Are mesophotic coral ecosystems distinct communities and can they serve as refugia for shallow reefs?

Semmler, Robert F.; Hoot, Whitney C.; Reaka, Marjorie L.

doi:10.1007/s00338-016-1530-0

Cited by 103 publications

(109 citation statements)

References 53 publications

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“…Similar to previous studies (Semmler et al 2016, Laverick et al 2017, our ecological analysis revealed two coral assemblages (clusters) between the surface and 100 m depth. The switch from shallow genera to mesophotic genera occurs around 40-50 m (Appendix S1: Table S2).…”

Section: Light Limitation and Solar Stress May Control The Shallow-tosupporting

confidence: 88%

Light environment drives the shallow‐to‐mesophotic coral community transition

et al. 2019

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Light quality is a crucial physical factor driving coral distribution along depth gradients. Currently, a 30 m depth limit, based on SCUBA regulations, separates shallow and deep mesophotic coral ecosystems (MCEs). This definition, however, fails to explicitly accommodate environmental variation. Here, we posit a novel definition for a regional or reef‐to‐reef outlook of MCEs based on the light vs. coral community–structure relationship. A combination of physical and ecological methods enabled us to clarify the ambiguity in relation to the mesophotic definition. To characterize coral community structure with respect to the light environment, we conducted wide‐scale spatial studies at five sites along shallow and MCEs of the Gulf of Eilat/Aqaba (0–100 m depth). Surveys were conducted by technical‐diving and drop‐cameras, in addition to one year of light spectral measurements. We quantify two distinct coral assemblages: shallow (<40 m) and MCEs (40–100 m), exhibiting markedly different relationships with light. The depth ranges and morphology of 47 coral genera were better explained by light than depth, mainly, due to photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) (1% at 76 and 36 m, respectively). Branching coral species were found mainly at shallower depths, that is, down to 36 m. Among the abundant upper‐mesophotic specialist corals, Leptoseris glabra, Euphyllia paradivisa, and Alveopora spp. were found strictly between 40 and 80 m depth. The only lower‐mesophotic specialist, Leptoseris fragilis, was found deeper than 80 m. We suggest that shallow coral genera are light‐limited below a level of 1.25% surface PAR and that the optimal PAR for mesophotic communities is at 7.5%. This study contributes to moving MCE ecology from a descriptive phase into identifying key ecological and physiological processes structuring MCE coral communities. Moreover, it may serve as a model enabling the description of a coral zonation worldwide on the basis of light quality data.

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Section: Light Limitation and Solar Stress May Control The Shallow-tosupporting

confidence: 88%

Light environment drives the shallow‐to‐mesophotic coral community transition

et al. 2019

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“…Mixing results have been also reported at the community level (Riegl and Piller , Semmler et al. ), revealing the need for more explicit evaluations of this important hypothesis.…”

Section: Introductionmentioning

confidence: 76%

“…, Semmler et al. ). For instance, the assumption that cooler environments protect corals from bleaching has been recently challenged, as Caribbean mesophotic corals (30–75 m depth) have lower bleaching threshold temperatures than shallow corals (Smith et al.…”

Section: Introductionmentioning

confidence: 98%

“…Despite many researchers have discussed their results in light of the DRRH framework (Lesser et al 2009, Bongaerts et al 2010, Loya et al 2016, the number of studies explicitly designed to validate the assumptions or test the predictions of the DRRH is still limited (Smith et al 2016, Bongaerts et al 2017, Semmler et al 2017. For instance, the assumption that cooler environments protect corals from bleaching has been recently challenged, as Caribbean mesophotic corals (30-75 m depth) have lower bleaching threshold temperatures than shallow corals (Smith et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Limited potential of deep reefs to serve as refuges for tropical Southwestern Atlantic corals

Morais

Santos

2018

Ecosphere

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The deep reef refuge hypothesis (DRRH) predicts that deep coral reefs may act as refuges against major disturbances affecting shallow reefs, but to date, a few studies have explicitly examined its validity at the community level. We sampled 19 Brazilian reefs distributed between 3 and 61 m depth and tested five DRRH predictions regarding species diversity, distribution, and functional profile of communities. The first prediction was that deep reefs (>30 m depth) should host greater gamma diversity to be able to export species to shallow reefs (<30 m). Second, depth‐generalist species should dominate the shallow reefs; otherwise, local extirpation in shallow areas could not be reverted by the deep reefs. Third, alpha diversity should be greater in deep reefs due to reduced anthropogenic pressure in deeper areas. Fourth, beta diversity should be smaller among shallow than deep reefs due to the human‐induced spread of a few disturbance‐adapted species near sea surface. Finally, the functional composition of shallow reefs should be a subset from that of deep reefs to allow functional recovering of shallower areas. Contrary to expectations, coral communities presented twice more gamma diversity in shallow than deep reefs (13 vs. seven effective species) and only three out of 17 species occurred along the entire gradient. Additionally, the alpha diversity of rare, typical, and dominant species was similar between shallow and deep reefs, and the beta diversity of rare and typical species was about 50% greater in shallow than deep reefs. Supporting the DRRH, coral communities of both reefs were dominated by reef‐building, zooxanthellated, gonochoric corals with brooding or broadcast reproductive mode (Siderastrea stellata and Montastraea cavernosa). However, soft corals were observed only in shallow reefs and azooxanthellated corals were recorded only in deep reefs. These findings revealed a limited potential of deep reefs to serve as refuges for Southwestern Atlantic coral communities, though they may work for two depth‐generalist dominant species. We strongly recommend preventing human disturbances at any depth and including both shallow and deep reefs in regional conservation actions.

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“…Far from the coast and surface, this coral reef is not impacted by coastal pollution and water temperature fluctuations that affect most shallow water reefs. It has been hypothesized that mesophotic coral reefs such as Pulley Ridge can be an important source of larvae for the more vulnerable shallow water reefs like the Dry Tortugas and the Florida Keys (Bongaerts et al, ; Semmler et al, ; Serrano et al, ). To protect those critical ecosystems, the GoM Fishery Management Council is considering the extension of the Florida Keys National Marine Sanctuary to Pulley Ridge (Baker et al, ; Reed, ).…”

Section: Introductionmentioning

confidence: 99%

Connectivity of Pulley Ridge With Remote Locations as Inferred From Satellite‐Tracked Drifter Trajectories

et al. 2018

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Using historical (1994–2017) satellite‐tracked surface drifter trajectory data, we conduct a probabilistic Lagrangian circulation study which sheds light on the connectivity of Pulley Ridge with other locations in the Gulf of Mexico and adjacent areas. The analysis reveals that Pulley Ridge is connected with the North Atlantic, the Caribbean Sea, and most of the Gulf of Mexico. Preferred connecting pathways are identified and arrival times to potential reef sites computed. The study demonstrates the importance of Pulley Ridge as a source for neighboring regions like the Dry Tortugasa, the Florida Keys, Campeche Bank, and the east Florida coast as well as a self‐recruitment area for species with short competence time. The study further suggests that the reefs in the Caribbean Sea, the Dry Tortugas, the western Florida Keys, and the West Florida Shelf can act as sources for Pulley Ridge, indicating the importance of Pulley Ridge as a central refugium for species in the Gulf of Mexico.

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Are mesophotic coral ecosystems distinct communities and can they serve as refugia for shallow reefs?

Cited by 103 publications

References 53 publications

Light environment drives the shallow‐to‐mesophotic coral community transition

Light environment drives the shallow‐to‐mesophotic coral community transition

Limited potential of deep reefs to serve as refuges for tropical Southwestern Atlantic corals

Connectivity of Pulley Ridge With Remote Locations as Inferred From Satellite‐Tracked Drifter Trajectories

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