https://hdl.handle.net/10481/49199 2026-04-11T12:34:12Z https://hdl.handle.net/10481/106471 Understanding the influence of marine nutrients on insectivorous and herbivorous reptiles in the Gulf of California islands Barraza-Soltero, Ilse K.; Blázquez, M Carmen; Hernández-Vázquez, Salvador; Delgado Huertas, Antonio; Muro-Torres, Victor M. Marine subsidies in the extremely arid islands of the northern Gulf of California have been shown to be important enhancing primary productivity and fueling the terrestrial food webs. This effect has been proved in plants, insects, lizards and rodents. The aims of our study were first to determine whether insectivorous lizards from a wide array of islands, including some in the central and southern part of the Gulf, are consuming marine derived products, and secondly to assess its impact on herbivore lizards as well. We hypothesized that the availability and use of marine nutrients for lizards would vary depending on island aridity, island size, and the presence of seabird colonies nearby. To test the hypothesis, we analyzed the isotopic niches of 13 populations of insectivorous lizards (genus Uta) and 9 populations of herbivore iguanas (genera Dipsosarus, Ctenosaura, and Sauromalus) across 16 islands spanning 5 latitude degrees and 350 nautical miles. Our results showed that the proximity of seabird colonies play a key role in reinforcing the presence of marine origin nutrients in both insectivorous and herbivore populations. The ubiquity of seabird colonies on the northern islands combined with higher aridity in the northern part of the Gulf, creates a northward gradient in the importance of marine subsidies for both insectivorous and herbivore lizards, across the Gulf islands. δ13C variation in insectivorous lizards’ tissues was significantly correlated with island aridity/latitude, while the presence of significant seabird colonies nearby was significantly correlated with δ15N variation. The results were less clear in the herbivore group of species. Insectivorous and herbivorous share a large portion (70%) of their isotopic space. The incorporation of the highly enriched 15N to both type of lizards is happening for the two possible ways, the presence of guano, that may be driving plant fertilization, and the direct consumption of insects associated to the birds (or birds’ products, as eggs or corpses); but we could not differentiate between them. The size of the islands was not relevant in our results, possibly due to our sampling design. Additional isotopic analysis of plants and arthropods and in a gradient coast-inland could provide a more comprehensive view of the nutrient flow within these island ecosystems and the effect of the island size. https://hdl.handle.net/10481/106217 Comparing in situ and satellite-derived primary production estimates in the Canary Current upwelling region Hernández-Hernández, Nauzet; Santana-Falcon, Yeray; Montero, María F.; Benavides, Mar; Delgado-Huertas, Antonio; Álvarez-Salgado, Xosé A.; Land, Peter; Arístegui, Javier Satellite-based Net Primary Production (NPP) estimates are arguably the best way to improve our understanding of large-scale ocean productivity and to validate Earth System Models. Despite significant progress over recent decades, satellite-derived NPP estimates still suffer from large uncertainties, primarily due to the limited number of in situ primary production (PP) measurements available for their validation. In addition, the most widely used algorithms lead to different, sometimes even contradictory, results. Along with measurements of chlorophyll a concentration (Chla) and phytoplankton biomass (Cphyto), here we present in situ measurements of PP using 14C uptake and 13C isotope tracing, as well as O2 and 18O2 evolution inside incubation bottles, across the transition zone from the coastal Canary Eastern Boundary Upwelling System (CanEBUS) to the open ocean waters of the Cape Verde Frontal Zone (17–23◦N; 16–26◦W). We also calculate assimilation numbers (Pb opt) and growth rates (μ) from in situ measurements. First, we compared in situ PP estimates measured concurrently using the four abovementioned techniques. We then tested the performance of four widely-used models including the Vertically Generalized Production Model (VGPM) and its variant based on Eppley’s description of the growth function (Eppley), the Carbon-based Productivity Model (CbPM), and the Carbon, Absorption and Fluorescence Euphoticresolving model (CAFE), along with the satellite-derived input variables that feed these algorithms. We found that the Chla-based VGPM and Eppley models were significantly correlated with in situ estimates, regardless of the satellite source used as input data. As for models based on Cphyto, only the CbPM from the Visible Infrared Imaging Radiometer Suite (VIIRS) data demonstrated performance comparable to that of the Chla-based models. In all other cases, Cphyto-based models were uncorrelated with in situ PP estimates. Our results indicate that the bias associated with the VGPM and Eppley models is primarily due to the algorithms’ inability to accurately assess Popt b . Meanwhile, the retrieval of both satellite-derived Cphyto and μ leads to a poor estimate of NPP by the CbPM. Our findings suggest that enhancing the accuracy of NPP estimates derived from satellite-based models necessitates the refinement of the methodology employed in deriving the input data and their subsequent validation, rather than developing increasingly complex models. https://hdl.handle.net/10481/105212 Illitization of montmorillonite in ammonium solutions under hydrothermal conditions Bentabol, María; Lamarca-Irisarri, Daniel; Van Driessche, Alexander Edgard Suzanne; Ryan, Peter C.; Huertas, F. Javier In diagenetic solutions, ammonium may be incorporated into smectites as an exchangeable cation and become fixed within the interlayer space of illites and other white micas. To study the potential impact of NH4+ on the smectite-to-illite transformation reaction, a series of hydrothermal experiments were carried out at 100, 150 and 200 °C, spanning reaction duration from 15 to 90 days, and two NH4+ concentrations (0.1 and 0.2 M). The solids resulting from these alteration experiments were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and transmission and analytical electron microscopy (TEM and AEM). The XRD analysis revealed that, under the specified experimental conditions, smectite incorporates NH4+ in the structure, leading to the formation of non-swelling layers, resulting in partial transformation to illite layers and producing packets of disordered illite/smectite (I/S). In addition, a minor XRD peak at ∼10 Å suggests the formation of discrete illite crystals. The FTIR spectra demonstrated the uptake of NH4+, with deformation bands observed at 1400 and 1430 cm−1, corresponding to exchangeable NH4+ in smectite and fixed NH4+ in high-charge layers, respectively. TEM analysis revealed that smectite particles exhibited wavy stacks comprising a few layers with abundant defects and lateral discontinuities. The interlayer spacing in these particles ranged from 12 to 15 Å and became thinner and more plate-like with increasing temperature and time. Moreover, they contained inclusions of 10–10.3 Å layers, either as discrete layers or in packets of several layers, indicating the formation of disordered mixed-layer illite-smectite. Lateral transitions from 12 to 15 Å to 10 Å layers were frequently observed and interpreted as reaction fronts due to local rearrangement. At 150 and 200 °C, isolated packets of 10 Å layers were identified as discrete illite crystals that precipitated directly from solution. Analysis of the chemical composition of individual particles revealed an increase in octahedral charge (MgVI for AlVI substitution) in smectite particles, followed by increase in tetrahedral charge in I/S particles. Interlayer NH4+ played a stabilizing role in the high-charge layers and favored the smectite-to-illite conversion process. https://hdl.handle.net/10481/104627 Correlation between nanomechanical properties and microstructural design concepts of bivalve muscle attachment sites Hoerl, Sebastian; Micheletti, Chiara; Amini, Shahrouz; Griesshaber, Erika; Hess, Kai Uwe; Checa González, Antonio G.; Peharda, Melita; Schmahl, Wolfgang Wilhelm Bivalves populate various marine environments and follow diverse lifestyles: attaching to substrates, burrowing into sediments or swimming in water. Their shells play a crucial role in the survival of organisms as they shield the soft tissue from external attacks and facilitate their respective lifestyles. Valve movement is controlled by one or two adductor muscles and the hinge. While the function and structure of adductor muscles can vary, the shell-muscle attachment develops the myostracum, a unique microstructural design. Sectioned parallel and perpendicular to the inner shell surface, we investigated myostracal and non-myostracal microstructures, textures and nanomechanical properties for three bivalve species: The burrowing Glycymeris pilosa, the sessile Chama arcana and the swimming Placopecten magellanicus. Analyses were conducted using electron backscatter diffraction measurements, laser confocal and backscatter electron imaging, nanoindentation testing and thermogravimetric analysis. We find that the myostracal microstructure is generated mainly through physical determinants, regardless of the bivalve lifestyle and adductor muscle structure. If aragonitic, we show that adjacent shell layers are used as templates for the formation of the myostracal microstructure and highlight how bivalves use the adjacent crystal arrangement to predetermine myostracal microstructure up to inner shell surfaces. Furthermore, this study demonstrates how myostracal layers exceed the hardness of the non-myostracal valves and that of geological aragonite, irrespective of grain size and morphology. Due to the anisotropy of aragonite, we show that aragonite c-axis orientation notably affects the hardness of crystals. The highest hardness is measured when indentation is normal to the shell surface in aragonite c-axes direction. W. W. S., E. G., and S.H. were funded by the German Research Council Programmes GR 9/1234, SCHM 930/11-2. A. G. C. was funded by the project PID2020116660GB-I00 of the Spanish Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033/). A. G. C. acknowledges the Research Group RNM363 (CEICE, JA) and the Unidad Científica de Excelencia UCE-PP2016-05 (University of Granada). https://hdl.handle.net/10481/103975 Climate dynamics during the last 3000 years forced environmental and sedimentation changes in southern Spain: The Laguna Grande de Archidona record Jiménez Moreno, Gonzalo; García-Alix Daroca, Antonio; Gázquez, Fernando; Castillo-Baquera, Aurora; Martegani, Lucía; Rodríguez-Rodríguez, Miguel; Rodrigo Gámiz, Marta; Jiménez-Espejo, Francisco A geochemical, mineralogical, and sedimentological analysis of the sedimentary record from Laguna Grande de Archidona (LGA), a lake in southern Spain, produced a high-resolution climate and human activity record for the southwestern Mediterranean over the past three millennia. Lake level changes, organic matter, and gypsum intervals were primarily driven by precipitation and hydrological shifts. From 3300 to 2600 cal yr BP, dry conditions prevailed, particularly from 3050 to 2600 cal yr BP, coinciding with a regional drought tied to a positive North Atlantic Oscillation (NAO). The wettest period, from 2600 to 1400 cal yr BP during the Iberian Roman Humid Period (IRHP), was marked by increased groundwater and lake stratification due to negative NAO, which generated the precipitation of gypsum and manganese oxides. However, this relatively wetter period was interrupted by two arid events between 2300–2200 and 2150–2050 cal yr BP. A dry phase spanned the Dark Ages through the Medieval Climate Anomaly (MCA; 1400–700 cal yr BP), while the Little Ice Age (LIA) showed varied but generally wetter conditions, followed by an arid period from ∼1600–1850 CE. The Industrial Epoch (1850–1957 CE) also saw dryness, with late 20th-century changes attributed to modern climate impacts and irrigation practices. This study was supported by projects PID2021-125619OB-C21/C22 and PID2021-123980OA-I00 (GYPCLIMATE), funded by the Ministerio de Ciencia e Innovación of Spain, the Agencia Estatal de Investigación and the Fondo Europeo de Desarrollo Regional FEDER MCIN/AEI/10.13039/501100011033/FEDER, UE” and CGL2017-85415-R,; Junta de Andalucía I + D + i Junta de Andalucía 2020 Retos P-20-00059, UGR-FEDER B-RNM-144-UGR18, UGR-FEDER A-RNM-336-UGR20, Project cofinanced by FEDER and LifeWatch-Eric LifeWatch-2019-10-UGR-01 and the research group RNM-190 (Junta de Andalucía). Funding also came from "Red de investigación temática PALEONET (RED24-153734-T) financiada por la Agencia Estatal de Investigación del Ministerio de Ciencia, Innovación y Universidades". F.G acknowledges the Ramón y Cajal fellowship, RYC2020-029811-I de la Agencia Estatal de Investigación and the grant PPIT-UAL, Junta de Andalucía-FEDER 2022-2026 (RyC-PPI2021-01). L.M. was funded by the FPU21/06924 grant of the Ministerio de Educación y Formación Profesional of Spain.