Tracking thorium-234 to study particle dynamics in a coastal hypersaline lagoon: implications for environmental degradation in Mar Menor (SE Spain)
Miralles Vidal, Marina
Mostazo Alsina, Paula
Alorda-Kleinglass, Aaron , tut. (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Roca Martí, Montserrat , tut. (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Universitat Autònoma de Barcelona. Facultat de Ciències

Data:	2024
Descripció:	38 pag.
Resum:	Coastal lagoons are complex socio-ecological systems that sustain biodiversity as well as several economical activities. Their over-exploitation has caused a rapid degradation in the last decades. Understanding the dynamics and complexity of coastal lagoons is a must to be able to protect these habitats. Radioactive isotopes have been widely used as tracers to track, measure and quantify a wide range of environmental processes in aquatic systems. For instance, the pair of radionuclides thorium-234/uranium-238 (234Th/238U), due to its physicochemical characteristics, is very useful for tracking the movement of particles in the open ocean. However, it has been recently suggested as potential tool to use in coastal areas. Although the use of 234Th/238U pair in these areas may have limitations, it could be a potential tool for studying particle fluxes and particle dynamics in shallower waters. The Mar Menor lagoon (SE Spain), is one of the biggest hypersaline coastal lagoons in the Mediterranean Sea and harbors the habitat of endangered species. Mar Menor has suffered in the past from eutrophication and anoxic conditions as it has historically been a heavily human-pressured environment. Eutrophication events are triggered by torrential rains as well as submarine groundwater discharge as they supply enormous amounts of nutrients and particles which are net contributors to devastating algal blooms in the lagoon. However, resuspension has lately been proposed to be another contributor that causes the algae blooms, so this study aims to assess if 234Th/238U pair could be a potential tracer for resuspension in Mar Menor. To route this innovative line of study on 234Th/238U, a field campaign was conducted in Mar Menor lagoon from January 25th to February 1st, 2024. Background physicochemical data was recorded daily during the campaign by local authorities. This data was used in combination with three different types of samples (i. e. , water samples, sediment traps and sediment cores) which were collected in four sampling stations. The results varied among the types of samples. On the first hand, water samples results reflected a large quantity of particles along the water column and stations. This hypothesis is supported by the high turbidity measured throughout the water column 2 days before sampling, and thus enhancing the presence of particles along the water column. On the other hand, sediment traps and cores samples showed a different trend depending on the stations. Regarding sediment traps samples, the westernmost station recorded higher values of 234Th flux and sedimentation rate, probably because of a turbidity event during sample collection that only affected that station. Finally, sediment core samples showed no potential evidence to recent sedimentation in this same station as it is located in an area characterized by particle dragging and not sedimentation processes. This study has made it possible to collect information about particle dynamics in Mar Menor by the early 2024. A new path of research could be open for 234Th/238U as a tool to potentially track particle fluxes in shallow water systems. Results seen are consistent enough to prove 234Th as an effective particle tracer in Mar Menor since our findings suggest evidence for both vertical and horizontal particle fluxes. Nevertheless, no clear sign of resuspension was found. Finally, considering some limitations were found, recommendations for future research are suggested. Since there are not many studies in this field, this pilot study aims to pave the way for newer applications.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra, i la creació d'obres derivades, sempre que no sigui amb finalitats comercials i que es distribueixin sota la mateixa llicència que regula l'obra original. Cal que es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Titulació:	Ciències Ambientals [2504604]
Pla d'estudis:	Grau en Ciències Ambientals [1535]
Document:	Treball final de grau
Matèria:	Mar Menor ; Water ; Sediment traps ; Cores

39 p, 1.8 MB

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