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Marine litter is considered a common concern of humankind that poses a serious risk to marine life, human health and the economy. One of the most abundant and harmful types of marine litter is abandoned, lost or otherwise discarded fishing gear. As it comprises of durable mate-rials like nylon or polyethylene it can continue to catch fish for years before it breaks down into smaller pieces. The smaller pieces can then be ingested with possibly fatal consequences. To mitigate those impacts, derelict fishing gear [DFG] is increasingly retrieved from the ocean. However, apart from landfilling there is currently no established waste treatment system to process this material in Europe. In the context of the European Interregional project MARELITT Baltic and in collaboration with WWF Germany and PreZero, this thesis investigated the retrieval and alternative waste treatment options for DFG. In total, four scenarios, namely the (1) mechanical recycling, (2) chemical recycling, (3) energy recovery and (4) disposal were evaluated to assess their poten-tial environmental impact and feasibility. For this, industrial experiments and a life cycle as-sessment (LCA) were conducted. The experiments highlighted DFG as a challenging mix of materials. Apart from large bulky items such as anchors, chains and cables, also smaller contaminants like sediments, salt and lead were contained. While this made the pre-treatment very time-consuming, a technical fea-sibility of the recycling techniques could be shown. The LCA results indicate that the mechan-ical recycling and energy recovery achieve the lowest potential environmental impacts. The chemical recycling scenario was too energy intensive to be environmentally competitive. Due to the determined lead content of up to 13.5% by weight in DFG, a disposal should be avoided as it poses a significant potential impact to human toxicity. For the establishment of a waste treatment system and as far as possible, existing infrastructure such as local incineration plants or recycling facilities for end-of-life fishing gear should be used. As this requires the setup of a pre-treatment process, harbour personnel or other stake-holders should be encouraged to conduct those tasks. Further work is required to include social, economic and possibly other aspects, before a decision on the most appropriate waste treatment system can be made. Still, given DFG’s harmful nature and challenging composition, preven-tive measures like the introduction of an extended producer responsibility scheme for fishing gear are key.

The cellular plasma membrane encloses all mammalian cells and is a heterogeneous structure organised on small length- and short timescales. Separation from the exterior milieu allows non-equilibrium processes and renders the membrane the first point of contact in cell-cell interactions or the first line of defence in cell-pathogen encounters. Unravelling the mechanisms contributing to the dynamic membrane architecture offers the opportunity to shed light on one of the biggest mysteries of cell biology: How do structure and organisation emerge from a seemingly chaotic and fluid plasma membrane? This thesis describes the development and application of new fluorescence microscopy-based methods to understand the nature of membrane heterogeneity, such as compartmentalisation to facilitate receptor engagement. Taking snapshots of cellular processes using imaging techniques yields detailed insights into the static structure of the cells, yet overlooks fast and transient interactions, which are increasingly recognised as drivers of molecular organisation. In this work, imaging and spectroscopy approaches are used together to show that molecular diffusion dynamics can serve as a readout for membrane heterogeneity. A combination of super-resolution stimulated emission depletion (STED) microscopy and fluorescence correlation spectroscopy (FCS) is employed to obtain dynamic information at the nano-scale and developed further to measure the diffusion behaviour of lipids and proteins in living cells and model membrane systems across space at sub-diffraction resolution. Special emphasis is given to the evaluation of new detection equipment allowing flexible, robust, and easy-to-perform measurements. Additionally, a novel analysis pipeline based on confocal FCS is introduced to enable advanced diffusion measurements in live cell membranes with conventional equipment. Finally, the developed approaches are exploited to elucidate the organisation of a crucial T-cell signalling protein, the Src-kinase Lck, in model membrane systems as well as in live resting T cells and during their activation.