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MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS?
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MCEs have only been studied in a few places. As a rule
of thumb, the best studied MCEs are also the most easily
accessed by scientists and have infrastructure in place to
support deep diving (e.g. a diving chamber and gas mixing
facilities) and the use of undersea technologies (e.g. vessels
with dynamic positioning for remotely operated vehicles
and winches for launching heavy equipment). Thus, most
work to date has been conducted in the Caribbean, the Gulf
of Mexico, the Hawaiian Islands, the Red Sea, the main
Palau Island group, Japan and the Great Barrier Reef. This
has left major geographic gaps in our understanding of
MCEs, particularly in the equatorial regions of the Indo-
West Pacific (see Chapter 2, Figure 2.3). Large reef systems
Like shallow coral reefs, MCEs are patchily distributed.
Why well-developed MCEs are found in some areas and
not others needs to be better understood. In La Parguera,
Puerto Rico (see the case study in Chapter 3.10), scientists
found only five well-developedMCEs within a 20 km stretch
off the coast. Geological processes strongly influenced the
siting of these MCEs, with the best developed ones located
on topographic highs on steep southwest facing slopes
where sedimentation was lowest. Meanwhile in Hawai‘i,
the best developed MCEs were found where there was clear
water for deep light penetration and a submerged terrace
located at the right depth for MCEs, forming a natural
flume that improves water flow and enhances productivity
(Costa et al. 2015, Pyle pers. com.).
As we learned in Chapter 4, MCEs harbour complex and diverse
assemblages of flora and fauna. Discoveries of flora and fauna
that are new to science are common occurrences at mesophotic
depths, and known species are being documented in new areas.
The mantra for mesophotic scientists should be “The more we
look, the more we find”. Because only a few areas have been
studied, opportunities abound to enhance our knowledge of the
breadth of organisms that inhabit MCEs. Species inventories
are needed for understanding biodiversity in MCEs. This
information must go beyond presence/absence data to include
quantitative information on the number of individuals in order
to determine population size for mobile species, and per cent
cover for sessile species. Quantitative information will make it
possible to calculate the degree of biodiversity and determine the
number of unique or endemic species that occur in mesophotic
habitats. In addition to quantitative information, collection and
preservation of whole organisms along with genetic samples
and in situ photographs are needed to enable species to be
appropriately documented and identified.
in the “coral triangle” (Indonesia, the Philippines, Papua
New Guinea and Solomon Islands), Micronesia, Polynesia
and Melanesia, as well as the Maldives, the Chagos area,
the Seychelles and the large banks of the central Indian
Ocean, remain poorly documented. Knowledge of potential
MCEs in the tropical regions off the west coast of Africa and
the Pacific coasts of Mexico, Central America and South
America remain a complete mystery.
Research Need
: Locate where MCEs exist, with a priority
in the equatorial regions of the Indo-West Pacific region,
eastern Atlantic Ocean, and the Pacific coasts of Mexico,
Central America and South America.
Better knowledge of basic physical information on mesophotic
reefs, particularly long-term datasets, would greatly enhance
our ability to understand these ecosystems. Determining the
role of water temperature, light levels, water currents, vertical
water movements, sediment flux and turbidity coupled with
high-resolution bathymetric data will help to better identify
the parameters defining where MCEs are found, as well as to
develop models to predict where MCEs are located. The use of
models can help researchers and managers to identify priority
areas with the potential to harbourMCEs, to ensure that limited
funding for in situ research is targeted (Costa et al. 2015).
Research Need:
Understand the geological and physical
processes that control MCE distribution to enable us to predict
where MCE’s occur.
Understanding which species are commonly found in MCEs
will also help our understanding of relationships between
species. Are there ecologically-important species, without
whose presence the MCE ceases to function normally? How
are these habitats utilized by species and does their utilization
change over time? Are MCEs used by commercially- and/or
ecologically-important species? All these questions are key to
determining how to appropriately protect and conserve these
ecosystems and yet, our understanding of them is limited and
mostly relies on our knowledge of shallow coral reefs.
Research Need:
Characterize MCE biodiversity to better
understand, protect and conserve MCEs.
ResearchNeed:
Characterize community structure, including
patterns of distribution and abundance.
Research Need:
Understand the role of MCEs in supporting
various life stages of living marine resources and the processes
that regulate these ecosystems.
7.2.
Where are mesophotic coral ecosystems located?
7.3.
What controlswheremesophotic coral ecosystemsare found?
7.4.
What ecological role do mesophotic coral ecosystems play
and what organisms are found in them?