Effects of surface geometry on light exposure, photoacclimation and photosynthetic energy acquisition in zooxanthellate corals.

Symbiotic corals display a great array of morphologies, each of which has unique effects on light interception and the photosynthetic performance of in hospite zooxanthellae. Changes in light availability elicit photoacclimation responses to optimize the energy balances in primary producers, extensively documented for corals exposed to contrasting light regimes along depth gradients. Yet, response variation driven by coral colony geometry and its energetic implications on colonies with contrasting morphologies remain largely unknown.

Phenotypic plasticity for improved light harvesting, in tandem with methylome repatterning in reef-building corals.

Acclimatization through phenotypic plasticity represents a more rapid response to environmental change than adaptation and is vital to optimize organisms' performance in different conditions. Generally, animals are less phenotypically plastic than plants, but reef-building corals exhibit plant-like properties. They are light dependent with a sessile and modular construction that facilitates rapid morphological changes within their lifetime.

The δN in Orbicella faveolata organic matter reveals anthropogenic impact by sewage inputs in a Mexican Caribbean coral reef lagoon.

Coral-reef ecosystems provide essentials services to human societies, representing the most important source of income (e.g., tourism and artisanal fishing) for many coastal developing countries.

Evaluation of the current understanding of the impact of climate change on coral physiology after three decades of experimental research.

After three decades of coral research on the impacts of climate change, there is a wide consensus on the adverse effects of heat-stress, but the impacts of ocean acidification (OA) are not well established. Using a review of published studies and an experimental analysis, we confirm the large species-specific component of the OA response, which predicts moderate impacts on coral physiology and pigmentation by 2100 (scenario-B1 or SSP2-4.5), in contrast with the severe disturbances induced by only +2 °C of thermal anomaly.

Photosynthetic usable energy explains vertical patterns of biodiversity in zooxanthellate corals.

The biodiversity in coral reef ecosystems is distributed heterogeneously across spatial and temporal scales, being commonly influenced by biogeographic factors, habitat area and disturbance frequency. A potential association between gradients of usable energy and biodiversity patterns has received little empirical support in these ecosystems. Here, we analyzed the productivity and biodiversity variation over depth gradients in symbiotic coral communities, whose members rely on the energy translocated by photosynthetic algal symbionts (zooxanthellae).

The role of the endolithic alga Ostreobium spp. during coral bleaching recovery.

In this study, we explore how the Caribbean coral Orbicella faveolata recovers after bleaching, using fragments from 13 coral colonies exposed to heat stress (32 °C) for ten days. Biological parameters and coral optical properties were monitored during and after the stress. Increases in both, the excitation pressure over photosystem II (Qm) and pigment specific absorption (a*) were observed in the stressed corals, associated with reductions in light absorption at the chlorophyll a red peak (D) and symbiont population density.

Elucidating gene expression adaptation of phylogenetically divergent coral holobionts under heat stress.

As coral reefs struggle to survive under climate change, it is crucial to know whether they have the capacity to withstand changing conditions, particularly increasing seawater temperatures. Thermal tolerance requires the integrative response of the different components of the coral holobiont (coral host, algal photosymbiont, and associated microbiome). Here, using a controlled thermal stress experiment across three divergent Caribbean coral species, we attempt to dissect holobiont member metatranscriptome responses from coral taxa with different sensitivities to heat stress and use phylogenetic ANOVA to study the evolution of gene expression adaptation.

Validation of parameters and protocols derived from chlorophyll fluorescence commonly utilised in marine ecophysiological studies.

This study documents the first validation of the suitability of the most common parameters and protocols used in marine ecophysiology to characterise photosynthesis by means of chlorophyll a fluorescence tools. We demonstrate that the effective yield of PSII (ΔF /F m ') is significantly underestimated when using short inductions times (≤1 min) following the rapid light curve protocol (RLC). The consequent electron transport rates (ETR) underestimations are species-specific and highly variable with irradiance and the photoacclimatory condition of the sample.

Unraveling the structure and composition of Varadero Reef, an improbable and imperiled coral reef in the Colombian Caribbean.

Coral reefs are commonly associated with oligotrophic, well-illuminated waters. In 2013, a healthy coral reef was discovered in one of the least expected places within the Colombian Caribbean: at the entrance of Cartagena Bay, a highly-polluted system that receives industrial and sewage waste, as well as high sediment and freshwater loads from an outlet of the Magdalena River (the longest and most populated river basin in Colombia). Here we provide the first characterization of Varadero Reef's geomorphology and biological diversity.

Seasonal variation modulates coral sensibility to heat-stress and explains annual changes in coral productivity.

The potential effects of seasonal acclimatization on coral sensitivity to heat-stress, has received limited attention despite differing bleaching thresholds for summer and winter. In this study, we examined the response of two contrasting phenotypes, termed winter and summer, of four Caribbean reef corals to similar light and heat-stress levels. The four species investigated were categorized into two groups: species with the ability to harbour large number of symbionts, Orbicella annularis and O.

Absorptance determinations on multicellular tissues.

The analysis of the variation of the capacity and efficiency of photosynthetic tissues to collect solar energy is fundamental to understand the differences among species in their ability to transform this energy into organic molecules. This analysis may also help to understand natural changes in species distribution and/or abundance, and differences in species ability to colonize contrasting light environments or respond to environmental changes. Unfortunately, the challenge that optical determinations on highly dispersive samples represent has strongly limited the progression of this analysis on multicellular tissues, limiting our knowledge of the role that optical properties of photosynthetic tissues may play in the optimization of photosynthesis and growth of benthonic primary producers.

Key functional role of the optical properties of coral skeletons in coral ecology and evolution.

Multiple scattering of light on coral skeleton enhances light absorption efficiency of coral symbionts and plays a key role in the regulation of their internal diffuse light field. To understand the dependence of this enhancement on skeleton meso- and macrostructure, we analysed the scattering abilities of naked coral skeletons for 74 Indo-Pacific species. Sensitive morphotypes to thermal and light stress, flat-extraplanate and branching corals, showed the most efficient structures, while massive-robust species were less efficient.

The effects of elevated seawater temperatures on Caribbean gorgonian corals and their algal symbionts, Symbiodinium spp.

Global climate change not only leads to elevated seawater temperatures but also to episodic anomalously high or low temperatures lasting for several hours to days. Scleractinian corals are detrimentally affected by thermal fluctuations, which often lead to an uncoupling of their mutualism with Symbiodinium spp. (coral bleaching) and potentially coral death.

Empty Niches after Extinctions Increase Population Sizes of Modern Corals.

Large environmental fluctuations often cause mass extinctions, extirpating species and transforming communities [1, 2]. While the effects on community structure are evident in the fossil record, demographic consequences for populations of individual species are harder to evaluate because fossils reveal relative, but not absolute, abundances. However, genomic analyses of living species that have survived a mass extinction event offer the potential for understanding the demographic effects of such environmental fluctuations on extant species.

Microbial composition of biofilms associated with lithifying rubble of Acropora palmata branches.

Coral reefs are among the most productive ecosystems on the planet, but are rapidly declining due to global-warming-mediated changes in the oceans. Particularly for the Caribbean region, Acropora sp. stony corals have lost ∼80% of their original coverage, resulting in vast extensions of dead coral rubble.

Global inequities between polluters and the polluted: climate change impacts on coral reefs.

For many ecosystem services, it remains uncertain whether the impacts of climate change will be mostly negative or positive and how these changes will be geographically distributed. These unknowns hamper the identification of regional winners and losers, which can influence debate over climate policy. Here, we use coral reefs to explore the spatial variability of climate stress by modelling the ecological impacts of rising sea temperatures and ocean acidification, two important coral stressors associated with increasing greenhouse gas (GHG) emissions.

Microbial invasion of the Caribbean by an Indo-Pacific coral zooxanthella.

Human-induced environmental changes have ushered in the rapid decline of coral reef ecosystems, particularly by disrupting the symbioses between reef-building corals and their photosymbionts. However, escalating stressful conditions enable some symbionts to thrive as opportunists. We present evidence that a stress-tolerant "zooxanthella" from the Indo-Pacific Ocean, Symbiodinium trenchii, has rapidly spread to coral communities across the Greater Caribbean.

Symbiodinium photosynthesis in Caribbean octocorals.

Symbioses with the dinoflagellate Symbiodinium form the foundation of tropical coral reef communities. Symbiodinium photosynthesis fuels the growth of an array of marine invertebrates, including cnidarians such as scleractinian corals and octocorals (e.g.

Benthic primary production budget of a Caribbean reef lagoon (Puerto Morelos, Mexico).

High photosynthetic benthic primary production (P) represents a key ecosystem service provided by tropical coral reef systems. However, benthic P budgets of specific ecosystem compartments such as macrophyte-dominated reef lagoons are still scarce. To address this, we quantified individual and lagoon-wide net (Pn) and gross (Pg) primary production by all dominant functional groups of benthic primary producers in a typical macrophyte-dominated Caribbean reef lagoon near Puerto Morelos (Mexico) via measurement of O₂ fluxes in incubation experiments.

Shifts in coral-assemblage composition do not ensure persistence of reef functionality.

Coral communities are changing rapidly worldwide through loss of coral cover and shifts in species composition. Although many reef-building corals are likely to decline, some weedy opportunistic species might increase in abundance. Here we explore whether the reshuffling of species can maintain ecosystem integrity and functioning.

The PsbO homolog from Symbiodinium kawagutii (Dinophyceae) characterized using biochemical and molecular methods.

A photosystem II component, the PsbO protein is essential for maximum rates of oxygen production during photosynthesis, and has been extensively characterized in plants and cyanobacteria but not in symbiotic dinoflagellates. Its close interaction with D1 protein has important environmental implications since D1 has been identified as the primary site of damage in endosymbiotic dinoflagellates after thermal stress. We identified and biochemically characterized the PsbO homolog from Symbiodinium kawagutii as a 28-kDa protein, and immunolocalized it to chloroplast membranes.

Avoiding coral reef functional collapse requires local and global action.

Coral reefs face multiple anthropogenic threats, from pollution and overfishing to the dual effects of greenhouse gas emissions: rising sea temperature and ocean acidification. While the abundance of coral has declined in recent decades, the implications for humanity are difficult to quantify because they depend on ecosystem function rather than the corals themselves. Most reef functions and ecosystem services are founded on the ability of reefs to maintain their three-dimensional structure through net carbonate accumulation.

Induction of glycerol synthesis and release in cultured Symbiodinium.

Background: Symbiotic dinoflagellates transfer a substantial amount of their photosynthetic products to their animal hosts. This amount has been estimated to represent up to 90% of the photosynthetically fixed carbon and can satisfy in some instances the full respiratory requirements of the host. Although in several cnidarian-dinoflagellate symbioses glycerol is the primary photosynthetic product translocated to the host, the mechanism for its production and release has not been demonstrated conclusively.