Papers by Rolando Cardenas
Proceedings of the 2nd International Conference on BioGeoSciences
In this chapter, we outline general ideas to quantify habitability, starting with a general abiog... more In this chapter, we outline general ideas to quantify habitability, starting with a general abiogenesis–biogenesis conceptual model. We connect this model with the approach of the astrobiological school of quantitative habitability, specifically with quantitative habitability theory, to devise habitability indexes. We present two indexes devised by us: the Aquatic Primary Habitability for photosynthesis-based ecosystems, and the Chemosynthetic Habitability Index for chemoautotrophy-based ones. As a case study, we present the application of the last one to hydrothermal vents. It is also mentioned the possibility of embedding parameters such as net primary productivity, calculated using habitability indexes, into greater ecological models with several trophic models, making a clear connection between the astrobiological and ecological approaches of quantitative habitability.
It is investigated the potential short-term influence of a solar storm on micro-algal photosynthe... more It is investigated the potential short-term influence of a solar storm on micro-algal photosynthesis. From the secondary cosmic rays at sea level we focus on muons, given their high penetrating power, and it is considered that a ‘’generic’’ solar storm would imply an increase of 10% in both muon fluxes and their average energy. It is then assumed an exponential decay of muon fluxes down the water column and a direct proportionality between their penetrating power and energy. This allows obtaining a function of ionizing radiation to be embedded in a physical-mathematical model for photosynthesis previously modified by some of us to include particulate ionizing radiation. It is finally shown that solar storms can cause a significant short-term depletion of photosynthesis in both ocean and coastal waters.
An Aquatic Habitability Index is proposed, based on Quantitative Habitability Theory, and conside... more An Aquatic Habitability Index is proposed, based on Quantitative Habitability Theory, and considering a very general model for life. It is a primary habitability index, measuring habitability for phytoplankton in the first place. The index is applied to some case studies, such as the habitability changes in Earth due to environmental perturbations caused by asteroid impacts.
a) Toxicological Center (CENTOX), Universidad de Ciencias Médicas, Santa Clara, Cuba. liubajc@ucm... more a) Toxicological Center (CENTOX), Universidad de Ciencias Médicas, Santa Clara, Cuba. [email protected]† b) Department of Physics, Universidad Central de Las Villas, Santa Clara, Cuba. [email protected]‡ c) Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados,CSIC – UIB. España. [email protected]* † corresponding author (Recibido 17/2/2014; Aceptado 1/11/2014)
In this work, a few models of the Universe which include, in particular, dark energy are presente... more In this work, a few models of the Universe which include, in particular, dark energy are presented. In some of them, dark energy is considered to be only a slowly rolling scalar field (quintessence), while in others, its presence is simulated through a negative cosmological constant. The scalar field is minimally coupled to gravity and does not interact with matter, so these models are to be used after decoupling of radiation and matter. However, this ansatz, and a proper normalization, allow to find new general classes of solutions for the cosmological equations. The inclusion of the negative cosmological constant results in the possibility of the future gravitational collapse of the universe; this inclusion solves the horizon problem which prevents the consistent formulation of string theory.
E3S Web of Conferences, 2019
Radiation plays an essential role in the establishment and proliferation of biota in natural envi... more Radiation plays an essential role in the establishment and proliferation of biota in natural environments. The photosynthetic process determines the existence of all life forms, since it supplies the energy that this photobiological process needs for the reaction, it is carried out by absorbing photons in the visible and infrared bands of the electromagnetic spectrum, while ultraviolet (UV) photons and ionizing radiation tends to inhibit it (decreasing, by various mechanisms, its quantum yield). The speed of photosynthesis, measured by the amount of O2 released in the unit of time (or CO2 absorbed) depends on the intensity of the incident light, in the last three decades this radiation has been increased by the decrease of stratospheric ozone in the South latitudes of our planet, for this reason the UV values in the aquatic ecosystems of Chile have been high as well as a considerable increase in the surface temperature of the bodies of water, having possible implications in the prim...
General Relativity and Gravitation, 2019
A scalar cosmological Higgs field is expected to exist in our universe in order to create inertia... more A scalar cosmological Higgs field is expected to exist in our universe in order to create inertial mass. Some results obtained at LHC suggest that this idea must be reconsidered. The cosmological effects of scalar fields have been proposed as a mechanism to drive the evolution of the universe in various scenarios. In this paper we investigate, from the dynamical systems perspective, the evolution of a Universe consisting of a matter component ρ together with a scalar field φ exhibiting a quartic polynomial self-interacting potential. We consider an homogeneous and isotropic flat Friedmann-Robertson-Walker metric. Center Manifold Theory is employed to investigate the dynamics near a non-hyperbolic critical point. We prove that there are two possible late time attractors corresponding to stable de Sitter solutions.
E3S Web of Conferences, 2018
It is reviewed the potential influence of solar and geomagnetic storms on terrestrial photosynthe... more It is reviewed the potential influence of solar and geomagnetic storms on terrestrial photosynthesis. Then it is presented a modification of a physical-mathematical model of photosynthesis published by some of us, which allows quantifying the influence of particulate ionizing radiation on this biological process. Some guidelines to obtain this new model from first principles are mentioned and it is applied to some case studies including atmospheric and geomagnetic perturbation due to solar storms.
Halting eternal acceleration with a negative cosmological constant
AIP Conference Proceedings, 2008
One of the biggest challenges for current cosmology is the late time speed-up of the universe. Am... more One of the biggest challenges for current cosmology is the late time speed-up of the universe. Among the several mechanisms that have been suggested to explain this problem we focus our attention in a model including both a negative cosmological constant Λ and a scalar field evolving under the action of an exponential potential. We conclude that a negative Λ is indeed allowed and could represent a viable mechanism to halt eternal acceleration. We reconstruct the gravity Lagrangian f(R) of a fourth order theory of gravity predicting the same dynamics (scale factor and Hubble parameter) as the starting model. We thus end up with a f(R) theory able to both fit the data and solve the problem of eternal acceleration without the need of an unusual negative Λ and ad hoc scalar fields.
Possibilities of life around Alpha Centauri B
We make a preliminary assessment on the habitability of potential rocky exoplanets around Alpha C... more We make a preliminary assessment on the habitability of potential rocky exoplanets around Alpha Centauri B. We use several indexes: the Earth Similarity Index, a mathematical model for photosynthesis, and a biological productivity model. Considering the atmospheres of the exoplanets similar to current Earth's atmosphere, we find consistent predictions of both the Earth Similarity Index and the biological productivity model. The mathematical model for photosynthesis clearly failed because does not consider the temperature explicitly. For the case of Alpha Centauri B, several simulation runs give 11 planets in the habitable zone. Applying to them above mentioned indexes, we select the five exoplanets more prone for photosynthetic life; showing that two of them in principle have better conditions than Earth for this kind of life.
On the habitability of exoplanets orbiting Proxima Centauri
We apply a mathematical model for photosynthesis to quantitatively assess the habitability of a h... more We apply a mathematical model for photosynthesis to quantitatively assess the habitability of a hypothetical planet orbiting Proxima Centauri, inside the so called habitability zone. Results suggest significant viability for primary biological productivity, provided living organisms have evolved to reach the ability of using infrared light for photosynthesis.
International Journal of Astrobiology, 2013
We modify a mathematical model of photosynthesis to quantify the perturbations that high energy m... more We modify a mathematical model of photosynthesis to quantify the perturbations that high energy muons could make on aquatic primary productivity. Then, we apply this in the context of the extragalactic shock model, according to which Earth receives an enhanced dose of high-energy cosmic rays when it is at the galactic north. We obtain considerable reduction in the photosynthesis rates, consistent with potential drops in biodiversity.
The genetic signature of (astronomically induced) life extinctions
Remote Sensing of Environment, Nov 1, 2019
In this work, we analysed the satellite-based responses of sea surface temperature (SST) and chlo... more In this work, we analysed the satellite-based responses of sea surface temperature (SST) and chlorophylla (chl-a) concentration in the waters of the Exclusive Economic Zone (EEZ) of Cuba to hurricanes that crossed the EEZ between 1998 and 2016. We considered two spatial scales to capture the spatially heterogeneous nature of the effects of hurricanes. A first more fine-grained one where we considered 120 km radius disks centered at every consecutive hurricane position within the EEZ (scale 1) and a second more coarse grained one enclosing the entire EEZ (scale 2). We conclude that the hurricanes induced a weak cooling since 75 and 85% of the SST anomalies at scale 1 and 2, respectively, were smaller than-1 • C. The cooling was mainly caused by the wind, inducing mixing and/or upwelling of subsurface cool waters. The maximum chl-a responses were recorded in the first and second post-storm weeks, with 60% ranging between-0.01 and 0.04 mg m −3 at scale 1, and between-0.07 and 0.02 mg m −3 at scale 2. During those post-storm weeks SST and chl-a anomalies were 18 and 44% higher at scale 1 than at scale 2, respectively. We argue that the transport of chl-a from the deep chlorophyll maximum and/or the rich coastal waters are the dominant mechanisms determining the post-storm chl-a response in the EEZ. We also found that the magnitude of the Island Mass Effect in the EEZ after the passage of the hurricanes was 89% higher than before its passage.
Response of phytoplankton functional types to Hurricane Fabian (2003) in the Sargasso Sea
Marine Environmental Research, Jul 1, 2023
Journal of Marine Systems, Dec 1, 2020
In this work we assessed the spatio-temporal variability of the oceanographic conditions in the p... more In this work we assessed the spatio-temporal variability of the oceanographic conditions in the period 1998-2017 in four sectors of the Exclusive Economic Zone (EEZ) of Cuba, referred to as the northwest, northeast, southwest and southeast sectors (i.e., NWS, NES, SWS and SES, respectively). We relied upon remote-sensing observations of wind speed, sea surface temperature (SST), sea surface height anomaly (SSHA) and chlorophyll-a (chl-a) concentration along with model predictions of mixed layer depth (MLD), nitrate concentration and net primary production (NPP). We found evidence of the spatially heterogeneous oceanographic conditions of the EEZ of Cuba, since the analysed variables fluctuated spatially with meridional and zonal gradients. Overall, the southern sectors were warmer and less productive than the northern ones, thereby showing the influence of the Caribbean Sea. The NWS showed the highest variability of the physical and biological variables analysed, given the convergence of the Caribbean and the Gulf of Mexico waters and the Loop Current variability. The NES was strongly influenced by coastal conditions given its limited area and long coast line. Besides, a significant decadal increase in SSHA was linked to that in SST. Still, this warming trend was not reflected in the chl-a concentration and NPP trends, which is consistent with the fact that there has been no change over the studied 20 years in mean wind regime and MLD. Furthermore, the strong El Niño Southern Oscillation events of 1997-1998 and 2015-2016 appear to have considerably impacted the surface chl-a concentration, which was partially governed by the variability of the MLD.
Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on cli... more Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on climate change. Although the oceanic effects induced by individual TCs have been extensively investigated, studies on the oceanic response to the passage of consecutive TCs are rare. In this work, we assess the upper oceanic response to the passage of the Hurricanes Dorian and Humberto over the western Sargasso Sea in 2019 using satellite remote sensing and modelled data. We found that the combined effects of these slow-moving TCs led to an increased oceanic response during the third and fourth post-storm weeks of Dorian (accounting for both Dorian and Humberto effects) because of the induced mixing and upwelling at this time. Overall, anomalies of sea surface temperature, ocean heat content and mean temperature from the sea surface to a depth of 100 m were a 50, 63 and 57% smaller (more negative) in the third/fourth post-storm weeks than in the first/second poststorm weeks (accounting only for Dorian effects) of Dorian, respectively, while surface chlorophyll-a (chl-a) concentration anomalies, the mean ch-a concentration in the euphotic zone and the chl-a concentration in the deep chlorophyll maximum were 16, 4 and 16% higher in the third/fourth post-storm weeks than in the first/second post-storm weeks, respectively. The sea surface cooling and increased biological response induced by these TCs were significantly higher (Mann-Whitney test p < 0.05) as compared to climatological records. Our climatological analysis reveals that the strongest TC-induced oceanographic variability in the western Sargasso Sea can be associated with the occurrence of consecutive TCs and long-lasting TC forcing.
Aquatic Microbial Ecology, May 22, 2017
We used mathematical models of photosynthesis to quantify the effects of ultraviolet (UV) radiati... more We used mathematical models of photosynthesis to quantify the effects of ultraviolet (UV) radiation on the photosynthetic potential of Prochlorococcus and Synechococcus marine cyanobacteria living at 0° and 40°N/S latitude. We show that UV is an environmental stressor for these organisms near the ocean surface, accounting for roughly two-thirds of the potential photosynthetic inhibition. Prochlorococcus showed a higher inhibition and integrated photo synthetic potential throughout the water column than Synechococcus, since the former is more vulnerable to UV damage at the surface and more successful at greater depths compared to the latter. The maximum photosynthetic activity was reached beneath the photoactive zone, largely due to the harmful effects of UVA. UV inhibition varies with latitude, due to variability in repair capacity for Synechococcus, and the existence of more diverse mechanisms of acclimation to ir radiance and temperature for Prochlorococcus. The lowest photoinhibition is estimated to occur at 0° latitude, since the interactive effects of high temperature and irradiance have a positive effect on photoacclimation to UV damage.
Assessing the effects of ultraviolet radiation on the photosynthetic potential in Archean marine environments
International Journal of Astrobiology, Sep 9, 2016
In this work, the photosynthesis model presented by Avilaet al. in 2013 is extended and more scen... more In this work, the photosynthesis model presented by Avilaet al. in 2013 is extended and more scenarios inhabited by ancient cyanobacteria are investigated to quantify the effects of ultraviolet (UV) radiation on their photosynthetic potential in marine environments of the Archean eon. We consider ferrous ions as blockers of UV during the Early Archean, while the absorption spectrum of chlorophyllais used to quantify the fraction of photosynthetically active radiation absorbed by photosynthetic organisms. UV could have induced photoinhibition at the water surface, thereby strongly affecting the species with low light use efficiency. A higher photosynthetic potential in early marine environments was shown than in the Late Archean as a consequence of the attenuation of UVC and UVB by iron ions, which probably played an important role in the protection of ancient free-floating bacteria from high-intensity UV radiation. Photosynthetic organisms in Archean coastal and ocean environments were probably abundant in the first 5 and 25 m of the water column, respectively. However, species with a relatively high efficiency in the use of light could have inhabited ocean waters up to a depth of 200 m and show a Deep Chlorophyll Maximum near 60 m depth. We show that the electromagnetic radiation from the Sun, both UV and visible light, could have determined the vertical distribution of Archean marine photosynthetic organisms.
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Papers by Rolando Cardenas