Victoria Amores

Sediment phosphate fractionation and interstitial water phosphate concentration in two coastal lagoons (Albuferas de Adra, SE Spain)

The concentrations of o-phosphate and dissolved inorganic carbon were monitored in the interstitial water of the sediment in two highly eutrophic coastal lagoons, Laguna Honda and Laguna Nueva (SE, Spain) from July 2000 to August 2001. Additionally, the organic matter concentration and the P-fractions in the sediment were analysed. Despite their proximity, these two lagoons showed many significant differences (P<0.05). The P-concentration in the interstitial water of the top sediment was higher in the Laguna Honda (up to 1 mg l−1), especially during summer, when both sites registered their highest values. By contrast, the concentration of organic matter and organic P-fractions were higher in the sediment of the Laguna Nueva. The concentration of the organic matter in the vertical profile of the sediment decreased with depth in the Laguna Nueva (from 17% at 0 cm to 7% at 15 cm, annual mean value) while it increased in the sediment of Laguna Honda (from 9% at 0 cm to 12% at 15 cm, annual mean value). The P-concentration in the interstitial water and the organic matter in the top sediment of Laguna Honda followed a seasonal pattern and, were both correlated with the temperature of the bottom water (r=0.706, P<0.05 and r= -0.929, P<0.01, respectively). The inorg-P fractions comprised 63% of the Tot-phosphate in the sediment of Laguna Honda, whereas org-P fractions (68%) dominated in the sediment of Laguna Nueva. The concentrations of Tot-P in the sestonic material collected at three different depths of the water column averaged 2.2 mg g−1d.w. in Laguna Honda and 2.5 mg g−1d.w. in Laguna Nueva. The average atomic C:P ratio of the sestonic material was significantly higher in Laguna Honda than in Laguna Nueva, but the top sediment in Laguna Nueva had a C:P ratio significantly higher than that of the sestonic material (average: 416 and 162, respectively).The different biodegradability of the organic matter in the top sediment probably explained the differences found in sediment composition between these two lagoons. We suggest that the P-reclying from the sediment to the interstitial water was faster in Laguna Honda due to the higher biodegradability of the organic matter. By contrast, the lower biodegradability of the organic matter in the top sediment of Laguna Nueva was probably due to a higher contribution of vascular plants which could explain the organic matter accumulation detected in this lagoon.

Chemical interferences when using high gradient magnetic separation for phosphate removal: consequences for lake restoration.

A promising method for lake restoration is the treatment of lake inlets through the specific adsorption of phosphate (P) on strongly magnetizable particles (Fe) and their subsequent removal using in-flow high gradient magnetic separation (HGMS) techniques. In this work, we report an extensive investigation on the chemical interferences affecting P removal efficiencies in natural waters from 20 Mediterranean ponds and reservoirs. A set of three treatments were considered based on different Fe particles/P concentration ratios. High P removal efficiencies (>80%) were found in freshwater lakes (conductivities<600 μ S cm(-1)). However, a significant reduction in P removal was observed for extremely high mineralized waters. Correlation analysis showed that major cations (Mg(2+), Na(+) and K(+)) and anions (SO(4)(2-) and Cl(-)) played an essential role in P removal efficiency. Comparison between different treatments have shown that when increasing P and Fe concentrations at the same rate or when increasing Fe concentrations for a fixed P concentration, there exist systematic reductions in the slope of the regression lines relating P removal efficiency and the concentration of different chemical variables. These results evidence a general reduction in the chemical competition between P and other ions for adsorption sites on Fe particles. Additional analyses also revealed a reduction in water color, dissolved organic carbon (DOC) and reactive silicate (Si) concentrations with the addition of Fe microparticles.

LOW PREDICTABILITY IN THE DYNAMICS OF SHALLOW LAKES: IMPLICATIONS FOR THEIR MANAGEMENT AND RESTORATION

This study was conducted in two eutrophic shallow lakes (Lake Honda LH and Lake Nueva LN) that share geographic proximity but have contrasting hydrology, meteorology, biogeochemistry, and geomorphology. Our objective was to explore the inter-annual, seasonal, and daily variability in selected biological, physical, and chemical variables of these two systems. Although the study lakes demonstrated a notable inter-annual and seasonal variation in nutrient concentrations, water transparency was the only variable that was consistently more variable in LH than LN. The reason for the greater temporal variability in water transparency of LH is its major susceptibility to wind and rain events. The impact of wind events in this lake is favored by its shallowness and by its silty surface sediment; the high ratio of catchment area to lake area is responsible for the relatively higher susceptibility of LH to rain events than LN. By contrast, in the younger and deeper LN, ground-water discharge buffers certain water chemistry parameters such as conductivity, turbidity, and alkalinity. Interestingly, differences in turbidity and ground-water discharge do not seem to affect the variability in nutrient concentrations, which was similar between the lakes, although these factors may explain differences between the lakes in nutrient concentrations. This paper reveals that the unpredictability and frequency of events in Mediterranean aquatic ecosystems makes it necessary to increase data collection frequency to obtain more accurate simulations in water quality models.

Maslinic Acid: A Component of Olive Oil on Growth and Protein-turnover Rates

Publisher Summary This chapter describes an important application of maslinic acid that has been recently reported by a research group, namely the use of this compound as a feed additive for trout diets. In fish farming, the incorporation of new additives in the standard diet to achieve optimum fish growth and production with a reduction of cost is one of the main objectives of many research groups. Algae, steroids, antibiotics, or immunostimulants have been added to fish diets and their effects on growth have been reported. In many cases these compounds present particular problems related to their accumulation in fish that make fish consumption by humans hazardous. Some of these, such as antibiotic growth promoters, have been banned in some countries. Maslinic acid is a natural compound present in the Mediterranean diet that can be used as feed additive without the problems known of other additives.

Temporal and spatial trends in the sedimentation process in a canyon-type reservoir (El Gergal, Seville, Spain)

The seasonal and spatial (vertical and horizontal) variations in the magnitude of sestonic fluxes and the chemical composition (C, N, P and organic matter concentrations) of entrapped material have been studied over a year on a monthly basis in El Gergal, a mesotrophic canyon-type reservoir in the south of Spain. The chemical composition of settled particles and of surficial sediment was compared in trying to elucidate the role of some relevant processes like mineralization and resuspension of unconsolidated sediment. A very clear increasing tendency in the magnitude of settling fluxes from the down-reservoir to the up-reservoir zone as a consequence of the prevailing wind direction and of water level fluctuations has been found. Vertical gradients in sestonic rates can mainly be explained by the different contribution of resuspension processes that can be ultimately related to the thermal and hydrologic regime. A comparison of the chemical composition of the total settled matter and of the surficial sediment revealed a predominantly inorganic matrix, which reflects the dominating role of inorganic allochthonous material input.

EL PLANCTON DE LAS LAGUNAS DE SIERRA NEVADA: NECESIDAD DE ESTUDIOS TRANSDISCIPLINARES

La correcta valoracion de los procesos ecologicos, como base para el mantenimiento de la integridad ecologica del ecosistema, se ha convertido en una de las tareas de mas dificil cumplimiento en las labores de conservacion de los ecosistemas mediterraneos. La busqueda y desarrollo de herramientas en la deteccion y prevencion de alteraciones ambientales nos ha llevado a centrar la atencion en las lagunas de alta montana del Parque Nacional de Sierra Nevada, ecosistemas que presentan un singular valor ecologico dentro del ambiente mediterraneo, por su caracter oligotrofico, por su situacion a gran altitud y por la adaptacion de sus comunidades a condiciones ambientales extremas. El presente texto describe una propuesta de estudio integral en estos ecosistemas con una aproximacion basada en el analisis de las estructuras de tamano de las comunidades del plancton como herramienta descriptora y predictiva de las respuestas de esas comunidades a los cambios ambientales.