scholarly journals Light-induced polyp retraction and tissue rupture in the photosensitive, reef-building coral Acropora muricata

2019 ◽  
Author(s):  
Pierre Philippe Laissue ◽  
Yan Gu ◽  
Chen Qian ◽  
David J. Smith
Keyword(s):  
Coral Reefs ◽  
Light Exposure ◽  
Larval Settlement ◽  
Light Sheet ◽  
Tissue Reaction ◽  
Dynamic Imaging ◽  
Coral Tissue ◽  
High Temporal Resolution ◽  
Imaging Tool ◽  
Tissue Rupture

ABSTRACTCoral reefs are in alarming decline due to climate emergency, pollution and other man-made disturbances. The numerous ecosystem services derived from coral reefs are underpinned by the growth and physical complexity of reef-forming corals. Our knowledge of their fundamental biology is limited by available technology. We need a better understanding of larval settlement and development, skeletogenesis, interactions with pathogens and symbionts, and how this biology interacts with environmental factors such as light exposure, temperature, and ocean acidification. We here focus on a fast-growing key coloniser, Acropora muricata. To enable dynamic imaging of the photosensitive organism at different scales, we developed light-sheet illumination for fluorescence microscopy of small coral colonies. Our approach reveals live polyps in previously unseen detail. An imaging range for Acropora muricata with no measurable photodamage is defined based upon polyp expansion, coral tissue reaction, and photobleaching. We quantify polyp retraction as a photosensitive behavioural response and show sparse zooxanthellar expulsion and coral tissue rupture at higher intensities of blue light. The simple and flexible technique enables non-invasive continuous dynamic imaging of highly photosensitive organisms with sizes between 1 mm3 and 5 cm3, for eight hours, at high temporal resolution, on a scale from multiple polyps down to cellular resolution. This live imaging tool opens a new window into the dynamics of reef-building corals.

Predicting cold-water bleaching in corals: role of temperature, and potential integration of light exposure

2020 ◽  
Vol 642 ◽  
pp. 133-146
Author(s):  
PC González-Espinosa ◽  
SD Donner
Keyword(s):  
Coral Bleaching ◽  
Cold Water ◽  
Light Exposure ◽  
Light Attenuation ◽  
Florida Keys ◽  
Cold Temperature ◽  
Warm Water ◽  
Coral Tissue ◽  
Effect Of Temperature ◽  
Type I

Warm-water growth and survival of corals are constrained by a set of environmental conditions such as temperature, light, nutrient levels and salinity. Water temperatures of 1 to 2°C above the usual summer maximum can trigger a phenomenon known as coral bleaching, whereby disruption of the symbiosis between coral and dinoflagellate micro-algae, living within the coral tissue, reveals the white skeleton of coral. Anomalously cold water can also lead to coral bleaching but has been the subject of limited research. Although cold-water bleaching events are less common, they can produce similar impacts on coral reefs as warm-water events. In this study, we explored the effect of temperature and light on the likelihood of cold-water coral bleaching from 1998-2017 using available bleaching observations from the Eastern Tropical Pacific and the Florida Keys. Using satellite-derived sea surface temperature, photosynthetically available radiation and light attenuation data, cold temperature and light exposure metrics were developed and then tested against the bleaching observations using logistic regression. The results show that cold-water bleaching can be best predicted with an accumulated cold-temperature metric, i.e. ‘degree cooling weeks’, analogous to the heat stress metric ‘degree heating weeks’, with high accuracy (90%) and fewer Type I and Type II errors in comparison with other models. Although light, when also considered, improved prediction accuracy, we found that the most reliable framework for cold-water bleaching prediction may be based solely on cold-temperature exposure.

scholarly journals Coralivoría del gasterópodo Jenneria pustulata (Ovulidae: Pediculariinae) en dos arrecifes coralinos del PNN isla Gorgona

2018 ◽  
Vol 47 (2) ◽  
Author(s):  
Mauro Giovanni Zucconi ◽  
Levy D. Obonaga ◽  
Edgardo Londoño-Cruz
Keyword(s):  
Coral Reefs ◽  
Coral Species ◽  
Size Structure ◽  
Coral Tissue ◽  
Laboratory Conditions ◽  
Set Up ◽  
Biological Dynamics ◽  
Colombian Pacific

Coral reefs are very important and highly biodiverse ecosystems that are exposed to various stressors, including biological ones, such as parasitism and corallivory – the direct consumption of coral tissue by a predator. Knowledge on the effects of corallivory on the coral reefs in the Colombian Pacific is poor. Therefore a study was set up to quantify the abundance of and the corallivory rate by the snail Jenneria pustulata in La Azufrada and Playa Blanca coral reefs (Gorgona Island, Colombia). Snails were manually sampled from the underside of Pocillopora sp. colonies and measured in situ to determine their size structure for each reef. To measure possible damage caused by corallivory, several snails were kept under controlled laboratory conditions for 24 h. Snail sizes and corallivory varied significantly between reefs (P=0.0001; P«0.001). Snails from Playa Blanca were larger than snails from La Azufrada, while corallivory was higher in La Azufrada than in Playa Blanca. Although corallivory rates by J. pustulata are smaller than rates reported for other predators in different coral species, it is recommended to continue this kind of investigations in order to increase the knowledge on biological dynamics of this species and to understand how they affect the reefs at Gorgona Island.

scholarly journals ECOLOGÍA QUÍMICA DE LAS ESPONJAS EXCAVADORAS CLIONA APRICA, C. CARIBBAEA, C. DELITRIX Y C. TENUIS

2016 ◽  
Vol 34 ◽  
Author(s):  
Andia Chaves Fonnegra ◽  
Mateo López Victoria ◽  
Fernando Parra Velandia ◽  
Sven Zea
Keyword(s):  
Larval Settlement ◽  
Coral Tissue ◽  
Live Coral ◽  
Stegastes Partitus ◽  
Excavating Sponges ◽  
Natural Concentration ◽  
Experimental Media ◽  
Organic Extracts ◽  
Fouling Organisms ◽  
San Andres

The Caribbean encrusting and excavating sponges Cliona aprica, C. caribbaea, C. delitrix and C. tenuis (Porifera, Hadromerida, Clionaidae), aggresively undermine and displace live coral tissue. At San Andrés island and Islas del Rosario (Colombian Caribbean), in all 145 observed cases of direct contact of the sponges C. aprica, C. caribbaea and C. tenuis with 17 coral species, corals showed unhealthy signs in their tissue. It was also noticed that the surface of these sponges is colonized by few organisms and that they are rarely preyed upon. To establish the possible use of chemical substances by these sponges in competition for space with corals (allelopathy), as inhibitors of larval settlement (antifouling), and as feeding deterrents against generalist fish (antipredatory), the activity of crude organic extracts was experimentally evaluated. Extracts were prepared in methanol and 1:2 metanol:dichloromethane and incorporated in experimental media at the natural concentration within the sponges. Using an unpublished method being developed by J. Pawlik (University of North Caroline at Wilmington) and M. Ilan (Tel Aviv University), PhytagelTM disks with crude extracts of each of the four sponge species, placed on the coral Montastrea cavernosa, produced a greater degree of polyp mortality than control gels without extract. Gels with extracts of the sponges C. aprica and C. caribbaea + C. tenuis, served in Petri dishes and used as substratum in the field, inhibited significantly the settlement of fouling organisms, in comparison to control gels. In laboratory trials, wheat flour pellets with extracts C. delitrix and C. caribbaea + C. tenuis were significantly rejected by the omnivore reef damselfish, Stegastes partitus, whereas pellets with extract of C. aprica did not deter feeding. These results suggest that substances present in the crude organic extracts of these sponges may be responsible in part for their ability to compete for reef substrata and to defend themselves from potential aggressors.

scholarly journals Zooxanthellae Harvested by Ciliates Associated with Brown Band Syndrome of Corals Remain Photosynthetically Competent

2007 ◽  
Vol 73 (6) ◽  
pp. 1968-1975 ◽  
Author(s):  
Karin E. Ulstrup ◽  
Michael Kühl ◽  
David G. Bourne
Keyword(s):  
Steady State ◽  
Light Curve ◽  
Light Exposure ◽  
Fluorescence Analysis ◽  
Coral Tissue ◽  
Quantum Yields ◽  
Symbiotic Association ◽  
Gross Photosynthesis ◽  
Brown Band ◽  
Oxygen Measurements

ABSTRACT Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae.

scholarly journals A Total Variation-Based Reconstruction Method for Dynamic MRI

2008 ◽  
Vol 9 (1) ◽  
pp. 69-80 ◽  
Author(s):  
Germana Landi ◽  
Elena Loli Piccolomini ◽  
Fabiana Zama
Keyword(s):  
Magnetic Resonance ◽  
Total Variation ◽  
Dynamic Mri ◽  
Magnetic Resonance Images ◽  
Dynamic Imaging ◽  
Test Problems ◽  
High Temporal Resolution ◽  
Reconstruction Method ◽  
Dynamic Magnetic Resonance ◽  
Tv Regularization

In recent years, total variation (TV) regularization has become a popular and powerful tool for image restoration and enhancement. In this work, we apply TV minimization to improve the quality of dynamic magnetic resonance images. Dynamic magnetic resonance imaging is an increasingly popular clinical technique used to monitor spatio-temporal changes in tissue structure. Fast data acquisition is necessary in order to capture the dynamic process. Most commonly, the requirement of high temporal resolution is fulfilled by sacrificing spatial resolution. Therefore, the numerical methods have to address the issue of images reconstruction from limited Fourier data. One of the most successful techniques for dynamic imaging applications is the reduced-encoded imaging by generalized-series reconstruction method of Liang and Lauterbur. However, even if this method utilizesa prioridata for optimal image reconstruction, the produced dynamic images are degraded by truncation artifacts, most notably Gibbs ringing, due to the spatial low resolution of the data. We use a TV regularization strategy in order to reduce these truncation artifacts in the dynamic images. The resulting TV minimization problem is solved by the fixed point iteration method of Vogel and Oman. The results of test problems with simulated and real data are presented to illustrate the effectiveness of the proposed approach in reducing the truncation artifacts of the reconstructed images.

scholarly journals Detecting sedimentation impacts to coral reefs resulting from dredging the Port of Miami, Florida USA

2016 ◽  
Author(s):  
Margaret W Miller ◽  
Jocelyn Karazsia ◽  
Carolyn E Groves ◽  
Sean Griffin ◽  
Tom Moore ◽  
...  
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Coral Disease ◽  
Sediment Accumulation ◽  
Biological Response ◽  
Time Frame ◽  
Tissue Loss ◽  
Coral Tissue ◽  
Live Coral ◽  
Monitoring Methods

The federal channel at Port of Miami, Florida, USA, was dredged between late 2013 and early 2015, to widen and deepen the channel. While the precise effects of the dredging on surrounding coral reefs are not well quantified, previously published remote sensing analyses, as well as agency and anecdotal reports suggest the most severe and largest area of sedimentation occurred on a coral reef feature referred to as the Inner Reef, particularly in the sector north of the channel. A regional warm-water mass bleaching event followed by a coral disease outbreak during this same time frame confounded the assessment of dredging-related impacts to coral reefs adjacent to the federal channel. In-water field assessments conducted after the completion of dredging and a time series analysis of tagged corals photographed pre-, during, and post-dredging, are used to discern dredging-related sedimentation impacts for the Inner Reef north. Results indicate increased sediment accumulation, severe in certain times and places, and an associated biological response, including significantly greater proportion of live coral tissue loss, occurred within coral reef sites located closer to the channel. Dredging projects near valuable and sensitive habitats subject to local and global stressors require monitoring methods capable of discerning non-dredging related impacts and adaptive management to ensure predicted and unpredicted project-related impacts are quantified. Anticipated increasing frequency and intensity of warming stress also suggests that manageable- but- unavoidable local stressors such as dredging should be partitioned from the warmest times of year.

scholarly journals Optical properties of living corals determined with diffuse reflectance spectroscopy

2019 ◽  
Author(s):  
Steven L. Jacques ◽  
Daniel Wangpraseurt ◽  
Michael Kühl
Keyword(s):  
Optical Properties ◽  
Diffuse Reflectance ◽  
Fiber Optic ◽  
Diffuse Reflectance Spectroscopy ◽  
Light Exposure ◽  
Diffusion Theory ◽  
Reflectance Spectroscopy ◽  
Lateral Spread ◽  
Coral Tissue ◽  
Live Coral

AbstractThe internal light field and thus light exposure of the photosymbiotic microalgae (Symbiodinium sp.) in corals is strongly modulated by the optical properties of coral tissue and skeleton. While there are numerous studies documenting the light microenvironment in corals, there are only few measurements of the inherent optical properties of corals in the literature, and this has hampered a more quantitative understanding of coral optics. Here we present a study of the optical properties of 26 live coral samples, representative of 11 coral species and spanning a variety of morphotypes. We employed well-established fiber-optic reflectance spectroscopy techniques from biomedical optics using two methods: (1) A source and a detection fiber separated by a variable distance measured the lateral spread of light in corals, dominated by the skeleton; (2) A fiber-optic field radiance probe measured the diffuse reflectance from the coral surface, dominated by the living coral tissue. Analysis based on diffusion theory and Monte Carlo simulation yielded estimates of the bulk scattering and absorption coefficients of the coral tissue and skeleton, in the 750-1030 nm wavelength range. Extrapolating into the spectral region of photosynthetically active radiation (PAR, 400-700 nm) allowed estimation of the optical depth of absorption by the main Symbiodinium photopigment chlorophyll a. Coral tissue scattering was on average ~1.9x stronger than the scattering of the skeleton, consistent with the model that corals trap photons by high scattering to enhance absorption by algal pigments, while the lower scattering of the skeleton allows spread of light to otherwise shaded coral tissue areas.

scholarly journals Automated screening by 3D light-sheet microscopy with high spatial and temporal resolution reveals mitotic phenotypes

2020 ◽  
Author(s):  
Björn Eismann ◽  
Teresa G Krieger ◽  
Jürgen Beneke ◽  
Ruben Bulkescher ◽  
Lukas Adam ◽  
...  
Keyword(s):  
Cell Cultures ◽  
High Throughput ◽  
Light Exposure ◽  
Epigenetic Modification ◽  
Fluorescent Microscopy ◽  
Light Sheet ◽  
Drug Candidate ◽  
Light Sheet Microscopy ◽  
Phenotype Classification ◽  
3D Cell Cultures

Abstract3D cell cultures enable the in vitro study of dynamic biological processes such as the cell cycle, but their use in high-throughput screens remains impractical with conventional fluorescent microscopy. Here, we present a screening workflow for the automated evaluation of mitotic phenotypes in 3D cell cultures by light-sheet microscopy. After sample preparation by a liquid handling robot, three-dimensional cell spheroids are imaged for 24 hours in toto with a dual inverted selective plane illumination (diSPIM) microscope with a much improved signal-to-noise ratio, higher imaging speed, isotropic resolution and reduced light exposure compared to a spinning disc confocal microscope. A dedicated high-content image processing pipeline implements convolutional neural network based phenotype classification. We illustrate the potential of our approach by siRNA knock-down and epigenetic modification of 28 mitotic target genes for assessing their phenotypic role in mitosis. By rendering light-sheet microscopy operational for high-throughput screening applications, this workflow enables target gene characterization or drug candidate evaluation in tissue-like 3D cell culture models.

A Dual Modality Dynamic Imaging System

2008 ◽  
Author(s):  
Mehmet Burcin Unlu ◽  
Yuting Lin ◽  
Orhan Nalcioglu ◽  
Gultekin Gulsen
Keyword(s):  
Imaging System ◽  
Optical Tomography ◽  
Dynamic Imaging ◽  
Optical Data ◽  
High Temporal Resolution ◽  
Optical Parameters ◽  
Combined System ◽  
Optical Contrast Agents ◽  
Animal Imaging ◽  
Wide Range

Diffuse optical tomography (DOT) is a recently emerging technique that uses arrays of sources and detectors to obtain spatially dependent optical parameters of tissue. DOT techniques have been applied for a wide range of applications, especially for breast and head as well as animal imaging. We have developed an integrated dynamic MR/DOT imaging system. This combined system can acquire MR and optical data simultaneously with a high temporal resolution. Hence, the enhancement kinetics of multiple MR and optical contrast agents can be monitored independently.

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