ALBERT

Beschreibung: A combined geochemical, mineralogical, petrographic and geological approach has allowed to constrain the dolomitization process responsible for the formation of massive dolomitic body within the Messinian evaporitic series. We focused our investigations on an example of massive dolomite body, outcropping over the marginal area of the evaporitic basin in the Peloritani Mountains (NE area of Sicily region, Italy). Field observations allowed recognizing several sedimentary structures, such as erosion surfaces, lenses of conglomerates and ripples highlighting a clastic origin. The petrographic study revealed fne-grained and massive structure, scarce porosity, light to pink color and absence of micro-fossils. The chondritenormalized trace element pattern shows a general enrichment in LREE and depletion in HREE. The isotopic signatures of the studied dolomites (δ18O=– 4.38–1.24‰, V-PDB; δ13C=– 1.48–1.94‰, V-PDB) are comparable with those of type-3 “Calcare di Base” which is the common reference to record the Messinian salinity crisis. The positive co-variant relationship between the δ18O and δ13C values suggests a dolomitization process in the seawater/freshwater mixing zone. The occurrence of the studied dolomites in the evaporitic sequence coupled with the results we gained point towards an origin from “early diagenetic” processes. As a consequence, a model explaining the genetic mechanism for the studied dolomitic rocks can be essentially summarized as: (1) the massive dolostones were originally deposited as evaporitic limestones under rather highsalinity conditions; (2) the dolomitization process occurred in the seawater/freshwater mixing zone that provided Mg-rich fuids over uplifted submarine masses.

Beschreibung: Published

Beschreibung: id 29

Beschreibung: 7SR AMBIENTE – Servizi e ricerca per la società

Beschreibung: JCR Journal

Beschreibung: The quantification of the maximum runout, invaded area, volume, and total grain-size distribution (TGSD) of pyroclastic density currents (PDC) is a critically important task because such parameters represent the needed necessary input quantities for physical modeling and hazard assessment of PDCs. In this work, new and well-established methods for the quantification of these parameters are applied to a large stratigraphic dataset of three PDC units from two eruptions of Somma-Vesuvius (the AD 79 Pompeii and the AD 472 Pollena eruptions), representative of a large spectrum of transport and depositional processes. Maximum runout and invaded area are defined on the basis of the available volcanological and topographical constraints. The related uncertainties are evaluated with an expert judgment procedure, which considersed the different sectors of the volcano separately. Quite large uncertainty estimates of dispersal area (20–40%) may have important implications in terms of hazard assessment. The testing of different methods for estimating the volume (and mass) of a PDC deposit suggests that integration, over the invaded area, of thickness (and deposit density) data using the triangulated irregular network method can minimize and localize data extrapolation. Such calculations, however, bear an intrinsic additional uncertainty (at least 10% of the total PDC deposit) related to loss or new formation of fine material during transport (at least 10% of the total PDC deposit). Different interpolation methods for TGSD produce multimodal distributions, likely reflecting the different response of each grain size class to transport and deposition processes. These data, when integrated with information on the related co-ignimbrite deposits, can give a more accurate picture of the pyroclastic mixture feeding the current.

Beschreibung: Published

Beschreibung: Id 65

Beschreibung: 5V. Processi eruttivi e post-eruttivi

Beschreibung: JCR Journal

Beschreibung: This work offers a novel methodological framework to address the problem of generating data-driven earthquake shaking fields at different vibration periods, which are key to support decision making and civil protection planning. We propose to analyse the entire profiles of spectral accelerations and project their information content to unsampled locations in the system, based on the theory of Object Oriented Spatial Statistics. The proposed methodology combines a non-ergodic ground motion model with a fully functional model for the residual term, the latter consisting of (i) the spatially-varying systematic effects due to source, site and path, and (ii) the remaining aleatory error. The proposed methodology allows to generate multiple shaking scenarios conditioned on the data, jointly and consistently for all the vibration periods, overcoming the intrinsic limitations of existing multivariate approaches to the problem. The approach is tested on a vast dataset of ground motion records collected in the study-area of the Po Plain (Northern Italy), for which a region-specific fully non-ergodic GMM was previously calibrated. Our validation tests demonstrate the potentiality of the approach, which is capable to effectively simulate spectral acceleration profiles, while keeping the ability to capture the main physical features of ground motion patterns in the region.

Beschreibung: Published

Beschreibung: 1607–1627

Beschreibung: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Beschreibung: JCR Journal

Beschreibung: Biological clocks are universal to all living organisms on Earth. Their ubiquity is testament to their importance to life: from cells to organs and from the simplest cyanobacteria to plants and primates, they are central to orchestrating life on this planet. Biological clocks are usually set by the day–night cycle, so what happens in polar regions during the Polar Night or Polar Day when there are periods of 24! hours of darkness or light? How would a biological clock function without a timekeeper!cycle? This chapter details evidence that biological clocks are central to structuring daily and seasonal activities in organisms at high latitudes. Importantly, despite a strongly reduced or absent day–night cycle, biological clocks in the Polar Night still appear to be regulated by background illumination. Here we explore evidence for highly cyclic activity, from behaviour patterns to clock gene expression, in copepods, krill and bivalves. The ultimate goal will be to understand the role of endogenous clocks in driving important daily and seasonal life cycle functions and to determine scope for plasticity in a rapidly changing environment.

Beschreibung: We explore the predictability of tropical Atlantic sea surface temperature (SST) and the potential influence of climate model bias on SST predictions over the tropical Atlantic. Two statistical methods are used to examine the skill in forecasting tropical Atlantic SST anomalies (SSTAs): linear inverse modeling (LIM) and analogue forecast (AF). The statistical models are trained either with observations or with data from two control integrations of the Kiel Climate Model (KCM), which only differ with respect to the resolution of its atmospheric component. Observed SSTAs suggest that Tropical Atlantic climatic changes are potentially predictable at lead times of up to 6 months over large parts of the Tropical Atlantic. The SSTAs from the KCM version employing a high-resolution atmosphere model (KCM-HRES) is potentially predictable at a level comparable to that derived from the observations, whereas the SSTAs from the KCM version employing a low-resolution atmosphere model (KCM-LRES) is considerably less potentially predictable. We show that the enhanced potential predictability in the former KCM version can be very likely related to the improved representation of ENSO-like dynamics and its seasonality. We used the statistical models in true forecast mode, i.e. the prediction schemes were trained from data independent of the forecast period. Using observed SSTAs to train the LIM yields significant skill in forecasting observed SSTAs at lead times of up to 4 months across all calendar months, which is mostly restricted to the northern and equatorial western Tropical Atlantic. Similar patterns, but with lower skill, are found when the models’ SSTAs are used, in which LIM trained with the KCM-HRES generally yields higher skills than that from the KCM-LRES. Applying AF yields significant skills in predicting observed SSTAs over the same regions, but the forecast skills are considerably smaller. When the SSTAs together with either sea level pressure (SLP) anomalies or dynamic sea level (DSL) anomalies from the KCM are used to construct the statistical models, the prediction of observed equatorial Atlantic SSTAs can be improved, with significant skill enhancement at lead times of up to 4 months in limited regions. An optimal initial SSTA pattern is found, which results in the largest transient anomaly growth over the entire domain. Independent of external forces, this amplification is developed internally; meaning that the seasonal forecast might be more sensitive to initial conditions than currently thought.

Beschreibung: The 1888 Ritter Island volcanic sector collapse triggered a regionally damaging tsunami. Historic eyewitness accounts allow the reconstruction of the arrival time, phase and height of the tsunami wave at multiple locations around the coast of New Guinea and New Britain. 3D seismic interpretations and sedimentological analyses indicate that the catastrophic collapse of Ritter Island was preceded by a phase of deep-seated gradual spreading within the volcanic edifice and accompanied by a submarine explosive eruption, as the volcanic conduit was cut beneath sea level. However, the potential impact of the deep-seated deformation and the explosive eruption on tsunami genesis is unclear. For the first time, it is possible to parameterise the different components of the Ritter Island collapse with 3D seismic data, and thereby test their relative contributions to the tsunami. The modelled tsunami arrival times and heights are in good agreement with the historic eyewitness accounts. Our simulations reveal that the tsunami was primarily controlled by the displacement of the water column by the collapsing cone at the subaerial-submarine boundary and that the submerged fraction of the slide mass and its mobility had only a minor effect on tsunami genesis. This indicates that the total slide volume, when incorporating the deep-seated deforming mass, is not directly scalable for the resulting tsunami height. Furthermore, the simulations show that the tsunamigenic impact of the explosive eruption energy during the Ritter Island collapse was only minor. However, this relationship may be different for other volcanogenic tsunami events with smaller slide volumes or larger magnitude eruptions, and should not be neglected in tsunami simulations and hazard assessment.

Beschreibung: The Hikurangi Margin off the east coast of the North Island (Te Ika-a-Māui) is a tectonically active subduction zone and the location of New Zealand’s largest gas hydrate province. Faults are internally complex volumetric zones that may play a significant role in the migration of fluids beneath the seafloor. The combined processes of deformation and fluid migration result in the formation of concentrated hydrate accumulations along accretionary ridges. It is not fully understood to what extent faults control fluid migration along the Hikurangi Margin, and whether deep-seated thrust faults provide a pathway for thermogenic gas to migrate up from sources at depth. Using 2D models based on seismic data from the region we investigated the role of thrust faults in facilitating fluid migration and contributing to the formation of concentrated gas hydrates. By altering permeability properties of the fault zones in these transient state models we can determine whether faults are required to act as fluid flow pathways. In this study we focus on two study sites offshore southern Wairarapa, using realistic yet simplified fault geometries derived from 2D seismic lines. The results of these models allow us to start to disentangle the complex relationship between fault zone structure, permeability, geometry, fluid migration and gas hydrate formation. Based on the model outputs we propose that faults act as primary pathways facilitating fluid migration and are critical in the formation of concentrated gas hydrate deposits.

Beschreibung: We project changes of the Aleutian Low (AL) under global warming using ensemble simulations with a fully coupled ocean-atmosphere-sea ice model, the Kiel Climate Model (KCM). In the global warming simulations, the carbon dioxide (CO2) concentration increases by 1% per year from the preindustrial level of 286.2 ppm to a quadruple value in 140 years. Results from the 40 members of an ensemble simulation show an intensification of the AL such that ensemble mean North Pacific Index (NPI) is decreased by 2.71 hPa. It is also accompanied with an expansion of the AL to north. While the effect of weakened land-ocean thermal contrast and SST warming in the eastern tropical Pacific on the AL strength are relatively weak and marginally significant, sea ice loss in the marginal seas of the North Pacific, such as the Bering Sea and the Sea of Okhotsk, increases the surface air temperature and makes pressure lower over the Bering Sea and the Aleutian Islands. Especially, sea ice loss in the Okhotsk Sea drives the SLP change around the Aleutian Islands and contributes to the strengthening of the AL.

Beschreibung: Shell formation and repair occurs under the control of mantle epithelial cells in bivalve molluscs. However, limited information is available on the precise acid–base regulatory machinery present within these cells, which are fundamental to calcification. Here, we isolate mantle epithelial cells from the Pacific oyster, Crassostrea gigas and utilise live cell imaging in combination with the fluorescent dye, BCECF-AM to study intracellular pH (pHi) regulation. To elucidate the involvement of various ion transport mechanisms, modified seawater solutions (low sodium, low bicarbonate) and specific inhibitors for acid–base proteins were used. Diminished pH recovery in the absence of Na+ and under inhibition of sodium/hydrogen exchangers (NHEs) implicate the involvement of a sodium dependent cellular proton extrusion mechanism. In addition, pH recovery was reduced under inhibition of carbonic anhydrases. These data provide the foundation for a better understanding of acid–base regulation underlying the physiology of calcification in bivalves.

Beschreibung: Biodiversity is generally believed to be a main determinant of ecosystem functioning. This principle also applies to the microbiome and could consequently contribute to host health. According to ecological theory, communities are shaped by top predators whose direct and indirect interactions with community members cause stability and diversity. Bdellovibrio and like organisms (BALOs) are a neglected group of predatory bacteria that feed on Gram-negative bacteria and can thereby influence microbiome composition. We asked whether BALOs can predict biodiversity levels in microbiomes from distinct host groups and environments. We demonstrate that genetic signatures of BALOs are commonly found within the 16S rRNA reads from diverse host taxa. In many cases, their presence, abundance, and especially richness are positively correlated with overall microbiome diversity. Our findings suggest that BALOs can act as drivers of microbial alpha-diversity and should therefore be considered candidates for the restoration of microbiomes and the prevention of dysbiosis.

Beschreibung: High-resolution bathymetry collected with an autonomous underwater vehicle (AUV) along the flanks of three ridges of the accretionary prism offshore southwestern (SW) Taiwan revealed more than 650 elongated depressions in water depths ranging from 1155 to 1420 m. The depressions are between 12 and 129 m long, 5 to 70 m wide, and up 9 m deep at their center and shallowing downslope to about 1-m depth. Due to their shape in downslope cross section, they are termed comet-shaped depressions (CSD). The CSD occur in patches of more than 100 with densities of 53 to 98 CSD/km2. In addition, seven topographic mounds were mapped and interpreted as pingos, which remotely operate vehicle (ROV) observations and sampling show to be covered with authigenic carbonate. These features overlie areas where multichannel seismic reflection (MCS) profiles show bottom simulating reflectors (BSR) and dipping strata extending from below the BSR to near the seafloor. We consider comet-shaped depression, a new type of pockmark, forms on a sloping seafloor where fluids expulsion occurred. We also suggest that the two types of distinctive geomorphic features are attributed to fluid venting which occurs at different rates, with the mounds developing slowly over time, but the CSD forming in discrete events perhaps associated with large earthquakes.

Beschreibung: Kiloniella laminariae is a true marine bacterium and the first member of the family and order, the Kiloniellaceae and Kiloniellales. K. laminariae LD81T (= DSM 19542T) was isolated from the marine macroalga Saccharina latissima and is a mesophilic, typical marine chemoheterotrophic aerobic bacterium with antifungal activity. Phylogenetic analysis of 16S rRNA gene sequence revealed the similarity of K. laminariae LD81T not only with three validly described species of the genus Kiloniella, but also with undescribed isolates and clone sequences from marine samples in the range of 93.6–96.7%. We report on the analysis of the draft genome of this alphaproteobacterium and describe some selected features. The 4.4 Mb genome has a G + C content of 51.4%, contains 4213 coding sequences including 51 RNA genes as well as 4162 protein-coding genes, and is a part of the Genomic Encyclopaedia of Bacteria and Archaea (GEBA) project. The genome provides insights into a number of metabolic properties, such as carbon and sulfur metabolism, and indicates the potential for denitrification and the biosynthesis of secondary metabolites. Comparative genome analysis was performed with K. laminariae LD81T and the animal-associated species Kiloniella majae M56.1T from a spider crab, Kiloniella spongiae MEBiC09566T from a sponge as well as Kiloniella litopenai P1-1 from a white shrimp, which all inhabit quite different marine habitats. The analysis revealed that the K. laminariae LD81T contains 1397 unique genes, more than twice the amount of the other species. Unique among others is a mixed PKS/NRPS biosynthetic gene cluster with similarity to the biosynthetic gene cluster responsible for the production of syringomycin.

Beschreibung: Cold-water corals (CWC), dominantly Desmophyllum pertusum (previously Lophelia pertusa), and their mounds have been in the focus of marine research during the last two decades; however, little is known about the mound-forming capacity of other CWC species. Here, we present new 230Th/U age constraints of the relatively rarely studied framework-building CWC Solenosmilia variabilis from a mound structure off the Brazilian margin combined with computed tomography (CT) acquisition. Our results show that S. variabilis can also contribute to mound formation, but reveal coral-free intervals of hemipelagic sediment deposits, which is in contrast to most of the previously studied CWC mound structures. We demonstrate that S. variabilis only occurs in short episodes of 〈 4 kyr characterized by a coral content of up to 31 vol%. In particular, it is possible to identify distinct clusters of enhanced aggradation rates (AR) between 54 and 80 cm ka−1. The determined AR are close to the maximal growth rates of individual S. variabilis specimens, but are still up to one order of magnitude smaller than the AR of D. pertusum mounds. Periods of enhanced S. variabilis AR predominantly fall into glacial periods and glacial terminations that were characterized by a 60–90 m lower sea level. The formation of nearby D. pertusum mounds is also associated with the last glacial termination. We suggest that the short-term periods of coral growth and mound formation benefited from enhanced organic matter supply, either from the adjacent exposed shelf and coast and/or from enhanced sea-surface productivity. This organic matter became concentrated on a deeper water-mass boundary between South Atlantic Central Water and the Antarctic Intermediate Water and may have been distributed by a stronger hydrodynamic regime. Finally, periods of enhanced coral mound formation can also be linked to advection of nutrient-rich intermediate water masses that in turn might have (directly or indirectly) further facilitated coral growth and mound formation.

Beschreibung: The tsunami hazard for the Maltese Islands is poorly defined, and historic records are available for only two recent events. Most of the population and touristic infrastructure of the archipelago is concentrated along the eastern low-lying coastline, which is exposed to tsunamis from near-field and far-field sources. In this study we present a scenario-based tsunami inundation study to assess the impact of potential significant cases. We simulated four scenarios—two submarine landslide sources (outer Malta Plateau slide and Gela Basin slide) and two earthquake sources mimicking events comparable to the 365 A.D. western Hellenic Arc event and the 1693 south-east of Sicily event. We find that all scenarios cause inundation in densely populated low-lying bays or rias of Mellieha Bay, Xemxija, Salini, Gzira, Msida, Marsaskala, St Thomas Bay, Marsaxlokk and Birzebbuga. The largest inundation extents and flow depths (〉 10 m) are produced by the two landslide sources and the western Hellenic Arc earthquake. Of interest is the role of the Malta Escarpment and Sicily in amplifying and reflecting tsunami waves, and in generating consistent hot spots along the eastern coastline of Malta.

Beschreibung: Control strategies for established populations of invasive alien species can be costly and complex endeavours, which are frequently unsuccessful. Therefore, rapid-reaction techniques that are capable of maximising efficacy whilst minimising environmental damage are urgently required. The Asian clam (Corbicula fluminea Müller, 1774), and the zebra mussel (Dreissena polymorpha Pallas, 1771), are invaders capable of adversely affecting the functioning and biodiversity of freshwater ecosystems. Despite efforts to implement substantial population-control measures, both species continue to spread and persist within freshwater environments. As bivalve beds often become exposed during low-water conditions, this study examined the efficacy of steam-spray (≥100 °C, 350 kPa) and open-flame burn treatments (~1000 °C) to kill exposed individuals. Direct steam exposure lasting for 5 min caused 100% mortality of C. fluminea buried at a depth of 3 cm. Further, combined rake and thermal shock treatments, whereby the substrate is disturbed between each application of either a steam or open flame, caused 100% mortality of C. fluminea specimens residing within a 4-cm deep substrate patch, following three consecutive treatment applications. However, deeper 8-cm patches and water-saturated substrate reduced maximum bivalve species mortality rates to 77% and 70%, respectively. Finally, 100% of D. polymorpha specimens were killed following exposure to steam and open-flame treatments lasting for 30 s and 5 s, respectively. Overall, our results confirm the efficacy of thermal shock treatments as a potential tool for substantial control of low-water-exposed bivalves. Although promising, our results require validation through upscaling to field application, with consideration of other substrate types, increased substrate depth, greater bivalve densities, non-target and long-term treatment effects.

Beschreibung: The interdisciplinary exchange in climate engineering research offers a unique opportunity to make assumptions more explicit for such research projects. While making assumptions explicit is the standard in all disciplinary sciences, some assumptions in the context of societal challenges can only be usefully unveiled, discussed, and verified from the perspective of other research disciplines. Results from successful interdisciplinary collaborations are then more accessible and more generalizable to actors beyond the confines of the academic community. We aim to illustrate how interdisciplinary exchange helps to unveil assumptions in research endeavors and why this is important for successful interdisciplinary collaborations. We therefore follow different stages of the German Priority Program on Climate Engineering (SPP 1689), which we use as an example case of a successful interdisciplinary project. SPP 1689 focused on risks, challenges, and opportunities of Climate Engineering from the perspectives of numerous disciplines. Major results were that the initial assessments of technologies had to be sobered, the consideration of trade-offs is crucial for the potential assessment, and governance issues appeared larger than previously considered. From the reflections of SPP 1689, we conclude with three lessons learned: (1) The project profited from egalitarian organizational structures and communicative practices, preventing the predominance from single disciplines. (2) Within the project continuous efforts were undertaken to foster interdisciplinary understanding. In addition, the flexible project structure allowed for the accommodation of research needs arising as a result of these exchanges. (3) SPP 1689 offered early career researchers a platform for professional exchange on common challenges and best practices of being a part of an interdisciplinary research project.

Beschreibung: Ecological theory suggests that a combination of local and regional factors regulate biodiversity and community functioning in metacommunities. The relative importance of different factors structuring communities likely changes over successional time, but to date this concept is scarcely documented. In addition, the few studies describing successional dynamics in metacommunity regulation have only focused on a single group of organisms. Here, we report results of an experimental study testing the effect size of initial local community composition and dispersal between local patches on community dynamics of benthic microalgae and their associated bacteria over community succession. Our results show that over time dispersal outweighed initial effects of community composition on microalgal evenness and biomass, microalgal β-diversity, and the ratio of bacteria to microalgae. At the end of the experiment (ca. 20 microalgae generations), dispersal significantly decreased microalgal evenness and β-diversity by promoting one regionally superior competitor. Dispersal also decreased the ratio of bacteria to microalgae, while it significantly increased microalgal biomass. These results suggest that the dispersal-mediated establishment of a dominant and superior microalgae species prevented bacteria from gaining competitive advantage over the autotrophs in these metacommunities, ultimately maintaining the provision of autotrophic biomass. Our study emphasizes the importance of time for dispersal to be a relevant community-structuring mechanism. Moreover, we highlight the need for considering multiple competitors in complex metacommunity systems to properly pinpoint the consequences of local change in dominance through dispersal for metacommunity function.

Beschreibung: Hans Peter Cornelius was a squeamishly and accurately mapping field geologist with an eye for the finest detail as well as for the large-scale architectural structure of mountain ranges. His excellent work concerned the Rhaetian and Allgau Alps, South Tyrol, the Valais and Ticino in Switzerland and many regions in Austria. His publications on the Err-Julier Group, the Insubric Line, the Grossglockner Group, the Rax-Schneeberg Group, the alpine Grauwackenzone, and the Penninic series of the Western and Eastern Alps became particularly important.

Beschreibung: In order to expand the fragmentary knowledge on the interactions between the environment and copepod distribution in the deep offshore Adriatic Sea, microcopepod assemblages were investigated during 31 cruises in the 1200-m deep central part of the South Adriatic Pit (SAP), from May 1998 to December 2009. Samples were collected in 8 depth layers, using a 53-μm mesh Nansen net equipped with a closing system. The taxonomic composition and vertical and temporal distributions of copepod abundances were analyzed, considering naupliar stages for all species combined, total calanoid copepodites, copepodite stages and adults separately for oithonids and oncaeids, and all post-naupliar stages combined of harpacticoids and mormonilloids. Corycaeid copepods are not considered in the present study. Data are presented for 41 non-calanoid copepod species, as well as for 7 undetermined morphospecies. Within the family Oncaeidae, four species new to the Adriatic Sea fauna are registered. Nauplii were generally the numerically dominant group, especially in the upper epipelagic layers, where they outnumbered all total post-naupliar stages by a factor of an average 3.5. Oncaeids were notably abundant, accounting in total post-naupliar copepods for an average proportion of 33% in the upper 50 m and 74% between 300- and 400-m depth. In the epipelagic zone, copepod abundances were enhanced by the cyclonic circulation which enriches the central part of the SAP with new primary production. A strong advection of Levantine Intermediate Water (LIW) influenced the post-naupliar abundances also in mesopelagic and deeper layers, by promoting the sinking of heavy water mass from the connected middle Adriatic sub-basin which enhances the trophic conditions and transports new organisms into the deeper layers of the SAP. Therefore, the variability in copepod abundances was influenced not only by the seasonal temperature fluctuations but also by the productivity conditions in the SAP which are connected to the movements of regional water masses and the resulting effects on the internal Adriatic circulation.

Beschreibung: South-Eastern Brazil experienced a devastating drought associated with significant agricultural losses in austral summer 2014. The drought was linked to the development of a quasi-stationary anticyclone in the South Atlantic in early 2014 that affected local precipitation patterns over South-East Brazil. Previous studies have suggested that the unusual blocking was triggered by tropical Pacific sea surface temperature (SST) anomalies and, more recently, by convection over the Indian Ocean related to the Madden-Julian Oscillation. Further investigation of the proposed teleconnections appears crucial for anticipating future economic impacts. In this study, we use numerical experiments with an idealized atmospheric general circulation model forced with the observed 2013/2014 SST anomalies in different ocean basins to understand the dominant mechanism that initiated the 2014 South Atlantic anticyclonic anomaly. We show that a forcing with global 2013/2014 SST anomalies enhances the chance for the occurrence of positive geopotential height anomalies in the South Atlantic. However, further sensitivity experiments with SST forcings in separate ocean basins suggest that neither the Indian Ocean nor tropical Pacific SST anomalies alone have contributed significantly to the anomalous atmospheric circulation that led to the 2014 South-East Brazil drought. The model study rather points to an important role of remote forcing from the South Pacific, local South Atlantic SSTs, and internal atmospheric variability in driving the persistent blocking over the South Atlantic.

Beschreibung: Mts. Kalnik and Požeška gora volcaniclastic sequences hold valuable information concerning the Miocene syn-rift evolution of the North Croatian Basin, and the evolution of the Carpathian–Pannonian Region and the Central Paratethys. We present volcanological, high-precision geochronological, and compositional data of volcanic glass to constrain their tephrochronology, magmatic provenance, and timing of the initial Central Paratethys flooding of the North Croatian Basin. Based on CA-ID-TIMS U–Pb zircon ages (18.060 ± 0.023 Ma for Mt. Kalnik and 15.345 ± 0.020 Ma for Mt. Požeška gora) and coeval 40Ar/39Ar sanidine ages (18.14 ± 0.38 Ma and 18.25 ± 0.38 Ma for Mt. Kalnik and 15.34 ± 0.32 Ma and 15.43 ± 0.32 Ma for Mt. Požeška gora), Mt. Kalnik rhyolitic massive ignimbrites and Mt. Požeška gora rhyolitic primary volcaniclastic turbidites are coeval with Carpathian–Pannonian Region Miocene post-collisional silicic volcanism, which was caused by lithospheric thinning of the Pannonian Basin. Their affiliation to Carpathian–Pannonian Region magmatic activity is supported by their subduction-related geochemical signatures. Although Mts. Kalnik and Požeška gora volcaniclastics are coeval with the Bükkalja Volcanic Field Csv-2 rhyolitic ignimbrites, North Alpine Foreland Basin, Styrian Basin, Vienna Basin, and Dinaride Lake System bentonites and volcaniclastic deposits, reliable tephrochronological interpretations based on comparison of volcanic glass geochemical composition are not possible due to a lack of data and/or methodological discrepancies. Our new high-precision geochronology data prove that the initial Middle Miocene (Badenian) marine flooding of parts of the North Croatian Basin occurred at least ~ 0.35 Ma (during the NN4 Zone) before the generally accepted ~ 15 Ma maximum flooding age at the basin scale, calibrating the timing of the onset of the widespread “mid-Langhian” Central Paratethys flooding.

Beschreibung: Purpose of Review: Assessment of the impact of ocean resolution in Earth System models on the mean state, variability, and future projections and discussion of prospects for improved parameterisations to represent the ocean mesoscale. Recent Findings: The majority of centres participating in CMIP6 employ ocean components with resolutions of about 1 degree in their full Earth System models (eddy-parameterising models). In contrast, there are also models submitted to CMIP6 (both DECK and HighResMIP) that employ ocean components of approximately 1/4 degree and 1/10 degree (eddy-present and eddy-rich models). Evidence to date suggests that whether the ocean mesoscale is explicitly represented or parameterised affects not only the mean state of the ocean but also the climate variability and the future climate response, particularly in terms of the Atlantic meridional overturning circulation (AMOC) and the Southern Ocean. Recent developments in scale-aware parameterisations of the mesoscale are being developed and will be included in future Earth System models. Summary: Although the choice of ocean resolution in Earth System models will always be limited by computational considerations, for the foreseeable future, this choice is likely to affect projections of climate variability and change as well as other aspects of the Earth System. Future Earth System models will be able to choose increased ocean resolution and/or improved parameterisation of processes to capture physical processes with greater fidelity.

Beschreibung: In the Western Baltic Sea, climate change is happening at much faster rate than in most other seas and organisms are additionally exposed to a steep and variable salinity gradient. Climate change has previously been shown to affect parasite transmission in other marine ecosystems, yet little is known about potential effects of warming and desalination on parasite–host interactions. In laboratory experiments, we determined the combined effects of projected seawater warming and freshening on the emergence, activity, survival, and infectivity of cercariae (free-swimming infectious stage) of the trematode Himasthla elongata (Mehlis 1831), shed from its first intermediate host, the periwinkle Littorina littorea (Linnaeus 1758), in the Baltic Sea. We also assessed the susceptibility of the second intermediate host, the mussel Mytilus edulis Linnaeus, 1758, to cercarial infections. Generally, salinity was the main driver, particularly of cercarial activity, infectivity, and mussel susceptibility to infection. At the lowest salinity (13), cercariae were 50% less active compared to the highest salinity (19). Infection success and host susceptibility followed a similar pattern, with 47% and 43% less metacercariae (encysted stage) present at salinity 13 than at salinity 19, respectively. In contrast, effects of simulated warming were found only for cercarial survival, with cercarial longevity being higher at 19 than at 23 °C. No significant interactions between temperature and salinity were found. In contrast to the literature, the results suggest that a climate change-driven freshening (partly also warming) may lead to a general decline of marine trematodes, with possible beneficial effects for the involved hosts.

Beschreibung: The Pacific oyster, Magallana gigas, is an extremely successful invader with established populations in marine and estuarine habitats almost all over the world. Ecological implications of the introduction of this species to indigenous communities are well documented. However, the processes by which this species successfully establishes in a recipient community is still insufficiently understood. The early detection of the oyster at the island of Helgoland (North Sea) provided the ideal opportunity to investigate whether physical mechanisms, such as wave-exposure, influence their successful colonisation. We hypothesized that oyster colonisation benefits from wave-protected conditions. For this purpose, we evaluated colonisation success of M. gigas among wave-protected sites and wave-exposed sites along the island's pier system. The densities of M. gigas were significantly higher at wave-protected sites than at wave-exposed sites, and the frequency distributions of oyster lengths indicated better growth and higher survival rates in the harbours. This higher colonisation success at wave-protected sites may be explained by the relative retention time of water masses in the harbours, probably resulting in both reduced larval drift and lower energy demands for secretion formation (i.e. firmer binding to the substrate). The fact that the density of M. gigas can vary greatly on small spatial scales depending on exposure corroborates a multiple exposure sampling approach to monitor oyster populations in order to avoid potential overestimations of population sizes in given areas.

Beschreibung: Establishment of adequate conservation areas represents a challenging but crucial task in the conservation of genetic diversity and biological variability. Anthropogenic pressures on marine ecosystems and organisms are steadily increasing. Whether and to what extent these pressures influence marine genetic biodiversity is only starting to be revealed. Using 16S rRNA gene amplicon sequencing, we analysed the microbial community structure of 33 individuals of the habitat-forming glass sponge Vazella pourtalesii, as well as reference seawater, sediment, and biofilm samples. We assessed how two anthropogenic impacts, i.e. habitat destruction by trawling and artificial substrate provision (moorings made of composite plastic), correspond with in situ V. pourtalesii microbiome variability. In addition, we evaluated the role of two bottom fishery closures in preserving sponge-associated microbial diversity on the Scotian Shelf, Canada. Our results illustrate that V. pourtalesii sponges collected from pristine sites within fishery closures contained distinct and taxonomically largely novel microbial communities. At the trawled site we recorded significant quantitative differences in distinct microbial phyla, such as a reduction in Nitrospinae in sponges and environmental references. Individuals of V. pourtalesii growing on the mooring were significantly enriched in Bacteroidetes, Verrucomicrobia and Cyanobacteria in comparison to sponge individuals growing on the natural seabed. Due to a concomitant enrichment of these taxa in the mooring biofilm, we propose that biofilms on artificial substrates may ‘prime’ sponge-associated microbial communities when small sponges settle on such substrates. These observations likely have relevant management implications when considering the increase of artificial substrates in the marine environment, e.g., marine litter, off-shore wind parks, and petroleum platforms.

Beschreibung: This study aims to provide a more detailed understanding of the behavior of 231Pa/230Th under varying ocean circulation regimes. The North Atlantic provides a unique sedimentary setting with its ice-rafted detritus (IRD) layers deposited during glacial times. These layers have been found north of 40° N (Ruddiman Belt) and are most pronounced during Heinrich Stadials. Most of these sediments have been recovered from the deep North Atlantic basin typically below 3000 m water depth. This study reports sedimentological and sediment geochemical data from one of the few sites at intermediate depth of the open North Atlantic (core SU90-I02, 45° N 39° W, 1965 m water depth) within the Ruddiman Belt. The time periods of Heinrich Stadials 1 and 2 of this core were identified with the help of the major element composition by XRF scanning and by IRD counting. Along the core profile, the sedimentary 231Pa/230Th activity ratio has been measured as a kinematic proxy for the circulation strength. The 231Pa/230Th record shows highest values during the Holocene and Last Glacial Maximum, above the natural production ratio of these isotopes. During Heinrich Stadials 1 and 2, when Atlantic meridional overturning circulation was most reduced, the 231Pa/230Th record shows overall lowest values below the production ratio. This behavior is contrary to classical findings of 231Pa/230Th from the northwestern Atlantic where a strong Holocene circulation is associated with low values. However, this behavior at the presented location is in agreement with results from simulations of the 231Pa/230Th-enabled Bern3D Earth system model.

Beschreibung: A prominent weakening in equatorial Atlantic sea surface temperature (SST) variability, occurring around the year 2000, is investigated by means of observations, reanalysis products and the linear recharge oscillator (ReOsc) model. Compared to the time period 1982–1999, during 2000–2017 the May–June–July SST variability in the eastern equatorial Atlantic has decreased by more than 30%. Coupled air–sea feedbacks, namely the positive Bjerknes feedback and the negative net heat flux damping are important drivers for the equatorial Atlantic interannual SST variability. We find that the Bjerknes feedback weakened after 2000 while the net heat flux damping increased. The weakening of the Bjerknes feedback does not appear to be fully explainable by changes in the mean state of the tropical Atlantic. The increased net heat flux damping is related to an enhanced response of the latent heat flux to the SST anomalies (SSTa). Strengthened trade winds as well as warmer SSTs are suggested to increase the air–sea specific humidity difference and hence, enhancing the latent heat flux response to SSTa. A combined effect of those two processes is proposed to be responsible for the weakened SST variability in the eastern equatorial Atlantic. The ReOsc model supports the link between reduced SST variability, weaker Bjerknes feedback and stronger net heat flux damping.

Beschreibung: Aquatic ecosystems face a multitude of environmental stressors, including warming and acidification. While warming is expected to have a pronounced effect on plankton communities, many components of the plankton seem fairly robust towards realistic end-of-century acidification conditions. However, interactions of the two stressors and the inclusion of further factors such as nutrient concentration and trophic interactions are expected to change this outcome. We investigated the effects of warming and high CO2 on a nutrient-deplete late summer plankton community from the Kiel Fjord, Baltic Sea, using a mesocosm setup crossing two temperatures with a gradient of CO2. Phytoplankton and microzooplankton (MZP) growth rates as well as biomass, taxonomic composition, and grazing rates of MZP were analysed. We observed effects of high CO2, warming, and their interactions on all measured parameters. The occurrence and direction of the effects were dependent on the phytoplankton or MZP community composition. In addition, the abundance of small-sized phytoplankton was identified as one of the most important factors in shaping the MZP community composition. Overall, our results indicate that an estuarine MZP community used to strong natural fluctuations in CO2 can still be affected by a moderate increase in CO2 if it occurs in combination with warming and during a nutrient-deplete post-bloom situation. This highlights the importance of including trophic interactions and seasonality aspects when assessing climate change effects on marine zooplankton communities.

Beschreibung: Reefs formed by scleractinian cold-water corals represent unique biodiversity hot spots in the deep sea, preferring aphotic water depths of 200–1000 m. The distribution of the most prominent reef-building species Lophelia pertusa is controlled by various environmental factors including dissolved oxygen concentrations and temperature. Consequently, the expected ocean deoxygenation and warming triggered by human-induced global change are considered as a serious threat to cold-water coral reefs. Here, we present results on recently discovered reefs in the SE Atlantic, where L. pertusa thrives in hypoxic and rather warm waters. This sheds new light on its capability to adapt to extreme conditions, which is facilitated by high surface ocean productivity, resulting in extensive food supply. Putting our data in an Atlantic-wide perspective clearly demonstrates L. pertusa’s ability to develop population-specific adaptations, which are up to now hardly considered in assessing its present and future distributions.

Beschreibung: The variability of the Atlantic Meridional Overturning Circulation (AMOC) and the Meridional Freshwater Transport (Mov) at 24°N, 11°S, and 30°S, simulated with the GFDL-CM3 model under the historical (1860–2005) and RCP 4.5 and 8.5 scenarios (2006–2100) are examined. The results are compared with the climatology and observations in the search for salinity biases that would compromise the accuracy of the state of the future climate predicted by this model. The AMOC wavelet analysis shows a predominant decadal variability at 24°N, whereas the annual signal is more prominent in the South Atlantic. The Mov magnitude varies considerably among the latitudes: increasing at 24°N, rather stable at 11°S and decreasing at 30°S. Such a pattern is followed by an AMOC weakening regardless of the latitude until the end of the 21st century, indicating that a reduction in Mov in the southern South Atlantic and an increase in the North Atlantic are potential drivers of the AMOC destabilization. Both model and observations agree on the stability of the circulation, even though the model projects a stronger AMOC than the latter. Besides the AMOC weakening, a shoaling of its upper limb is also observed. Salinity biases were found mostly in the South Atlantic in the upper 1000 m of the water column, with the model results significantly deviating from the observations and climatology in the mid-Atlantic, especially at 30°S. Possible causes for the abovementioned results, including potential drivers for salinity biases are discussed.

Beschreibung: Many climate models strongly underestimate the two most important atmospheric feedbacks operating in El Niño/Southern Oscillation (ENSO), the positive (amplifying) zonal surface wind feedback and negative (damping) surface-heat flux feedback (hereafter ENSO atmospheric feedbacks, EAF), hampering realistic representation of ENSO dynamics in these models. Here we show that the atmospheric components of climate models participating in the 5th phase of the Coupled Model Intercomparison Project (CMIP5) when forced by observed sea surface temperatures (SST), already underestimate EAF on average by 23%, but less than their coupled counterparts (on average by 54%). There is a pronounced tendency of atmosphere models to simulate stronger EAF, when they exhibit a stronger mean deep convection and enhanced cloud cover over the western equatorial Pacific (WEP), indicative of a stronger rising branch of the Pacific Walker Circulation (PWC). Further, differences in the mean deep convection over the WEP between the coupled and uncoupled models explain a large part of the differences in EAF, with the deep convection in the coupled models strongly depending on the equatorial Pacific SST bias. Experiments with a single atmosphere model support the relation between the equatorial Pacific atmospheric mean state, the SST bias and the EAF. An implemented cold SST bias in the observed SST forcing weakens deep convection and reduces cloud cover in the rising branch of the PWC, causing weaker EAF. A warm SST bias has the opposite effect. Our results elucidate how biases in the mean state of the PWC and equatorial SST hamper a realistic simulation of the EAF.

Beschreibung: Due to the complexity of installations and connections of subsea production equipment and the massive structures involved in a challenging environment, the failure of subsea production equipment could induce enormous loss to the safety and reliability of structures in addition to the cost of the oilfield development. One of the challenges that the subsea production structures face, as it moves to ultra-deep water and polar underwater equipment, is to design subsea shell structures capable of withstanding high external pressures. Hence, a subsea function chamber (SFC) has been lately proposed as a viable solution, which has a high level of safety and reliability, and a technique for the subsea production system. This paper presents a general and efficient buckling and collapse analysis strategy. In this work, the SFC is composed of cylindrical and hemispherical shaped steel material. Initial imperfection-based nonlinear buckling analysis has been carried out to investigate the buckling and risks associated with different thicknesses of the structure. Linear and nonlinear static buckling analyses have been carried out using ABAQUS software. By introducing the nonlinear properties of materials, the nonlinear numerical model of SFC is established. The effects of the thickness of different models and the number of stiffeners on the buckling modes are discussed. The wall thickness is calculated by the Donnell equation and Timoshenko’s classical method. It has been found that the classical solutions given by the Donnell and Timoshenko equations are more accurate for structures with larger lengths and diam. The thickness and number of stiffeners have a great influence on the ultimate buckling external pressure load of SFC structure

Beschreibung: This paper reflects on a number of trends towards a more open and reproducible approach to geographic and spatial data science over recent years. In particular, it considers trends towards Big Data, and the impacts this is having on spatial data analysis and modelling. It identifies a turn in academia towards coding as a core analytic tool, and away from proprietary software tools offering ‘black boxes’ where the internal workings of the analysis are not revealed. It is argued that this closed form software is problematic and considers a number of ways in which issues identified in spatial data analysis (such as the MAUP) could be overlooked when working with closed tools, leading to problems of interpretation and possibly inappropriate actions and policies based on these. In addition, this paper considers the role that reproducible and open spatial science may play in such an approach, taking into account the issues raised. It highlights the dangers of failing to account for the geographical properties of data, now that all data are spatial (they are collected somewhere), the problems of a desire for $$n$$ n  = all observations in data science and it identifies the need for a critical approach. This is one in which openness, transparency, sharing and reproducibility provide a mantra for defensible and robust spatial data science.

Beschreibung: This article aims to contribute to the literature on the quest for resilient cities by focusing on the climate change resilience building discourse in peri-urban areas, and specifically by exploring the role of social capital-an under-researched topic. The article examines bonding social capital and bridging social capital, with a focus on how they can potentially contribute to, or inhibit, the socio-ecological system resilience building processes in the context of climate change reality in peri-urban areas. Theoretically, the author draws on the existing social capital and resilience related literatures; empirically, the article presents findings from a study conducted in the peri-urban areas of Pugu and Kazimzumbwi forest reserves on the outskirts of Dar es Salaam city in Tanzania. The study deployed a household survey and key informant interviews. It found that both bonding and bridging social capital were strong in the research area, suggesting the feasibility of building resilience to climate change effects. Examples are given of a number of resilience building interventions that were established through synergies between social capital actors and local communities, although some doubt is cast over the sustainability of these initiatives. Overall, both theoretical and empirical evidence suggests the importance of including a focus on social capital in exploring the building of climate change resilience pathways in peri-urban areas, and especially in the context of the global south.

Beschreibung: We observe an anomalously high electric field of terahertz (THz) radiation acting on a two-dimensional electron gas (2DEG) placed beneath a thin gold film, which, however, is supposed to be opaque at THz frequencies. We show that the anomalously strong penetration of the THz electric field through a very high conductive gold film emerges if two conditions are fulfilled simultaneously: (i) the film’s thickness is less than the skin depth and (ii) the THz electric field is measured beneath the film at distances substantially smaller than the radiation wavelength. We demonstrate that under these conditions, the strength of the field acting on a 2DEG is almost the same as it would be in the absence of the gold film. The effect is detected for macroscopically homogeneous perforation-free gold films illuminated by THz laser radiation with a spot smaller than the film area. This eliminates the near field of the edge diffraction as a possible cause of the anomalous penetration. The microscopic origin of the effect remains unexplained in its details, yet. The observed effect can be used for the development of THz devices based on two-dimensional materials requiring robust highly conducting top gates placed at less than nanometer distance from the electron gas location.

Beschreibung: Twenty years have passed since Bivand and Gebhardt (J Geogr Syst 2(3):307–317, 2000. 10.1007/PL00011460) indicated that there was a good match between the then nascent open-source R programming language and environment and the needs of researchers analysing spatial data. Recalling the development of classes for spatial data presented in book form in Bivand et al. (Applied spatial data analysis with R. Springer, New York, 2008, Applied spatial data analysis with R, 2nd edn. Springer, New York, 2013), it is important to present the progress now occurring in representation of spatial data, and possible consequences for spatial data handling and the statistical analysis of spatial data. Beyond this, it is imperative to discuss the relationships between R-spatial software and the larger open-source geospatial software community on whose work R packages crucially depend.

Beschreibung: Many manufacturing systems need more than one type of resource to co-work with. Commonly studied flexible job shop scheduling problems merely consider the main resource such as machines and ignore the impact of other types of resource. As a result, scheduling solutions may not put into practice. This paper therefore studies the dual resource constrained flexible job shop scheduling problem when loading and unloading time (DRFJSP-LU) of the fixtures is considered. It formulates a multi-objective mathematical model to jointly minimize the makespan and the total setup time. Considering the influence of resource requirement similarity among different operations, we propose a similarity-based scheduling algorithm for setup-time reduction (SSA4STR) and then an improved non-dominated sorting genetic algorithm II (NSGA-II) to optimize the DRFJSP-LU. Experimental results show that the SSA4STR can effectively reduce the loading and unloading time of fixtures while ensuring a level of makespan. The experiments also verify that the scheduling solution with multiple resources has a greater guiding effect on production than the scheduling result with a single resource.

Beschreibung: Rare earth elements (REEs) are key constituents of modern technology and play important roles in various chemical and industrial applications. They also are increasingly used in agricultural and zootechnical applications, such as fertilizers and feed additives. Early applications of REEs in agriculture have originated in China over the past several decades with the objective of increasing crop productivity and improving livestock yield (e.g., egg production or piglet growth). Outside China, REE agricultural or zootechnical uses are not currently practiced. A number of peer-reviewed manuscripts have evaluated the adverse and the positive effects of some light REEs (lanthanum and cerium salts) or REE mixtures both in plant growth and in livestock yield. This information was never systematically evaluated from the growing body of scientific literature. The present review was designed to evaluate the available evidence for adverse and/or positive effects of REE exposures in plant and animal biota and the cellular/molecular evidence for the REE-associated effects. The overall information points to shifts from toxic to favorable effects in plant systems at lower REE concentrations (possibly suggesting hormesis). The available evidence for REE use as feed additives may suggest positive outcomes at certain doses but requires further investigations before extending this use for zootechnical purposes.

Beschreibung: Oxidative stress occurs in extrinsic skin aging processes and diseases when the enhanced production of free radicals exceeds the homeostatic antioxidant capacity of the skin. The spin probe, 3-(carboxy)-2,2,5,5-tetramethylpyrrolidin-1-oxyl (PCA), is frequently used to study the cutaneous radical production by electron paramagnetic resonance (EPR) spectroscopy. This approach requires delivering PCA into the skin, yet solvent effects on the skin penetration and spatial distribution of PCA have not been thoroughly investigated. Three solvents of ethanol, phosphate-buffered saline (PBS) and ethanol-PBS (1:1) were studied. For both human and porcine skin ex vivo, the amount of PCA in the stratum corneum (SC) was the lowest when using ethanol and very similar for PBS and ethanol-PBS. The highest amount of PCA in the viable skin layers was detected for ethanol-PBS, yet it only took up less than 5% of the total amount. The majority of PCA was localized in the SC, among which PCA with high mobility was predominantly distributed in the hydrophilic microenvironment of corneocytes and PCA with lower mobility was mainly in the less hydrophilic microenvironment of intercellular skin lipids. A higher ethanol concentration in the solvent could improve the distribution of PCA in the hydrophilic microenvironments of the SC. The results suggest that ethanol-PBS (1:1) is best-suited for delivering most PCA deep into the skin. This work enhances the understanding of solvent effects on the skin penetration and distribution of PCA and supports the utilization of PCA in studying cutaneous radical production.

Beschreibung: The decomposition of coarse woody debris (CWD) affects the energy flow and nutrient cycling in forest ecosystems. Previous studies on CWD have focused on the input, decomposition, reserve dynamics, and CWD functions, but coarse woody debris decomposition is complex and the results from different regions vary considerably. It is not clear which factors affect decay rate (k), especially at different decomposition stages. In this study, a single-exponential decay model was used to analyze the characteristics of CWD decomposition in Larix gmelinii forests over the 33 years following a fire in the Greater Khingan Mountains. The results show that the decay rate of coarse woody debris was positively correlated to decay class. The average decomposition rate was 0.019, and 41 years and 176 years are needed for a 50% and 95% mass loss, respectively. CWD nutrient content, density, and water content could explain the variance in the decay rate (~ 42%) of the decay factors such as amount of leaching, degree of fragmentation, respiration of the debris, and biotransformation, and varied significantly between different decay classes. Using the space–time substitution method, this study arranged the coarse woody debris of different mortality times to form a 33 year chronosequence which revealed the decomposition process. It was concluded that the decay rate was mainly explained by structural component of the debris and its nitrogen and water contents. This paper quantifies the indicators affecting CWD decay to explain the decomposition process.

Beschreibung: This study attempted to evaluate the groundwater quality, with a special emphasis on nutrients, of a riverine coastal island near Kodungallur, Kerala. Water quality parameters were analyzed in the collected samples over pre- and post-monsoon seasons. A considerable variation in groundwater chemistry was observed in the two periods. During pre-monsoon season, many wells were contaminated with TDS, Cl, Fe, Ca and Mg in certain locations. Whereas, post-monsoon water was relatively fresh, indicating the dilution process as well as aquifer recharge by the monsoon rain and consequent regression of saline water. A higher concentration of Fe was observed in the pre-monsoon season (41%) than in the post-monsoon season (24%). Nitrate and phosphates were analyzed to assess the nutrients and the observed concentration was below their corresponding permissible limits. Results show that overexploitation of the aquifer as well as the decreased flow of the River Periyar during the pre-monsoon period increased the threat from seawater intrusion and groundwater contamination. An interesting groundwater recharge mechanism locally known as backwashing—the diversion of rainwater from rooftops to dug wells—is being practiced in the study area and has been found to be effective in raising water levels and improving water quality.