Coastal observatories are key to improve the understanding of processes within the coastal area and their interactions with regional and global environmental changes. The land-sea transition zone is an essential area that allows research on unique scientific questions under anthropogenic and natural influences. Amid the Wadden Sea UNESCO world natural heritage site – the largest tidal flat region worldwide – the barrier island Spiekeroog is an excellent location for an observatory studying land-sea interactions. The integrated Spiekeroog Coastal Observatory (SCO) operated by the Institute for Chemistry and Biology of the Marine Environment (ICBM, University of Oldenburg) is dedicated to interdisciplinary marine and terrestrial ecosystem research. Its position within the tidal area and the multitude of research-field addressed establishes the SCO as a unique coastal observatory with the potential to identify patterns in long-term variability and simultaneously understanding short-term changes. The establishment of the Time-Series Station (TSS) Spiekeroog in a tidal channel west of Spiekeroog back in 2002 laid the foundation of the SCO. Since then, the observatory is expanding continuously and is now representing a valuable asset supporting education, industry, government, and environmental conservation efforts in the area. Summing up the infrastructure and technical components, the importance of the SCO is evident, and individual projects greatly benefit from the collaboration with the partners in and the elements of the SCO. Harmonizing the infrastructure and competences of contributing partners will be a next step to further consolidate the SCO. A challenge poses the maintenance of the SCO based on projects, which is focused on the addition of new facilities, not maintaining, refurbishing, or (if necessary) deconstructing existing infrastructure. Therefore, structural support and funding opportunities not linked to projects but aiming to sustain observational capacities are required.

Abstract. In the last century an increasing number of extreme weather events have been experienced across the globe. These events have also been linked to changes in water quality especially due to heavy rains, flooding, or droughts. In terms of blue economic activities, one major threat are harmful algal bloom events that tend to be widespread and can last up to several days. We present and discuss advanced measurements of a bloom involving the cyanobacterium Nodularia spumigena conducted by hyperspectral optical technologies through experiments-of-opportunity. Absorption coefficients, absorbance and fluorescence were measured in the laboratory and these are available via (https://doi.org/10.4121/21610995.v1 (Wollschläger et al., 2022), https://doi.org/10.4121/21822051.v1 (Miranda et al., 2023) and https://doi.org/10.4121/21904632.v1 (Miranda and Garaba, 2023). Data used to derive the above-water reflectance is available via https://doi.org/10.4121/21814977.v1 (Garaba, 2023) and https://doi.org/10.4121/21814773.v1 (Garaba and Albinus, 2023). Additionally, hyperspectral fluorescence measurements of the dissolved compounds in the water were done. The hyperspectral measurements were conducted over a wide spectrum (200–2500 nm). Identification of the cyanobacterium was completed by visual analyses under a microscope. Diagnostic optical features were determined using robust statistical techniques. Water clarity was inferred from Secchi disk measurements https://doi.org/10.1594/PANGAEA.951239 (Garaba and Albinus, 2022). Full sequences were obtained of the 16S rRNA and rbcL genes revealing a very strong match to Nodularia spumigena, data available via GenBank https://www.ncbi.nlm.nih.gov/nuccore/OP918142/ (Garaba and Bonthond, 2022b) and https://www.ncbi.nlm.nih.gov/nuccore/OP925098 (Garaba and Bonthond, 2022a). The chlorophyll-a and phycocyanin levels determined are in open-access https://doi.org/10.4121/21792665.v1 (Rohde et al., 2023). Our experiments-of-opportunity echo the importance of sustainable, simplified, coordinated and continuous water quality monitoring as a way to thrive for the targets 2 set in the United Nations Sustainable Goals (e.g., Goals 6, 11, 12 and 14) or European Union Framework Directives (e.g. Water, Marine Strategy).

<p>In this study, the major characteristics of the circulation in the tidal inlet between the East Frisian Islands Spiekeroog and Wangerooge (Harle, Southern North Sea) are depicted by investigating current parameters using in situ Acoustic Doppler Current Profiler (ADCP) transect data. The focus is to reveal flow patterns in the area as a response to the submerged training wall Groyne H (GH) and the mesotidal impact prevailing at the East Frisian Islands. The circulation in the Harle is determined by semidiurnal tides, forcing the water to the southwest (ebb) resp. northeast (flood), thereby surrounding and overflowing the GH. The structure enhances the discharge and velocity in the main channel by blocking two thirds of the inlet horizontally and vertically.  It is assumed that depending on the water level above the groyne crest and the morphology of the inlet, vertical and/or horizontal recirculation cells develop on either the upstream or downstream side. An attempt is made to detect such cells and to give an explanation of the underlying physical processes. Therefore, ADCP transect data were obtained during two tidal cycles performing cross-sectional transects parallel to GH and a cross pattern in the groyne field south of GH. Data analysis particularly targets the computation of flow fields to resolve the circulation on a spatial scale and decompose velocity profiles into their 2D-components. Moreover, flow data is divided into different depth layers comparing surface versus average velocity over the transect to ascertain areas of velocity shearing. The consequences on each downstream side are a) the deceleration of flow in the groyne field by about 30-50 % b) a dynamic eddy at the groyne tip forming a low-velocity zone and c) a vertical recirculation cell rotating towards the groyne sole. For the latter, additional measurements need to be conducted to resolve such a cell in more detail and to analyze a broader area for the presence of horizontal circulation cells. </p> <p> </p>

The issue of marine plastic pollution has been extensively studied by various scientific disciplines in recent decades due to its global threat. However, owing to its complexity, it requires an interdisciplinary approach to develop effective management strategies. The multidisciplinary scientific approach presented here focuses on understanding the sources and pathways of macroplastic litter and developing abatement strategies in the southern North Sea region. Over 2.5 years, more than 63,400 biodegradable wooden drifters were deployed with the help of citizen science to study the sources, pathways, and accumulation areas of floating marine litter. Rivers act as sinks of most of the floating marine litter released within their waterways. Short-term field experiments were also conducted to analyse the hydrodynamic and atmospheric processes that govern the transport of floating litter particles at the sea surface. Numerical models were used to examine the transport of virtual litter particles in the entire North Sea and in coastal regions. It was found that there are no permanent accumulation areas in the North Sea, and the Skagerrak and fronts can increase the residence times of floating marine litter and favour sinking. Field surveys revealed that the majority of litter objects originate from fisheries and consumer waste. To develop effective abatement strategies, the key stakeholder landscape was analysed on a regional level. The interdisciplinary approach developed in this study highlights the importance of synergizing scientific resources from multiple disciplines for a better understanding of marine plastic pollution and the development of effective management strategies.