Trophic amplification: A model intercomparison of climate driven changes in marine food webs.

Marine animal biomass is expected to decrease in the 21st century due to climate driven changes in ocean environmental conditions. Previous studies suggest that the magnitude of the decline in primary production on apex predators could be amplified through the trophodynamics of marine food webs, leading to larger decreases in the biomass of predators relative to the decrease in primary production, a mechanism called trophic amplification. We compared relative changes in producer and consumer biomass or production in the global ocean to assess the extent of trophic amplification. We used simulations from nine marine ecosystem models (MEMs) from the Fisheries and Marine Ecosystem Models Intercomparison Project forced by two Earth System Models under the high greenhouse gas emissions Shared Socioeconomic Pathways (SSP5-8.5) and a scenario of no fishing. Globally, total consumer biomass is projected to decrease by 16.7 ± 9.5% more than net primary production (NPP) by 2090-2099 relative to 1995-2014, with substantial variations among MEMs and regions. Total consumer biomass is projected to decrease almost everywhere in the ocean (80% of the world's oceans) in the model ensemble. In 40% of the world's oceans, consumer biomass was projected to decrease more than NPP. Additionally, in another 36% of the world's oceans consumer biomass is expected to decrease even as projected NPP increases. By analysing the biomass response within food webs in available MEMs, we found that model parameters and structures contributed to more complex responses than a consistent amplification of climate impacts of higher trophic levels. Our study provides additional insights into the ecological mechanisms that will impact marine ecosystems, thereby informing model and scenario development.

Ocean iron fertilization may amplify climate change pressures on marine animal biomass for limited climate benefit.

Climate change scenarios suggest that large-scale carbon dioxide removal (CDR) will be required to maintain global warming below 2°C, leading to renewed attention on ocean iron fertilization (OIF). Previous OIF modelling has found that while carbon export increases, nutrient transport to lower latitude ecosystems declines, resulting in a modest impact on atmospheric CO2 . However, the interaction of these CDR responses with ongoing climate change is unknown. Here, we combine global ocean biogeochemistry and ecosystem models to show that, while stimulating carbon sequestration, OIF may amplify climate-induced declines in tropical ocean productivity and ecosystem biomass under a high-emission scenario, with very limited potential atmospheric CO2 drawdown. The 'biogeochemical fingerprint' of climate change, that leads to depletion of upper ocean major nutrients due to upper ocean stratification, is reinforced by OIF due to greater major nutrient consumption. Our simulations show that reductions in upper trophic level animal biomass in tropical regions due to climate change would be exacerbated by OIF within ~20 years, especially in coastal exclusive economic zones (EEZs), with potential implications for fisheries that underpin the livelihoods and economies of coastal communities. Any fertilization-based CDR should therefore consider its interaction with ongoing climate-driven changes and the ensuing ecosystem impacts in national EEZs.

The role of water mass advection in staging of the Southern Ocean Salpa thompsoni populations.

Salpa thompsoni is an important grazer in the Southern Ocean. Their abundance in the western Antarctic Peninsula is highly variable, varying by up to 5000-fold inter-annually. Here, we use a particle-tracking model to simulate the potential dispersal of salp populations from a source location in the Antarctic Circumpolar Current (ACC) to the Palmer Long Term Ecological Research (PAL LTER) study area. Tracking simulations are run from 1998 to 2015, and compared against both a stationary salp population model simulated at the PAL LTER study area and observations from the PAL LTER program. The tracking simulation was able to recreate closely the long-term trend and the higher abundances at the slope stations. The higher abundances observed at slope stations are likely due to the advection of salp populations from a source location in the ACC, highlighting the significant role of water mass circulation in the distribution and abundance of Southern Ocean salp populations.

Large-scale connectivity of the sandy beach clam Mesodesma mactroides along the Atlantic coast of South America, and climate change implications.

The yellow clam Mesodesma mactroides is a cool-water species that typifies sandy beaches of the Southwestern Atlantic Ocean (SAO), which embraces one of the strongest ocean warming hotspots. The region is influenced by the Rio de la Plata (RdlP), which represents a zoogeographic barrier that restricts its larval exchange. We investigated yellow clam larval connectivity patterns using an individual based model (IBM). The IBM combined outputs from a 3D hydrodynamic model with a clam submodel that considered salinity- and temperature-dependent mortality for the planktonic larvae. Connectivity across the RdlP estuary occurred only for larvae released in spring during a strong La Niña event. Mortality due to freshwater precluded larval transport across the RdlP, whereas larval mortality induced by warmer waters reduced connectivity, leading to self-recruitment in most areas. Warming acceleration in this hotspot could further restrict larval connectivity between populations in the SAO, with conservation implications for this threatened species.

Next-generation ensemble projections reveal higher climate risks for marine ecosystems.

Projections of climate change impacts on marine ecosystems have revealed long-term declines in global marine animal biomass and unevenly distributed impacts on fisheries. Here we apply an enhanced suite of global marine ecosystem models from the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish-MIP), forced by new-generation Earth system model outputs from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), to provide insights into how projected climate change will affect future ocean ecosystems. Compared with the previous generation CMIP5-forced Fish-MIP ensemble, the new ensemble ecosystem simulations show a greater decline in mean global ocean animal biomass under both strong-mitigation and high-emissions scenarios due to elevated warming, despite greater uncertainty in net primary production in the high-emissions scenario. Regional shifts in the direction of biomass changes highlight the continued and urgent need to reduce uncertainty in the projected responses of marine ecosystems to climate change to help support adaptation planning.

Influence of Polymorphism on the Magnetic Properties of Co5TeO8 Spinel.

This study presents the influence of polymorphism on the magnetic properties of Co5TeO8. This compound with a spinel-like structure [Co2]A[Co3Te]BO8 was synthesized into two polymorphs: one disordered within a cubic Fd3̅m structure, where Co2+ and Te6+ ions are randomly distributed on the octahedral B sites [the disordered polymorph can also be presented as an inverse spinel of the formula Co(Co1.5Te0.5)O4] and the other ordered with a cubic P4332 structure where Co2+ and Te6+ ions are ordered on the B sites. The macroscopic magnetic measurements showed that both polymorphs present a ferrimagnetic ordering, below ∼40 K, and a second transition is also observed at 27 K for the ordered polymorph. Neutron powder diffraction data between room temperature and 1.7 K showed as well the presence of short-range magnetic ordered clusters, which appears for both polymorphs below 200 K. At lower temperature, these short-range orders are transformed into long-range ferrimagnetic orders. Below TC = 40 K, the colinear ferrimagnetic structure of the disordered polymorph is described with the I41/am'd' space group. The ordered polymorph undergoes an incommensurate ferrimagnetic spiral spin ordering below TC1 = 45 K, followed by a second magnetic phase transition at TC2 = 27 K. This last transition is associated with the emergence of an additional ferrimagnetic component and an abrupt change in the magnitude of the magnetic propagation vector k = [0, 0, γ] from γ = 0.086 at T = 30 K to γ ≈ 0.14 in the range between 27 and 1.7 K. The magnetic symmetry of the ordered polymorph is described with the P43(00γ)0 magnetic superspace group. We evidenced that the ordering of Co2+/Te6+ on the B sites changes all of the Co-Co and Co-O distances and thus all JAB, JAA, and JBB exchange interactions, between the A and B sites, which are able to stabilize the incommensurate spin modulation in the ordered polymorph.

Synthesis of Discrete CHA Zeolite Nanocrystals without Organic Templates for Selective CO2 Capture.

Small-pore zeolites such as chabazite (CHA) are excellent candidates for the selective separation of CO2 ; however, the current synthesis involves several steps and the use of organic structure-directing agent (OSDA), increasing their cost and energy requirements. We report the synthesis of small-pore zeolite crystals (aluminosilicate) with CHA-type framework structure by direct synthesis in a colloidal suspension containing a mixture of inorganic cations only (Na+ , K+ , and Cs+ ). The location of CO2 molecules in the host structure was revealed by 3D electron diffraction (3D ED). The high sorption capacity for CO2 (3.8 mmol g-1 at 121 kPa), structural stability and regenerability of the discreate CHA zeolite nanocrystals is maintained for 10 consecutive cycles without any visible degradation. The CHA zeolite (Si:Al=2) reaches an almost perfect CO2 storage capacity (8 CO2 per unit cell) and high selectivity (no CH4 was adsorbed).

An iron cycle cascade governs the response of equatorial Pacific ecosystems to climate change.

Earth System Models project that global climate change will reduce ocean net primary production (NPP), upper trophic level biota biomass and potential fisheries catches in the future, especially in the eastern equatorial Pacific. However, projections from Earth System Models are undermined by poorly constrained assumptions regarding the biological cycling of iron, which is the main limiting resource for NPP over large parts of the ocean. In this study, we show that the climate change trends in NPP and the biomass of upper trophic levels are strongly affected by modifying assumptions associated with phytoplankton iron uptake. Using a suite of model experiments, we find 21st century climate change impacts on regional NPP range from -12.3% to +2.4% under a high emissions climate change scenario. This wide range arises from variations in the efficiency of iron retention in the upper ocean in the eastern equatorial Pacific across different scenarios of biological iron uptake, which affect the strength of regional iron limitation. Those scenarios where nitrogen limitation replaced iron limitation showed the largest projected NPP declines, while those where iron limitation was more resilient displayed little future change. All model scenarios have similar skill in reproducing past inter-annual variations in regional ocean NPP, largely due to limited change in the historical period. Ultimately, projections of end of century upper trophic level biomass change are altered by 50%-80% across all plausible scenarios. Overall, we find that uncertainties in the biological iron cycle cascade through open ocean pelagic ecosystems, from plankton to fish, affecting their evolution under climate change. This highlights additional challenges to developing effective conservation and fisheries management policies under climate change.

Modeling larval dispersal for the gilthead seabream in the northwestern Mediterranean Sea.

To investigate dispersal and connectivity between spawning and lagoon nursery habitats of the gilthead seabream, Sparus aurata, in the Gulf of Lions (northwestern Mediterranean Sea), we modeled the potential transport of the species' larvae between its supposed main spawning site in the region (the Planier Island) and two of its main local nursery areas (the coastal lagoons of Thau and Salses-Leucate). Passive larval drift simulations using a dispersal biophysical model showed a large variability in the possible trajectories from spawning to nursery areas and in the predicted ages for larvae arrival on the two nursery sites. The most common ages at arrival obtained in the simulations (20-60 days) are broadly consistent with previous modeling studies but contrast with the actual ages of the S. aurata post-larvae collected in 2016 and 2017 at time of the lagoon entrances (60-90 days, from otolith readings). The period between 25 and 70 days being critical for gilthead seabream larvae to acquire sufficient swimming, osmoregulatory, and olfactory abilities to enter coastal lagoons, we argue that ontogenic development plays a crucial role in the transport and local retention of S. aurata larvae in the studied region, explaining the discrepancy between simulation results and observed data.

Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change.

While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends.

Direct Evidence for Single Molybdenum Atoms Incorporated in the Framework of MFI Zeolite Nanocrystals.

Direct evidence of the successful incorporation of atomically dispersed molybdenum (Mo) atoms into the framework of nanosized MFI zeolite is demonstrated for the first time. Homogeneous distribution of Mo with a size of 0.05 nm is observed by scanning transmission electron microscopy high-angle annular dark-field imaging (STEM-HAADF). 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) and Fourier-transform infrared (FT-IR) spectroscopy, using trimethylphosphine oxide (TMPO) and deuterated acetonitrile as probe molecules, reveal a homogeneous distribution of Mo in the framework of MFI nanozeolite, and the presence of Lewis acidity. 31P MAS NMR using TMPO shows probe molecules interacting with isolated Mo atoms in the framework, and physisorbed probe molecules in the zeolite channels. Moreover, 2D 31P-31P MAS radio frequency-driven recoupling NMR indicates the presence of one type of Mo species in different crystallographic positions in the MFI framework. The substitution of framework Si by Mo significantly reduces the silanol defect content, making the resulting zeolite highly hydrophobic. In addition, the insertion of Mo into the MFI structure induces a symmetry lowering, from orthorhombic ( Pnma), typical of high silica MFI, to monoclinic ( P21/ n), as well as an expansion of unit cell volume. The novel material opens many opportunities of catalysts design for application in mature and emerging fields.

Uniform Generation of Sub-nanometer Silver Clusters in Zeolite Cages Exhibiting High Photocatalytic Activity under Visible Light.

Sub-nanometer silver clusters that exhibit discrete electronic structure with molecular-like properties are highly desirable in various technologies. However, the methods for their preparation suffer from limitations related with the reproducibility and particles uniformity and/or the possibility of the scale-up. Another critical drawback is that free sub-nanometer silver clusters tend to aggregate into larger particles. In this work, a new approach that successfully overcomes the above limitations is developed. It allows, for the first time, an ultrafast preparation of sub-nanometer silver particles with high abundance, uniformity (7 Å), and stability into the cages of nanosized zeolite crystals. The new method consists of UV excitation of a water suspension of nanozeolite containing photoactive vanadate clusters in the presence of ethanol (as an electron donor) and silver precursor. The characteristic features of sub-nanometer silver particles are presented, and the mechanism of their formation is discussed. Sub-nanometer Ag clusters exhibit exceptional photocatalytic activity and selectivity in the reforming of formic acid to H2 and CO2 under visible light.

Stairlike Aurivillius Phases in the Pseudobinary Bi5Nb3O15-ABi2Nb2O9 (A = Ba and Sr) System: A Comprehensive Analysis Using Superspace Group Formalism.

We report the possibility of extending the so-called stairlike Aurivilius phases in the pseudobinary Bi5Nb3O15-ABi2Nb2O9 (A = Ba and Sr) over a wide range of compositions. These phases are characterized by a discontinuous stacking of [Bi2O2] slabs and perovskite blocks, leading to long-period intergrowths stabilized as a single phase. When analyses from precession electron diffraction tomography and X-ray and neutron powder diffraction are combined, the monoclinic incommensurately modulated structure with q = αa* + γc* previously proposed for the ABi7Nb5O24 composition could be generalized to the Bi5Nb3O15-ABi2Nb2O9 (A = Ba and Sr) compounds. Considering the compositions expressed as (A,Bi)1- xNb xO3-3 x, the stacking sequence associated with compositions ranging from x = 2/5 to 3/8 is governed by the component γ of the modulation vector and can be predicted following a Farey tree hierarchy independently to the A cation. The length of the steps, characteristic of the stairlike nature, is controlled by the α component and depends on the substitution ratio A/Bi and the nature of A (A = Ba and Sr). This study highlights the compositional flexibility of stairlike Aurivillius phases.

Mn2TeO6: a Distorted Inverse Trirutile Structure.

Inverse trirutile Mn2TeO6 was investigated using in situ neutron and X-ray powder diffraction between 700 °C and room temperature. When the temperature was decreased, a structural phase transition was observed around 400 °C, from a tetragonal (P42/mnm) to a monoclinic phase (P21/c), involving a doubling of the cell parameter along b. This complex monoclinic structure has been solved by combining electron, neutron, and synchrotron powder diffraction techniques at room temperature. It can be described as a distorted superstructure of the inverse trirutile structure, in which compressed and elongated MnO6 octahedra alternate with more regular TeO6 octahedra, forming a herringbone-like pattern. Rietveld refinements, carried out with symmetry-adapted modes, show that the structural transition, arguably of Jahn-Teller origin, is driven by a single primary mode.

A new ß-CdTeO3 polymorph with a structure related to α-CdTeO3.

A new ß-CdTeO3 polymorph was obtained by hydrothermal synthesis and its structure was solved ab initio from powder X-ray diffraction data. It appears that the structure of ß-CdTeO3 (Pnma, Z = 16, a = 7.45850(3) Å, b = 14.52185(6) Å, c = 11.04584(5) Å) is closely related to that of α-CdTeO3 (P21/c, Z = 8, a = 7.790(1) Å, b = 11.253(2) Å, c = 7.418(1) Å, ß = 113.5(1)°) previously reported. The 3D framework of ß-CdTeO3 is built of both [CdO6] distorted octahedra and [CdO7] mono-capped trigonal prisms and three different tellurium polyhedra: trigonal pyramids [TeIVO3E] and trigonal bipyramids [TeIVO4E] and [TeIVO3+1E] (E denotes the lone pair of TeIV). The electronic structure calculations based on density functional theory methods show that at the ground state α-CdTeO3 is slightly more stable than ß-CdTeO3 with an energy difference of 4.64 kJ mol-1. The band structures confirm the results of optical UV-Vis spectroscopy measurements: both polymorphs are wide bandgap semiconductors with Eg = 3.55 eV for ß-CdTeO3 and Eg = 3.91 eV for α-CdTeO3. The DOS calculations for both polymorphs enable one to understand that the presence of the [TeIVO4E] polyhedra in ß-CdTeO3 (absent in α-CdTeO3) lowers its bandgap. Above 540 °C ß-CdTeO3 transforms into α-CdTeO3 in a first order phase transition.

Unusual Relaxor Ferroelectric Behavior in Stairlike Aurivillius Phases.

New ferroelectric layered materials were found in the pseudobinary system Bi5Nb3O15-ABi2Nb2O9 (A= Ba, Sr and Pb). Preliminary observations made by transmission electron microscopy indicate that these compounds exhibit a complex incommensurately modulated structure. A (3 + 1)D structural model is obtained using ab initio phasing by charge flipping based on the analysis of precession electron diffraction tomography data. The (3 + 1)D structure is further validated by a refinement against neutron powder diffraction. These materials possess a layered structure with discontinuous [Bi2O2] slabs and perovskite blocks. While these structural units are characteristics of Aurivillius phases, the existence of periodic crystallographic shear planes offers strong similarities with collapsed or stairlike structures known in high-Tc superconductors and related compounds. Using dielectric spectroscopy, we study the phase transitions of these new layered materials. For A = Ba and Sr, a Vögel-Fulcher-like behavior characteristic of the so-called relaxor ferroelectrics is observed and compared to "canonical" relaxors. For A = Sr, the absence of a Burns temperature separated from the freezing temperature appears as a rather unusual behavior.

Hydrothermal Synthesis and Dehydration of CaTeO3(H2O): An Original Route to Generate New CaTeO3 Polymorphs.

CaTeO3(H2O) was obtained from microwave-assisted hydrothermal synthesis as a polycrystalline sample material. The dehydration reaction was followed by thermal analysis (thermogravimetric/differential scanning calorimetry) and temperature-dependent powder X-ray diffraction and leads to a new δ-CaTeO3 polymorph. The crystal structures of CaTeO3(H2O) and δ-CaTeO3 were solved ab initio from PXRD data. CaTeO3(H2O) is non-centrosymmetric: P21cn; Z = 8; a = 14.785 49(4) Å; b = 6.791 94(3) Å; c = 8.062 62(3) Å. This layered structure is related to the ones of MTeO3(H2O) (M = Sr, Ba) with layers built of edge-sharing [CaO6(H2O)] polyhedra and are capped of each side by [Te(IV)O3E] units. Adjacent layers are stacked along the a-axis and are held together by H-bonds via the water molecules. The dehydration reaction starts above 120 °C. The transformation of CaTeO3(H2O) into δ-CaTeO3 (P21ca; Z = 8; a = 13.3647(6) Å; b = 6.5330(3) Å; c = 8.1896(3) Å) results from topotactic process with layer condensation along the a-axis and the 1/2b⃗ translation of intermediate layers. Thus, δ-CaTeO3 stays non-centrosymmetric. The characteristic layers of CaTeO3(H2O) are also maintained in δ-CaTeO3 but held together via van der Waals bonds instead of H-bonds through water molecules. Electron localization function and dipole moment calculations were also performed. For both structures and over each unit cell, the dipole moments are aligned antiparallel with net dipole moments of 3.94 and 0.47 D for CaTeO3(H2O) and δ-CaTeO3, respectively. The temperature-resolved second harmonic generation (TR-SHG) measurements, between 30 and 400 °C, show the decreasing of the SHG intensity response from 0.39 to 0.06 × quartz for CaTeO3(H2O) and δ-CaTeO3, respectively.

Precession electron diffraction tomography for solving complex modulated structures: the case of Bi5Nb3O15.

The crystal structure of the 1D incommensurately modulated phase Bi5Nb3O15 [superspace group X2mb(0b0)000, a = 5.46781(7) Å, b = 5.47381(8) Å, c = 41.9005(5) Å, and q = 0.17588(8)b*] is solved by electron diffraction using a tomography technique combined with precession of the electron beam. The (3 + 1)D structure is further validated by a refinement against powder X-ray diffraction (PXRD). A coherent picture of the true nature of this compound is obtained, conciliating experimental observations made by different groups using transmission electron microscopy and PXRD. Bi5Nb3O15 does not have a mixed-layer Aurivillius-type structure but does contain structural elements, [Bi2O2](2+) slabs, and perovskite-like blocks, characteristic of Aurivillius phases. The presence of aperiodic crystallographic shear planes (CSPs) along the modulated direction b leads to the formation of an original layered structure containing both continuous and discontinuous [Bi2O2](2+) and perovskite-like octahedral layers. Between CSPs, the stacking of these two structural elements exhibits an unprecedented nonuniform sequence referring to Aurivillius phases.

Structural study of hydrated/dehydrated manganese thiophene-2,5-diphosphonate metal organic frameworks, Mn2(O3P-C4H2S-PO3)·2H2O.

Synthesis of thiophene-2,5-diphosphonic acid 2 is reported, and its use for synthesis of the original pristine materials Mn(2)(O(3)P-C(4)H(2)S-PO(3))·2H(2)O 3 is reported. The structure of material 3 has been fully resolved from single-crystal X-ray diffraction. Mn(2)(O(3)P-C(4)H(2)S-PO(3))·2H(2)O 3 crystallizes in a monoclinic cell (space group P2) with the following parameters: a = 11.60(1) Å, b = 4.943(5) Å, c = 19.614(13) Å, ß = 107.22°. A noticeable feature of the structure of compound 3 is the orientation of the thiophene heterocycles that adopt two different orientations in two successive layers (along c). Thermal analysis of compound 3 indicates that the water molecules are easily removed from 160 to 230 °C while the dehydrated structure is stable up to 500 °C. The dehydrated compound obtained from 3 can be rehydrated to give the polymorphic compound Mn(2)(O(3)P-C(4)H(2)S-PO(3))·2H(2)O 4, which crystallizes in an orthorhombic cell (space group Pnam) with the following parameters: a = 7.5359(3) Å, b = 7.5524(3) Å, c = 18.3050(9) Å. The main difference between the structures of 3 and 4 arises from both the orientation of the thiophene rings (herringbone-type organization in 4) and the structure of the inorganic layers. The thiophene-2,5-diphosphonic acid moieties engaged in materials 3 and 4 adopt a different orientation likely due to rotation around the P-C bonds and via the dehydrated state 5, which is likely more flexible than the hydrated states. Study of the magnetic properties performed on compound 3 and 4 and on the dehydrated compounds Mn(2)(O(3)P-C(4)H(2)S-PO(3)) 5 complemented by the structural study has permitted us to characterize the antiferromagnetic ground state of sample 3, a weak ferromagnetic component in sample 4, and complete paramagnetic behavior in sample 5.

The dehydration of SrTeO3(H2O)--a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase ε-SrTeO3.

Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO(3)(H(2)O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 °C for 30 min. A temperature of 220 °C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO(3)(H(2)O) was determined from single crystal X-ray diffraction data: P2(1)/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5) Å, ß = 107.210(1)°, V = 443.42(5) Å(3), 1403 structure factors, 63 parameters, R[F(2)>2σ(F(2))] = 0.0208, wR(F(2) all) = 0.0516, S = 1.031. SrTeO(3)(H(2)O) is isotypic with the homologous BaTeO(3)(H(2)O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO(6)(H(2)O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO(3)] units. The cohesion of the structure is accomplished by moderate O-H···O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO(3)(H(2)O) condensates above 150 °C to the metastable phase ε-SrTeO(3) and transforms upon further heating to δ-SrTeO(3). The crystal structure of ε-SrTeO(3), the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P2(1)/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2) Å, ß = 126.4980(7)°, V = 341.20(18) Å(3), R(Fobs) = 0.0166, R(Bobs) = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of ε-SrTeO(3) shows the same basic set-up as SrTeO(3)(H(2)O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO(3)(H(2)O) and ε-SrTeO(3) are complemented by thermal analysis and vibrational spectroscopic measurements.