• European Marine Science
• Open Access close
• Electronic Publication Information Center close

Ocean acidification (OA) has been identified as one of the major climate-change related threats, mainly due to its significant impacts on marine calcifiers. Among those are the calcareous green algae of the genus Halimeda that are known to be major carbonate producers in shallow tropical and subtropical seas. Hence, any negative OA impacts on these organisms may translate into significant declines in regional and global carbonate production. In this study, we compiled the available information regarding Halimeda spp. responses to OA (experimental, in situ), with special focus on the calcification responses, one of the most studied response parameters in this group. Furthermore, among the compiled studies (n = 31), we selected those reporting quantitative data of OA effects on algal net calcification in an attempt to identify potential general patterns of species- and/or regional-specific OA responses and hence, impacts on carbonate production. While obtaining general patterns was largely hampered by the often scarce number of studies on individual species and/or regions, the currently available information indicates species-specific susceptibility to OA, seemingly unrelated to evolutionary lineages (and associated differences in morphology), that is often accompanied by differences in a species� response across different regions. Thus, for projections of future declines in Halimeda-associated carbonate production, we used available regional reports of species-specific carbonate production in conjunction with experimental OA responses for the respective species and regions. Based on the available information, declines can be expected worldwide, though some regions harbouring more sensitive species might be more impacted than others.

The marine habitat beneath Antarctica's ice shelves spans ∼1.6 million km2, and life in this vast and extreme environment is among Earth's least accessible, least disturbed and least known, yet likely to be impacted by climate-forced warming and environmental change. Although competition among biota is a fundamental structuring force of ecological communities, hence ecosystem functions and services, nothing was known of competition for resources under ice shelves, until this study. Boreholes drilled through a ∼ 200 m thick ice shelf enabled collections of novel sub-ice-shelf seabed sediment which contained fragments of biogenic substrata rich in encrusting (lithophilic) macrobenthos, principally bryozoans – a globally-ubiquitous phylum sensitive to environmental change. Analysis of sub-glacial biogenic substrata, by stereo microscopy, provided first evidence of spatial contest competition, enabling generation of a new range of competition measures for the sub-ice-shelf benthic space. Measures were compared with those of global open-water datasets traversing polar, temperate and tropical latitudes (and encompassing both hemispheres). Spatial competition in sub-ice-shelf samples was found to be higher in intensity and severity than all other global means. The likelihood of sub-ice-shelf competition being intraspecific was three times lower than for open-sea polar continental shelf areas, and competition complexity, in terms of the number of different types of competitor pairings, was two-fold higher. As posited for an enduring disturbance minimum, a specific bryozoan clade was especially competitively dominant in sub-ice-shelf samples compared with both contemporary and fossil assemblage records. Overall, spatial competition under an Antarctic ice shelf, as characterised by bryozoan interactions, was strikingly different from that of open-sea polar continental shelf sites, and more closely resembled tropical and temperate latitudes. This study represents the first analysis of sub-ice-shelf macrobenthic spatial competition and provides a new ecological baseline for exploring, monitoring and comparing ecosystem response to environmental change in a warming world.

Cold-water corals (CWCs) are considered vulnerable to environmental changes. However, previous studies have focused on adult CWCs and mainly investigated the short-term effects of single stressors. So far, the effects of environmental changes on different CWC life stages are unknown, both for single and multiple stressors and over long time periods. Therefore, we conducted a six-month aquarium experiment with three life stages of Car- yophyllia huinayensis to study their physiological response (survival, somatic growth, calcification and respira- tion) to the interactive effects of aragonite saturation (0.8 and 2.5), temperature (11 and 15 ◦C) and food availability (8 and 87 μg C L−1). The response clearly differed between life stages and measured traits. Elevated temperature and reduced feeding had the greatest effects, pushing the corals to their physiological limits. Highest mortality was observed in adult corals, while calcification rates decreased the most in juveniles. We observed a three-month delay in response, presumably because energy reserves declined, suggesting that short-term ex- periments overestimate coral resilience. Elevated summer temperatures and reduced food supply are likely to have the greatest impact on live CWCs in the future, leading to reduced coral growth and population shifts due to delayed juvenile maturation and high adult mortality.

The Maritime Continent (MC) forms the western boundary of the tropical Pacific Ocean, and relatively small changes in this region can impact the climate locally and remotely. In the mid-Piacenzian warm period of the Pliocene (mPWP; 3.264 to 3.025 Ma) atmospheric CO2 concentrations were ∼ 400 ppm, and the subaerial Sunda and Sahul shelves made the land–sea distribution of the MC different to today. Topographic changes and elevated levels of CO2, combined with other forcings, are therefore expected to have driven a substantial climate signal in the MC region at this time. By using the results from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2), we study the mean climatic features of the MC in the mPWP and changes in Indonesian Throughflow (ITF) with respect to the preindustrial. Results show a warmer and wetter mPWP climate of the MC and lower sea surface salinity in the surrounding ocean compared with the preindustrial. Furthermore, we quantify the volume transfer through the ITF; although the ITF may be expected to be hindered by the subaerial shelves, 10 out of 15 models show an increased volume transport compared with the preindustrial. In order to avoid undue influence from closely related models that are present in the PlioMIP2 ensemble, we introduce a new metric, the multi-cluster mean (MCM), which is based on cluster analysis of the individual models. We study the effect that the choice of MCM versus the more traditional analysis of multi-model mean (MMM) and individual models has on the discrepancy between model results and data. We find that models, which reproduce modern MC climate well, are not always good at simulating the mPWP climate anomaly of the MC. By comparing with individual models, the MMM and MCM reproduce the preindustrial sea surface temperature (SST) of the reanalysis better than most individual models and produce less discrepancy with reconstructed sea surface temperature anomalies (SSTA) than most individual models in the MC. In addition, the clusters reveal spatial signals that are not captured by the MMM, so that the MCM provides us with a new way to explore the results from model ensembles that include similar models.

Global climate change is a current problem that is discussed in many publications. The data provides only limited possibilities for the detection of future consequences. Surface water dynamics are described with some examples, but these give only a small insight into the complexity of this system. Using remote sensing methods, past and present dynamics can be analyzed. Nevertheless, the number of data sets with global data series is very small. Due to modifications of the "System Earth" caused by climate change, the global surface water dynamics is also changing. In high latitudes this is still poorly understood and an analysis of the data can provide an important insight into future consequences. Therefore, it is important to monitor Arctic surface water dynamics. In this master's thesis, the datasets of PICKENS et al. (2020) and PEKEL et al. (2016) are compared with respect to their results in surface water dynamics for Arctic permafrost areas from 2000 to 2020. In regards to this, both datasets were homogenized using the program "Google Earth Engine" and examined in an accuracy analysis. Any areas where both datasets show different results are detected and checked for possible causes. For this purpose, different reference datasets were used, which visually cover the topography, vegetation cover, landscape classification and permafrost content as indicators. Subsequently, in the program "Microsoft Excel", the data from the accuracy analysis were processed for each study area and analyzed in regards to the results. This shows that permanent water body areas in each study area were classified almost identically between the data sets. The largest differences between the results of PICKENS et al. (2020) and PEKEL et al. (2016) were found for seasonal water areas. The "Producer and Consumer Accuracy" calculations even yielded accuracy values below 65% in one study area. In these scenic areas, the problem of mixed pixels exists where, depending on pixel size and current water level, accurate classification becomes difficult. Also other factors, like seasonal events, cloud formations or technical errors cannot be excluded and have a share in the differences between the results of the data sets. Based on topography, the forest cover, the landscape classes and the permafrost content, differences between the data sets were recognized and distinctive shapes determined.

The Antarctic and Greenland ice sheets will play a major role for global sea level rise in the decades and centuries to come. Antarctic climate and mass balance have been highlighted by the Intergovernmental Panel on Climate Change (IPCC) as key sources of uncertainty when predicting the future climate system and sea level, and that significant challenges remain in understanding and representing the dynamics of the Antarctic ice sheets. At the same time, the ice sheets are a unique archive of the paleo atmosphere. The European project “Beyond EPICA” started to retrieve an ice core going back 1.5 Ma, into the Mid-Pleistocene Transition (MPT). Both aspects, correctly estimating future sea-level contributions and deciphering the paleo-climate archive, rely on decrypting the physical processes that control ice-sheet evolution over time. In this seminar, I will present the USIAS project “Characterising ice-sheet properties and processes with novel seismic monitoring technology”, with which we establish new methodologies to be employed during the “Beyond EPICA” drilling to improve our knowledge of ice-sheet properties and dynamics. Apart from methodological advances, I will also put the work into the context of the global climate warming - which already became a climate crisis - and point out possible futures for our planet.

Presentation about the disastrous influence of climate change on sea level rise