Ecotoxicity screening of novel phosphorus adsorbents used for lake restoration

Short-term standardized laboratory tests were carried out for evaluating acute and chronic toxicological effects of novel phosphorus (P) adsorbents on Raphidocelis subcapitata (algal growth rate inhibition) and on Daphnia magna (immobilization, with direct and indirect exposure to adsorbents, and uptake-depuration tests). Four P adsorbents were tested: two magnetic (HQ and Fe3O4) and two non magnetic (CFH-12® and Phoslock®). For the case of the algal growth inhibition test, the EC50 was 1.5 and 0.42 g L 1 for HQ and CFH-12®, respectively, and no inhibition patterns were observed neither for Fe3O4 nor for Phoslock®. When organisms were exposed to a direct contact, in the D. magna immobilization test, no statistically significant differences were found in the EC50 values among the four studied ad sorbents. The huge difference between direct and indirect contact experiments suggests that toxicity is mainly physically mediated. The uptake-depuration test evidenced a much faster uptake and depuration rates for Phoslock®, which was precisely the adsorbent with the highest particle size. In a realistic worst case scenario using data from Honda lake (Almería, Spain), where lake restoration is carried out by adding a single large dose to bind surplus P in the lake, the predicted environmental concentrations for all adsorbents were lower than EC50 for all adsorbents and they were found to exceed a provisional limit value for ecotoxicity after a short-term exposure. All in all, since neither accumulation nor longer term effects of P adsorbents in the pelagic phase is expected, this risk may however, on a case-to-case basis, be acceptabl

Warming and CO2 effects under oligotrophication on temperate phytoplankton 2 communities

Eutrophication, global warming, and rising carbon dioxide (CO2) levels are the three most prevalent pressures impacting the biosphere. Despite their individual effects are well-known, it remains untested how oligotrophication (i.e. nutrients reduction) can alter the planktonic community responses to warming and elevated CO2 levels. Here, we performed an indoor mesocosm experiment to investigate the warming×CO2 interaction under a nutrient reduction scenario (40%) mediated by an in-lake management strategy (i.e. addition of a commercial solid-phase phosphorus sorbent - Phoslock®) on a natural freshwater plankton community. Biomass production increased under warming×CO2 relative to present-day conditions; however, a Phoslock® -mediated oligotrophication reduced such values by 30-70%. Conversely, the warming×CO2×oligotrophication interaction stimulated the photosynthesis by 20% compared to ambient nutrient conditions, and matched with higher resource use efficiency (RUE) and nutrient demand. Surprisingly, at a group level, we found that the multi-stressors scenario increased the photosynthesis in eukaryotes by 25%, but greatly impaired in cyanobacteria (ca. -25%). This higher cyanobacterial sensitivity was coupled with a reduced light harvesting efficiency and compensation point. Since Phoslock® -induced oligotrophication unmasked a strong negative warming×CO2 effect on cyanobacteria, it becomes crucial to understand how the interplay between climate change and nutrient abatement actions may alter the, ecosystems functioning. With an integrative understanding of these processes, policy makers will design more appropriate management strategies to improve the ecological status of aquatic ecosystems without compromising their ecological attributes and functioning

Warming and CO2 effects under oligotrophication on temperate phytoplankton 2 communities

Eutrophication, global warming, and rising carbon dioxide (CO2) levels are the three most prevalent pressures impacting the biosphere. Despite their individual effects are well-known, it remains untested how oligotrophication (i.e. nutrients reduction) can alter the planktonic community responses to warming and elevated CO2 levels. Here, we performed an indoor mesocosm experiment to investigate the warming×CO2 interaction under a nutrient reduction scenario (40%) mediated by an in-lake management strategy (i.e. addition of a commercial solid-phase phosphorus sorbent - Phoslock®) on a natural freshwater plankton community. Biomass production increased under warming×CO2 relative to present-day conditions; however, a Phoslock® -mediated oligotrophication reduced such values by 30-70%. Conversely, the warming×CO2×oligotrophication interaction stimulated the photosynthesis by 20% compared to ambient nutrient conditions, and matched with higher resource use efficiency (RUE) and nutrient demand. Surprisingly, at a group level, we found that the multi-stressors scenario increased the photosynthesis in eukaryotes by 25%, but greatly impaired in cyanobacteria (ca. -25%). This higher cyanobacterial sensitivity was coupled with a reduced light harvesting efficiency and compensation point. Since Phoslock® -induced oligotrophication unmasked a strong negative warming×CO2 effect on cyanobacteria, it becomes crucial to understand how the interplay between climate change and nutrient abatement actions may alter the, ecosystems functioning. With an integrative understanding of these processes, policy makers will design more appropriate management strategies to improve the ecological status of aquatic ecosystems without compromising their ecological attributes and functioning

New insights on the use of magnetic particles for lake restoration: toxicity assessment and evaluation of the viability of recovered phosphorus as a fertilizer

Firstly, our results from single-species acute and chronic toxicity tests using phytoplankton (Chlorella sp. and Raphidocelis subcapitata), zooplankton (Daphnia magna and Brachionus calyciflorus) and benthic organisms (Chironomus sp.) have shown that using MPs for reducing P concentration in lake water and lake sediment is a risk-less (no toxic effect) and efficient (high P adsorption capacity) tool for lake restoration. This statement is based on the higher values measured in this PhD for the concentration of MPs that caused an effect (EC50) or the death (LC50) in 50% of organims compared to the required MPs concentration. At this point, it is worth to note x that MPs concentration to be added in a real lake restoriation project, can be estimated considering the 53 mg MPs: mg P mass ratio as the adsorption efficiency ratio (de Vicente et al., 2010) and the typical concentration of lake water P concentration in eutrophicated ecosystems. To get a comparison of the toxicity of MPs with other novel P adsorbents (magnetite, Phoslock® and CFH-12®), several toxicity tests were also run. In particular, the acute effects on both the green algae R. subcapitata (growth rate inhibition test) and on D. magna (immobilization) were assessed. To discriminate between chemical and physical effects of adsorbents on D. magna, the immobilization test was run both in direct and in indirect contact (by using a double beaker) with the different P adsorbents. Results evidenced that when organisms were exposed to a direct contact in the D. magna immobilization test, no statistically significant differences were found in the EC50 values among the four studied adsorbents. Additionally, the huge difference between direct and indirect contact experiments suggests that toxicity is mainly physically mediated. Finally, an uptake-depuration test was carried out for assessing the response of D. magna after being in direct contact with adsorbents for 24 h. Fe and La body burdens contents, monitored during 24 h-uptake and 24 h-depuration tests, showed that neither accumulation nor longer term effects of P adsorbents is expected. As a result, the risk for toxicity may, on a case-to-case basis, be acceptable. In order to get a more realistic effect of MPs addition on the whole zooplankton community, microcosm experiments containing lake water and lake sediment from an hypertrophic ecosystem (Honda lake, Almería) were carried out. Results confirmed that MPs adition did not significantly affect zooplankton total abundance, species richness and species diversity. The absence of any effect of MPs on zooplankton was explained because MPs did not significantly alter any of its physico-chemical (e.g. temperature, pH, O2) or biological (e.g. food quantity and quality) drivers. Secondly, we have proved the suitability of using MPs for removing P in treated wastewaters. Therefore, high values of both equilibrium adsorption capacity (q) and P removal efficiency of MPs have been measured when adding MPs to treated wastewaters with lastly discharge in the Fuente de Piedra Ramsar site. Accordingly, MPs addition can be proposed as a reliable countermeasure to reduce the impact of wastewater effluents in this Ramsar site. Even more, and considering both advantages (P removal efficiency, %) and disadvantages (economic price, € L-1) of using MPs, we xi have identified an optimum ratio ≥ 0.16 g MPs mg-1 P when adding MPs to treated wastewaters. In the last Chapter, and based on both nutrient concentrations used in previous studies and the cost-effectiveness of the method in a long-term, we select 0.1 M NH4OH (neutralized with H3PO4) as the best option for desorbing P from P loaded MPs. Actually, P concentration in the selected conditions was so high that it was necessary to dilute the supernatants, making profitable to use recovered P as a fertilizer. Fertirrigation experiments showed marked differences in the germination patterns among the three plants species. The first species in germinating was O. bassilicum but it later experienced a slower tendency and at the end of the experiment the highest percentage of germination was 80%, which corresponded to the control. The germination of the other two species, C. sativus and C. melo, started later (from day 4) and it generally reached values up to 100% at the end of the experiment. Even more, germination in the different treatments experienced notable differences among plants species. While in O. bassilicum, the germination in the Control was also higher than in the other treatments for any time of the experiment; for C. sativus and C. melo, the percentage of germination in all treatments was higher than in Control, evidencing the key role of adding nutrients for the germination of these species. In general, height and growth rate for the three plants species was significantly lower in control than in treatments. Additionally, it is worth to note that no significant differences were found when using commercial fertilizer or recovered P from the P loaded MPs. Similarly, shoot and root biomass as well as P concentration in shoot was significantly lower in control than in treatments while no significant differences when using a commercial fertilizer and recovered P were found. These results suggest that P desorbed from P loaded MPs can be used as a liquid fertilizer. As a result, our results are promising in order to counteract the widespread and coupled problems of the exhaustion of the P reserves and the eutrophication of aquatic ecosystems.En primer lugar, los resultados de los tests de toxicidad aguda y crónica con una única especie de fitoplancton (Chlorella sp. y Raphidocelis subcapitata), zooplancton (Daphnia magna y Brachionus calyciflorus) y organismos bénticos (Chironomus sp.) han demostrado que la utilización de MPs para la reducción de la concentración de P presenta una toxicidad reducida sobre los organismos acuáticos. Esta afirmación se basa xiii en que los valores de la concentración de MPs que causa un efecto (EC50) o la muerte (LC50) en el 50% de los organismos es superior a la concentración de MPs estimada para proyectos de restauración. En este punto, es importante tener presente que la concentración de MPs a adicionar se puede estimar considerando la relación 53 mg MP: mg P (de Vicente et al., 2010) así como la concentración típica en ecosistemas eutrofizados. Para obtener una comparación de la toxicidad de las MPs con otros novedosos adsorbentes de P (magnetita, Phoslock® y CFH-12®), también se realizaron varias pruebas de toxicidad. En particular, se evaluaron los efectos agudos tanto sobre R. subcapitata (prueba de inhibición de la tasa de crecimiento) como en D. magna (inmovilización). Para discriminar entre los efectos químicos y físicos de los adsorbentes en D. magna, la prueba de inmovilización se realizó en contacto directo e indirecto (utilizando un doble vaso de precipitados) con los diferentes adsorbentes de P. Los resultados han mostrado claramente el predominio de un efecto físico de los adsorbentes sobre los organismos. Finalmente, se llevó a cabo una prueba de asimilación-depuración para evaluar la respuesta de D. magna después de estar en contacto directo con los adsorbentes durante 24 h. La concentración de Fe y de La en los organismos reflejó la ausencia de acumulación así como de efectos a largo plazo de los adsorbentes de P. Por tanto, podemos concluir que el riesgo de toxicidad puede, según el caso, ser aceptable. Para obtener un efecto más realista de la adición de MPs en toda la comunidad de zooplancton, se llevaron a cabo experimentos de microcosmos que contenían agua y sedimento superficial de un lago hipereutrófico (laguna Honda, Almería). Los resultados confirmaron que la adición de MPs no causa efectos significativos ni en la abundancia total, ni en la riqueza de especies ni en la diversidad de especies del zooplancton. La ausencia de efectos de la adición de MPs sobre la comunidad zooplanctónica puede explicarse por la no alteración ni de los condicionantes físico-químicos (por ejemplo, temperatura, pH, O2) ni biológicos (por ejemplo, cantidad y calidad de alimento). En relación al segundo objetivo de esta Tesis, las MPs han mostrado una elevada eficiencia para retirar P en aguas residuales tratadas. Esta afirmación se basa tanto en la elevada capacidad de adsorción de P en equilibrio (q) así como en la eficiencia de retirada de P por las MPs. Teniendo en cuenta tanto las ventajas (eficiencia de retirada xiv de P) como las desventajas (coste económico) de usar MPs, hemos identificado que la dosis óptima a utilizar es ≥ 0.16 g MPs mg-1 P. En el último Capítulo, y tras la comparación de la concentración de P medida en los extractos al utilizar tres diferentes soluciones básicas (NaOH; KOH y NH4OH), podemos concluir que la mejor opción para desorber P es la utilización de 0.1 M NH4OH (neutralizado con H3PO4). De hecho, la concentración de P en las condiciones seleccionadas fue tan alta que fue necesario diluir los sobrenadantes, lo que optimiza el uso del P recuperado como fertilizante. Finalmente, en los experimentos de fertirrigación con O. bassilicum, C. sativus y C. melo, se observó que la altura y la tasa de crecimiento para las tres especies de plantas fue significativamente menor en el control (sin adición de nutrientes) que en los tratamientos. Más aún, es importante destacar la ausencia de diferencias significativas entre los tratamientos con fertilizante comercial y con P recuperado. De manera similar, la biomasa de las partes aéreas y de las raíces, así como la concentración de P en las partes aéreas fue significativamente más baja en los controles que en los tratamientos, mientras que no se encontraron diferencias significativas entre los tratamientos (fertilizante comercial vs P recuperado). Estos resultados sugieren que el P desorbido desde las MPs puede usarse como fertilizante líquido. Por tanto, las MPs podrían ser porpuestas para contrarrestar la alteración antrópica del ciclo biogeoquímico del P.Tesis Univ. Granada.Proyectos de Excelencia de la Junta de Andalucía P10-RNM-6630.Proyectos nacionales del Ministerio de Economía y Competitividad MINECO CTM 2013-46951-R.Fondo Europeo de Desarrollo Regional (FEDER)

Magnetic particles as new adsorbents for the reduction of phosphate inputs from a wastewater treatment plant to a Mediterranean Ramsar wetland (Southern Spain)

This study assessed the convenience of using magnetic particles (MPs) to reduce phosphorus (P) con centration in treated wastewater. The working hypothesis is that MP addition increases P removal in artificial wastewater treatment ponds. Water samples were collected at the inlet and outlet of a semi-natural pond receiving secondary municipal effluent that is discharged in a Ramsar site (Fuente de Piedra, Malaga, Spain). Then, laboratory batch experiments were run to (i) assess the effect of adding MPs on the chemical composition of treated wastewater, (ii) identify the number of adsorption cycles (by reusing MPs) which are able to trap a high percentage of P (>50%) and (iii) select the optimum ratio between MP mass and initial dissolved inorganic P (DIP) concentration. The results show the suitability of using MPs to remove P in treated wastewater due to both their high equilibrium adsorption capacity (q) and P removal efficiency. Lastly, considering its practical and economical relevance, based on the advantages (P removal efficiency) and disadvantages (economic price), the optimum dose of MPs (0.16 g MP mg-1 P) to achieve a high P removal efficiency (>50%) was identified

Evaluating the effect of CFH-12® and Phoslock® on phosphorus dynamics during anoxia and resuspension in shallow eutrophic lakes*

Laboratory experiments with intact sediment cores from a hypertrophic very windy exposed shallow lake were conducted to assess the combined effect of anoxia and sediment resuspension on phosphorus (P) dynamics after adding different P adsorbents (CFH-12® and Phoslock®). In this study we hypothesize that the addition of geoengineering materials will increase P retention in the sediment even at the worst physic-chemical conditions such as anoxia and sediment resuspension. Both adsorbents significantly reduced the P release from the sediments after a 54 days-anoxic incubation period (CFH-12® by 85% and Phoslock® by 98%) and even after resuspension events (CFH-12® by 84% and Phoslock® by 88%), indicating that both adsorbents are suitable P inactivating agents for restoring shallow eutrophicated lakes under such circumstances. CFH-12® did not release dissolved Fe to the water column neither after the anoxic period nor after resuspension events compared to Control (no adsorbents addition). The La concentration was significantly higher in Phoslock® (3.5e5.7 mg L-1 ) than in Control at all sampling days but it was not affected by resuspension. The high efficiency in P removal under anoxia and resuspension, the low risk of toxicity and the high maximum adsorption capacity makes CFH-12® a promising adsorbent for lake restoration. Nevertheless, further research about the influence of other factors (i.e. pH, alkalinity, interfering substances or strict anoxia) on the performance of CFH-12® is needed

Do magnetic phosphorus adsorbents used for lake restoration impact on zooplankton community?

Magnetic microparticles (MPs) have been recently proposed as innovative and promising dissolved inorganic phosphorus (DIP) adsorbents. However, before using them in a whole-lake restoration project, it is essential to assess their toxicological effects (direct and indirect) on aquatic biota. In the present study we hypothesized that zooplankton community is affected by MPs used for lake restoration. To test our hypothesis we designed a microcosms experiment (n = 15) containing lake water and surface sediment from a hypertrophic lake. Tempo ral changes (70 days) on physico-chemical conditions and on zooplankton structure (rotifers, copepods and branchiopods) were monitored under different scenarios. In particular, three different treatments were consid ered: no addition of MPs (control) and MPs addition (1.4 g MPs L−1) on the surface water layer (T-W) and on the sediment (T-S). After 24 h of contact time, MPs were removed with a magnetic rake. A total of 15 zooplankton species (12 rotifers, 1 branchiopod and 2 copepods) were recorded and a high abundance of zooplankton was registered during the experiment for all treatments. No significant differences (RM-ANOVA test; p N 0.05) in total abundance, species richness and species diversity among treatments were found. The absence of any effect of MPs on zooplankton can be explained because MPs did not significantly alter any of its physico-chemical (e.g. temperature, pH, O2) or biological (e.g. food quantity and quality) drivers. These results confirm the suitability of MPs as a promising tool for removing DIP in eutrophic aquatic ecosystem

Assessing the viability of recovered phosphorus from eutrophicated aquatic ecosystems as a liquid fertilizer

One of the most important worldwide environmental challenges is the alteration of the biogeochemical cycle of phosphorus (P). P is globally exported from terrestrial to aquatic ecosystems, causing the eutrophication of the receiving waters. In this context, magnetic microparticles (MPs) have been recently proposed for trapping P in natural eutrophicated ecosystems, as well as in treated wastewaters. The main advantage of using MPs is that both P and MPs can be recovered from the treated water. Thus, the working hypothesis of the present study is that P can be desorbed from P-loaded MPs and recovered P can be later used as a fertilizer. To test this hypothesis, the best working conditions for desorbing P from P-loaded MPs were identified; then, an experiment with different plant nutrient solutions (neutralized solutions containing recovered P and an unfertilized control) was carried out with three different plant species: Ocimum basilicum L., Cucumis sativus L. and Cucumis melo L. Finally, germination, height, root and shoot biomass and P concentration in root and shoot were compared among treatments. Our results show that the best conditions for P desorption from P-loaded MPs occurred when using 0.1 M NH4OH and using H3PO4 for neutralizing pH. The greenhouse fertirrigation pot experiment showed that the neutralized solution containing desorbed P from P-loaded MPs can be used as a liquid fertilizer, since its combination with macro and microelements significantly increased plant height, growth rate, shoot and root biomass and shoot and root P concentration. As a result, MPs can be proposed to be used for counteracting the widespread and coupled problems of the exhaustion of the P reserves and the eutrophication of aquatic ecosystems

Implications of Anthropic Activities in the Catchment Area of a Temporary Mediterranean Wetland Complex in the South of Spain

The Lagunas de Campillos Natural Reserve and adjacent ponds are fundamentally surrounded by regularly fertilized crop fields and livestock industry, producing leachates which can be found in the ponds. The interest in this Site of European Importance and the RAMSAR wetland complex lies in the habitats within it, which are included in the Directive on Habitats of Community Interest. It is essential to determine the trophic status of the ponds and the quality of these habitats, as well as whether corrective measures need to be established in order to maintain a good environmental status. To characterize and compare the ponds, different parameters were measured, such as conductivity, pH, nutrient concentration, Chl-a concentration, phytoplankton composition, phytoplankton abundance (<20 μm), and the quantification of heterotrophic microorganisms indicating contamination of the aquifers. The obtained results showed that all ponds, except a mesotrophic pond, are eutrophic or even hypertrophic, with high levels of total nitrogen (>8 mg L−1), total phosphorous (>165 μg L−1), and chlorophyll-a concentration. These findings explain the high densities of phytoplankton observed, with the predominant presence of small cells (<3.6 μm ESD). In addition, concentrations of heterotrophs and coliforms are, in some ponds, higher than expected. Eutrophication hinders ecological functions and ecosystem services, which finally affects biodiversity and human wellbeing. Five of the six analyzed ponds are within various protection figures for their essential importance to local and migrating avifauna. Therefore, ponds’ status analysis and the implementation of measures for maintaining ecosystem services and trophic state are fundamental for the sustainable management of the studied area.Plan Propio Universidad de Málag