BIO 475 Lecture 18: Mesophotic Reefs
Mesophotic Reefs
● Top Mesophotic zone ~ 30m
● Bottom mesophotic ~150-200m
○ Set by light availability
● Shallow water coral reefs on trajectory to decline and degrade
● Deeper you go, less effect on corals (water temp and other anthropogenic _
● Mesophotic reefs could serve as refuge
○ Deeper depths, reefs have better chance of survival
● Submersible Surveys
○ Manned submersibles 2-3 people
■ Take notes and video on what they see
■ Arm to take samples
○ ROV’s
■ Specimen collection
■ HD cameras
○ Monitor physical environment with glider
■ Take measurements of pH, salinity, conductivity, echo sounds, plankton
abundance
■ Can’t take samples
● In Situ Surveys
○ Technical diving
■ Nitrox
■ Really deep depths require Helium; trimix
■ Have to switch gasses as you ascend to aid in decompression
○ Rebreather
■ Stay deeper and longer
■ Recycle air you're breathing
■ Could breathe off the tanks for 8 hours
● Mesophotic vs shallow
○ Shallow - surface to 30m
■ Dominated by symbiotic scleractinian coral and octo corals, algae and
sponges
■ Lighter
■ Stratified water with high residence times
● Extreme highs, extreme lows
■ High turbulence and waves breaking (suspended sediment )
○ Mesophotic coral ecosystems (MCEs) - 30 to 40m
■ Corals become more plate like, less abundant, black corals, more algae
and sponges
■ Darker
■ Variable temperatures regimes, oscillations of deep water waves, and
upwelling
■ Dissipated turbulence with depth
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Document Summary
Shallow water coral reefs on trajectory to decline and degrade. Deeper you go, less effect on corals (water temp and other anthropogenic _ Deeper depths, reefs have better chance of survival. Take notes and video on what they see. Take measurements of ph, salinity, conductivity, echo sounds, plankton abundance. Have to switch gasses as you ascend to aid in decompression. Could breathe off the tanks for 8 hours. Dominated by symbiotic scleractinian coral and octo corals, algae and sponges. High turbulence and waves breaking (suspended sediment ) Mesophotic coral ecosystems (mces) - 30 to 40m. Corals become more plate like, less abundant, black corals, more algae and sponges. Variable temperatures regimes, oscillations of deep water waves, and upwelling. As sea levels rose, reefs deposited along higher slope, sea level rises more and you get inshore reefs, and continues to rise; now the mce"s becoming deep. Couldn"t keep up with sea level rising. Reef environment and light reaching the mesophotic zone.
