Antonio Camacho González - Academia.edu (original) (raw)
Papers by Antonio Camacho González
Limnetica, 2013
Spectrophotometric methods for the determination of photosynthetic pigments in stratified lakes: ... more Spectrophotometric methods for the determination of photosynthetic pigments in stratified lakes: a critical analysis based on comparisons with HPLC determinations in a model lake High-performance liquid chromatography (HPLC) is an accurate method for photosynthetic pigment analysis; however, spectrophotometric equations are also frequently used for pigment quantification in aquatic systems. Here, we present a critical analysis of the most-used spectrophotometric equations by comparing the results obtained using these equations with unambiguous HPLC determinations. The study was performed in Lake La Cruz (central Spain). In this meromictic lake with strong thermal stratification, photosynthetic populations occur in different, vertically stratified layers. Eukaryotic algae and picocyanobacteria are mostly located in oxic layers, whereas purple sulphur bacteria grow at the oxic-anoxic interface and below, and green sulphur bacteria occur primarily in deeper anoxic layers. This broad diversity of photosynthetic microorganisms involves a complex mixture of photosynthetic pigments that often exhibit overlapping absorption spectra. We tested spectrophotometric equations using samples that represented the entire range of spatial and temporal variability of the lake. For chlorophyll-a, the best correlations with all tested equations were observed for oxic layers. Regardless of where the sample was obtained, the best fit for chlorophyll-a was produced by the equation of Overmann & Tilzer, which is specifically designed to handle mixtures of chlorophyll-a and bacteriochlorophyll-d from green sulphur bacteria. Trichromatic equations for determining chlorophyll-b and-c exhibited strong interferences in anoxic waters, whereas in the upper layers of the lake, concentrations of these pigments were usually below the detection limit, restricting the use of these equations. The equations of Takahashi & Ichimura for bacterial pigments slightly overestimated both bacteriochlorophyll-a and-d by approximately 10 % and underestimated bacteriochlorophyll-c by nearly 23 %, although for bacteriochlorophyll-d, the correlation was better than those obtained using the dichromatic equations of Parkin & Brock and Overmann & Tilzer, respectively. Total carotenoid abundance can be assessed with the equation designed for this purpose by Strickland & Parsons (1972); however, the accuracy of the results differs with depth and is strongly biased by the presence of the bacterial carotenoid okenone. On the other hand, dual-wavelength carotenoid-to-chlorophyll-a ratios (430/665 and 480/665) only produced acceptable results in the epilimnion, with the occurrence of the bacterial carotenoid okenone in the microaerobic and anoxic layers again producing significant interference. Additionally, the wide variation with depth of the carotenoid composition undermined the validity of these dual-wavelength ratios. In conclusion, our findings indicate that a complete and unambiguous study of photosynthetic pigments in highly stratified lakes with overlapping populations of phototrophic microorganisms requires the use of HPLC techniques. Anyway, our results demonstrate that chlorophyll-a and bacteriochlorophyll-a and-d can be directly measured in oxic and anoxic layers, respectively, using spectrophotometric methods with an error lower than 10 %. However, according to our results, chlorophyll-b and-c and bacteriochlorophyll-c cannot be accurately estimated by spectrophotometric methods in stratified lakes.
Although environmental flow regime assessments are becoming increasingly holistic, they rarely pr... more Although environmental flow regime assessments are becoming increasingly holistic, they rarely provoke water managers to enact the adaptive water reallocation mechanisms required to secure environmental water for wetlands. The conditions that cause science-based environmental flow assessments to succeed or fail in informing the management of environmental water requirements remain unclear. To begin to resolve these conditions, we used process tracing to deconstruct the sequence of activities required to manage environmental water in four case studies of seasonally ponding wetlands in Mediterranean and Mesoamerican watersheds. We hypothesized that, when the flexibility and equitability of the socioeconomic system do not match the complexity of the biophysical system, this leads to a failure of managers to integrate scientific guidance in their allocation of environmental water. Diagnostic evidence gathered indicates that science-management partnerships are essential to align institut...
Ambienta, Mar 2012
El conocimiento actual sobre el funcionamiento de lagos y humedales permite afirmar que este tipo... more El conocimiento actual sobre el funcionamiento de lagos y humedales permite afirmar que este tipo de sistemas naturales desempeñan un papel fundamental en incontables procesos de carácter hidrológico, geomorfológico, ecológico? (Mitsch y Gosselink, 2003), al tiempo que son depositarios de significativos valores estéticos y de valiosas nociones al respecto de los usos tradicionales del suelo, etc. En muchas regiones no sólo constituyen un componente elemental del sistema natural sino también del socio-económico, descansando sobre ellos, incluso, una parte del patrimonio popular, y siendo una herramienta de gran valor en la educación ambiental. No es exagerado afirmar, por tanto, que lagos y humedales, y especialmente estos últimos, suponen una de las principales reservas de biodiversidad a nivel planetario, además de una fuente elemental de servicios ecosistémicos para la sociedad, tanto de abastecimiento como de regulación o de tipo cultural (Millenium Ecosystem Assessment. 2005). El presente trabajo, que resume lo referido a este tipo de ecosistemas en la Evaluación de los Ecosistemas del Milenio de España (2011), se centra precisamente en la revisión de la situación en la que se encuentran los servicios que prestan a la sociedad española los lagos y humedales al tiempo que se analiza su tendencia a medio-largo plazo.
La estructura trófica de las comunidades planctónicas de los lagos antárticos se caracteriza por ... more La estructura trófica de las comunidades planctónicas de los lagos antárticos se caracteriza por su sencillez, estando funcionalmente dominada por microorganismos. En estas cadenas tróficas el zooplancton, cuando está presente, ocupa generalmente la posición de consumidores superiores. Estos sistemas constituyen un marco muy adecuado en el que evaluar ciertos aspectos de la ecología trófica y funcional. Nuestro propósito ha sido valorar la aplicabilidad de una serie de teorías ecológicas, relativas a las relaciones tróficas, al flujo de energía y a la relativa importancia de los factores tanto abióticos como bióticos como elementos que expliquen el funcionamiento de estos ecosistemas en zonas polares sometidas a un fuerte control físico. Estudios experimentales llevados a cabo en lagos de la Península Byers (Isla Livingston) por nuestro grupo de investigación han puesto de manifiesto como determinadas interacciones bióticas, como la depredación, podrían ejercer este efecto estructur...
LA LAGUNA DE ARCAS (CUENCA) PRESENTA UNA ESTRATIFICACION VERTICAL DE SUS AGUAS DURANTE EL PERIODO... more LA LAGUNA DE ARCAS (CUENCA) PRESENTA UNA ESTRATIFICACION VERTICAL DE SUS AGUAS DURANTE EL PERIODO ESTIVAL, FORMANDOSE UN HIPOLIMNION ANOXICO RICO EN SULFHIDRICO EN SUS AGUAS PROFUNDAS. EN LA QUIMIOCLINA DEL LAGO SE DESARROLLAN DENSAS POBLACIONES DE MICROORGANISMOS FOTOSINTETICOS, ENCONTRANDOSE LAS MAXIMAS DENSIDADES POBLACIONALES DE CRYPTOMONAS SPP. EN AGUAS MICROAREOBIAS, POR DEBAJO DE LAS CUALES, EN AGUAS RICAS EN SULFHIDRICOS, APARECEN LOS MAXIMOS DE OSCILLATORIA ORNATA Y CHROMATIUM WEISSEI. LAS TASAS DE FOTOASIMILACION EN LA QUIMIOCLINA SON ELEVADAS (HASTA 200 MG. C M-3 H-1) PERO SE DAN EN UN RANGO MUY ESTRECHO DE PROFUNDIDADES, POR LO QUE SOLO APORTAN UN 18-% DE LA PRODUCCION FOTOSINTETICA DEL LAGO. UN 35-% DE LA FOTOASIMILACION EN LA QUIMIOCLINA SE DEBE A LA FOTOSINTESIS OXIGENICA EN PRESENCIA DE SULFHIDRICO POR PARTE DE O.ORNATA, PROCESO QUE SE HA DEMOSTRADO POR PRIMERA VEZ PARA UNA CIANOBACTERIA PLANCTONICA, TANTO IN SITU COMO EN EXPERIMENTOS DE LABORATORIO. TAMBIEN SE HA ES...
Historically, studies about ecological communities have been developed on a single spatial scale,... more Historically, studies about ecological communities have been developed on a single spatial scale, considering they were both isolated and closed systems. However, other ecological processes occur on multiple scales, such as source-sink dynamics. The metacommunity concept helps ecologists to understand this multi-scale nature, although applied works are still scarce. Nowadays an effort exists to standardize this research and provide comprehensive software. This study aims to analyze one metacommunity in a multi-scale framework, using ostracods from shallow lakes in Central Spain (Biosphere Reserve of La Mancha Humeda). For this purpose, twenty-five shallow lakes were sampled in January-May 2013 with hand-nets (250 ƒÊm mesh) on a wide ecological gradient in order to obtain the highest ostracod diversity. A set of environmental variables were collected for each lake and MEMs (Moran Eigenvector Maps) were calculated to represent both broad-scale and fine-scale spatial fractions. Environ...
Journal of Plankton Research, 2012
Aquatic Microbial Ecology, 2003
The effect of the increase in availability of inorganic nutrients (nitrogen and phosphorus) on a ... more The effect of the increase in availability of inorganic nutrients (nitrogen and phosphorus) on a benthic microbial mat from the hypersaline Lake Salada de Chiprana (NE Spain) was assayed by nutrient-addition experiments in mesocosms, using 16 d incubation periods. The upper layer of the mat was dominated by diatoms, whereas the cyanobacterium Microcoleus chthonoplastes and filamentous green bacteria containing Bacteriochlorophyll (Bchl) d dominated deeper layers. The addition of nitrogen alone favoured an increase in total abundance of diatoms with respect to cyanobacteria, although without significant changes in the relative abundance of different diatom genera. Furthermore, this treatment resulted in decreased rates of gross oxygenic photosynthesis. In contrast, phosphorus additions, either alone or supplemented with nitrogen, increased the relative abundance of cyanobacteria with respect to diatoms. No direct effects of the different treatments on green bacteria were observed. The balanced availability of high amounts of both N and P supported an increase in biomass of oxygenic phototrophic populations, especially cyanobacteria. This was attributed to a combination of stimulating active growth and decreasing senescence; the latter was reflected by more than 3-fold increase of the ratio of chl a to phaeophytin a. Dinitrogen fixation was measured indirectly as acetylene reduction activity (ARA). ARA rates were low at the start of the experiments and remained low in the N treatment, while a strong stimulation was found in the control, P and N+P treatments. Because M. chthonoplastes is not capable of fixing dinitrogen, the stimulation of ARA was attributed to nitrogenase activities of heterotrophic bacteria. Our findings are generally in agreement with the resource ratio theory that predicts directional changes of community structure as a consequence of changing resource supply ratios. In addition to the effect of nutrient supply regimes on taxonomic structure of benthic communities, we also observed changes in some of their functional properties. However, application of this theory to sediment systems is not straightforward, because nutrient supply rates depend on the combined effect of mass transfer from the water column to the sediment, internal recycling and geochemical processes (precipitation/ dissolution) in the sediment. Sediment processes are difficult to quantify.
Polar Biology, 2010
The present study shows the occurrence of remarkable interannual variation in the meteorological ... more The present study shows the occurrence of remarkable interannual variation in the meteorological conditions at Byers Peninsula (Livingston Island, South Shetlands Islands, Antarctica), in which one of the summers was significantly colder than the others. Within this climatic scenario, a limnological study was carried out at Lake Limnopolar during three consecutive summer seasons
Limnetica, 2006
During the lakes' stratification period, planktonic primary producers, such as some eukaryotic al... more During the lakes' stratification period, planktonic primary producers, such as some eukaryotic algae and cyanobacteria, can achieve abundance maxima at considerable depths, especially in oligotrophic and mesotrophic lakes (Fee, 1976; Moll and Stoermer, 1982; Margalef, 1983). However, during the mixing period these maxima would not occur because turbulence mixes water preventing the accumulation of phototrophs at certain depths (Reynolds, 1994), as it happens when fall mixing occurs promoting the disappearance of these populations (Abbott et al., 1984). Reynolds (1992) reviewed the key factors that govern the onset, maintenance, and dissipation of vertical structure of the water column and the responses of phytoplankton to this structu
This data are part of the activities for the accurate description of the limnetic systems in Byer... more This data are part of the activities for the accurate description of the limnetic systems in Byers Peninsula (Livingston Island), considered one of the most important freshwater zones in the Maritime Antarctica.Data are the abundances of Virus-like particles at different experimental conditions of a mesocosm assay performed in the Lake Limnopolar with the aim to evaluate the role of both biotic and abiotic interactions in the pelagic community
Toxics, 2022
Physical and chemical alterations may affect the microbiota of soils as much as the specific pres... more Physical and chemical alterations may affect the microbiota of soils as much as the specific presence of toxic pollutants. The relationship between the microbial diversity patterns and the soil quality in a Mediterranean context is studied here to test the hypothesis that soil microbiota is strongly affected by the level of anthropogenic soil alteration. Our aim has been to determine the potential effect of organic matter loss and associated changes in soil microbiota of poorly evolved Mediterranean soils (Leptosols and Regosols) suffering anthropogenic stress (i.e., cropping and deforestation). The studied soils correspond to nine different sites which differed in some features, such as the parent material, vegetation cover, or soil use and types. A methodological approach has been used that combines the classical physical and chemical study of soils with molecular characterization of the microbial assemblages using specific primers for Bacteria, Archaea and ectomycorrhizal Fungi. ...
Polar Biology, 2016
Cyanobacteria-based microbial mats are common in Antarctic terrestrial freshwater ecosystems such... more Cyanobacteria-based microbial mats are common in Antarctic terrestrial freshwater ecosystems such as the extensive wetland seepages that cover Byers Peninsula on Livingston Island (South Shetland Islands), maritime Antarctica, where they play an important role in biomass generation and productivity. Although cyanobacteria, microfauna and fungal communities have been described for such microbial mats, to date, little is known about trophic interactions within the mats, which are likely important to overcome nutrient constraints in oligotrophic polar freshwater ecosystems. We therefore carried out a biomass assessment of the different taxonomic components and their trophic interactions using DNA analysis and stable isotope analysis, as well as physiological activities such as primary and secondary production and nitrogen uptake within the mat food web throughout an austral spring and summer season. Our results suggested, based on a Bayesian mixing model, that carbon flow from cyanobacteria to upper trophic levels was limited to tardigrades and rotifers, whereas fungal and bacterial activity were likely the main connectors between consumers and producers via a heterotrophic loop. This suggests that homeostatic state displayed in freshwater microbial mats from maritime Antarctica provides stability to the microbial mats under the fluctuating environmental conditions commonly found in permanently cold shallow terrestrial aquatic ecosystems in Antarctica.
Limnetica, 2013
Spectrophotometric methods for the determination of photosynthetic pigments in stratified lakes: ... more Spectrophotometric methods for the determination of photosynthetic pigments in stratified lakes: a critical analysis based on comparisons with HPLC determinations in a model lake High-performance liquid chromatography (HPLC) is an accurate method for photosynthetic pigment analysis; however, spectrophotometric equations are also frequently used for pigment quantification in aquatic systems. Here, we present a critical analysis of the most-used spectrophotometric equations by comparing the results obtained using these equations with unambiguous HPLC determinations. The study was performed in Lake La Cruz (central Spain). In this meromictic lake with strong thermal stratification, photosynthetic populations occur in different, vertically stratified layers. Eukaryotic algae and picocyanobacteria are mostly located in oxic layers, whereas purple sulphur bacteria grow at the oxic-anoxic interface and below, and green sulphur bacteria occur primarily in deeper anoxic layers. This broad diversity of photosynthetic microorganisms involves a complex mixture of photosynthetic pigments that often exhibit overlapping absorption spectra. We tested spectrophotometric equations using samples that represented the entire range of spatial and temporal variability of the lake. For chlorophyll-a, the best correlations with all tested equations were observed for oxic layers. Regardless of where the sample was obtained, the best fit for chlorophyll-a was produced by the equation of Overmann & Tilzer, which is specifically designed to handle mixtures of chlorophyll-a and bacteriochlorophyll-d from green sulphur bacteria. Trichromatic equations for determining chlorophyll-b and-c exhibited strong interferences in anoxic waters, whereas in the upper layers of the lake, concentrations of these pigments were usually below the detection limit, restricting the use of these equations. The equations of Takahashi & Ichimura for bacterial pigments slightly overestimated both bacteriochlorophyll-a and-d by approximately 10 % and underestimated bacteriochlorophyll-c by nearly 23 %, although for bacteriochlorophyll-d, the correlation was better than those obtained using the dichromatic equations of Parkin & Brock and Overmann & Tilzer, respectively. Total carotenoid abundance can be assessed with the equation designed for this purpose by Strickland & Parsons (1972); however, the accuracy of the results differs with depth and is strongly biased by the presence of the bacterial carotenoid okenone. On the other hand, dual-wavelength carotenoid-to-chlorophyll-a ratios (430/665 and 480/665) only produced acceptable results in the epilimnion, with the occurrence of the bacterial carotenoid okenone in the microaerobic and anoxic layers again producing significant interference. Additionally, the wide variation with depth of the carotenoid composition undermined the validity of these dual-wavelength ratios. In conclusion, our findings indicate that a complete and unambiguous study of photosynthetic pigments in highly stratified lakes with overlapping populations of phototrophic microorganisms requires the use of HPLC techniques. Anyway, our results demonstrate that chlorophyll-a and bacteriochlorophyll-a and-d can be directly measured in oxic and anoxic layers, respectively, using spectrophotometric methods with an error lower than 10 %. However, according to our results, chlorophyll-b and-c and bacteriochlorophyll-c cannot be accurately estimated by spectrophotometric methods in stratified lakes.
Although environmental flow regime assessments are becoming increasingly holistic, they rarely pr... more Although environmental flow regime assessments are becoming increasingly holistic, they rarely provoke water managers to enact the adaptive water reallocation mechanisms required to secure environmental water for wetlands. The conditions that cause science-based environmental flow assessments to succeed or fail in informing the management of environmental water requirements remain unclear. To begin to resolve these conditions, we used process tracing to deconstruct the sequence of activities required to manage environmental water in four case studies of seasonally ponding wetlands in Mediterranean and Mesoamerican watersheds. We hypothesized that, when the flexibility and equitability of the socioeconomic system do not match the complexity of the biophysical system, this leads to a failure of managers to integrate scientific guidance in their allocation of environmental water. Diagnostic evidence gathered indicates that science-management partnerships are essential to align institut...
Ambienta, Mar 2012
El conocimiento actual sobre el funcionamiento de lagos y humedales permite afirmar que este tipo... more El conocimiento actual sobre el funcionamiento de lagos y humedales permite afirmar que este tipo de sistemas naturales desempeñan un papel fundamental en incontables procesos de carácter hidrológico, geomorfológico, ecológico? (Mitsch y Gosselink, 2003), al tiempo que son depositarios de significativos valores estéticos y de valiosas nociones al respecto de los usos tradicionales del suelo, etc. En muchas regiones no sólo constituyen un componente elemental del sistema natural sino también del socio-económico, descansando sobre ellos, incluso, una parte del patrimonio popular, y siendo una herramienta de gran valor en la educación ambiental. No es exagerado afirmar, por tanto, que lagos y humedales, y especialmente estos últimos, suponen una de las principales reservas de biodiversidad a nivel planetario, además de una fuente elemental de servicios ecosistémicos para la sociedad, tanto de abastecimiento como de regulación o de tipo cultural (Millenium Ecosystem Assessment. 2005). El presente trabajo, que resume lo referido a este tipo de ecosistemas en la Evaluación de los Ecosistemas del Milenio de España (2011), se centra precisamente en la revisión de la situación en la que se encuentran los servicios que prestan a la sociedad española los lagos y humedales al tiempo que se analiza su tendencia a medio-largo plazo.
La estructura trófica de las comunidades planctónicas de los lagos antárticos se caracteriza por ... more La estructura trófica de las comunidades planctónicas de los lagos antárticos se caracteriza por su sencillez, estando funcionalmente dominada por microorganismos. En estas cadenas tróficas el zooplancton, cuando está presente, ocupa generalmente la posición de consumidores superiores. Estos sistemas constituyen un marco muy adecuado en el que evaluar ciertos aspectos de la ecología trófica y funcional. Nuestro propósito ha sido valorar la aplicabilidad de una serie de teorías ecológicas, relativas a las relaciones tróficas, al flujo de energía y a la relativa importancia de los factores tanto abióticos como bióticos como elementos que expliquen el funcionamiento de estos ecosistemas en zonas polares sometidas a un fuerte control físico. Estudios experimentales llevados a cabo en lagos de la Península Byers (Isla Livingston) por nuestro grupo de investigación han puesto de manifiesto como determinadas interacciones bióticas, como la depredación, podrían ejercer este efecto estructur...
LA LAGUNA DE ARCAS (CUENCA) PRESENTA UNA ESTRATIFICACION VERTICAL DE SUS AGUAS DURANTE EL PERIODO... more LA LAGUNA DE ARCAS (CUENCA) PRESENTA UNA ESTRATIFICACION VERTICAL DE SUS AGUAS DURANTE EL PERIODO ESTIVAL, FORMANDOSE UN HIPOLIMNION ANOXICO RICO EN SULFHIDRICO EN SUS AGUAS PROFUNDAS. EN LA QUIMIOCLINA DEL LAGO SE DESARROLLAN DENSAS POBLACIONES DE MICROORGANISMOS FOTOSINTETICOS, ENCONTRANDOSE LAS MAXIMAS DENSIDADES POBLACIONALES DE CRYPTOMONAS SPP. EN AGUAS MICROAREOBIAS, POR DEBAJO DE LAS CUALES, EN AGUAS RICAS EN SULFHIDRICOS, APARECEN LOS MAXIMOS DE OSCILLATORIA ORNATA Y CHROMATIUM WEISSEI. LAS TASAS DE FOTOASIMILACION EN LA QUIMIOCLINA SON ELEVADAS (HASTA 200 MG. C M-3 H-1) PERO SE DAN EN UN RANGO MUY ESTRECHO DE PROFUNDIDADES, POR LO QUE SOLO APORTAN UN 18-% DE LA PRODUCCION FOTOSINTETICA DEL LAGO. UN 35-% DE LA FOTOASIMILACION EN LA QUIMIOCLINA SE DEBE A LA FOTOSINTESIS OXIGENICA EN PRESENCIA DE SULFHIDRICO POR PARTE DE O.ORNATA, PROCESO QUE SE HA DEMOSTRADO POR PRIMERA VEZ PARA UNA CIANOBACTERIA PLANCTONICA, TANTO IN SITU COMO EN EXPERIMENTOS DE LABORATORIO. TAMBIEN SE HA ES...
Historically, studies about ecological communities have been developed on a single spatial scale,... more Historically, studies about ecological communities have been developed on a single spatial scale, considering they were both isolated and closed systems. However, other ecological processes occur on multiple scales, such as source-sink dynamics. The metacommunity concept helps ecologists to understand this multi-scale nature, although applied works are still scarce. Nowadays an effort exists to standardize this research and provide comprehensive software. This study aims to analyze one metacommunity in a multi-scale framework, using ostracods from shallow lakes in Central Spain (Biosphere Reserve of La Mancha Humeda). For this purpose, twenty-five shallow lakes were sampled in January-May 2013 with hand-nets (250 ƒÊm mesh) on a wide ecological gradient in order to obtain the highest ostracod diversity. A set of environmental variables were collected for each lake and MEMs (Moran Eigenvector Maps) were calculated to represent both broad-scale and fine-scale spatial fractions. Environ...
Journal of Plankton Research, 2012
Aquatic Microbial Ecology, 2003
The effect of the increase in availability of inorganic nutrients (nitrogen and phosphorus) on a ... more The effect of the increase in availability of inorganic nutrients (nitrogen and phosphorus) on a benthic microbial mat from the hypersaline Lake Salada de Chiprana (NE Spain) was assayed by nutrient-addition experiments in mesocosms, using 16 d incubation periods. The upper layer of the mat was dominated by diatoms, whereas the cyanobacterium Microcoleus chthonoplastes and filamentous green bacteria containing Bacteriochlorophyll (Bchl) d dominated deeper layers. The addition of nitrogen alone favoured an increase in total abundance of diatoms with respect to cyanobacteria, although without significant changes in the relative abundance of different diatom genera. Furthermore, this treatment resulted in decreased rates of gross oxygenic photosynthesis. In contrast, phosphorus additions, either alone or supplemented with nitrogen, increased the relative abundance of cyanobacteria with respect to diatoms. No direct effects of the different treatments on green bacteria were observed. The balanced availability of high amounts of both N and P supported an increase in biomass of oxygenic phototrophic populations, especially cyanobacteria. This was attributed to a combination of stimulating active growth and decreasing senescence; the latter was reflected by more than 3-fold increase of the ratio of chl a to phaeophytin a. Dinitrogen fixation was measured indirectly as acetylene reduction activity (ARA). ARA rates were low at the start of the experiments and remained low in the N treatment, while a strong stimulation was found in the control, P and N+P treatments. Because M. chthonoplastes is not capable of fixing dinitrogen, the stimulation of ARA was attributed to nitrogenase activities of heterotrophic bacteria. Our findings are generally in agreement with the resource ratio theory that predicts directional changes of community structure as a consequence of changing resource supply ratios. In addition to the effect of nutrient supply regimes on taxonomic structure of benthic communities, we also observed changes in some of their functional properties. However, application of this theory to sediment systems is not straightforward, because nutrient supply rates depend on the combined effect of mass transfer from the water column to the sediment, internal recycling and geochemical processes (precipitation/ dissolution) in the sediment. Sediment processes are difficult to quantify.
Polar Biology, 2010
The present study shows the occurrence of remarkable interannual variation in the meteorological ... more The present study shows the occurrence of remarkable interannual variation in the meteorological conditions at Byers Peninsula (Livingston Island, South Shetlands Islands, Antarctica), in which one of the summers was significantly colder than the others. Within this climatic scenario, a limnological study was carried out at Lake Limnopolar during three consecutive summer seasons
Limnetica, 2006
During the lakes' stratification period, planktonic primary producers, such as some eukaryotic al... more During the lakes' stratification period, planktonic primary producers, such as some eukaryotic algae and cyanobacteria, can achieve abundance maxima at considerable depths, especially in oligotrophic and mesotrophic lakes (Fee, 1976; Moll and Stoermer, 1982; Margalef, 1983). However, during the mixing period these maxima would not occur because turbulence mixes water preventing the accumulation of phototrophs at certain depths (Reynolds, 1994), as it happens when fall mixing occurs promoting the disappearance of these populations (Abbott et al., 1984). Reynolds (1992) reviewed the key factors that govern the onset, maintenance, and dissipation of vertical structure of the water column and the responses of phytoplankton to this structu
This data are part of the activities for the accurate description of the limnetic systems in Byer... more This data are part of the activities for the accurate description of the limnetic systems in Byers Peninsula (Livingston Island), considered one of the most important freshwater zones in the Maritime Antarctica.Data are the abundances of Virus-like particles at different experimental conditions of a mesocosm assay performed in the Lake Limnopolar with the aim to evaluate the role of both biotic and abiotic interactions in the pelagic community
Toxics, 2022
Physical and chemical alterations may affect the microbiota of soils as much as the specific pres... more Physical and chemical alterations may affect the microbiota of soils as much as the specific presence of toxic pollutants. The relationship between the microbial diversity patterns and the soil quality in a Mediterranean context is studied here to test the hypothesis that soil microbiota is strongly affected by the level of anthropogenic soil alteration. Our aim has been to determine the potential effect of organic matter loss and associated changes in soil microbiota of poorly evolved Mediterranean soils (Leptosols and Regosols) suffering anthropogenic stress (i.e., cropping and deforestation). The studied soils correspond to nine different sites which differed in some features, such as the parent material, vegetation cover, or soil use and types. A methodological approach has been used that combines the classical physical and chemical study of soils with molecular characterization of the microbial assemblages using specific primers for Bacteria, Archaea and ectomycorrhizal Fungi. ...
Polar Biology, 2016
Cyanobacteria-based microbial mats are common in Antarctic terrestrial freshwater ecosystems such... more Cyanobacteria-based microbial mats are common in Antarctic terrestrial freshwater ecosystems such as the extensive wetland seepages that cover Byers Peninsula on Livingston Island (South Shetland Islands), maritime Antarctica, where they play an important role in biomass generation and productivity. Although cyanobacteria, microfauna and fungal communities have been described for such microbial mats, to date, little is known about trophic interactions within the mats, which are likely important to overcome nutrient constraints in oligotrophic polar freshwater ecosystems. We therefore carried out a biomass assessment of the different taxonomic components and their trophic interactions using DNA analysis and stable isotope analysis, as well as physiological activities such as primary and secondary production and nitrogen uptake within the mat food web throughout an austral spring and summer season. Our results suggested, based on a Bayesian mixing model, that carbon flow from cyanobacteria to upper trophic levels was limited to tardigrades and rotifers, whereas fungal and bacterial activity were likely the main connectors between consumers and producers via a heterotrophic loop. This suggests that homeostatic state displayed in freshwater microbial mats from maritime Antarctica provides stability to the microbial mats under the fluctuating environmental conditions commonly found in permanently cold shallow terrestrial aquatic ecosystems in Antarctica.
The Spanish National Ecosystem Assessment (SNEA), supported by the Biodiversity Foundation of the... more The Spanish National Ecosystem Assessment (SNEA), supported by the Biodiversity Foundation of the Ministry of Environment, is the first analysis conducted on the status and trends of ecosystem services in terrestrial and aquatic ecosystems of Spain. The results of the SNEA are expected to help build bridges between interdisciplinary scientific knowledge and decision making to visualize the complex relationships that exist between the conservation of ecosystems and human wellbeing. The SNEA has involved approximately 60 scientists from the biophysical and social sciences. This report presents a synthesis and integration of the key findings of the project presented in the Technical Report of which was completed in 2012 (www.ecomilenio.es).
La biodiversidad es esencial para la supervivencia del ser humano en la Tierra. Del buen funciona... more La biodiversidad es esencial para la supervivencia del ser humano en la Tierra. Del buen funcionamiento de los ecosistemas acuáticos y terrestres españoles y de la biodiversidad que albergan, depende en buena medida el futuro social, cultural y económico de la población, ya que constituyen el capital natural de nuestro país. El bienestar humano en España estriba, de esta forma, en la capacidad de los ecosistemas para generar servicios esenciales: agua limpia, alimentos, regulación climática, polinización, actividades recreativas, etc. Por tanto, la conservación de los ecosistemas, además de ser una res ponsabilidad ética, se presenta como una necesidad crucial, y no como un lujo, para el bienestar de la sociedad española. Desde el Ministerio de Medio Ambiente, y Medio Rural y Marino trabajamos para preservar el buen estado de los ecosistemas, restaurar su funcionalidad y garantizar el mantenimiento de los importantes servicios que prestan a la sociedad. Por ello, somos conscientes d...