Theme section on “Mesophotic Coral Ecosystems: Characterization, Ecology, and Management”
- 2.3k Downloads
Mesophotic coral ecosystems (MCEs) are characterized by the presence of light-dependent corals and associated communities that are typically found at depths ranging from 30 to 40 m and extending to over 150 m in tropical and subtropical regions. The dominant communities providing structural habitat in the mesophotic zone can be comprised of coral, sponge, and algal species. Because working in this depth range is constrained by traditional SCUBA limits, less is known about corals and associated organisms there compared to shallower coral communities. Following the first-ever gathering of international scientists to review and discuss existing knowledge of MCEs, this issue focuses on the ecological characterization, geomorphology, and concept of MCEs as refugia for shallow-water populations. The review and research papers comprising this special issue reflect the current scientific understanding of these ecosystems and the underlying mechanisms that regulate them, as well as potential resource management implications. It is important to understand the value and role of mesophotic coral ecosystems in tropical and subtropical regions as these areas face increasing environmental change and human impacts
KeywordsMesophotic coral ecosystem Biodiversity Geomorphology Connectivity Community structure Resource management
Mesophotic coral ecosystem workshop
On 12–15 July 2008, a scientific workshop was held in Jupiter, Florida, to identify critical research and resource management needs for mesophotic coral ecosystems (MCEs) (Puglise et al. 2009). The workshop was hosted by the Perry Institute for Marine Science (PIMS) and organized by two offices of the U.S. National Oceanic and Atmospheric Administration (NOAA): the Center for Sponsored Coastal Ocean Research (CSCOR) and the Office of Ocean Exploration and Research/NOAA’s Undersea Research Program (OER/NURP) and also by the U.S. Geological Survey (USGS). The workshop gathered scientists and managers from governmental and non-governmental organizations for the first time to discuss MCE-related topics. The inception for this workshop grew out of NOAA/CSCOR’s Coral Reef Ecosystems Studies program, which identified the need for further investigations of MCEs.
The goal of the workshop was to review and discuss current knowledge about the characterization (biodiversity, geomorphology, microbiology), ecology (connectivity, community structure/dynamics), and management of MCEs. Three primary products resulted from the workshop: (1) this special Theme Section of Coral Reefs, focused on MCEs; (2) a MCEs Research Strategy (Puglise et al. 2009); and (3) a MCE information portal found at www.mesophotic.org (Bongaerts et al. 2008).
The following articles provide a description of the current state of knowledge about the science and management of MCEs. This information is intended to serve as the baseline for further research initiatives that address the characterization, ecology, and management of MCEs.
Introduction to mesophotic coral ecosystems
In the study of marine ecosystems, much attention has been devoted to the ecology of shallow-water (<30 m) coastal communities. Over the last several decades, there also has been a marked increase in the study of deep-sea environments. However, intermediate depths, particularly coastal environments in the 30–150 m depth range, have received relatively little attention.
Coral ecosystems at intermediate depths are by no means new to science; in fact, Darwin (1889) was one of the first to report the existence of hermatypic corals at depths up to 128 m, while Gardiner (1903) and Vaughan (1907) noted unique geomorphic characteristics of corals at intermediate depths. The 1960s and early 1970s saw the beginning of direct observations on deep coral environments and experimentation with new diving technologies (Stark and Stark 1972; Starck and Colin 1978). However, the physiologically imposed depth limits of sampling with conventional SCUBA, and the impracticality and expense of using submersibles in deep coral environments, limited exploration of the deeper portions of zooxanthellate coral communities (Lang 1974; James and Ginsburg 1979; Nelson and Appeldoorn 1985; Reed 1985; Hanisak and Blair 1988; Liddell and Ohlhorst 1988; Aponte and Ballantine 2001). As a consequence, fully two-thirds of the total depth range of zooxanthellate coral environments remain largely unexplored (Pyle 1996, 2000; Feitoza et al. 2005).
Advances in technical diving methods and instrumentation, such as mixed gas diving, rebreathers, and autonomous underwater vehicles, as well as in imaging techniques, e.g., see Gleason et al. (2010), are increasingly providing easier access to study coral ecosystems in the intermediate depth realm (Pyle et al. 2008). Kahng et al. (2010) review the geographic distribution of studies of MCEs and conclude that although some generalizations may be made about community structure and distribution of MCE in the Caribbean, these generalizations cannot be made for the vastly understudied Indo-Pacific regions. In all areas, major gaps of knowledge still exist.
Coral ecosystems in this depth range have sometimes been referred to as the “upper Twilight Zone” (Fricke and Knauer 1986) or “Coral-reef Twilight Zone” (Pyle 1996; Brokovich et al. 2008), or simply “deep coral reefs”. The term “twilight zone” has also been ascribed to a much deeper zone in the open ocean, depths between the euphotic zone and 1,000 m (Buesseler et al. 2007). The term “deep coral reefs” is both technically inaccurate (in the context of the geological definition of “reef”), and “deep coral” is often applied to the clearly distinct cold-water, aphotic deep-sea coral communities, which can occur at much greater depths. To avoid confusion, we follow Ginsburg (2007) in referring to the zone in deeper water where zooxanthellate corals occur as “mesophotic”.
Considered as extensions of shallower coral reef ecosystems, MCEs are likely to have biological, physical, and chemical connectivity with these reefs and associated communities, as well as unique assemblages, and extensions to deep biota. Although these ecosystems harbor species found in their shallower counterparts, they may also be colonized by a number of depth-restricted species of fishes, invertebrates, and algae, and a lower diversity of corals (Hanisak and Blair 1988; Pyle 2000; Ballantine and Aponte 2003, 2005; Jarrett et al. 2005; Armstrong et al. 2006; Brokovich et al. 2008; Garcia-Sais 2010). To this end, MCEs that serve as refugia for shallow and mid-depth species (Glynn 1996; Armstrong et al. 2006) may warrant special resource management attention and protection to help maintain local and regional biodiversity (Riegl and Piller 2003), However, the review by Bongaerts et al. (2010) demonstrates how little is known about deep reefs and coral reproduction over depth, and thus they propose a list of urgent research priorities to determine the extent to which deep reefs may act as a refuge in the face of global reef decline. In addition, MCEs are thought to serve as spawning grounds and may function as a larval supply for some shallow-water species (Armstrong et al. 2006; Brokovich et al. 2007; García-Sais et al. 2008).
Because MCEs are deep and can occur in remote localities (Kahng et al. 2010; Locker et al. 2010), there is a common assumption that they are less likely to be impacted by anthropogenic (e.g., overfishing, pollution) or natural (e.g., hurricanes, tsunamis, elevated temperatures) disturbances. To the extent to which such assumptions are borne out, MCEs may serve as a reference point for ecosystem condition in comparison with adjacent compromised, shallower coral reefs. For example, Bak et al. (2005) documented a lack of anthropogenically driven declines on reefs at 30–40 m in Curacao and Bonaire in contrast to the reefs at 10–20 m depth.
However, there is reason to suspect that this assumption is not valid for certain MCEs. For example, some fishing industries specifically target the larger predatory fishes that inhabit these depths. A small increase in shallow-water turbidity due to coastal development, watershed runoff, and pollution may have a greater and more devastating impact on MCEs (at the lower limits of photosynthetically viable light levels) than it would on the shallow reefs that are more directly exposed to the disturbance. While hurricanes and tsunamis have a smaller direct impact at greater depths, they may wash limestone rubble down the reef slope, potentially smothering MCEs (Bak et al. 2005).
Moreover, there is some indication that oscillations in sea temperatures, such as those caused by internal waves, cold-water intrusion, and down-welling of warmer waters, may extend to deeper depths and cause depauperate zones, stress, bleaching, and eventually death (Hickey et al. 2000; Smith 2001; Wolanski et al. 2004; Colin 2009; Smith et al. 2010). Although such potential threats are mostly speculative at this time, in certain locations encroaching threats have begun to adversely affect the condition of MCEs (Menza et al. 2007). Coral mortality events and shifting baselines at mesophotic depths have been documented by scientists, and the causes and consequences may be quite different from shallow-water reefs (Bak et al. 2005; Leichter and Genovese 2006; Menza et al. 2007; Smith et al. 2010). A better understanding of these environments is needed and will likely offer potential findings of major interest for conservation and resource management.
To determine where potential MCEs may exist and to ascertain their underlying geomorphology, Locker et al. (2010) describe regional mapping efforts that have been initiated that use a variety of manned and unmanned survey techniques. These have resulted in an increase in knowledge of the geographic extent of MCEs and a glimpse of the community structure of the MCEs found, e.g., in Hawaii, Rooney et al. (2010); and in Tutuila, American Samoa, Bare et al. (2010). Sherman et al. (2010) provide a more detailed analysis of the evolution of the underlying geological structure supporting the extant MCEs in southwestern Puerto Rico, relating their results to Caribbean sea level change models.
The results of this workshop give a glimpse of the complexity of MCEs but also emphasize the large gaps in our knowledge that currently exist. It is important to understand the value and role of mesophotic coral ecosystems in tropical and subtropical regions as these areas face increasing environmental change and human impacts.
NOAA, USGS, and PIMS wish to thank all the individuals and organizations that participated in the workshop and the writing, editing, and reviewing of this collection of manuscripts. Publication of this issue is supported by the offices of NOAA/NCCOS/CSCOR and NOAA/OER/NURP. We hope the time and effort committed to this initiative will result in increased collaboration between countries, institutions, and agencies with interests in understanding more about mesophotic coral ecosystems.
- Armstrong RA, Singh H, Torres J, Nemeth RS, Can A, Roman C, Eustice R, Riggs L, Garcia-Moliner G (2006) Characterizing the deep insular shelf coral reef habitat of the Hind Bank Marine Conservation District (US Virgin Islands) using the Seabed autonomous underwater vehicle. Cont Shelf Res 26:194–205CrossRefGoogle Scholar
- Bare AY, Grimshaw KL, Rooney JJ, Sabater MG, Fenner D, Carroll B (2010) Mesophotic communities of the insular shelf at Tutuila, American Samoa. Coral Reefs 29 (this issue). doi:10.1007/s00338-010-0600-y
- Bongaerts P, Martinez FA, Hinderstein LM (2008) Mesophotic Coral Ecosystems Database. Center for Sponsored Coastal Ocean Research (CSCOR/NOAA), Perry Institute of Marine Science (PIMS) and the Centre for Marine Studies (CMS/University of Queensland) www.mesophotic.org
- Bongaerts P, Ridgeway T, Sampayo EM, Hoegh-Guldberg O (2010) Assessing the ‘deep reef refugia’ hypothesis: focus on Caribbean reefs. Coral Reefs 29 (this issue). doi:10.1007/s00338-009-0581-x
- Buesseler KO, Lamborg CH, Boyd PW, Lam PJ, Trull TW, Bidigare RR, Bishop JKB, Casciotti KL, Dehairs F, Elskens M, Honda M, Karl DM, Siegel DA, Silver MW, Steinberg DK, Valdes J, Van Mooy B, Wilson S (2007) Revisiting carbon flux through the ocean’s twilight zone. Science 316:567–570CrossRefPubMedGoogle Scholar
- Colin PL (2009) Marine environments of Palau. Coral Reef Research Foundation, Koror, p 410Google Scholar
- Darwin C (1889) The structure and distribution of coral reefs. Smith, Elder, & Co., LondonGoogle Scholar
- Feitoza BM, Rosa RS, Rocha LA (2005) Ecology and zoogeography of deep reef fishes in northeastern Brazil. Bull Mar Sci 76:725–742Google Scholar
- Garcia-Sais JR (2010) Reef habitats and associated sessile-benthic and fish assemblages across a euphotic-mesophotic depth gradient in Isla Desecheo, Puerto Rico. Coral Reefs 29 (this issue). doi:10.1007/s00338-009-0582-9
- García-Sais J, Appeldoorn R, Battista T, Bauer L, Bruckner A, Caldow C, Carrubba L, Corredor J, Diaz E, Lilyestrom C, García-Moliner G, Hernández-Delgado E, Menza C, Morell J, Pait A, Sabater J, Weil E, Williams E, Williams S (2008) The state of coral reef ecosystems of Puerto Rico. In: Waddell J, Clarke A (eds) The state of coral reef ecosystems of the United States and Pacific Freely Associated States: 2008. NOAA Technical Memorandum, Silver Spring, MD, pp 75–117Google Scholar
- Gardiner JS (1903) The Maldive and Laccadive groups, with notes on other coral formations in the Indian Ocean. In: Gardiner JS (ed) The fauna and geography of the Maldive and Laccadive archipelagoes. Cambridge University Press, Cambridge, pp 146–183Google Scholar
- Ginsburg R (2007) Mesophotic coral reefs are the frontier of reef exploration and research. In: Proceedings of the 33rd scientific meeting of the Association of Marine Laboratories of the Caribbean (AMLC) 56 (Suppl. 1): xiiGoogle Scholar
- Gleason ACR, Gracias N, Lirman D, Gintert BE, Smith TB, Dick MC, Reid RP (2010) Landscape video mosaic from a mesophotic coral ecosystem. Coral Reefs 29 (this issue). doi:10.1007/s00338-009-0544-2
- James NP, Ginsburg RN (1979) The seaward margin of the Belize barrier and atoll reefs. Blackwell Scientific Publications, Oxford, p 191Google Scholar
- Jarrett BD, Hine AC, Halley RB, Naar DF, Locker SD, Neumann AC, Twichell D, Hu C, Donahue BT, Jaap WC, Palandro D, Ciembronowicz K (2005) Strange bedfellows—a deep-water hermatypic coral reef superimposed on a drowned barrier island; southern Pulley Ridge, SW Florida platform margin. Mar Geol 214:295–307CrossRefGoogle Scholar
- Kahng SE, Garcia-Sais JR, Spalding HL, Brokovich E, Wagner D, Weil E, Hinderstein L, Toonen RJ (2010) A review of community ecology of mesophotic coral ecosystems. Coral Reefs 29 (this issue). doi:10.1007/s00338-010-0593-6
- Lang JC (1974) Biological zonation at the base of the reef. Am Sci 62:272–281Google Scholar
- Locker SD, Armstrong RA, Battista TA, Rooney JJ, Sherman C, Zawada DG (2010) Geomorphology of mesophotic coral ecosystems: current perspectives on morphology, distribution, and mapping strategies. Coral Reefs 29 (this issue). doi:10.1007/s00338-010-0613-6
- Nelson WR, Appeldoorn RS (1985) Cruise Report R/V Seward Johnson. A submersible survey of the continental slope of Puerto Rico and the U. S. Virgin Islands. NOAA, NMFS, SEFC, Mississippi Laboratories. University of Puerto Rico, Department of Marine Sciences 76Google Scholar
- Puglise KA, Hinderstein LM, Marr JCA, Dowgiallo MJ, Martinez FA (2009) Mesophotic coral ecosystems research strategy: International workshop to prioritize research and management needs for Mesophotic Coral Ecosystems. Jupiter, Florida, 12–15 July 2008. Silver Spring, MD: NOAA National Centers for Coastal Ocean Science, Center for Sponsored Coastal Ocean Research, and Office of Ocean Exploration and Research, NOAA Undersea Research Program. NOAA Technical Memorandum NOS NCCOS 98 and OAR OER 2. p 24Google Scholar
- Pyle RL (1996) The twilight zone. Nat Hist 105:59–62Google Scholar
- Pyle RL, Earle JL, Greene BD (2008) Five new species of the damselfish genus Chromis (Perciformes: Labroidei: Pomacentridae) from deep coral reefs in the tropical western Pacific. Zootaxa 1671:3–31Google Scholar
- Reed JK (1985) Deepest distribution of Atlantic hermatypic corals discovered in the Bahamas. In: Proceedings of the 5th international coral reef symposium, vol 6, pp 249–254Google Scholar
- Rooney J, Donham E, Montgomery A, Spalding H, Parrish F, Boland R, Fenner D, Gove J, Vetter O (2010) Mesophotic coral ecosystems in the Hawaiian Archipelago. Coral Reefs 29 (this issue). doi:10.1007/s00338-010-0596-3
- Sherman C, Nemeth M, Ruíz H, Bejarano I, Appeldoorn R, Pagán F, Schärer M, Weil E (2010) Geomorphology and benthic cover of mesophotic coral ecosystems of the upper insular slope of southwest Puerto Rico. Coral Reefs 29 (this issue). doi:10.1007/s00338-010-0607-4
- Smith TB, Blondeau J, Nemeth RS, Pittman SJ, Calnan JM, Kadison E, Gass J (2010) Benthic structure and cryptic mortality in a Caribbean mesophotic coral reef bank system, the Hind Bank Marine Conservation District, U.S. Virgin Islands. Coral Reefs 29 (this issue). doi:10.1007/s00338-009-0575-8
- Starck WA II, Colin PL (1978) Gramma linki: a new species of grammid fish from the tropical western Atlantic. Bull Mar Sci 28(1):146–152Google Scholar
- Starck WA II, Starck JD (1972) Probing the deep reef’s hidden realm. Natl Geogr Mag 142(6):867–886Google Scholar
- Vaughan TW (1907) Recent Madreporaria of the Hawaiian Islands and Laysan. Bull US Natl Mus 59:1–427Google Scholar