Heavy metals effects on life traits of juveniles of Procambarus clarkii

An incubation experiment of juvenile crayfish (Procambarus clarkii) following a three- level treatment design approach was performed to assess the effect of different heavy metal concentrations on their life history traits (lifespan, growth, moult and feeding activity). The aims were to: (1) address the response of the life traits; (2) check for the correlation between heavy metal concentrations in crayfish whole bodies with the ones of the experimental solutions; (3) analyse the variation of crayfish carbon and nitrogen stable isotopes signatures grown under these treatments. Treatments were: control or absence of pollutants (C); low level contamination (L) similar to those found in the water of the Guadiamar River (SW, Spain) one year after the Aznalcóllar mine accident, and high level contamination (H) maximum concentrations of metals measured in the water of the river after the spill. The study concludes that the H treatment produced lethal effects on juveniles of crayfish, whereas those undergoing the L treatment showed less marked effects. Crayfish’s juveniles grown in L treatment seemed able to regulate and manage this range of pollution while maintaining their biological traits. Juvenile’s capacity to bioaccumulate toxic substances also changes with the nature of the particular metals. The reduction in lifespan was mainly influenced by Cu, Zn and As. 13C of C and juveniles from L treatment had similar values but different from those individuals of H treatment, reflecting the isotopic signature of the food source used (liver), and were also influenced by the concentration of Cu and AsThis work was part of the PICOVER program financed by the “Consejería de Medio Ambiente, Junta de Andalucía“ – Project title: Uso del cangrejo rojo americano (Procambarus clarkii) como especie centinela en el Corredor Verde del Guadiamar – Implicaciones de la especie en las redes tróficas – in 2002–200

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

The trophic ecology of the red swamp crayfish (Procambarus clarkii) in Mediterranean aquatic ecosystems : a stable isotope study

The red swamp crayfish(Procambarus clarkii)is an invasive species in most of its current distribution range.As an omnivorous species that feeds on items of many trophic levels and is eaten by many others, it occupies a key trophic position within the invaded food webs. This trophic position, in combination with its active physiology, makes P. clarkii a suitable organism for ecotoxicological studies and, more specifically, a bioindicator of heavy metal pollution. These characteristics also make P. clarkii a likely vector of contaminants toward higher trophic levels. In this study, we (i) describe aquatic food webs in three contrasting Mediterranean wetlands in the lower Guadalquivir River Basin, southwestern Spain, each populated by invasive P. clarkii but having a different heavy metal concentration, (ii) assess the trophic role of crayfish and temporal trends in its diet using stable isotope analysis (d13 C and d15 N), and (iii) assess the relationship of crayfish isotopic signatures to the content of heavy metals (Cu, Zn, Pb, Cd, As) bioaccumulated in crayfish body tissues. We detected significant between-site differences in carbon and nitrogen isotopic signatures but found significant between-date differences only for nitrogen signatures. Between-site changes in carbon and nitrogen isotopes were due primarily to variations in the relative contribution of autochthonous vs. allochthonous primary producers and shifts in crayfish abundance through time, respectively. Isotopic food web models were used to distinguish between systems driven by a detritus-based energy pathway and systems supported by detritus and primary producers. The trophic positions estimated for crayfish and other invertebrates at each site were low, suggesting the prevalence of omnivory and the occurrence of a trophic continuum rather than discrete levels. Isotopically, crayfish occupy a predator position in the observed food webs, which is consistent with the predominance of animal food sources in the species' diet. No significant changes were found between crayfish ontogenetic stages using isotopic ratios. The site with the highest concentration of heavy metals showed the highest d13C and d15N values, and a significant correlation was found between five heavy metal elements (As, Cd, Zn. Cu, Pb) measured in crayfish and their nitrogen isotope signatures (r = 0.72, p <0.0001), thus reinforcing its contamination biomarker role.El cangrejo rojo (Procambarus clarkii) es una especie invasora en la mayor parte de su área de distribución actual. Ocupa un estatus trófico clave dentro de las redes tróficas invadidas al ser una especie omnívora que se alimenta de muchos recursos tróficos, además de ser presa de otros consumidores. Tal posición de especie clave, junto con su activa fisiología, hace que sea un vector potencial de contaminantes a posiciones superiores en las redes tróficas, y por lo tanto, un excelente bioindicador de contaminación por metales pesados que ha sido muy utilizado en estudios ecotoxicológicos. En este estudio describimos las redes tróficas de tres humedales mediterráneos de la cuenca del Bajo Guadalquivir (SO, España), que poseen densas poblaciones de P. clarkii y que muestran diferentes grados de afección por contaminación de metales pesados, usando isótoposestables(d13 C and d15 N).Además,se explora la relación que existe entre las señales isotópicas y las concentraciones de metales pesados (Cu, Zn, Pb, Cd, As) bioacumuladas en sus tejidos. Se detectaron diferencias significativas en las señales isotópicas de carbono y nitrógeno entre las diferentes localidades, mientras que las diferencias temporales sólo fueron reflejadas por la señal del nitrógeno. Los cambios medios que se dan en las señales del carbono y nitrógeno en cada localidad son debidas a la contribución relativa de los productores primarios autóctonos respecto a la de los alóctonos y cambios en la abundancia de cangrejos a lo largo del tiempo, respectivamente. La descripción de las redes tróficas realizada a través de los isótopos estables distingue entre los sistemas con flujos energéticos basados en detritus, y los basados en productores primarios junto con detritus. Las posiciones tróficas estimadas para los cangrejos e invertebrados en cada localidad fueron bajas, sugiriendo que existe un predominio de la omnivoría y la existencia de un "continuo trófico" mas que la existencia de niveles discretos. Isotópicamente, los cangrejos ocupan una posición de depredador en las redes tróficas que concuerda con el predominio de recursos de origen animal en su dieta. No se encontraron cambios ontogenéticos en la dieta de los distintos estadíos de cangrejo según las señales isotópicas. La localidad con una mayor contaminación de metales pesados mostró una relación directamente proporcional significativa con las señales isotópicas de d13C y d15N (r = 0.72, p <0.0001), reforzando así su papel como biomarcador

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