to fishing by various national legislations. The
oil and gas industry also operates in regions and at depths where extensive reef structures
can are found, and there is a level of concern over the potential negative impact this industry
may have on these ecosystems.
The variation in faunal composition across and between reefs has only been investigated in
a few studies to date. Likewise, the fundamental functioning of some of the key ecosystem
species, such as Lophelia pertusa, is not well understood. In this thesis a selection of
techniques were used to fill some of these knowledge gaps.
A novel method was developed utilising machine-learning algorithms to swiftly and semiautomatically
quantify percentage coverage of substrate by living coral polyps. The system
was used to assess live coral coverage across a trawl damaged region of the Tisler reef,
Norway. The machine-learning algorithm method performed as accurately as a human in
quantifying coverage (using standard methodologies), but in considerably less time.
Distribution of a selection of fauna across and between Norwegian reefs was investigated
using a large dataset collected as part of the Hotspot Research on the Margin of European
Seas (HERMES) project. Previously unreported distribution patterns were observed on a
variety of spatial scales for a number of the species investigated.
Laboratory work was conducted to determine the degree to which flow velocity related to net
zooplankton capture rates by Lophelia pertusa. The investigation clearly indicated that a
significantly higher capture rate was attainable under 0.025 m s -1 than 0.05 m s -1 flow
velocity, a surprising result given the high flow velocities often prevalent at reef locations.
Additional laboratory investigations subjecting Lophelia pertusa polyps to doses of various
anthropogenic materials (waste from drilling operations, trawl resuspended sediments) were
conducted, with results indicating a general resilience of the species to particle exposure.