GEOMAR Helmholtz Centre for Ocean Research Kiel
Recent publications
It is unequivocal that human influence has warmed the planet, which is seriously affecting the planetary health including human health. Adapting climate change should not only be a slogan, but requires a united, holistic action and a paradigm shift from crisis response to an ambitious and integrated approach immediately. Recognizing the urgent needs to tackle the risk connection between climate change and One Health, the four key messages and recommendations that with the intent to guide further research and to promote international cooperation to achieve a more climate-resilient world are provided. Graphical Abstract
Carbon capture and storage is a key mitigation strategy proposed for keeping the global temperature rise below 1.5 °C. Offshore storage can provide up to 13% of the global CO2 reduction required to achieve the Intergovernmental Panel on Climate Change goals. The public must be assured that potential leakages from storage reservoirs can be detected and that therefore the CO2 is safely contained. We conducted a controlled release of 675 kg CO2 within sediments at 120 m water depth, to simulate a leak and test novel detection, quantification and attribution approaches. We show that even at a very low release rate (6 kg day⁻¹), CO2 can be detected within sediments and in the water column. Alongside detection we show the fluxes of both dissolved and gaseous CO2 can be quantified. The CO2 source was verified using natural and added tracers. The experiment demonstrates that existing technologies and techniques can detect, attribute and quantify any escape of CO2 from sub-seabed reservoirs as required for public assurance, regulatory oversight and emissions trading schemes.
This study documents how the abundance of microplastics (<5 mm) in the Atlantic cod, Gadus morhua, relates to the changes of the fish diet during years with contrasting levels of anoxia for example following years of low or high major Baltic inflows (MBI). A MultiNet Maxi trawl and CTD were deployed annually to collect microplastic samples alongside oxygen, temperature, and salinity conditions. Microplastics were homogenously distributed both within the water column and across years. Gadus morhua diet shifted from dominantly benthic invertebrates (61 %) under oxygenated conditions to dominantly Sprattus sprattus (81 %) under anoxic conditions. The proportion of G. morhua with microplastics in their digestive tract increased when they fed on pelagic fish (38 %) versus on benthic invertebrates (15 %). The proportion of S. sprattus which ingested microplastics (~18 %) did not vary. As anoxia at depth is expected to increase due to climate change, microplastic ingestion by G. morhua will potentially increase.
Dust storms are an important component of the global climate system. At the same time, they also bear a risk for human health by causing pulmonary diseases. Today, East Asian dust storms account for as much as half of the global dust emissions and temporarily affect highly populated areas. Therefore, understanding their mechanisms and predicting their evolution under warmer near-future climate conditions is of major interest. The mid-Pliocene Warm Period (mPWP; 3.264–3.025 Ma) is considered one of the best analogues from the past for anthropogenic climate change. Consequently, understanding the climate dynamics and associated environmental change during the mPWP can help with predicting the environmental effects of warmer-than-present climates. In order to reconstruct Asian dust storm evolution during the mPWP we have analyzed a sediment core from the northern South China Sea (SCS) for its elemental composition, grain-size variations and radiogenic isotope signature for the interval spanning from 3.69 to 2.96 Ma. We show that shortly after the first strong northern hemisphere glaciation (Marine Isotope Stage [MIS] M2; 3.25 Ma) atmospherically transported dust appeared in the northern SCS and this dust deposition prevailed throughout the mPWP. Atmospheric dust input further intensified with the onset of the MIS KM2 glaciation at 3.15 Ma, with distinct and strong dust storms occurring periodically from that time onwards. The increase in atmospherically transported dust can be attributed to the cooling and drying of interior Asia over the course of the mPWP along with an intensification of the East Asian Winter Monsoon and a potential southward shift of the westerlies.
Plain Language Summary Over the recent past the oxygen content of the global ocean has been declining, with consequences for marine ecosystems. Ocean eddies (rotating currents of water on the order ≈100 km diameter) have been identified as vehicles of extremely low oxygen concentrations but are understudied in the context of biogeochemical extreme events in the ocean. This investigation is the first of its kind to use a four‐dimensional data set (time, latitude, longitude, depth) to create a regional scale census of eddies and their oxygen conditions across the period 1992–2018 as they travel offshore from typically low oxygen waters of the near‐coastal Atlantic and Pacific, carrying and modifying low oxygen signals into otherwise more oxygenated ocean regions. We track eddies associated with low oxygen conditions and assess how much they contribute to low oxygen extreme events. In some places eddies contribute to more than half of the simulated low oxygen extreme events, signaling the need to further explore the role that eddies play in marine extreme events.
Predicting future changes in interspecific interactions continues to be a challenge for environmental managers. This uncertainty is exacerbated by increasing biological invasions and the likelihood that the strength of trophic interactions among native species will change. Abiotic variables influence predator resource utilisation and abundance as well as resource population dynamics. Currently no practical metric or impact prediction methodology can adequately account for all of these factors. Functional Response (FR) methods successfully incorporate resource utilisation rates with regards to resource density to quantify consumer-resource interactions under varying abiotic contexts. This approach has been extended to create the Relative Impact Potential (RIP) metric to compare invader vs native impact. However, this does not incorporate resource abundance dynamics, which clearly can also change with abiotic context. We propose a Resource Reproduction Qualifier (RRQ) be incorporated into the RIP metric, whereby RRQ is the reciprocal of the fraction or proportion to which reproduction (e.g. of prey species) changes under an environmental context. This modifies the RIP score to give a more informative RIP q value, which may be contextually increased or decreased. We empirically demonstrate the utility and benefits of including RRQ into impact potential predictions with an invasive species (the lionfish Pterois volitans) and two European native species (shanny fish Lipophyris pholis and lesser spotted dogfish Scy-liorhinus canicula) under different abiotic contexts. Despite high FR and abundance, lionfish impacts were reduced by increasing prey recruitment at higher temperatures, however, remained high impact overall. Shanny predatory impact increased with increasing temperature and was exacerbated by decreasing prey fecundity. Two population increase scenarios (50% and 80%) were assessed for lesser spotted dogfish under predicted temperature increases, preying upon E. marinus. Both scenarios indicated heightened predatory impact with increasing predator FR and decreasing prey fecundity. Our new metric demonstrates that accounting for resource reproductive responses to abiotic drivers, in tandem with the consumer per capita and abundance responses, better estimate the magnitudes of predicted inter-species interactions and ecological impacts. This can be used in stock assessments and predictions, as well as invasive species risk assessments in a comprehensive yet user-friendly manner..
Ocean warming and acidification will be most pronounced in the Arctic. Both phenomena severely threaten thecosome pteropods (holoplanktonic marine gastropods) by reducing their survival (warming) and causing the dissolution of their aragonitic shell (acidification). Lipids, particularly phospholipids, play a major role in veligers and juveniles of the polar thecosome pteropod Limacina helicina comprising more than two-thirds of their total lipids. Membrane lipids (phospholipids) are important for the temperature acclimation of ectotherms. Hence, we experimentally investigated ocean warming and acidification effects on total lipids, lipid classes, and fatty acids of Arctic early-stage L. helicina . The temperature and pCO 2 treatments chosen resembled Representative Concentration Pathway model scenarios for this century. We found a massive decrease in total lipids at elevated temperatures and at the highest CO 2 concentration (1,100 μ atm) of the in situ temperature. Clearly, temperature was the overriding factor. Total lipids were reduced by 47%–70%, mainly caused by a reduction of phospholipids by up to 60%. Further, based on pH T development in the incubation water of pteropods during the experiment, some evidence exists for metabolic downregulation in pteropods at high factor levels of temperature and pCO 2 . Consequently, the cell differentiation and energy balance of early-stage larvae were probably severely compromised. Comparison of our experimental with ‘wild’ organisms suggests phospholipid reduction to values clearly outside natural variability. Based on the well-known significance of phospholipids for membranogenesis, early development, and reproduction, negative warming effects on such a basal metabolic function may be a much more immediate threat for pteropods than so far anticipated shell dissolution effects due to acidification.
Zooplankton plays a major role in ocean food webs and biogeochemical cycles, and provides major ecosystem services as a main driver of the biological carbon pump and in sustaining fish communities. Zooplankton is also sensitive to its environment and reacts to its changes. To better understand the importance of zooplankton, and to inform prognostic models that try to represent them, spatially-resolved biomass estimates of key plankton taxa are desirable. In this study we predict, for the first time, the global biomass distribution of 19 zooplankton taxa (1-50 mm Equivalent Spherical Diameter) using observations with the Underwater Vision Profiler 5, a quantitative in situ imaging instrument. After classification of 466,872 organisms from more than 3,549 profiles (0-500 m) obtained between 2008 and 2019 throughout the globe, we estimated their individual biovolumes and converted them to biomass using taxa-specific conversion factors. We then associated these biomass estimates with climatologies of environmental variables (temperature, salinity, oxygen, etc.), to build habitat models using boosted regression trees. The results reveal maximal zooplankton biomass values around 60°N and 55°S as well as minimal values around the oceanic gyres. An increased zooplankton biomass is also predicted for the equator. Global integrated biomass (0-500 m) was estimated at 0.403 PgC. It was largely dominated by Copepoda (35.7%, mostly in polar regions), followed by Eumalacostraca (26.6%) Rhizaria (16.4%, mostly in the intertropical convergence zone). The machine learning approach used here is sensitive to the size of the training set and generates reliable predictions for abundant groups such as Copepoda (R2 ≈ 20-66%) but not for rare ones (Ctenophora, Cnidaria, R2 < 5%). Still, this study offers a first protocol to estimate global, spatially resolved zooplankton biomass and community composition from in situ imaging observations of individual organisms. The underlying dataset covers a period of 10 years while approaches that rely on net samples utilized datasets gathered since the 1960s. Increased use of digital imaging approaches should enable us to obtain zooplankton biomass distribution estimates at basin to global scales in shorter time frames in the future.
The increased fraction of first year ice (FYI) at the expense of old ice (second-year ice (SYI) and multi-year ice (MYI)) likely affects the permeability of the Arctic ice cover. This in turn influences the pathways of gases circulating therein and the exchange at interfaces with the atmosphere and ocean. We present sea ice temperature and salinity time series from different ice types relevant to temporal development of sea ice permeability and brine drainage efficiency from freeze-up in October to the onset of spring warming in May. Our study is based on a dataset collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 and 2020. These physical properties were used to derive sea ice permeability and Rayleigh numbers. The main sites included FYI and SYI. The latter was composed of an upper layer of residual ice that had desalinated but survived the previous summer melt and became SYI. Below this ice a layer of new first-year ice formed. As the layer of new first-year ice has no direct contact with the atmosphere, we call it insulated first-year ice (IFYI). The residual/SYI-layer also contained refrozen melt ponds in some areas. During the freezing season, the residual/SYI-layer was consistently impermeable, acting as barrier for gas exchange between the atmosphere and ocean. While both FYI and SYI temperatures responded similarly to atmospheric warming events, SYI was more resilient to brine volume fraction changes because of its low salinity ( < 2). Furthermore, later bottom ice growth during spring warming was observed for SYI in comparison to FYI. The projected increase in the fraction of more permeable FYI in autumn and spring in the coming decades may favor gas exchange at the atmosphere-ice interface when sea ice acts as a source relative to the atmosphere. While the areal extent of old ice is decreasing, so is its thickness at the onset of freeze-up. Our study sets the foundation for studies on gas dynamics within the ice column and the gas exchange at both ice interfaces, i.e. with the atmosphere and the ocean.
Wetlands are amongst the world’s most important ecosystems, providing direct and indirect benefits to local communities. However, wetlands worldwide continue to be degraded due to unsustainable use and improper resource management. In this paper, we assess the perceptions, importance, management and utilisation of wetlands among local community members using a household questionnaire and field observations within the seven Thulamela municipality wetlands, Vhembe Biosphere Reserve in South Africa. Seven wetlands were chosen for the study, with 140 household respondents randomly selected for a questionnaire survey. The study indicated that wetlands were beneficial in supporting local communities through resource provisioning. The unemployment rate and household respondents’ income were the main contributors to increased wetland dependency and utilisation. We found that urban and rural developments, unregulated use and extensive agricultural practices (i.e., cultivation, livestock grazing) have resulted in wetland degradation. We observed that the local communities around the wetlands were interested in the benefits they receive from wetlands when compared to their conservation. Furthermore, the study observed poor wetland co-management or collaboration among the local stakeholders. This has resulted in a lack of openly known, active platforms to discuss wetlands management issues. These results highlight that centralized, top–down approaches to wetland use are insufficient for maintaining and managing wetland ecosystems, posing a challenge to sustainable wetland management. Therefore, there is a need to develop a shared understanding through bottom-up approaches to wetland management nested within national regulatory frameworks, ideally combined with awareness building and knowledge sharing on ecological benefits and management of wetlands.
Invasive species can successfully and rapidly colonize new niches and expand ranges via founder effects and enhanced tolerance towards environmental stresses. However, the underpinning molecular mechanisms (i.e., gene expression changes) facilitating rapid adaptation to harsh environments are still poorly understood. The red seaweed Gracilaria vermiculophylla, which is native to the northwest Pacific but invaded North American and European coastal habitats over the last 100 years, provides an excellent model to examine whether enhanced tolerance at the level of gene expression contributed to its invasion success. We collected G. vermiculophylla from its native range in Japan and from two non-native regions along the Delmarva Peninsula (Eastern United States) and in Germany. Thalli were reared in a common garden for four months at which time we performed comparative transcriptome (mRNA) and microRNA (miRNA) sequencing. MRNA-expression profiling identified 59 genes that were differently expressed between native and non-native thalli. Of these genes, most were involved in metabolic pathways, including photosynthesis, abiotic stress, and biosynthesis of products and hormones in all four non-native sites. MiRNA-based target-gene correlation analysis in native/non-native pairs revealed that some target genes are positively or negatively regulated via epigenetic mechanisms. Importantly, these genes are mostly associated with metabolism and defense capability. Thus, our gene expression results indicate that resource reallocation to metabolic processes is most likely a predominant mechanism contributing to the range-wide persistence and adaptation of G. vermiculophylla in the invaded range. This study therefore provides a novel molecular insight into the speed and nature of invasion-mediated rapid adaption.
Using observational data, satellite altimeters, and reanalysis model products, we have investigated eddy-induced seawater anomalies and heat and salt transport in the northeastern tropical Pacific Ocean. An eddy detection algorithm (EDA) was used to identify eddy formation at the Mexican Tehuantepec Gulf (TT) in July 2018 during an unusually strong summer wind event. The eddy separated from the coast with a mean translation velocity of 11 cm s−1 and a mean radius of 115 km and traveled 2050–2400 km westwards off the Central American coast, where it was followed at approx 114∘ W and 11∘ N for oceanographic observation between April and May 2019. The in situ observations show that the major eddy impacts are restricted to the upper 300 m of the water column and are traceable down to 1500 m water depth. In the eddy core at 92 m water depth an extreme positive temperature anomaly of 8.2 ∘C, a negative salinity anomaly of −0.78 psu, a positive fluorescence anomaly of +0.8 mg m−3, and a positive dissolved oxygen concentration anomaly of 137 µmol kg−1 are observed. Compared with annual climatological averages in 2018, the water trapped within the eddy is estimated to transport an average positive westward zonal heat anomaly of 85×1012 W and an average westward negative salt anomaly of -2.1×106 kg s−1. The heat transport is the equivalent of 1 % of the total annual zonal eddy-induced heat transport at this latitude in the Pacific Ocean. Understanding the dynamics of long-lived mesoscale eddies that may reach the seafloor in this region of the Pacific Ocean is especially important in light of potential deep-sea mining activities that are being targeted on this area.
Abrupt fluid emissions from shallow marine sediments pose a threat to seafloor installations like wind farms and offshore cables. Quantifying such fluid emissions and linking pockmarks, the seafloor manifestations of fluid escape, to flow in the sub-seafloor remains notoriously difficult due to an incomplete understanding of the underlying physical processes. Here, using a compositional multi-phase flow model, we test plausible gas sources for pockmarks in the south-eastern North Sea, which recent observations suggest have formed in response to major storms. We find that the mobilization of pre-existing gas pockets is unlikely because free gas, due to its high compressibility, damps the propagation of storm-induced pressure changes deeper into the subsurface. Rather, our results point to spontaneous appearance of a free gas phase via storm-induced gas exsolution from pore fluids. This mechanism is primarily driven by the pressure-sensitivity of gas solubility, and the appearance of free gas is largely confined to sediments in the vicinity of the seafloor. We show that in highly permeable sediments containing gas-rich pore fluids, wave-induced pressure changes result in the appearance of a persistent gas phase. This suggests that seafloor fluid escape structures are not always proxies for overpressured shallow gas and that periodic seafloor pressure changes can induce persistent free gas phase to spontaneously appear.
Avian schistosomes, comprise a diverse and widespread group of trematodes known for their surprising ability to switch into new hosts and habitats. Despite the considerable research attention on avian schistosomes as causatives of the human cercarial dermatitis, less it is known about the diversity, geographical range and host associations of the marine representatives. Our molecular analyses inferred from cox1 and 28S DNA sequence data revealed presence of two schistosome species, Ornithobilharzia canaliculata (Rudolphi, 1819) Odhner, 1912 and a putative new species of Austrobilharzia Johnston, 1917. Molecular elucidation of the life-cycle of O. canaliculata was achieved for the first time via matching novel and published sequence data from adult and larval stages. This is the first record of Ornithobilharzia from the Persian Gulf and globally the first record of this genus in a potamidid snail host. Our study provides: (i) new host and distribution records for major etiological agents of cercarial dermatitis and contributes important information on host-parasite relationships; (ii) highlights the importance of the molecular systematics in the assessment of schistosome diversity; and (iii) calls for further surveys to reach a better understanding of the schistosome diversity and patterns of relationships among them, host associations, transmission strategies and distribution coverage.
Dissolved organic matter (DOM) is a distinct component of Earth’s hydrosphere and provides a link between the biogeochemical cycles of carbon, nutrients, and trace metals (TMs). Binding of TMs to DOM is thought to result in a TM pool with DOM-like biogeochemistry. Here, we determined elemental stoichiometries of aluminum, iron, copper, nickel, zinc, cobalt, and manganese associated with a fraction of the DOM pool isolated by solid-phase extraction at ambient pH (DOM SPE-amb ) from the Amazon plume. We found that the rank order of TM stoichiometry within the DOM SPE-amb fraction was underpinned by the chemical periodicity of the TM. Furthermore, the removal of the TM SPE-amb pool at low salinity was related to the chemical hardness of the TM ion. Thus, the biogeochemistry of TMs bound to the DOM SPE-amb component in the Amazon plume was determined by the chemical nature of the TM and not by that of the DOM SPE-amb .
This paper discusses the challenges of applying a data analytics pipeline for a large volume of data as can be found in natural and life sciences. To address this challenge, we attempt to elaborate an approach for an improved detection of outliers. We discuss an approach for outlier quantification for bathymetric data. As a use case, we selected ocean science (multibeam) data to calculate the outlierness for each data point. The benefit of outlier quantification is a more accurate estimation of which outliers should be removed or further analyzed. To shed light on the subject, this paper is structured as follows: first, a summary of related works on outlier detection is provided. The usefulness for a structured approach of outlier quantification is then discussed using multibeam data. This is followed by a presentation of the challenges for a suitable solution, and the paper concludes with a summary.
The effect of anthropogenic climate change in the ocean is challenging to project because atmosphere-ocean general circulation models (AOGCMs) respond differently to forcing. This study focuses on changes in the Atlantic Meridional Overturning Circulation (AMOC), ocean heat content ( $$\Delta$$ Δ OHC), and the spatial pattern of ocean dynamic sea level ( $$\Delta \zeta$$ Δ ζ ). We analyse experiments following the FAFMIP protocol, in which AOGCMs are forced at the ocean surface with standardised heat, freshwater and momentum flux perturbations, typical of those produced by doubling $$\hbox {CO}_{{2}}$$ CO 2 . Using two new heat-flux-forced experiments, we find that the AMOC weakening is mainly caused by and linearly related to the North Atlantic heat flux perturbation, and further weakened by a positive coupled heat flux feedback. The quantitative relationships are model-dependent, but few models show significant AMOC change due to freshwater or momentum forcing, or to heat flux forcing outside the North Atlantic. AMOC decline causes warming at the South Atlantic-Southern Ocean interface. It does not strongly affect the global-mean vertical distribution of $$\Delta$$ Δ OHC, which is dominated by the Southern Ocean. AMOC decline strongly affects $$\Delta \zeta$$ Δ ζ in the North Atlantic, with smaller effects in the Southern Ocean and North Pacific. The ensemble-mean $$\Delta \zeta$$ Δ ζ and $$\Delta$$ Δ OHC patterns are mostly attributable to the heat added by the flux perturbation, with smaller effects from ocean heat and salinity redistribution. The ensemble spread, on the other hand, is largely due to redistribution, with pronounced disagreement among the AOGCMs.
Similar to their tropical counterparts, cold-water corals (CWCs) are able to build large three-dimensional reef structures. These unique ecosystems are at risk due to ongoing climate change. In particular, ocean warming, ocean acidification and changes in the hydrological cycle may jeopardize the existence of CWCs. In order to predict how CWCs and their reefs or mounds will develop in the near future one important strategy is to study past fossil CWC mounds and especially shallow CWC ecosystems as they experience a greater environmental variability compared to other deep-water CWC ecosystems. We present results from a CWC mound off southern Norway. A sediment core drilled from this relatively shallow (~ 100 m) CWC mound exposes in full detail hydrographical changes during the late Holocene, which were crucial for mound build-up. We applied computed tomography, 230Th/U dating, and foraminiferal geochemical proxy reconstructions of bottom-water-temperature (Mg/Ca-based BWT), δ18O for seawater density, and the combination of both to infer salinity changes. Our results demonstrate that the CWC mound formed in the late Holocene between 4 kiloannum (ka) and 1.5 ka with an average aggradation rate of 104 cm/kiloyears (kyr), which is significantly lower than other Holocene Norwegian mounds. The reconstructed BWTMg/Ca and seawater density exhibit large variations throughout the entire period of mound formation, but are strikingly similar to modern in situ observations in the nearby Tisler Reef. We argue that BWT does not exert a primary control on CWC mound formation. Instead, strong salinity and seawater density variation throughout the entire mound sequence appears to be controlled by the interplay between the Atlantic Water (AW) inflow and the overlying, outflowing Baltic-Sea water. CWC growth and mound formation in the NE Skagerrak was supported by strong current flow, oxygen replenishment, the presence of a strong boundary layer and larval dispersal through the AW, but possibly inhibited by the influence of fresh Baltic Water during the late Holocene. Our study therefore highlights that modern shallow Norwegian CWC reefs may be particularly endangered due to changes in water-column stratification associated with increasing net precipitation caused by climate change. Supplementary information: The online version contains supplementary material available at 10.1007/s00338-022-02249-4.
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545 members
Claas Hiebenthal
  • Division of Marine Ecology
Wolfgang Koeve
  • Division of Biogeochemical Modelling
Kristina Bayer
  • Division of Marine Microbiology
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