Biology subjects

Loya, Y.

Publications and source records attributed to Loya, Y..

5 recordsLinked to original sources

bioRxiv2022

3D Imaging Reveals Resilience: Storm Impact on Coral Reef Structural Complexity

Extreme weather events are increasing in frequency and magnitude. Consequently, it is important to understand their effects and remediation. Resilience reflects the ability of an ecosystem to absorb change, which is important for understanding ecological dynamics and trajectories. To describe the impact of a powerful storm on coral reef structural complexity, we used novel computational tools and detailed 3D reconstructions captured at three time points over three years. Our data-set Reefs4D of 21 co-registered image-based models enabled us to calculate the differences at seven sites over time and is released with the paper. We employed six geometrical metrics, two of which are new algorithms for calculating fractal dimension of reefs in full 3D. We conducted a multivariate analysis to reveal which sites were affected the most and their relative recovery. We also explored the changes in fractal dimension per size category using our cube-counting algorithm. Three metrics showed a signicant difference between time points, i.e., decline and subsequent recovery in structural complexity. The multivariate analysis and the results per size category showed a similar trend. Coral reef resilience has been the subject of seminal studies in ecology. We add important information to the discussion by focusing on 3D structure through image-based modeling. The full picture shows resilience in structural complexity, suggesting that the reef has not gone through a catastrophic phase shift. Our novel analysis framework is widely transferable and useful for research, monitoring, and management. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/519015v3_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@888999org.highwire.dtl.DTLVardef@1c51dorg.highwire.dtl.DTLVardef@340d97org.highwire.dtl.DTLVardef@16865d8_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThe effect of storms on coral reef 3D structure is poorly understood. C_LIO_LIWe studied the impact of a storm on coral reefs using a novel 3D imaging framework. C_LIO_LIWe used geometrical metrics including new methods for calculating fractal dimension. C_LIO_LIThe reefs recovered in two years with regards to structural complexity. C_LIO_LIBased on 3D analysis the reefs exhibit structural resilience. C_LI

ecology↗

bioRxiv2021

Characterization of morpho-functional traits in mesophotic corals reveals optimized light capture and photosynthesis

The morphology and skeleton architecture of photosynthetic corals modulates the light capture and functioning of the coral-algal symbiosis on shallow-water corals. Since corals can thrive on mesophotic reefs under extreme light-limited conditions, we hypothesized that microskeletal coral features optimize light capture under low-light environments. Using micro-computed tomography scanning, we conducted a comprehensive three-dimensional (3D) assessment of small-scale skeleton morphology of the depth-generalist coral Stylophora pistillata collected from shallow (5 m) and mesophotic (45 m) depths. We detected a high phenotypic diversity between depths, resulting in two distinct morphotypes, with calyx diameter, theca height, and corallite marginal spacing contributing to most of the variation between depths. To determine whether such depth-specific morphotypes affect coral light capture and photosynthesis on the corallite-scale, we developed 3D simulations of light propagation based on photosynthesis-irradiance parameters. We found that corals associated with shallow morphotypes dissipated excess light through self-shading microskeletal features; while mesophotic morphotypes facilitated enhanced light absorption and photosynthesis under low-light conditions. We conclude that the mesophotic coral architecture provides a greater ability to trap solar energy and efficiently exploit the limited light conditions, and suggest that morphological modifications play a key role in the photoadaptation response to low-light.

ecology↗

bioRxiv2021

Symbiodiniaceae conduct under natural bleaching stress during advanced gametogenesis stages of the mesophotic coral Alveopora allingi

The mesophotic coral Alveopora allingi from the northern Gulf of Eilat/Aqaba, Red Sea, is affected by year-round partial coral-bleaching events. During these events, the migration of Symbiodiniaceae takes place from the coral-host mesoglea to the developed oocytes in bleached parts of colonies of A. allingi but not in the non-bleached parts. Additionally, these oocytes are abnormal, missing part of the structural material of the peripheral areas and are also significantly larger in the bleached areas of the colonies. Hence, we suggest a parasitic behavior of the symbionts or a commensalism relationship which enhance symbionts needs during bleaching periods and may boost the gametogenesis development in these corals. We propose that evolutionarily, this behavior may greatly contribute to the symbiont community survival throughout the bleaching period, and it can also be beneficial for the hosts persistence and adaptation to bleaching through the acquisition of a specific symbiont community following the bleaching event.

ecology↗

bioRxiv2020

Light-harvesting in mesophotic corals is powered by a spatially efficient photosymbiotic system between coral host and microalgae

The coral-algal photosymbiosis fuels global coral-reef primary productivity, extending from sea level to as deep as 150 m (i.e., mesophotic). Currently, it is largely unknown how such mesophotic reefs thrive despite extremely limited light conditions. Here, we show that corals exhibit a plastic response to mesophotic conditions that involves a spatially optimized regulation of the bio-optical properties by coral host and symbiont. In contrast to shallow corals, mesophotic corals absorbed up to three-fold more light, resulting in excellent photosynthetic response under light conditions of only ~3% of the incident surface irradiance. The enhanced light harvesting capacity of mesophotic corals is regulated by average refractive index fluctuations in the coral skeleton that give rise to optical scattering and facilitate light transport and absorption by densely pigmented host tissue. The results of this study provide fundamental insight into the energy efficiency and light-harvesting mechanisms underlying the productivity of mesophotic coral reef ecosystems, yet also raise concerns regarding their ability to withstand prolonged environmental disturbances.

biophysics↗

bioRxiv2019

Light environment drives the shallow to mesophotic coral community transition

AbstractLight 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 that issue. 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 Tech-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, was better explained by light than depth, mainly, due to the Photosynthetically Active Radiation (PAR) and Ultra Violet Radiation (1% at 76 m and 36 m, respectively). Branching coral species were found mainly at shallower depths i.e., down to 36 m. Among the abundant upper mesophotic specialist-corals, Leptoseris glabra, Euphyllia paradivisa and Alveopora spp., were found strictly between 36-76 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 MCEs 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 world-wide on the basis of light quality data.

ecology↗