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[spa] La basura marina está aumentando exponencialmente en los mares y océanos de todo el mundo. En los últimos años, se han reportado y documentado sus amenazas a la fauna marina y a los ecosistemas marinos en general. Por estas razones, se están fomentando medidas de mitigación y campañas de monitoreo para determinar cuáles son las zonas de acumulación de basura marina y evaluar la eficacia de las medidas propuestas. Sin embargo, todavía falta información para determinar los niveles basales de basura marina y mejorar las metodologías de monitoreo. El objetivo general de la presente tesis es estudiar la basura marina de manera interdisciplinar para tener una visión más amplia de sus potenciales efectos sobre los vertebrados marinos. En el primer capítulo, se investigan los macro-residuos flotantes mediante fotografía aérea desde drones y los macro-residuos flotantes y megafauna marina desde avionetas y se desarrolla un modelo de aprendizaje profundo para detectar y cuantificar los macro-residuos flotantes en las imágenes aéreas. Los resultados revelan que las técnicas de teledetección son igual o incluso más efectivas que las técnicas visuales para detectar macro-residuos flotantes y megafauna marina, y el modelo de aprendizaje profundo, instalado en una aplicación web, alcanza una efectividad del 81%. En el segundo capítulo, se utilizan tres especies potencialmente bioindicadoras (la boga (Boops boops), el rorcual común (Balaenoptera physalus) y el lobo marino antártico (Arctocephalus gazella)) para determinar la ocurrencia de microplásticos. Los resultados revelan la ocurrencia de microplásticos en el 46% y 52% de bogas de la costa catalana y rorcuales comunes del Atlántico Norte, respectivamente. Por lo contrario, no se encontraron microplásticos en los excrementos de lobo marino antártico, resultado que sugiere que las aguas del Estrecho de Bransfield presentan niveles muy bajos de contaminación plástica. En el tercer capítulo, se determina la concentración de aditivos plásticos en muestras de tejido de vertebrados marinos, para analizar su relación con las concentraciones de microplásticos e investigar los procesos de bioacumulación y biomagnificación de estos contaminantes. Los resultados muestran que las bogas del Mediterráneo presentan niveles considerables, pero no preocupantes, de ésteres organofosforados en sus tejidos musculares y que estas concentraciones no están relacionadas con la ocurrencia de microplásticos en sus tractos gastrointestinales. Además, los resultados muestran que los rorcuales comunes del Atlántico Norte presentan ésteres organofosforados y ftalatos en sus tejidos musculares y, aunque parece que los niveles no sean preocupantes para la viabilidad de sus poblaciones, una exposición a largo término podría desencadenar una toxicidad crónica. Además, parece ser que los ésteres organofosforados no se bioacumulan ni biomagnifican, y que los ftalatos no presentan diferencias intra-poblacionales ni temporales en rorcual común. En conjunto, los resultados de esta tesis proporcionan información de utilidad para mejorar los programas de monitoreo de basuras marinas y datos que pueden ser usados como referencia de los valores basales de macro-residuos flotantes, microplásticos y aditivos plásticos., [eng] Marine litter is increasing exponentially in the seas and oceans of the world. In recent years, its threats to marine fauna and marine ecosystems in general have been reported and documented. For these reasons, mitigation measures are being adopted and monitoring programmes are being set in place to determine accumulation zones and evaluate the effectiveness of adopted measures. However, the information needed to determine baseline levels of marine litter and to improve and standardize monitoring methodologies is still poor. The general objective of this thesis is to investigate marine litter through an interdisciplinary approach to gain a broader perspective of its potential effects on marine vertebrates. In the first chapter, floating marine macro-litter is investigated using aerial photography from drones; floating marine macro-litter and marine megafauna are observed with a combined visual- and photographic-based approach from aircraft, and a deep learning model is developed to detect and quantify the floating marine macro-litter in aerial images. Results reveal that remote sensing techniques are as effective or more effective than visual techniques in detecting floating marine macro-litter and marine megafauna, and the deep learning model, installed in a web application, achieves an accuracy of 81%. In the second chapter, three potential bioindicator species (i.e., the bogue (Boops boops), the fin whale (Balaenoptera physalus) and the Antarctic fur seal (Arctocephalus gazella)) are analysed to determine the occurrence of microplastics. Results reveal the occurrence of microplastics in 46% of the bogues sampled from the Catalan coast and in 52% of the North Atlantic fin whales, respectively, while no microplastics are found in Antarctic fur seal scats, suggesting that the waters of the Bransfield Strait have very low levels of plastic contamination. The third chapter aims to determine the concentration of plastic additives in samples of marine vertebrate tissues, analyse its relationship with the occurrence of ingested microplastics and investigate the processes of bioaccumulation and biomagnification of these pollutants. Results show that the levels of organophosphate esters in the muscle of the bogues from the Mediterranean Sea are considerable but not of concern and do not relate to the occurrence of microplastics in the fish gastrointestinal tracts. In addition, organophosphate esters and phthalates are detected in the muscle of North Atlantic fin whales, and although their levels do not seem of concern for the viability of the fin whale population, long-term exposure may lead to chronic toxicity. Finally, phthalate concentrations do not show intra-population or temporal differences in fin whales and organophosphate esters do not appear to bioaccumulate throughout the whale life-span and/or biomagnificate through the food web. The results of this thesis provide relevant information to improve marine litter monitoring programs as well as useful data to produce reference baseline values of floating marine macro-litter, microplastics and plastic additives.

International audience

Los residuos marinos se definen como cualquier material sólido persistente que ha sido manufacturado o procesado y después, desechado, perdido o abandonado en el medio marino o costero. Están presentes en todos los mares y océanos del mundo y amenazan todo tipo de fauna marina, desde invertebrados, peces y tortugas hasta mamíferos marinos.

Monitoring Floating Marine Macro Litter (FMML) is a global priority, stressed within international programs, and regulated for the European Seas by the Marine Strategy Framework Directive. Although some well-defined common protocols exist for the assessment of beach litter and ingested litter, methodologies for FMML monitoring still vary, leading to some inconsistent results and hampering the global assessment of this threat. Within the MEDSEALITTER project (2016–2019), field experiments were implemented to define optimal monitoring parameters for FMML visual monitoring at different spatial scales, by assessing the influence of platform speed, strip width, observers experience, weather conditions, and litter size on its detectability. Along with the results of these experiments, we present the FMML density ranges detected across the over 20,000 km surveyed, highlighting a decreasing gradient from river mouths to coastal areas and the open sea, and providing a valuable contribution to the assessment of FMML in the Mediterranean Sea.

Pollution by marine litter is raising major concerns due to its potential impact on marine biodiversity and, above all, on endangered mega-fauna species, such as cetaceans and sea turtles. The density and distribution of marine litter and mega-fauna have been traditionally monitored through observer-based methods, yet the advent of new technologies has introduced aerial photography as an alternative monitoring method. However, to integrate results produced by different monitoring techniques and consider the photographic method a viable alternative, this 'new' methodology must be validated. This study aims to compare observations obtained from the concurrent application of observer-based and photographic methods during aerial surveys. To do so, a Partenavia P-68 aircraft equipped with an RGB sensor was used to monitor the waters off the Spanish Mediterranean coast along 12 transects (941 km). Over 10000 images were collected and checked manually by a photo-interpreter to detect potential targets, which were classified as floating marine macro-litter, mega-fauna and seabirds. The two methods allowed the detection of items from the three categories and proved equally effective for the detection of cetaceans, sea turtles and large fish on the sea surface. However, the photographic method was more effective for floating litter detection and the observer-based method was more effective for seabird detection. These results provide the first validation of the use of aerial photography to monitor floating litter and mega-fauna over the marine surface.

Semi-natural grasslands are habitats that have not been sown by the hand of man, they show an important species richness, they have a great ecological and productive importance and, in addition, they show notable environmental functions. Only 2% of the Parc Natural de la Zona Volcànica de la Garrotxa (PNZVG) is constituted by semi-natural grasslands, moreover, they can quickly evolve depending on environmental changes and/or management, therefore, it is highly recommended to keep the information about its conservation state updated. One of the most used groups of invertebrates as a biologic indicator and that comply all the features to be a good bioindicator is the group of ants, because they are very important at an ecologic level, they carry out many functions inside the ecosystem, ants’ diversity in the world is high, they are found in abundance in most terrestrial ecosystems, they are relatively sedentary, they are sensitive to environmental change and are easily sampled, classified and identified. Thus, in order to study the conservation state of grasslands in more detail, our aim here is to verify if the ant community is a good biological indicator to determine the semi-natural grasslands’ floristic quality of the PNZVG and, at the same time, to study the ant community at functional group levels. The results show that up to 28 species have been identified in the semi-natural grasslands of the PNZVG. The results obtained on ants diversity and the other community variables in regards to the floristic quality of the semi-natural grasslands are not significant, although we could intuit a tendency to have more ant richness and diversity in higher semi-natural grasslands floristic quality. In functional group terms, in the semi-natural grasslands of the PNZVG there are 46% of disturbance bio indicator species, 43% of maturity bio indicator species and 11% of cryptic species, meaning that the disturbance and maturity indicators are even because they are managed by grazing or haymaking and, therefore, they are under the influence of a certain disturbance. The use of the ant community as a bio indicator of the semi-natural grasslands’ floristic quality of the PNZVG should confirm or refute over time when we make use of the methodology in a monitoring program for 1-3 years