Description: Seagrass is a foundation species within shallow water ecosystems because it provides habitat and food and thereby supports biodiversity. It has a function as atmospheric CO2 storage and improves the water quality by filtering nutrients (Greiner et al. 2013). Currently, seagrass meadows are facing multiple challenges such as ocean warming, reduced light caused by increasing nutrient input and more frequent disturbance events or direct anthropogenic impact (Unsworth et al. 2019). All these factors affect the performance of seagrass and thereby impair the ecosystem services seagrass meadows provide. This thesis represents a systematic review and meta-analysis of the physiological effects of temperature change on seagrass to provide a better understanding of the effect of rising temperatures on seagrass meadows worldwide. In this thesis, 766 papers were reviewed and a subsequent meta-analysis of 43 papers including 407 control-treatment temperature combinations matching the inclusion criteria were conducted. The log response ratio (lnR) was used for calculating the effect sizes, because it is more intuitive to interpret. Hedges’ g was further used to verify the results. It was tested for effects of the physiological parameters measured, the treatment type, the temperature direction, the experiment duration, the control temperature, latitude and longitude of the source population and the genus on relative seagrass performance (lnR). The key results of the meta-analysis showed that (I) plant physiological performance was reduced by an average of 39% by temperature change across all studies; (II) per 1°C experimental ocean warming a reduction in seagrass performance of 11% was observed; (III) the measured performance parameters (growth, biomass, photosynthesis and survival) showed differential susceptibility to warming, with survival being most affected and photosynthesis least affected; (IV) seagrass genera did not differ significantly in their response to experimental ocean warming but varied between locations. There was a strong geographic bias in this meta-analysis since most case studies were conducted in developed countries including Europe, the US and Australia. Thus, many species were underrepresented while also some climate conditions were not covered. Further, it was also not possible to make a statement about the recovery after experimental temperature stress had ceased, as there were too few studies focusing on recovery. Altogether, this thesis identified two profound knowledge gaps, which should be addressed by future studies. In conclusion, more frequent and intense heat waves are an increasing threat to seagrass meadows in the future. As seagrass provides important ecological services, it needs to be protected. It is particularly striking that every degree Celsius of temperature change matters for seagrass as it means a reduction in physiological and morphological performance, which is another indication that global warming should be kept below 2 degrees Celsius

Description: Modern digital scientific workflows - often implying Big Data challenges - require data infrastructures and innovative data science methods across disciplines and technologies. Diverse activities within and outside HGF deal with these challenges, on all levels. The series of Data Science Symposia fosters knowledge exchange and collaboration in the Earth and Environment research community.

Description: The AL561 cruise was conducted in the framework of the project APOC (“Anthropogenic impacts on Particulate Organic Carbon cycling in the North Sea”). This collaborative project between GEOMAR, AWI, HEREON, UHH, and BUND is to understand how particulate organic carbon (POC) cycling contributes to carbon sequestration in the North Sea and how this ecosystem service is compromised and interlinked with global change and a range of human pressures include fisheries (pelagic fisheries, bottom trawling), resource extraction (sand mining), sediment management (dredging and disposal of dredged sediments) and eutrophication. The main aim of the sampling activity during AL561 cruise was to recover undisturbed sediment from high accumulation sites in the Skagerrak/Kattegat and to subsample sediment/porewater at high resolution in order to investigate sedimentation transport processes, origin of sediment/POC and mineralization processes over the last 100- 200 years. Moreover, the actual processes of sedimentation and POC degradation in the water column and benthic layer will be addressed by sampling with CTD and Lander devices. In total 9 hydroacoustic surveys (59 profiles), 4 Gravity Corer, 7 Multicorer, 3 Lander and 4 CTD stations were successfully conducted during the AL561 cruise.

Description: Submarine landslides pose a hazard to coastal communities due to the tsunamis they can generate, and can damage critical seafloor infrastructure, such as the network of cables that underpin global data transfer and communications. These mass movements can be orders of magnitude larger than their onshore equivalents and are found on all of the world’s continental margins; from coastal zones to hadal trenches. Despite their prevalence, and importance to society, offshore monitoring studies have been limited by the largely unpredictable occurrence of submarine landslide and the need to cover large regions of extensive continental margins. Recent subsea monitoring has provided new insights into the preconditioning and run-out of submarine landslides using active geophysical techniques, but these tools only measure a very small spatial footprint, and are power and memory intensive, thus limiting long duration monitoring campaigns. Most landslide events therefore remain entirely unrecorded. Here we first show how passive acoustic and seismologic techniques can record acoustic emissions and ground motions created by terrestrial landslides. We then show how this terrestrial-focused research has catalysed advances in the detection and characterisation of submarine landslides, using both onshore and offshore networks of broadband seismometers, hydrophones and geophones. We then discuss some of the new insights into submarine landslide preconditioning, timing, location, velocity and their down-slope evolution that is arising from these advances. We finally outline some of the outstanding challenges, in particular emphasising the need for calibration of seismic and acoustic signals generated by submarine landslides and their run-out. Once confidence can be enhanced in submarine landslide signal detection and interpretation, passive seismic and acoustic sensing has strong potential to enable more complete hazard catalogues to be built, and opens the door to emerging techniques (such as fibre-optic sensing), to fill key, but outstanding, knowledge gaps concerning these important underwater phenomena.

Description: This contribution presents the detailed responses to the peer-review of Froese et al. (2019) “Estimating stock status from relative abundance and resilience” (ICES J. Mar. Sci. 2019) which outlined a method called “AMSY” for inferring biomass trends for stocks for which only catch-per-unit-effort and limited ancillary (‘priors’) data are available. The responses emphasize that the required priors are legitimate and straightforward to obtain, thus, making AMSY a method of choice in data-sparse situations. This is also a good example of the role of peer-review in validating and improving science.

Description: The tight program of scientific research cruises usually does not leave enough time for thorough tests of new research equipment and their system components, nor for extensive pilot and handling training. For this reason, ship time was requested for sea trials of two types of autonomous (not tethered) underwater vehicles owned by GEOMAR, the manned 400-meter submersible JAGO and the Hover-AUVs ANTON and LUISE, type Girona500. The aim was to test several technical and operational aspects with both vehicles at locations with differently structured terrain (from flat ground to steep rocky slopes) and to water depths of up to 500 meters. The Aeolian Islands in the Tyrrhenian Sea north of Sicily were chosen as test area. The volcanic islands offer sheltered sea conditions at their leeway, and bottom currents are usually weak or absent. Rocky and steep slopes are located in short distances to areas with flat underwater topography, providing ideal test conditions.

Description: The Taputapuatea marae of Ra'iatea is an emblematic landmark known throughout the world and sacred place for the Ma'ohi of Eastern Polynesia and the centre of a vast political- religious-cultural network in the Polynesian triangle. The erected stones constituting the ahu have been described as "limestone slabs" without precision by previous authors. These are in fact microatolls: corals (Porites) living in very shallow water and developing laterally, with a growth in height being limited by the lowest tide at the time of growth. A total of 38 samples were U/Th dated, of which 19 microatolls result in ages between 3 and 5 millennia. These are fossil microatolls that existed at a Holocene sea level of 0.80 m higher than today, when the Polynesians had not yet arrived. Other samples (molluscs, coral filling blocks) date back to the construction of the marae during the 17th-18th centuries. We hypothesize that the erected microatolls of the ahu were collected by Polynesians at the site and that others are still underground. Le marae Taputapuatea de Ra’iatea est un site emblématique mondialement considéré et un lieu sacré pour les Ma’ohi de la Polynésie orientale et le centre d’un vaste réseau politico-religieux-culturel du triangle polynésien. Les pierres érigées constituant l’ahu avaient été nommées « dalles calcaire » sans autre précision par les auteurs précédents. Ce sont des microatolls : coraux (Porites) vivant dans des eaux très peu profondes et se développant latéralement, la croissance en hauteur étant limitée par le bas niveau de la mer. Un total de 38 échantillons ont été datés (U/Th) sur 19 microatolls, donnant des âges de 3 et 5 millénaires. Il s’agit de microatolls fossiles dont l’existence remonte à un niveau de la mer Holocène de 0,80 m plus élevé qu’aujourd’hui, époque où les Polynésiens étaient absents. D’autres datations (mollusques, blocs de remplissage de corail) datent la construction du marae des xviie-xviiie siècles. Nous émettons l’hypothèse que les microatolls fossiles érigés de l’ahu ont été collectés par des Polynésiens sur le site et que d’autres sont toujours sous terre.