Mesophotic Coral Ecosystems of Puerto Rico and the US Virgin

IslandsRoy Armstrong, Ph.D.

Bio-optical Oceanography LaboratoryUniversity of Puerto Rico at Mayaguez

Mesophotic Coral Ecosystems

WHAT ARE THEY AND WHERE RE THEY FOUND?

• Light-dependent coral ecosystems

• Depths: from 30-40 m and extending to over 150 m

• Found in tropical and subtropical regions

• Dominant communities can be coral, algae, and sponge species

Penetration of Light in the Sea

Penetration of Light in the Sea

In very clear oligotrophic waters:

Why Study Deep (Mesophotic) Coral Reefs?

• In shallow waters (< 20 m) of the Caribbean Region, a coral decline of 80% over the last 30 years has been documented (Gardner et al. 2003).

• Mesophotic reefs (> 30 m) are largely unknown. • They appear to be healthier than shallow water reefs.• Habitats of commercially important fish species.• Source of coral larvae for recruitment and potential recovery of the

shallower reef areas.• There could be several times as much reef habitat deep as there is

shallow.

0 - 30 m0 - 30 m 43254325 56.7 56.7

30 - 50 m30 - 50 m 1738 1738 22.8 22.8

50 - 100 m50 - 100 m 1562 1562 20.5 20.5

Bathymetry of Puerto Rico -Virgin Islands Geological Platform Potential Reef Habitat

Examples of Mesophotic Coral Ecosystems

Hind Bank MCD, US Virgin IslandsDepth 40 m

Desecheo Island, Puerto RicoDepth 80 m

The Seabed AUV

The Seabed AUV was used in 2002, 2003, 2004 and 2008 to image and characterize mesophotic reefs in Puerto Rico and the U.S. Virgin Islands

Two Prosilica GC-1380C CCD cameras with 1360 x 1024 resolution 12 bit dynamic range (0 - 4,095 grey levels) From an altitude of 3 m, the images are 3.12 m wide by 2.3 m long,

covering an area of 7.17 m2

Spatial resolutions of 2.2 mm per pixel A 150 Ws strobe provides the only source of illumination Two cameras were used, a downward looking camera and a forward facing camera Over 100,000 images of mesophotic reefs in the Puerto Rico Shelf since 2002

Seabed Optical Imaging

Forward-looking camera image showing a red hind grouper (E. guttatus) (A) and enlargement of the fish (B)

Forward-looking Camera

Hind Bank MCD, U.S. Virgin Islands

33 34 35 36 37 38 39 40 41 42

L. cucullataC. natans

S. bournoniP. porites

P. astreoidesS. siderea

D. strigosaM. cavernosa

Mycetophyllia sp.Agaricia sp.

M. annularis complex

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Depths (m)

Found well-developed coral reefs with 43% mean living coral cover.Maximum coral cover was 70% at depths of 40 m.Dominance by M. annularis complex.Low diversity index (range 1.47 to 1.85).

2003 – MCD PR-03 TransectFound well-developed coral reefs with 28 % mean living coral coverFound well-developed coral reefs with 28 % mean living coral cover

Photo Mosaicking

Seven images were used from a depth of 35 m measuring approximately 6.3 m long and covering an area of about 20 m2

Bajo de Sico - 64 mLarge topographic feature off the west coast of Puerto RicoMesophotic reef begins at 45 m and extends to about 100 m

Desecheo - 80 m“Sponge – coral bioherm” at depths of 40 to 100 m

Mesophotic Coral Ecosystems

WHY ARE THEY IMPORTANT TO MANAGEMENT?

• Extensions of shallower coral reef ecosystems

• Potential refugia for impacted shallow-water species

• Some species are endemic to this depth range

• May serve as critical habitat for economically- and ecologically-important species

Photo courtesy of Jorge Sabater.

Deep Sea Corals and Habitats