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This study investigates the effects of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals naturally living at CO2 seeps and adjacent control sites from two locations (Dobu and Upa Upasina) in the Papua New Guinea underwater volcanic vent system. The seeps are characterized by seawater pH values ranging from 8.0 to about 7.7. The skeletal porosity of Galaxea fascicularis, Acropora millepora, massive Porites, and Pocillopora damicornis was higher (up to ~ 40%, depending on the species) at the seep sites compared to the control sites. Pocillopora damicornis also showed a decrease of micro-density (up to ~ 7%). Thus, further investigations conducted on this species showed an increase of the volume fraction of the larger pores (up to ~ 7%), a decrease of the intraskeletal organic matrix content (up to ~ 15%), and an increase of the intraskeletal water content (up to ~ 59%) at the seep sites. The organic matrix related strain and crystallite size did not vary between seep and control sites. This multi-species study showed a common phenotypic response among different zooxanthellate corals subjected to the same environmental pressures, leading to the development of a more porous skeletal phenotype under OA.

The plant hormone abscisic acid (ABA) coordinates responses to environmental signals with developmental changes and is important for stress resilience and crop yield. However, fundamental questions remain about how this phytohormone affects microalgae growth and stress regulation throughout the different stages of their life cycle. In this study, the effects of ABA on the physiology of the freshwater microalga Chlamydomonas reinhardtii at its different stages of life cycle were investigated. Exogenously added ABA enhanced the growth and photosynthesis of C. reinhardtii during the vegetative stage. The hormone also increased the tolerance of this alga to high salinity stress during gamete formation under nutrient depletion, as well as it extended their survival. We show that the level of reactive oxygen species (ROS) generated in the ABA-treated cells was significantly less than that in the untreated cells under inhibiting NaCl concentrations. Cell size examination showed that ABA prevents cells from forming palmella when exposed to high salinity. All together, these results suggest that ABA can support the vitality and survival of C. reinhardtii under high salt conditions.

Here, we explore the responses of photosynthesis and related cellular processes in the thermotolerant microalga Micractinium sp. acclimated to limiting and saturating irradiances combined with elevated temperatures, using a novel computer-controlled multi-sensor system. This system allows for the monitoring of online values of oxygen exchange during photosynthesis and respiration with high accuracy. Micractinium sp. cells showed maximum growth and net oxygen production rates under the optimal temperature of 25°C regardless of the light acclimation conditions. Our results show that the upper thermal threshold for Micractinium sp. photosynthesis and growth ranges between 35°C and 40°C. This microalga exhibited stable photosynthetic efficiency and effective non-photochemical quenching (NPQ) under saturating light, and was more susceptible to temperature change when acclimated to limiting light levels. These results demonstrate that the acclimation of thermotolerant microalgae to saturating light helps to enhance the thermal tolerance of PSII. This feature results from enhanced heat stability of PSII photochemistry and oxygen evolution.

Ocean acidification caused by shifts in ocean carbonate chemistry resulting from increased atmospheric CO2concentrations is threatening many calcifying organisms, including corals. Here we assessed autotrophy vs heterotrophy shifts in the Mediterranean zooxanthellate scleractinian coralBalanophyllia europaeaacclimatized to low pH/high pCO2conditions at a CO2vent off Panarea Island (Italy). Dinoflagellate endosymbiont densities were higher at lowest pH Sites where changes in the distribution of distinct haplotypes of a host-specific symbiont species, Philozoon balanophyllum,were observed. An increase in symbiont C/N ratios was observed at low pH, likely as a result of increased C fixation by higher symbiont cell densities. δ13C values of the symbionts and host tissue reached similar values at the lowest pH Site, suggesting an increased influence of autotrophy with increasing acidification. Host tissue δ15N values of 0‰ strongly suggest that diazotroph N2fixation is occurring within the coral tissue/mucus at the low pH Sites, likely explaining the decrease in host tissue C/N ratios with acidification. Overall, our findings show an acclimatization of this coral-dinoflagellate mutualism through trophic adjustment and symbiont haplotype differences with increasing acidification, highlighting that some corals are capable of acclimatizing to ocean acidification predicted under end-of-century scenarios.

The unprecedented devastation caused by the December 2004 tsunami (Reuters, 2005) was followed by environmentalists' claims that the human toll and overall impact were aggravated by disregard for conservation of coral reefs and mangrove forests (Channel News Asia, 2005; Cripps, 2005; Mangrove Action Project, 2005). Corals surround tropical shorelines (Spalding et al., 2001) and beyond them, on land, grow, in most cases, dense belts of mangroves (Chapman, 1977). These twin barriers are thought to protect shorelines from waves and may be capable of mitigating tsunami impact (Fig. 1). According to reports in the mass media, reefs and mangroves sheltered people from the tsunami's impact, whereas in the hardest hit areas in terms of human casualties, coral reefs and mangroves had been removed in order to make room for shrimp and fish mariculture (Kaban, 2005). Here we present an attempt to evaluate the potential of the combination of coral reefs and mangroves to attenuate tsunamis, and validate the claims regarding the protective function of reefs and mangroves. Special attention will be given to the extent of the recent destruction of reef and coral ecosystems in the region afflicted by the tsunami, and the importance of their conservation and of remediation and rehabilitation efforts (Kaban, 2005). Tsunamis have ravaged coastal communities since the earliest extant myths and written records (Table 1). The most prominent among these was the one generated by the volcanic eruption of Thera (Santorini), thought to have wiped out the Minoan civilization (Galanopoulos, 1960; Pararas-Carayannis, 1973), and sending survivors as far east as Canaan, where they settled as the biblical “Sea people” or Philistines, who competed with the Hebrews for what was to become the “Holy Land”. There are historical records of tsunamis with death tolls ranging from no victims to estimates of over 300,000 in the last one (Table 1). The Sumatra tsunami of December 2004 was the first to be witnessed via television in virtually every home, bringing the destructive potential of oceanic waves to unprecedented public awareness. In the wake of this tsunami, there have been several reports in the mass media regarding the reduction in the human death toll and overall destruction in areas that

Because of their high lipid content, microalgae are regarded as a potentially competitive source for biofuels. However, one of the main biotechnological challenges in algae-based biofuels is that cell division is arrested under conditions which promote lipid accumulation, resulting in reduced overall lipid yield. In this study, sethoxydim-resistant mutants of the promising thermotolerant green microalga Micractinium sp., which has a relatively fast growth rate and tolerance to outdoor high temperatures, were generated by UV-C mutagenesis for increased cellular triacylglycerol (TAG) without compromising on growth rate. Two Micractinium mutants were isolated (designated as Mut 3 and Mut 4) that displayed significant increase in TAG cell content up to 71% and 84%, with decreased chlorophyll content by 37% and 38%, respectively, compared with the wild-type cells. Final TAG culture productivity of Mut 3 and Mut 4 were also greater, reaching up to 0.61 ± 0.01 and 0.62 ± 0.02 g L−1, respectively, compared with the wild-type culture of 0.40 ± 0.03 g L−1. The mutants were stable without using antibiotics or any other chemicals during the experiments and preservation. These results highly nominate the mutants of Micractinium sp. isolated in this work as potential microalgae candidates to serve as a feedstock for sustainable and cost-effective biofuel production.

The biomineralization of corals occurs under conditions of high and low supersaturation with respect to aragonite, which corresponds to day- or night-time periods of their growth, respectively. Here, in vitro precipitation of aragonite in artificial seawater was investigated at a high supersaturation, allowing spontaneous nucleation and growth, as well as at low supersaturation conditions, which allowed only the crystal growth on the deliberately introduced aragonite seeds. In either chemical systems, soluble organic matrix (SOM) extracted from Balanophyllia europaea (light sensitive) or Leptopsammia pruvoti (light insensitive) was added. The analyses of the kinetic and thermodynamic data of aragonite precipitation and microscopic observations showed that, at high supersaturation, the SOMs increased the induction time, did not affect the growth rate and were incorporated within aggregates of nanoparticles. At low supersaturation, the SOMs affected the aggregation of overgrowing crystalline units and did not substantially change the growth rate. On the basis of the obtained results we can infer that at high supersaturation conditions the formation of nanoparticles, which is typically observed in the skeleton's early mineralization zone may occur, whereas at low supersaturation the overgrowth on prismatic seeds observed in the skeleton fiber zone is a predominant process. In conclusion, this research brings insight on coral skeletogenesis bridging physicochemical (supersaturation) and biological (role of SOM) models of coral biomineralization and provides a source of inspiration for the precipitation of composite materials under different conditions of supersaturation.

Atmospheric carbon dioxide enrichment alters seawater carbonate chemistry, thus threatening calcifying organisms such as corals. Coral populations at carbon dioxide vents are natural acidification experiments that mimic organism responses to seawater pH values projected for 2100. Even if demographic traits are paramount information to assess ecological relationships and habitat suitability, population dynamics studies on corals thriving under acidified conditions are lacking. Here, we investigate the demography and reproduction of populations of the solitary, symbiotic, temperate coral Balanophyllia europaea naturally living along a pH gradient at a Mediterranean CO2 vent. Gametogenesis and larval production were unaffected while recruitment efficiency collapsed at low and variable pH, contributing to coral abundance decline and suggesting that life stages between larval release and early polyp growth are hindered by acidification. Exploring these processes is crucial to assess coral fate in the forthcoming acidified oceans, to preserve coral ecosystems and the socioeconomic services they provide.

Coral reefs are undergoing a severe decline due to ocean acidification, seawater warming and anthropogenic eutrophication. We demonstrate the applicability of Deep Learning (DL) for following these changes. We examined the distribution and frequency appearance of the eleven most common coral species at four sites in the Gulf of Eilat. We compared deep learning with conventional census methods. The methods used in this research were natural sampling units via photographing the coral reef, line transects for estimating the cover percentage at the four test sites and deep convolutional neural networks, which proved to be an efficient sparse classification for coral species using the supervised deep learning method. The main research goal was to identify the common coral species at four test sites in the Gulf of Eilat, using DL to detect differences in coral cover and species composition among the sites, and relate these to ecological characteristics, such as depth and anthropogenic disturbance. The use of this method will produce a vital database to follow changes over time in coral reefs, identify trend lines and recommend remediation measures accordingly. We outline future monitoring needs and the corresponding system developments required to meet these.

We describe the application of the computerized deep learning methodology to the recognition of corals in a shallow reef in the Gulf of Eilat, Red Sea. This project is aimed at applying deep neural network analysis, based on thousands of underwater images, to the automatic recognition of some common species among the 100 species reported to be found in the Eilat coral reefs. This is a challenging task, since even in the same colony, corals exhibit significant within-species morphological variability, in terms of age, depth, current, light, geographic location, and inter-specific competition. Since deep learning procedures are based on photographic images, the task is further challenged by image quality, distance from the object, angle of view, and light conditions. We produced a large dataset of over 5,000 coral images that were classified into 11 species in the present automated deep learning classification scheme. We demonstrate the efficiency and reliability of the method, as compared to painstaking manual classification. Specifically, we demonstrated that this method is readily adaptable to include additional species, thereby providing an excellent tool for future studies in the region, that would allow for real time monitoring the detrimental effects of global climate change and anthropogenic impacts on the coral reefs of the Gulf of Eilat and elsewhere, and that would help assess the success of various bioremediation efforts.

Microalgae have gained significant importance in biotechnology development, providing valuable goods and services in multiple applications. Although there is a rising market for most of these applications, the incorporation and introduction of microalgae into new venues will extend in the near future. These advances are due to the vast biodiversity of microalgal species, recent genetic engineering tools, and culture techniques. There are three main possible approaches for novel algal compounds from: (1) recently isolated yet less known microalgae; (2) selectively stressed conditions; and (3) enzymatically adjusted compounds from conventional molecules. All these approaches can be combined in a specific manner. This review discusses the opportunities, potential and limitations of introducing novel microalgae-based products, and how the recent technologies can be deployed to make these products financially viable. To give an outlook to the future, an analysis of the developments and predicted future market that further enlarge the promise of cultivating microalgae for commercial purposes are considered.

The responses of corals and other marine calcifying organisms to ocean acidification (OA) are variable and span from no effect to severe responses. Here we investigated the effect of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals living at two CO2 vents in Papua New Guinea, namely in Dobu and Upa Upasina. The skeletal porosity of Galaxea fascicularis, Acropora millepora, and Pocillopora damicornis was higher (from 17% to 38%, depending on the species) at the seep site compared to the control only at Upa Upasina. Massive Porites showed no differences at any of the locations. Pocillopora damicornis also showed a ~ 7% decrease of micro-density and an increase of the volume fraction of the larger pores, a decrease of the intraskeletal organic matrix content with an increase of the intraskeletal water content, and no variation in the organic matrix related strain and crystallite size. The fact that the skeletal parameters varied only at one of the two seep sites suggests that other local environmental conditions interact with OA to modify the coral skeletal parameters. This might also contribute to explain the great deal of responses to OA reported for corals and other marine calcifying organisms.

We describe the use of a novel, computerized, multiple outdoor microalgal growth system to achieve conditions maximizing high photosynthesis and biomass production rates. We applied this system to determine the effects of multiple environmental and culture parameters such as light, temperature, pH, and mode of mixing and CO2 supply, and their combinations on the rates of algal photosynthesis, respiration, and growth. We continuously monitored the following parameters: pH, temperature, dissolved oxygen, and light, concomitantly with algal growth and biomass production rates. In particular, we likewise monitored and determined the dramatic effects of CO2 supply, mixing by paddle wheel or bubbling air modes, on algal biomass production. The isolated and synergistic effects of each factor and operation regime were measured and are discussed. We found that the diel range of maxima to minimal pH and oxygen levels strongly correlated with container performance, and were controllable by CO2 supply and mixing regime. We conclude that mixing by bubble aeration was the most important growth-rate controlling factor. It limited the build-up of high oxygen and pH levels that reduce photosynthesis that were measured by O2 evolution. In this study, OD measurements calibrated with biomass concentrations were used to calculate growth rates and estimate the photosynthetic rates of the microalgae. The potential of algae as a source of food, feed, biofuel, and fine chemicals has been widely recognized, but their competitiveness depends on areal yields. Our results allow us to recommend culture parameters that increase areal biomass yields, regardless of the algal species, thereby bringing microalgal mass culture closer to economic viability.

Ocean acidification, due to the increase of carbon dioxide (CO2) concentration in the atmosphere and its absorption by the oceans, affects many aspects of marine calcifying organisms' biology, including reproduction. Most of the available studies on low pH effects on coral reproduction have been conducted on tropical species under controlled conditions, while little information is reported for either tropical or temperate species in the field. This study describes the influence of decreasing pH on sexual reproduction of the temperate non-zooxanthellate colonial scleractinian Astroides calycularis, transplanted in four sites along a natural pH gradient at the underwater volcanic crater of Panarea Island (Tyrrhenian Sea, Italy). The average pH values of each site (range: pHTS 8.07–7.40) match different scenarios of the Intergovernmental Panel on Climate Change (IPCC) for the end of the century. After 3 months under experimental conditions, the reproductive parameters of both oocytes and spermaries (abundance, gonadal index, and diameters) seem to be unaffected by low pH. However, a delay in spermary development in the pre-fertilization period and a persistence of mature oocytes in the fertilization period were observed in the most acidic site. Furthermore, no embryos were found in colonies from the two most acidic sites, suggesting a delay or an interruption of the fertilization process due to acidified conditions. These findings suggest a negative effect of low pH on A. calycularis sexual reproduction. However, long-term experiments, including the synergistic impact of pH and temperature, are needed to predict if this species will be able to adapt to climate change over the next century.

Ocean acidification, due to the increase of carbon dioxide (CO

The effect of abscisic acid (ABA) to increase the osmotolerance of the freshwater microalga Chlamydomonas reinhardtii at its different stages of life cycle was investigated. Exogenously added ABA enhanced the growth and photosynthesis of C. reinhardtii during the vegetative stage. The hormone also increased the tolerance of this alga to oxidative stress during gamete formation under nutrient depletion and high salinity, as it supported their survival for a longer period. We show that the level of reactive oxygen species (ROS) generated in the ABA-treated cells was significantly less than that in the untreated cells under inhibiting NaCl concentrations. Cell size examination showed that ABA prevents cells from forming palmella when exposed to high salinity. All together, these results suggest that ABA increases the tolerance of C. reinhardtii to salt stress conditions.

The aim of this work was to use green and simply synthesized nitrogen-doped carbon dots (N@CDs) based on carbonized bovine serum albumin (BSA) to boost the accumulation of astaxanthin in microalgae. The BSA carbon dots revealed a high blue emission having a quantum yield of up to 44%, which is superior to all previously reported carbon dots. By directly adding the N@CDs at low concentrations (1 mg L− 1) to the algal culture of Haematococcus pluvialis, astaxanthin production increased more than two-fold (66 mg L− 1), compared to the control (29 mg L− 1), in a shorter time of 1 week instead of 2 weeks at the reddening stage. After 1 month of continuous irradiation, the HRTEM images and fluorescence spectra of N@CDs looked similar to as-prepared N@CDs, suggesting their photostability and reusability. Our novel N@CDs could be a promising tool for the future industry of natural astaxanthin and other value-added products from microalgae.

Coral age can be strictly related to size, but processes like fragmentation, fusion, and partial colony mortality can decouple this relationship. When these phenomena are negligible, such as in solitary corals, age-based growth and population dynamics models can be used. In this study, the population size, structure, and growth rates of the temperate solitary coral Caryophyllia inornata were assessed at Elba Island (north-western Mediterranean Sea). Growth rate of this species decreased exponentially with age. The two growth curves estimated by field measurements and by growth band analysis provided homogeneous relationships between size and age. The decreasing number of individuals with age indicated a steady state population, with a turnover time of 4 yr and a maximum life span of 22 yr. Maximum biomass yield and most reproductive output was by individuals of 8–15 yr age classes. The life strategy was characterized by high fecundity, continuous embryo production, high larval output, and high larval mortality.

Coastal pollution assessment is a pressing matter as the anthropogenic pressure continues to increase worldwide. A leading approach to assess coastal pollution is using bioindicators. However, identifying species is time-consuming and demands profound morphological knowledge. Our goal was to find the meiobenthic composition in each pollution level. By utilizing the meiobenthic assemblage’s ratios, we will be able to indicate the pollution level. We examined the meiobenthos distribution at three sites exposed to a pollution gradient. We quantified the changes in the fauna assemblage in the community phylum level, focusing on nematodes and foraminifera (90% of the total population). Over 400 samples were examined, covering an annual seasonal cycle. Nematodes population dominated in the polluted coast. Nematodes density increased with the pollution level, up to seemingly harmful levels of pollution. In contradiction, the foraminifera flourished in the control site and exhibited an inverse relationship to the nematodes. We witnessed drastic changes in the entire meiobenthic population in the winter, which we speculate that originated from winter turbulences. We suggest that nematodes-foraminifers’ population ratios may be utilized as bioindicators for assessing coast intertidal zone pollution levels.

Many calcifying organisms exert significant biological control over the construction and composition of biominerals which are thus generally depleted in oxygen-18 and carbon-13 relative to the isotopic ratios of abiogenic aragonite. The skeletal δ18O and δ13C values of specimens of Mediterranean zooxanthellate (Balanophyllia europaea and Cladocora caespitosa) and non-zooxanthellate corals (Leptopsammia pruvoti and Caryophyllia inornata) were assessed along an 8° latitudinal gradient along Western Italian coasts, spanning ~2 °C and ~37 W m-2 of annual average sea surface temperature and solar radiation (surface values), respectively. Seawater δ18O and δ13CDIC were surprisingly constant along the ~850 km latitudinal gradient while a ~2 and ~4 ‰ variation in skeletal δ18O and a ~4 and ~9 ‰ variation in skeletal δ13C was found in the zooxanthellate and non-zooxanthellate species, respectively. Albeit Mediterranean corals considered in this study are slow growing, only a limited number of non-zooxanthellate specimens exhibited skeletal δ18O equilibrium values while all δ13C values in the four species were depleted in comparison to the estimated isotopic equilibrium with ambient seawater, suggesting that these temperate corals cannot be used for thermometry-based seawater reconstruction. Calcification rate, linear extension rate and skeletal density were unrelated to isotopic compositions. The fact that skeletal δ18O and δ13C of zooxanthellate corals were confined to a narrower range at the most isotopically depleted end compared to non-zooxanthellate corals, suggests that the photosynthetic activity may restrict corals to a limited range of isotopic composition, away from isotopic equilibrium for both isotopes. Our data show that individual corals within the same species express the full range of isotope fractionation. These results suggest that metabolic and/or kinetic effects may act as controlling factors of isotope variability of skeleton composition along the transect, and that precipitation of coral skeletal aragonite occurs under controlling kinetic biological processes, rather than thermodynamic control, by yet unidentified mechanisms.

Here, we explore the responses of photosynthesis and related cellular processes in the thermotolerant microalga Micractinium sp. acclimated to limiting and saturating irradiances combined with elevated temperatures, using a novel computer-controlled multi-sensor system. This system allows for the monitoring of online values of oxygen exchange during photosynthesis and respiration with high accuracy. Micractinium sp. cells showed maximum growth and net oxygen production rates under the optimal temperature of 25°C regardless of the light acclimation conditions. Our results show that the upper thermal threshold for Micractinium sp. photosynthesis and growth ranges between 35°C and 40°C. This microalga exhibited stable photosynthetic efficiency and effective non-photochemical quenching (NPQ) under saturating light, and was more susceptible to temperature change when acclimated to limiting light levels. These results demonstrate that the acclimation of thermotolerant microalgae to saturating light helps to enhance the thermal tolerance of PSII. This feature results from enhanced heat stability of PSII photochemistry and oxygen evolution.

Astrogilosis is the response of astrocytes to brain trauma which manifest opposite roles on brain injury repair. On the one hand, astrocytes undergoing astrogliosis inhibit tissue regeneration by forming scar tissue, but, on the other hand, they enhance damage repair through secretion of neuro-protecting and neurotrophic factors. Therefore, identifying means that regulate astrogliosis can provide a control over progression and repair of brain damage. We have previously shown that the calcium carbonate skeleton of corals upregulates two manifestations of astrogliosis in astrocytes in culture-expression of the Glial Fibrillay Acidic Protein (GFAP), and shape conversion from non-spiky to reactive spiky cell morphology. Here, we investigated if the surface topography of the coralline skeleton plays a role in GFAP expression and the morphogenesis of reactive astrocytes. To address that, we utilized the non-porous exoskeleton of the coral Trachyphyllia geoffroyi, having three topographies of distinct heights on its surface: rough surface (made of30 μm height bumps), protrusions (50-250 μm) and ridges (250 μm). We observed that astrocytes reacted similarly to all three structures in terms of adhesion, acquisition of a spiky morphology and organization in networks. By contrast, the extent by which these cells expressed GFAP was structure-dependent. The expression was 2-fold higher on protrusions and ridges than on the rough surface and acquired. Accordingly, the distribution pattern of the GFAP overexpressing astrocytes followed that of the protrusions and ridges. Hence, fabricating coralline scaffolds with designed flatness/protrusions/ridges ratios can serve to control astrogliosis-derived regeneration in TBI wounds, and as a result improve the capacity to repair brain damage.

The precipitation of calcium carbonate was carried out in the presence of the intraskeletal organic matrix (OM) extracted from Mediterranean corals. They were diverse in growth form and trophic strategy, Balanophyllia europaea and Leptopsammia pruvoti—solitary corals, only the first zooxanthellate coral—and Cladocora caespitosa and Astroides calycularis—colonial corals, only the first zooxanthellate coral. The results showed that, although the OM marked differences among species, the diverse influence over the calcium carbonate precipitation was evident only for B. europaea. This OM was the most prone to favor the precipitation of aragonite in the absence of magnesium ions, according to overgrowth and solution precipitation experiments. In artificial seawater, where magnesium ions were present, this OM, as well the one from A. calycularis, precipitated mainly a form of amorphous calcium carbonate different from that obtained with SOM from L. pruvoti or C. caespitosa. The amorphous calcium carbonate from B. europaea was the most stable upon heating up to 100 °C and was the one that mainly converted into aragonite instead of magnesium calcite after heating at 300 °C. All this indicated a higher control of B. europaea OM over the calcium carbonate polymorphism than the other species. The influence of SOMs over precipitate morphology turned out to be also species related. In conclusion, this comparative study has shown that the influence of OM on in vitro precipitation of calcium carbonate was not related to the coral ecology, solitary vs colonial and zooxanthellate vs nonzooxanthellate, and suggested that the coral control over biomineralization process was species specific and encoded in coral genes.

Since the Industrial Revolution, increasing atmospheric CO2 has been causing a rise in the concentration of carbon dioxide dissolved in seawater. This process results in seawater acidification, which has a major impact on the physical and chemical parameters of the oceans, consequently affecting the numerous calcifying organisms in the marine environment. Calcifying organisms secrete calcium carbonate in their inner or outer skeleton and include plankton (e.g. coccolithophores and foraminifera), corals, mussels and some of the macroalgae. Calcifying macroalgae make a critical contribution to the structure and function of marine ecosystems in several coastal biotas, providing food and shelter to diverse organisms. The present review summarizes the current information about the brown alga Padina sp. and its ecophysiology, focusing on the environmental control of the calcification process; suggests possible benefits that seaweeds may derive from their calcium carbonate cover, and discuss different fu...

We present thorough this review the developments in the field, point out their current limitations, and outline its timelines and unique potential. In order to do so we introduce the methods used in each of the advances in the application of deep learning (DL) to coral research that took place between the years: 2016−2018. DL has unique capability of streamlining the description, analysis, and monitoring of coral reefs, saving time, and obtaining higher reliability and accuracy compared with error-prone human performance. Coral reefs are the most diverse and complex of marine ecosystems, undergoing a severe decline worldwide resulting from the adverse synergistic influences of global climate change, ocean acidification, and seawater warming, exacerbated by anthropogenic eutrophication and pollution. DL is an extension of some of the concepts originating from machine learning that join several multilayered neural networks. Machine learning refers to algorithms that automatically detect patterns in data. In the case of corals these data are underwater photographic images. Based on “learned” patterns, such programs can recognize new images. The novelty of DL is in the use of state-of-art computerized image analyses technologies, and its fully automated methodology of dealing with large data sets of images. Automated Image recognition refers to technologies that identify and detect objects or attributes in a digital video or image automatically. Image recognition classifies data into selected categories out of many. We show that Neural Network methods are already reliable in distinguishing corals from other benthos and non-coral organisms. Automated recognition of live coral cover is a powerful indicator of reef response to slow and transient changes in the environment. Improving automated recognition of coral species, DL methods already recognize decline of coral diversity due to natural and anthropogenic stressors. Diversity indicators can document the effectiveness of reef bioremediation initiatives. We explored the current applications of deep learning for corals and benthic image classification by discussing the most recent studies conducted by researchers. We review the developments in the field, point out their current limitations, and outline their timelines and unique potential. We also discussed a few future research directions in the fields of deep learning. Future needs are the age detection of single species, in order to track trends in their population recruitment, decline, and recovery. Fine resolution, at the polyp level, is still to be developed, in order to allow separation of species with similar macroscopic features. That refinement of DL will allow such comparisons and their analyses. We conclude that the usefulness of future, more refined automatic identification will allow reef comparison, and tracking long term changes in species diversity. The hitherto unused addition of intraspecific coral color parameters, will add the inclusion of physiological coral responses to environmental conditions and change thereof. The core aim of this review was to underscore the strength and reliability of the DL approach for documenting coral reef features based on an evaluation of the currently available published uses of this method. We expect that this review will encourage researchers from computer vision and marine societies to collaborate on similar long-term joint ventures.