Microplastic pollution in sublittoral coastal sediments and marine organisms

• Autores: Cristina Villanova Solano
• Directores de la Tesis: Cintia Hernández Sánchez (codir. tes.), Javier Hernández Borges (dir. tes.)
• Lectura: En la Universidad de La Laguna ( España ) en 2026
• Idioma: inglés
• Tribunal Calificador de la Tesis: Javier Bayo Bernal (presid.), María Sabrina Clemente Martín (secret.), Mariacristina Cocca (voc.)
• Programa de doctorado: Programa de Doctorado en Biodiversidad y Conservación por la Universidad de La Laguna
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• Resumen

  • Plastic pollution has become one of the most widespread environmental problems affecting marine ecosystems worldwide. Among the different forms of plastic debris, anthropogenic particles like microplasticas have received increasing scientific attention due to their persistence, small size, and capacity to disperse across marine environments. Oceanic island systems are particularly vulnerable to this type of contamination because they are influenced not only by local human activities but also by long-distance transport of marine debris through large-scale ocean circulation. In this context, the Macaronesian region, and especially the Canary Islands, represents a strategic area for studying the distribution, sources, and ecological implications of anthropogenic particulate pollution in marine ecosystems. The main objective of this PhD Thesis was to assess the presence, distribution, characteristics, and environmental significance of anthropogenic particles in marine environments of the Macaronesian region. The research focused on understanding how these particles are distributed across environmental compartments and incorporated into marine organisms, as well as identifying the processes that control their transport, accumulation, and potential ecological transfer within marine ecosystems. To address these objectives, a multidisciplinary approach combining field sampling and laboratory analysis was applied. Samples were collected from multiple environmental matrices, including coastal sublittoral sediments, seawater, and marine organisms representing different ecological niches and trophic levels. The biological component included species such as sea urchins (Arbacia lixula), deposit feeding holothurians (Holothuria sanctori), and northern krill (Meganyctiphanes norvegica), allowing the evaluation of particle exposure and incorporation across benthic and pelagic environments. In addition, the study examined coastal habitats with high structural complexity, particularly seagrass meadows dominated by Cymodocea nodosa, which play a key role in sediment dynamics and particle retention. Laboratory analyses were conducted using standardized procedures designed to improve the reliability and comparability of microplastic studies. These procedures included organic matter digestion, density separation through multiple flotation steps, microscopic characterization of particles, and polymer identification through spectroscopic techniques. Strict contamination control protocols were implemented throughout the analytical process to minimize airborne fibre contamination and ensure the accuracy of results. The methodological framework developed in this thesis contributes to the harmonization of microplastic analysis and addresses one of the main challenges in current research: the lack of standardized protocols for the extraction and identification of anthropogenic particles in complex environmental matrices. The results obtained demonstrate the widespread presence of anthropogenic particles in all analysed environmental compartments, confirming that these particles have become ubiquitous components of marine ecosystems in the Macaronesian region. Anthropogenic fibres were consistently the most abundant particle type across sediments, seawater, and biological samples. Most fibres were colourless or blue and typically ranged from several hundred micrometres to a few millimetres in length. Chemical characterization indicated that many fibres corresponded to natural or semi-synthetic cellulosic materials derived mainly from textile sources, although synthetic polymers such as polyester and PVC were also detected. These findings highlight the important contribution of anthropogenic fibres to marine particulate pollution and challenge the traditional perspective that focuses exclusively on fully synthetic plastics. Although many of the detected fibres are not strictly plastic, their anthropogenic origin and environmental persistence suggest that they should be considered within monitoring frameworks addressing plastic pollution in marine ecosystems. The analysis of environmental matrices revealed strong connectivity among marine compartments. Similar particle characteristics across seawater, sediments, and organisms suggest that common transport and deposition processes regulate the distribution of anthropogenic particles in coastal environments. Hydrodynamic conditions, including wave exposure and coastal circulation, influence the spatial accumulation of particles, while coastal sediments function as long-term sinks where particles accumulate and interact with benthic communities. Seagrass meadows dominated by Cymodocea nodosa were identified as particularly effective sinks for anthropogenic particles. The structural complexity of seagrass canopies enhances sediment stabilization and promotes the trapping and retention of particles within the meadow environment. As a result, these habitats can accumulate anthropogenic particles even within areas considered environmentally protected. Biological analyses confirmed the incorporation of anthropogenic particles into marine organisms through different exposure pathways. In deposit-feeding holothurians, sediment ingestion represents the primary mechanism of particle uptake, although continuous interaction with surrounding seawater may also contribute to exposure. Similarly, the detection of particles in sea urchins reflects the constant presence of anthropogenic particles within coastal habitats. The presence of anthropogenic particles in northern krill provides additional evidence of their occurrence within pelagic ecosystems. Although particle abundance in krill was relatively low, the consistent detection of fibres suggests that these organisms may facilitate the transfer of anthropogenic particles through marine food webs. Considering the ecological importance of krill as a key trophic link between lower and higher trophic levels, their interaction with anthropogenic particles highlights the potential for trophic transfer to fish, seabirds, and marine mammals. Overall, this thesis demonstrates that anthropogenic particulate pollution affects multiple environmental compartments and trophic levels in the Macaronesian marine environment. The results support the concept of the Plastic Cycle, which describes the continuous exchange of plastic particles between water, sediments, and biota. Understanding these interconnected processes is essential for accurately assessing the environmental fate of anthropogenic particles and their potential ecological impacts. Beyond its regional focus, this research contributes to the broader scientific understanding of microplastic pollution in oceanic island systems. The findings highlight the importance of considering both local and transoceanic sources of marine debris and emphasize the need for integrated monitoring strategies capable of addressing the complexity of plastic pollution in marine ecosystems. Finally, this work underscores the importance of continued research, methodological harmonization, and international collaboration to improve the monitoring and management of anthropogenic particulate pollution. The development of standardized analytical protocols, regulatory frameworks, and coordinated mitigation strategies will be essential to reduce the growing impact of plastic pollution on marine ecosystems. Through its integrative and multidisciplinary approach, this thesis provides a scientific basis for future environmental monitoring and management efforts aimed at addressing plastic contamination in the Macaronesian region and other oceanic island systems