Light, Temperature, Photosynthesis, Heterotrophy, and the Lower Depth Limits of Mesophotic Coral Ecosystems

Kahng, Samuel E.; Akkaynak, Derya; Shlesinger, Tom; Hochberg, Eric J.; Wiedenmann, Jörg; Tamir, Raz; Tchernov, Dan

doi:10.1007/978-3-319-92735-0_42

Cited by 109 publications

(127 citation statements)

References 245 publications

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“…Both clusters are characterized by different morphological forms, which may reflect adaptations to physical conditions (Kahng et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…It may also be possible that competitive interactions with shallow taxa, which are better able to tolerate brighter conditions, restrict mesophotic taxa to darker reef niches. Both clusters are characterized by different morphological forms, which may reflect adaptations to physical conditions (Kahng et al 2019).…”

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

confidence: 99%

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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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“…Both clusters are characterized by different morphological forms, which may reflect adaptations to physical conditions (Kahng et al. ).…”

Section: Discussionmentioning

confidence: 99%

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

confidence: 99%

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

et al. 2019

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“…Although on average larger colonies were observed in the MCEs, in most cases the coral species at these depths exhibited balanced population size-structures. It is widely accepted that mesophotic coral species have slower growth rates than their shallow congeners, since light, the primary energy source, is decreasing exponentially with depth (Kirk, 2011;Lesser et al, 2018;Kahng et al, 2019). Slower growth rates at the mesophotic depths are further linked to the dominant growth forms prevalent at these depths (Kahng et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…It is widely accepted that mesophotic coral species have slower growth rates than their shallow congeners, since light, the primary energy source, is decreasing exponentially with depth (Kirk, 2011;Lesser et al, 2018;Kahng et al, 2019). Slower growth rates at the mesophotic depths are further linked to the dominant growth forms prevalent at these depths (Kahng et al, 2019). Plate-like and encrusting coral growth forms have been long known to exhibit slower growth rates and are typically more abundant at deeper habitats (Buddemeier and Kinzie, 1976;Fricke and Meischner, 1985).…”

Section: Discussionmentioning

confidence: 99%

Coral Morphology Portrays the Spatial Distribution and Population Size-Structure Along a 5–100 m Depth Gradient

et al. 2020

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Population size structure provides information on demographic characteristics, such as growth and decline, enabling post-hoc assessment of spatial differences in susceptibility to disturbance. Nevertheless, very few studies have quantified size data of scleractinian corals along a shallow-mesophotic gradient, partly because of previously inaccessible depths. Here, we report the coral size-frequency distributions at the morphology level (six growth forms) and at the species level for ten representative locally abundant species along a broad depth gradient (5-100 m) in the Gulf of Eilat/Aqaba (GoE/A). A total of 18,865 colonies belonging to 14 families and 45 genera were recorded and measured over four reef sites. Colonies were found to be 11.2% more abundant at mesophotic (40-100 m; 55.6%) depths compared with shallow (5-30 m; 44.4%). The coral taxa exhibited heterogeneity in their size-structure, with marked differences among depths, morphological growth forms, and species. Branching and corymbose corals were more prevalent in shallow waters, while encrusting and laminar forms comprised the majority of mesophotic corals. Nevertheless, massive morphology was the most abundant growth form across all sites and depths (39%), followed by laminar (26%) and encrusting (20%). Corymbose corals (primarily Acroporidae) revealed constrained size at all depths; with the lack of small-size groups indicating populations at risk of decline. Depth-generalist species belonging to massive and laminar morphologies generally exhibited a larger colony size at the mesophotic depths, but were typified by a higher number of small colonies. Furthermore, we refute the widely and longaccepted assertion that Stylophora pistillata is the most abundant coral in the northern GoE/A, and assert that Leptoseris glabra is the one. Here, we provide a baseline for future monitoring of coral population structures, insights to recent ecological dynamics, retrospective assessment of coral community recovery following disturbances and grounds for conservation assessments and management actions.

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“…In fact, it has been previously shown that coral larvae deriving from high light adapted parents were larger than larvae belonging to low light adapted adults . Specifically, higher light availability in shallow reef conditions may result in higher energetic reserves, enabling larvae from the shallow reef to obtain a larger size compared to deep larvae, which might not be able to support a similar size range given the limited light energy available on the mesophotic reef (Lesser et al, 2018;Kahng et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

Physiological Characteristics of Stylophora pistillata Larvae Across a Depth Gradient

et al. 2020

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Depth related parameters, specifically light, affect different aspects of corals physiology, including fluorescence. Green fluorescence protein (GFP)-like pigments found in many coral species have been suggested to serve a variety of functions, including photo-protection and photo-enhancement. Using fluorescence imaging and molecular analysis, we further investigated the role of these proteins on the physiology of the coral Stylophora pistillata and its algal partners. Fluorescence was found to differ significantly between depths for larvae and adult colonies. Larvae from the shallow reef presented a higher GFP expression and a greater fluorescence intensity compared to the larvae from the mesophotic reef, reflecting the elevated need for photo-protection against high light levels characteristic of the shallow reef, thus supporting the "sunscreen" hypothesis. Additionally, given the lower but still occurring protein expression under non-damaging low light conditions, our results suggest that GFP-like proteins might act to regulate the amount of photosynthetically usable light for the benefit of the symbiotic algae. Moreover, we propose that the differences in GFP expression and green fluorescence between shallow and deep larvae indicate that the GFPs within coral larvae might serve to attract and retain different symbiont clades, increasing the chances of survival when encountering new environments.

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Light, Temperature, Photosynthesis, Heterotrophy, and the Lower Depth Limits of Mesophotic Coral Ecosystems

Cited by 109 publications

References 245 publications

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

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

Coral Morphology Portrays the Spatial Distribution and Population Size-Structure Along a 5–100 m Depth Gradient

Physiological Characteristics of Stylophora pistillata Larvae Across a Depth Gradient

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