Modeling the Population Dynamics of the Red Swamp Crayfish (Procambarus clarkii) in Doñana: Application to the Harvesting Strategies

The aim of this work is to propose an alternative management and control strategy of crayfishing Procambarus clarkii in the Doñana area. A simulation model was developed (Stella 8.0) to evaluate the effects of different fishing effort on crayfish populations during certain times of the year. Then different management options were simulated: Strategy 0: No fishing activity, Strategy 1: Obtaining the maximum yield of crayfish following the current fishing effort regulations, and Strategy 2: Obtaining the maximum yield of crayfish by restricting the fishing effort to the period of the greatest production. The model explained 73.68% of the variance in population biomass. A review and resetting of the crayfishing regulations in this area according to the periods proposed in Strategy 2, was recommended. This management proposal in the developed model was the one that ensures sustainable yields at the same time that preserves biodiversity by restricting the harvesting of crayfish to rice fields and channels from April to Septembe

Ecological impact of recreational bathing at Las Presillas (Lozoya River, Sierra de Guadarrama National Park, central Spain)

The ecological impacts of recreational uses on the rivers of Sierra de Guadarrama National Park (SGNP) have been scarcely studied. To assess the impacts of these uses at Las Presillas (an area with small dam along a section of the Lozoya River), and in the Lozoya River (upstream and downstream of the dams), the dynamics of the organic seston (FPOM), physicochemical vari-ables (electric conductivity, dissolved oxygen, Temperature, and pH) and biological variables (fecal coliforms, fecal streptococci, and aquatic macroinvertebrates) during the recreational (July to September) and nonrecreational (October) periods were assessed. The variations observed in the physicochemical parameters were associated with autumnal influence. However, at Las Presillas, different values were found than at the rest of the surveyed sites, characterized by an increase in the concentration of FPOM and, human fecal contamination (although they did not reach dangerous levels) and the response of the macroinvertebrate communities, which resulted in a clear decrease in the IBMWP index and other quality metrics, during the recreational period. These findings suggest that the combined effects of the dams and recreational activities at Las Presillas generate functional dynamics in that alter the habitat in summer. The identification and study of these impacts through the application of innovative indices and quality classes that integrate and contextualize Las Presillas in the SGNP monitoring network, have been identified as key management and conservation tool

Seeking for the best conditions for fish fossil preservation in Las Hoyas Konservat-Lagerstätte using microbial mats

Actuotaphonomic experiments demonstrate how microbial mats prevent or delay destructive processes. The rate at which carcasses are covered is a key to their preservation. Because of the growth rate of microbial mats depends on environmental conditions, a set of experiments have been carried out emulating the Barremian environmental conditions, analysed for temperatures at 14°C and 26°C (cooler and warmer seasons respectively) and atmospheric pCO2 (1000 ppm). For this purpose, the microbial mats were grown in mesocosms within an environmental chamber. Variations in primary production were quantified by measuring changes in dissolved O2 concentration in the water. Zebrafish carcasses were laid on the mats, and their coverage rates were calculated from the daily surface area covered by the mat. The results showed that the fish was covered twice as fast at 26°C, in coincidence with the highest values for the gross primary production and community respiration of the microbial mats. Therefore, for these Barremian conditions, the early stages of carcasses preservation would take place most effectively during the warmer seasons as decomposing activity would release nutrients that would enhance, together with temperature, the growth of matsThis study was funded by the Spanish Ministry of Science, Innovation and Universities [project PID2019-105546GB-I00

Origin, accumulation and fate of dissolved organic matter in an extreme hypersaline shallow lake

Hypersaline endorheic aquatic systems (H-SEAS) are lakes/shallow playas in arid and semiarid regions that undergo extreme oscillations in salinity and severe drought episodes. Although their geochemical uniqueness and microbiome have been deeply studied, very little is known about the availability and quality of dissolved organic matter (DOM) in the water column. A H-SEAS from the Monegros Desert (Zaragoza, NE Spain) was studied during a hydrological wetting-drying-rewetting cycle. DOM analysis included: (i) a dissolved organic carbon (DOC) mass balance; (ii) spectroscopy (absorbance and fluorescence) and (iii) a molecular characterization with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The studied system stored a large amount of DOC and under the highest salinity conditions, salt-saturated waters (i.e., brines with salinity > 30%) accumulated a disproportionate quantity of DOC, indicating a significant in-situ net DOM production. Simultaneously, during the hydrological transition from wet to dry, the DOM pool showed strong alterations of it molecular composition. Spectroscopic methods indicated that aromatic and degraded DOM was rapidly replaced by fresher, relatively small, microbial-derived moieties with a large C/N ratio. FT-ICR-MS highlighted the accumulation of small, saturated and oxidized molecules (molecular O/C > 0.5), with a remarkable increase in the relative contribution of highly oxygenated (molecular O/C > 0.9) compounds and a decrease of aliphatic and carboxyl-rich alicyclic moleculesThese results indicated that H-SEAS are extremely active in accumulating and processing DOM, with the notable release of organic solutes probably originated from decaying microplankton under large osmotic stress at extremely high salinitie

Las redes tróficas en las lagunas salinas temporales de Los Monegros (Zaragoza, España)

Los factores que condicionan la estructura de las redes tróficas y el funcionamiento de sus comunidades asociadas han sido muy discutidos durante las dos últimas décadas. Existen dos teorías que han tenido especial relevancia en este contexto. Una propone que las restricciones dinámicas del sistema, es decir, el comportamiento de la dinámica de las poblaciones ante las perturbaciones ambientales, son la clave para entender la estructura de las comunidades. La otra sostiene que son las restricciones energéticas, de modo que cuánta más energía entre en el sistema más complejas serán sus redes tróficas. Las lagunas salinas son ecosistemas que, por sus características de ambientes estresados de una duración determinada, se pueden considerar magníficos laboratorios naturales para abordar estudios sobre los factores que condicionan el ensamblaje de las comunidades y sus redes tróficas. Los factores que operan a una escala regional (duración de fase acuática y composición química del agua) son los ejercen una mayor influencia en la estructura de las redes. A escala local, se distinguen dos modelos de funcionamiento. Por un lado, los sistemas en los que la energía es canalizada desde las especies basales hacia niveles superiores, manejados por los productores primarios (tapetes microbianos); y por otro lado, los sistemas en los que los consumidores canalizan el metabolismo general desde arriba hacia abajo.CICYT AMB94-0827