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[SPA] El objetivo fue conocer la respuesta de humedales frente a elevadas concentraciones de P, valorando su capacidad de retención. Se ensayó en mesocosmos que se inundaron con aguas de diferente nivel de eutrofización (bajo nivel –BN: 6,1 mg L-1 PO43-; alto nivel –AN: 61 mg L-1 PO43-) durante 1 año. Tratamientos: BN + no planta; AN + no planta; BN+ Phragmites australis; AN + Phragmites. Se midió PO43- en el agua de poro y drenajes y las fracciones de P retenido en el suelo. A las 24 h de haber inundado ya se había producido una reducción del ~90% del PO43- del agua de inundación, independientemente de la carga de nutrientes y la presencia de Phragmites. El suelo actuó como sumidero de P, que quedó retenido sobre todo en los compuestos de Ca/Mg y óxidos metálicos. [ENG] The objective was to determine the response of wetlands against high concentrations of P, assessing their retention capacity. This was tested in mesocosms that were flooded with waters of different eutrophication levels (low level –BN: 6.1 mg L-1 PO43-; high level –AN: 61 mg L-1 PO43-) for 1 year. Treatments: BN + not plant; AN + not plant; BN + Phragmites australis; AN + Phragmites. The concentrations of PO43- were measured in soil solution and drainage samples and the different P fractions retained by the soil were determined. After 24 h of flooding the concentrations of PO43- in the soil solution were decreased ~90% compared to the flooding water, regardless the eutrophication level and the presence of Phragmites. The soil acted as s sink of P that was mainly fixated by the Ca/Mg compounds and the metal oxides. Proyecto financiado por el MINISTERIO DE CIENCIA E INNOVACIÓN (CGL2010–20214.)

[SPA] En este capítulo se resumen los resultados de diversos experimentos realizados con suelos (afectados y no afectados por residuos de minería) y plantas procedentes de dos humedales de la costa del Mar Menor: la Marina del Carmolí y el saladar de Lo Poyo. Se estudiaron los mecanismos biogeoquímicos que determinan la capacidad de estos ambientes para actuar como filtros verdes frente a las aguas eutrofizadas cargadas en nitratos (NO3 –) y fosfatos (PO4 3–), valorando el efecto de las plantas y del encalado de los suelos sobre dicha capacidad. También se cuantificó la transformación de NO3 – en óxido nitroso (N2O), un gas de efecto invernadero, y se discutieron los efectos negativos que pueden tener estos ambientes como emisores de dicho gas, que contribuye al calentamiento global, frente a los positivos para depurar las aguas que vierten al Mar Menor. Por otro lado, se analizaron los mecanismos implicados en la movilidad de los metales pesados en el sistema suelo-agua-planta en zonas afectadas por residuos mineros y se evaluaron alternativas de manejo para reducir los riesgos asociados a dichos metales. Como síntesis de las lecciones aprendidas podemos decir que: a) el papel de los humedales costeros del Mar Menor para depurar las aguas cargadas de NO3 – se produce a costa de emitir altas concentraciones de N2O a la atmósfera a través de la desnitrificación y la de depurar PO4 3– a costa de almacenar fósforo en los suelos; b) en suelos inundados la contribución de la vegetación (en particular carrizo, Phragmites australis) a la eliminación de NO3 – está más relacionada con crear un ambiente favorable para la actividad de los microorganismos en el entorno de sus raíces que en absorber dichos NO3 –; c) en suelos en fase de secado la absorción de NO3 – por el carrizo gana en importancia, contribuyendo a reducir la concentración de NO3 –disponible para la formación y emisión de N2O a la atmósfera a través del proceso de desnitrificación; d) muchas zonas de los humedales estudiados presentan una elevada concentración de metales pesados en sus suelos debido a la presencia de residuos mineros, lo que supone un riesgo para el medio ambiente y la salud de las personas; e) la solubilidad y movilidad de los metales depende del metal, de la humedad del suelo y de la presencia/ausencia de plantas (así como de la especie de planta), por lo que las medidas de manejo que impliquen la adición de enmiendas y la implantación de vegetación deben ser planificadas para cada caso particular conociendo con todo detalle las condiciones biogeoquímicas que van a existir tras las actuaciones que se realicen. [ENG] This chapter summarizes the results of a number of experiments carried out with soils (affected and unaffected by mining waste) and plants collected from two wetlands of the Mar Menor lagoon: the Marina del Carmolí and the Lo Poyo salt marsh. The biogeochemical mechanisms responsible for the capacity of these wetlands to act as green filters against eutrophic water with a high nitrate (NO3 –) and phosphate (PO4 3–) content were studied. The effect of plants and liming on this capacity were also evaluated. In an experiment, the transformation of NO3 – into N2O (a greenhouse gas) by denitrification was evaluated, and the negative consequences of N2O for global warming were discussed in relation with the positive effect of these wetlands in purifying eutrophic water that reaches the Mar Menor. The mechanisms influencing the solubility and mobility of heavy metals in the soil-water-plant system were also studied, and some proposals were suggested for the management of wetlands polluted by mine wastes. The lessons learned can be summed up as: a) the role of coastal wetlands of the Mar Menor in purifying eutrophic water with high NO3 – content implies high N2O emissions to the atmosphere, whilst their role in purifying PO4 3– implies that their soils act as phosphorus sinks; b) in flooded soils, the main role of plants (mainly Phragmites australis, common reed) in reducing NO3 – concentrations in eutrophic water is to promote microbial activity in the rhizosphere, which favours denitrification, the absorption of NO3 – by plants playing a secondary role; c) when soils are drying, however, the role of NO3 – absorption by Phragmites becomes more significant, this absorption reducing the NO3 available for N2O formation and emission via denitrification; d) extensive zones of the wetlands are affected by extremely high heavy metal concentrations in soil due to the presence of mining waste, which poses a risk for the environment and human health; e) the solubility and mobility of metals are specific for each metal and are influenced by soil moisture levels and the presence of different plant species; hence, the implementation of management strategies that imply the use of remedial actions and replanting must be planned on a case-by-case basis and only after a detailed analysis of the resulting biogeochemical conditions has been carried out.

The Mar Menor lagoon is one of the largest coastal lagoons (135 km2 surface) of the Mediterranean basin. It receives runoff waters coming from the nearby intensive agricultural area of Campo de Cartagena, which have led this lagoon to be declared as a sensitive area for eutrophication in June 2001 under European Directive 91/271/EEC and as a vulnerable zone for nitrates contamination in December 2002 under Directive 91/676/EEC. Moreover, the existence of mining activities (nowadays discontinued) in the nearby area of Sierra de Cartagena-La Union has caused the spread of metal polluted wastes into the Mar Menor lagoon and its salt marshes. As a consequence, huge coastal areas are buried by metal enriched wastes, and although most of them have been colonized by vegetation, others remain bare and exposed to erosive agents (e.g. wind, water). At the same time, the Mar Menor and its salt marshes have been included in the Ramsar Convention on Wetlands. Also, it is a Special Protected Area of Mediterranean Interest (SPAMI), a Specially Protected Area (SPA) under the EU Wild Birds Directive and a Site of Community Importance (SCI) to be integrated in the Nature 2000 Network (EU Habitats Directive). In addition, the Campo de Cartagena- Mar Menor zone hosts important economic activities related with agriculture, fisheries and tourism (Conesa and Jiménez-Cárceles, 2007). Hence, the habitat conservation and the uses of the territory must be compatible and overcome the environmental problems of the zone. This paper summarizes several studies carried out in the Mar Menor area from year 2000 till nowadays. The methodologies followed in these works were based on international scientific and technical protocols. The research included field and lab experiments. The first ones had the goal of answering questions such as what, where, when, by means of descriptive field survey studies (Álvarez-Rogel et al., 2000, 2001, 2006b, 2007a y c, Álvarez-Rogel et al., 2006a, 2007b; Jiménez-Cárceles, 2007; Jiménez-Cárceles et al., 2006; Jiménez-Cárceles and Álvarez-Rogel, 2008; Egea et al., 2011). Afterwards, the research had the goal of explaining how the processes occurred, by means of experimental set ups not included here (greenhouse experiments, columns, lab, etc.). This chapter deals with the field survey studies in order to describe the nutrient dynamics and eutrophication risks in the coastal areas of the Mar Menor lagoon

[SPA] El Mar Menor, localizado en el sureste de España, es una de las lagunas costeras más grandes de Europa y del Mediterráneo. A pesar de las diversas figuras de protección medioambiental que obstenta, esta laguna y sus humedales asociados se encuentran afectados por diversas actividades antrópicas, entre las que destacan la presencia de residuos mineros procedentes de la antigua zona minera de Cartagena-La Unión, transportados y depositados durante los periodos de lluvias torrenciales a través de las ramblas que drenan ese área. Como caso de estudio, el presente trabajo se centra en dos saladares, la Marina del Carmolí y Lo Poyo, y en la línea de costa del Mar Menor asociada a ambos parajes. [ENG] The present work focuses on two salt marshes, the Marina del Carmolí and Lo Poyo, and along the shoreline of the Mar Menor associated to both wetlands. Due to the activities that population develops in the area, which include harvesting of plants for feeding and adornment, sheepherding, capture of molluscs for eating, several recreational activities, and bathing, there may be some risks of toxicity and transfer of heavy metals and arsenic to the food chain. Thus, it was proposed a project with the following aims: (1) To carry out a first approximation to the risks of toxicity associated with the presence of heavy metals and arsenic in these environments, including their transfer to the food chain. (2) To study the biogeochemical processes associated with mobilization-immobilization of those toxic elements in the studied wetlands, under different flooding regimes either with or without rhizosphere. (3) To establish recommendations for use to preserve these ecosystems and reduce the risks associated with the presence of those contaminants. To achieve the first aim, the concentrations of heavy metals (cadmium, copper, manganese, lead, and zinc) and arsenic were determined in several rhizospheric and non-rhizospheric soil samples (total contents and the labile fraction extracted with 1 N hydrochloric acid) and in the most representative species of plants of both salt marshes, including those consumed by population and those used for sheepherding. Litter, roots, rhizomes, bulbs, green stems, ligneous stems, and leaves were separately analyzed. With the same objective, it was determined the accumulation of the same toxic elements in the sediments of the lagoon in sites adjacent to both salt marshes and in two species of marine molluscs collected that live in them and which are consumed by population: the carnivorous gastropod Hexaplex trunculus (commonly called 'seashell' or 'horn'), and a filter bivalve, the clam Tapes decussatus. Besides, it was determined the speciation of arsenic in H. trunculus because the different forms of this metalloid have very different toxicities. To achieve the second aim, it was performed a greenhouse experiment to study the influence of pH, flooding and rhizosphere on the mobilization of cited elements plus iron. For that, different pots were filled with mining wastes collected from two polluted areas: one acidic (from Lo Poyo salt marsh) and one basic (from the Marina del Carmolí salt marsh). For each mining waste, small specimens of Sarcocornia fruticosa and Phragmites australis were planted in the pots. Also, it was prepared pots without plant. Two different flooding regime were applied: (1) pots flooded three months and afterwards drying, and (2) pots flooded one month and another drying, alternately for six months. The water used to irrigate the pots was a mixture of water collected from two of the main surface watercourses of the zone. The Eh and pH were measured weekly with appropriate electrodes. Also the solution was extracted weekly from the pots using Rhizon type samplers. After acidifying the solution with two drops of concentrated sulphuric acid, dissolved organic carbon and dissolved As, Cd, Cu, Mn, Pb, Zn and Fe were measured. To achieve the third aim, the results and conclusions of the two previous points were integrated and combined. The results of field analyses indicated that the soils of the Marina del Carmolí and Lo Poyo salt marshes are strongly polluted by As, Cd, Mn, Pb, and Zn, but not for copper. Besides, the contents extracted with 1 N hydrochloric acid (a labile fraction) were high, which indicate that there is a risk of mobilization of those elements. Therefore, according to field and greenhouse data, it can be proposed some recommendations in order to minimize the risks due to metallic pollution. A possible strategy would be the continuous flooding of the polluted areas, together with the planting of the most appropriate species to perform a phytostabilization program. Based on the capacity to grow in the wettest soils and on their capability to accumulate toxic elements in roots, Arthrocnemum macrostachyum, Sarcocornia fruticosa, Juncus maritimus, Scirpus holoschoenus, and Phragmites australis, would be the most suitable species. The presence of vegetation also would prevent the erosion and the dragging of the mining wastes. Nevertheless, these practices should be accompanied with the addition of some kind of amendment to further immobilize the contaminants, as for example carbonates. After the addition of amendments it is necessary to follow a monitoring program in the areas in restoration in order to check that those actions are effective enough in short and long term. Universidad Politécnica de Cartagena

[SPA] Los humedales naturales y artificiales son sistemas capaces de transformar y/o eliminar compuestos nocivos, depurando las aguas eutrofizadas y/o contaminadas que fluyen a través de los mismos. Su papel como filtros verdes está determinado, fundamentalmente, por los procesos biogeoquímicos asociados a los cambios en las condiciones de oxidación-reducción, tales como la desnitrificación, así como por la fijación de contaminantes a diversos componentes del suelo, su precipitación y co-precipitación con otros compuestos e inmovilización en la biomasa vegetal. La laguna del Mar Menor y sus humedales asociados (por ejemplo, la Marina del Carmolí), se encuentran afectados por vertidos de aguas eutrofizadas de origen agrícola y urbano, con altas concentraciones de N y P. El deterioro de la calidad de las aguas de la laguna se ha acentuado en los últimos años, debido principalmente al aumento del grado de eutrofización, conduciendo a una crisis medioambiental en 2016. El objetivo principal de la Tesis fue estudiar, en condiciones experimentales, los procesos biogeoquímicos, microbiológicos y fisiológicos en el sistema suelo-agua-planta de humedales del entorno del Mar Menor afectados por aguas eutrofizadas, bajo condiciones alternantes de inundación-secado, a fin de determinar en qué medida la presencia de plantas de Phragmites australis, la carga de nutrientes (C orgánico, N y P) y el periodo del año influyen en la capacidad de estos sistemas para depurar aguas eutrofizadas y su relación con la emisión de CO2 y N2O. Los objetivos específicos fueron: 1. Evaluar el papel de la carga de nutrientes del agua de inundación y la presencia de Phragmites australis en la variabilidad estacional de las propiedades físico-químicas y microbiológicas del suelo, así como de las emisiones de CO2, en humedales afectados por aguas eutrofizadas. 2. Evaluar la capacidad de eliminación de N-N2O del suelo, el humedales afectados por aguas eutrofizadas, y determinar si dichos procesos están condicionados por la carga de nutrientes, la presencia de Phragmites australis y el periodo del año. 3. Evaluar la capacidad de retención de P en humedales afectados por aguas eutrofizadas y determinar si dicha retención está condicionada por la carga de nutrientes, la presencia de Phragmites australis y el periodo del año, así como la contribución de las plantas y de diferentes componentes del suelo en la retención de P., [ENG] Wetlands have the capacity to transformand/or remove harmful compounds (e.g. nutrients), improving the quality of eutrophic and/or contaminated waters flowing through them. Their role as green filters mainly depend on the biogeochemical processes related to the changes in the oxidation reduction conditions, such as denitrification, as well as on the fixation of contaminants to various soil components, their precipitation or co –precipitation with other substances and their immobilization in plant biomass. The Mar Menor lagoon (SE Spain), with 135 km2 of surface area, is the largest coastal lagoon of the Mediterranean basin. The lagoon and its associated wetlands (e.g. Marina del Carmolí salt marsh) are affected by eutrophic waters of agricultural and urban origin, with high loads of nitrogen (N) and phosphorus (P). The wáter quality deterioration of the lagoon has increased in the last years, mainly due to its eutrophication, leading to an environmental crisis in 2016. The general objective of the PhD Thesis was to study, under experimental conditions, the biogeochemical, microbiological and physiological processes in the soil –water–plant system of the Mar Menor’s wetlands affected by eutrophic waters, under alternating flooding–drying conditions, in order to assess to what extent the presence of Phragmites australis ,the nutrient load (organic carbon, N and P) and the time of the year influence the capacity of these systems to depurate eutrophic waters and its relation to carbon dioxide (CO2) and nitrous oxide (N2O) emissions., Esta Tesis se ha realizado bajo la financiación del siguiente proyecto: Relaciones entre los ciclos biogeoquímicos y la función de los humedales como filtros verdes: efecto de la eutrofización, la especie vegetal y el periodo del año sobre el secuestro de carbono ”, cofinanciado por el Ministerio de Economía y Competitividad (CGL2010–20214)–Fondos FEDER, Escuela Internacional de Doctorado, Universidad Politécnica de Cartagena, Programa Doctorado en Técnicas Avanzadas en Investigación y Desarrollo Agrario y Alimentario