Deep-water coral reefs exist in every ocean at depths from 30 meters to over 3,000 meters. While they were only recently discovered, they can be as large as shallow coral reefs. The most common deep-water coral is Lophelia pertusa, which forms extensive reefs in the Atlantic through slow growth. Deep-water coral reefs provide important habitat for fish and invertebrates but are threatened by bottom trawling, oil spills, and ocean acidification due to climate change. Establishing protected areas and regulating harmful activities can help conserve these ecosystems.

1. DEEP-
WATER
CORAL
REEFS
David Fisher
Benthic Ecology

2. INTRODUCTION
-While they have only been relatively recently discovered and are just starting to be truly studied, deep-
water coral communities can be just as large as other coral reefs.
-There are approximately as many species of deep-sea corals as there are shallow-living species, yet just
a few of these are capable of growing large enough to form reefs.
-Deep-water corals are typically considered to be those at depths of 30 m or more (mesophotic zone
to 150 m), all the way down to the abyssal zone, up to 3,000 m deep
-Some light penetration from 30-150 m means that shallower corals can use some photosynthesis, but
most lack zooxanthellae and feed on plankton or nutrient particles
-These ecosystems are found in every ocean in some form, but most are in the Atlantic.

3. Lophelia pertusa- (Linnaeus1758)
◦ Primary reef-building deep-water coral
◦ Mostly 100-1,000 m deep, up to 3,000+ m
◦ No zooxanthellae, polyps use tentacles and nematocysts to
catch zooplankton including crustaceans up to the size of
krill
◦ Reefs are mostly found in Atlantic, around British islands
and Norway, and Southeast US (FL to NC)
◦ Madrepora oculata- associated, non-reef-forming

4. Lophelia continued
◦ Grows best in waters 40-50 ºF, cold-water coral (slow growth rate- ½ cm per year)
◦ Largest reefs- Norway: Røst Reef (largest in the world at 27 x 4 miles) & Sula Reef (~9 miles)
◦ Darwin Mounds- UK/Scotland, coral mounds scattered over 40 sq. miles at ~1000 m deep
◦ Lophelia Banks- scattered aggregations stretching from Florida
to Cape Hatteras (northermost point) at 300+ m deep
◦ Corals are limited by carbonate compensation and mineral
availability to make skeletons instead of light availability
Madrepora oculata- associated with Lophelia, but non-reef-forming

5. Oculina varicosa- Ivory Tree coral
◦ Western Atlantic species, found in Gulf of
Mexico, Caribbean, & Southeast US
◦ Largest reef- Oculina Banks (Florida), original area
23 x 4 miles, now a protected and regulated area
streching for over 130 miles along the coast of
Florida
◦ Extremely important spawning/nursery grounds
for grouper, sea bass, and other fish, trawling in
the 60s & 70s led to decline of the Florida fishery
industry until Oculina ecosystem was discovered &
protections were put in place starting in 1975
◦ Not a true reef-building coral, grows in
aggregations along shelfs & seamounts
◦ capable of growing in shallow water, those that
live in photic zone have zooxanthellae
https://oceanexplorer.noaa.gov/explorations/17sedci/background/oculina/media/thickets-500.jpg

6. History of Deep-Sea Coral Study
◦ 1700s- corals occasionally brought up in nets, deep-sea species first
studied and described (Linnaeus, Gunnerus)
◦ 1800s- as fishing increases, more corals are discovered
◦ 1900s- development of SCUBA diving technology
◦ 1960s- diving technology is refined: divers can now directly study
and observe deep-water coral reefs, unfortunately limited to depths
of 70-100 meters
◦ 1970s- industrial bottom-trawling activity increasing
◦ 1980s &1990s- camera technology improves, as does observation
submarines (manned and unmanned vehicles can now observe the
deepest corals where they are found)
◦ 2000s – Today- increasingly better mapping & newer data
https://www.researchgate.net/profile/Torkild_Bakken/publication/2
57733144/figure/download/fig1/AS:297506727579651@1447942539
451/Lophelia-pertusa-the-reef-building-cold-water-coral-common-in-
Norwegian-waters-This.png

7. Value of Deep-Water Corals
◦ Deep-water coral reefs are
extremely ecologically important
as spawning grounds for
countless species of fish. Many
fish valuable commercially use
deep-water reefs as refuge while
they grow to adults
◦ Damage to deep-water reefs
correlate with fishery decline in
several places (Norway, FL,
Mediterranean)
◦ Possibly also due to over-fishing,
declines started around the same
time trawling & commercial
fishery activities increased from
1960s-1980s before MPA
regulations started being
enforced- Oculina in FL, Cape
Fear Lophelia Banks HAPC
(Habitat Area of Particular
Concern) NC
The Oculina
community
gives refuge to
a wide variety
of fish,
inverts, and
many other
kinds of deep-
water corals
https://th.bing.com/th/
id/OIP.VNIqwQQN
ELSZJzGru-
azagHaFj?pid=ImgDet
&rs=1

8. Species of the Deep-Water Reef
Snowflake grouper Sea spiders
Basket star Pudgy cusk-eel

9. Bottom Trawling- damages deep-water reefs in
nearly every place that both occur (seen in Gulf
of Mexico, Southeast US, Norway, Scotland &
Ireland, Med. Sea, Caribbean Sea, Canada,
Australia, etc.)
Dredging- similar impacts, destroys corals while
disturbed silt & sediment buries corals, keeping
them from feeding and eventually killing them
(30-50% damaged)
Oil Spills- impacts seen after Gulf oil spill
Changing Conditions- changing pH, ocean
acidification weakens coral skeleton and stresses
the animal itself (density of the skeleton can
decrease by up to 30%)
THREATS

10. What can we do? What has been done to help?
◦ Establishment of MPAs and Habitat Areas of Particular Concern (HAPCs)
◦ Trawling and other harmful fishing methods prohibited (anchors, explosives)
◦ as mapping of deep-water coral communities improves and more information is gathered, we can better
protect these areas. However, illegal fishing is still an issue in many places
◦ Ocean Acidification- what can be done?
◦ Regulate CO₂ emissions-
◦ development of electric car industry
◦ Some countries contribute more than others
◦ Americas & China, Asia produce the most CO₂

11. Sources
Collier, Chip. (2017). “Southeast Deep Coral Initiative: Exploring Deep-Sea Coral Ecosystems off the
Southeast U.S.” The Oculina Bank: A History of Research and Protection: NOAA Office of
Ocean Exploration and Research, South Atlantic Fishery Management Council
Fosså J.H. et al. (2005) Mapping of Lophelia reefs in Norway: experiences and survey methods. In:
Freiwald A., Roberts J.M. (eds) “Cold-Water Corals and Ecosystems.” Erlangen Earth
Conference Series. Springer, Berlin, Heidelberg.
Fosså, J., Mortensen, P., & Furevik, D. (2002). “The deep-water coral Lophelia pertusa in Norwegian
waters: Distribution and fishery impacts.” Hydrobiologia, vol. 471(1-3), pp. 1-12
Hall–Spencer, Jason, et al. (2002) “Trawling Damage to Northeast Atlantic Ancient Coral Reefs.”
Proceedings of the Royal Society of London. Series B: Biological Sciences, vol. 269,
,(1490), pp. 507–511
Kühlmann, D.H.H. (1983). “Composition and ecology of deep-water coral associations.”
Helgoländer Meeresuntersuchungen vol. 36, pp. 183–204.
Lophelia.org, the Cold-Water Coral, Deep-Sea Coral and Deep-Water Coral Resource-
Changing Oceans Research Group

12. Sources continued
Necaise, Ann Marie D., and Steve W. Ross. (2003). “North Carolina Reef Systems.” NOAA Ocean
Explorer, National Oceanic and Atmospheric Administration
Øyvind Thiem, et al. “Food supply mechanisms for cold-water corals along a continental shelf edge.”
Journal of Marine Systems, vol. 60, (3–4), pp. 207-219
Roberts, J., Wheeler, A., & Freiwald, A. (2006). “Reefs of the Deep: The Biology and Geology of Cold-
Water Coral Ecosystems.” Science, vol. 312(5773), pp. 543-547.
Sulak, Kenneth J., and Steve W. Ross. (2001). “A Profile of the Lophelia Reefs.” NOAA Ocean
Explorer, National Oceanic and Atmospheric Administration
Williams, Althaus, et al. (2020). The fate of deep-sea coral reefs on seamounts in a fishery-seascape:
What are the impacts, what remains, and what is protected? Frontiers in Marine Science