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

SummaryThe 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.

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Nutrient and sediment loading affect multiple facets of functionality in a tropical branching coral

Journal of Experimental Biology ◽

10.1242/jeb.225045 ◽

2020 ◽

Vol 223 (21) ◽

pp. jeb225045

Author(s):

Danielle M. Becker ◽

Nyssa J. Silbiger

Keyword(s):

Coral Reef ◽

Nitrogen Content ◽

Thermal Performance ◽

Nutrient Loading ◽

Metabolic Responses ◽

Coral Host ◽

Percent Cover ◽

Sediment Loading ◽

Anthropogenic Stressors ◽

Coral Reef Ecosystems

ABSTRACTCoral reefs, one of the most diverse ecosystems in the world, face increasing pressures from global and local anthropogenic stressors. Therefore, a better understanding of the ecological ramifications of warming and land-based inputs (e.g. sedimentation and nutrient loading) on coral reef ecosystems is necessary. In this study, we measured how a natural nutrient and sedimentation gradient affected multiple facets of coral functionality, including endosymbiont and coral host response variables, holobiont metabolic responses and percent cover of Pocillopora acuta colonies in Mo′orea, French Polynesia. We used thermal performance curves to quantify the relationship between metabolic rates and temperature along the environmental gradient. We found that algal endosymbiont percent nitrogen content, endosymbiont densities and total chlorophyll a content increased with nutrient input, while endosymbiont nitrogen content per cell decreased, likely representing competition among the algal endosymbionts. Nutrient and sediment loading decreased coral metabolic responses to thermal stress in terms of their thermal performance and metabolic rate processes. The acute thermal optimum for dark respiration decreased, along with the maximal performance for gross photosynthetic and calcification rates. Gross photosynthetic and calcification rates normalized to a reference temperature (26.8°C) decreased along the gradient. Lastly, percent cover of P. acuta colonies decreased by nearly two orders of magnitude along the nutrient gradient. These findings illustrate that nutrient and sediment loading affect multiple levels of coral functionality. Understanding how local-scale anthropogenic stressors influence the responses of corals to temperature can inform coral reef management, particularly in relation to the mediation of land-based inputs into coastal coral reef ecosystems.

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Thermal Stress and Resilience of Corals in a Climate-Changing World

Journal of Marine Science and Engineering ◽

10.3390/jmse8010015 ◽

2019 ◽

Vol 8 (1) ◽

pp. 15

Author(s):

Rodrigo Carballo-Bolaños ◽

Derek Soto ◽

Chaolun Allen Chen

Keyword(s):

Thermal Stress ◽

Coral Reef ◽

Fossil Fuels ◽

High Temperature Stress ◽

Coral Host ◽

Physiological Diversity ◽

Coral Reef Ecosystems ◽

Adaptation Processes ◽

Symbiotic Organisms ◽

Ecological Functioning

Coral reef ecosystems are under the direct threat of increasing atmospheric greenhouse gases, which increase seawater temperatures in the oceans and lead to bleaching events. Global bleaching events are becoming more frequent and stronger, and understanding how corals can tolerate and survive high-temperature stress should be accorded paramount priority. Here, we review evidence of the different mechanisms that corals employ to mitigate thermal stress, which include association with thermally tolerant endosymbionts, acclimatisation, and adaptation processes. These differences highlight the physiological diversity and complexity of symbiotic organisms, such as scleractinian corals, where each species (coral host and microbial endosymbionts) responds differently to thermal stress. We conclude by offering some insights into the future of coral reefs and examining the strategies scientists are leveraging to ensure the survival of this valuable ecosystem. Without a reduction in greenhouse gas emissions and a divergence from our societal dependence on fossil fuels, natural mechanisms possessed by corals might be insufficient towards ensuring the ecological functioning of coral reef ecosystems.

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Nonreciprocal charge transport up to room temperature in bulk Rashba semiconductor α-GeTe

Nature Communications ◽

10.1038/s41467-020-20840-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yan Li ◽

Yang Li ◽

Peng Li ◽

Bin Fang ◽

Xu Yang ◽

...

Keyword(s):

Charge Transport ◽

Room Temperature ◽

Theoretical Calculations ◽

Ferromagnetic Layer ◽

Spin Splitting ◽

New Paradigm ◽

Rashba Spin ◽

Rashba Spin Splitting ◽

Fundamental Insight ◽

Insight Into

AbstractNonmagnetic Rashba systems with broken inversion symmetry are expected to exhibit nonreciprocal charge transport, a new paradigm of unidirectional magnetoresistance in the absence of ferromagnetic layer. So far, most work on nonreciprocal transport has been solely limited to cryogenic temperatures, which is a major obstacle for exploiting the room-temperature two-terminal devices based on such a nonreciprocal response. Here, we report a nonreciprocal charge transport behavior up to room temperature in semiconductor α-GeTe with coexisting the surface and bulk Rashba states. The combination of the band structure measurements and theoretical calculations strongly suggest that the nonreciprocal response is ascribed to the giant bulk Rashba spin splitting rather than the surface Rashba states. Remarkably, we find that the magnitude of the nonreciprocal response shows an unexpected non-monotonical dependence on temperature. The extended theoretical model based on the second-order spin–orbit coupled magnetotransport enables us to establish the correlation between the nonlinear magnetoresistance and the spin textures in the Rashba system. Our findings offer significant fundamental insight into the physics underlying the nonreciprocity and may pave a route for future rectification devices.

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Temporal hierarchy of intrinsic neural timescales converges with spatial core-periphery organization

Communications Biology ◽

10.1038/s42003-021-01785-z ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Mehrshad Golesorkhi ◽

Javier Gomez-Pilar ◽

Shankar Tumati ◽

Maia Fraser ◽

Georg Northoff

Keyword(s):

Time Window ◽

Human Cortex ◽

The Core ◽

Novel Variant ◽

Open Issue ◽

Task Differences ◽

Spatial Hierarchy ◽

Fundamental Insight ◽

Insight Into ◽

And Task

AbstractThe human cortex exhibits intrinsic neural timescales that shape a temporal hierarchy. Whether this temporal hierarchy follows the spatial hierarchy of its topography, namely the core-periphery organization, remains an open issue. Using magnetoencephalography data, we investigate intrinsic neural timescales during rest and task states; we measure the autocorrelation window in short (ACW-50) and, introducing a novel variant, long (ACW-0) windows. We demonstrate longer ACW-50 and ACW-0 in networks located at the core compared to those at the periphery with rest and task states showing a high ACW correlation. Calculating rest-task differences, i.e., subtracting the shared core-periphery organization, reveals task-specific ACW changes in distinct networks. Finally, employing kernel density estimation, machine learning, and simulation, we demonstrate that ACW-0 exhibits better prediction in classifying a region’s time window as core or periphery. Overall, our findings provide fundamental insight into how the human cortex’s temporal hierarchy converges with its spatial core-periphery hierarchy.

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