https://hdl.handle.net/10481/30693 2026-04-13T20:16:22Z 2026-04-13T20:16:22Z Fassnacht, Steven R Herrero, Javier Sanow, Jessica E. https://hdl.handle.net/10481/111939 2026-03-06T12:02:37Z

Snow Surface Roughness at a Ski Resort During Melt Fassnacht, Steven R; Herrero, Javier; Sanow, Jessica E. Whensnowispresent, the snow surface is the interface between the atmosphere and the Earth’s surface. The snowpack energybalance is dictated in part by snowsurfaceroughness, which can be quite dynamic. At the Sierra Nevada ski resort in Spain, we measured several snow surface forms: natural, with the presence of dust, with the presence of sun cups, and groomed snow (tracked and between tracks). The snow surface was assessed in 2-dimensions from snow roughness boards and in 3-dimensions from iPad surface scanning to measure across resolutions. Both data collection methods yielded similar roughness estimates via random roughness (RR) and variogram analysis (scale break, SB, and fractal dimension, D) for each distinct surface, yet the roughness differences between the surfaces were substantial. The geometry-based aerodynamic roughness length (z0) was computed for the iPad-scanned surfaces, yielding an order-of-magnitude variability in z0. This produced an order-of-magnitude difference in modelled sublimation. This work can inform snow management at ski areas and reflects some of the snow-surface conditions encountered in a natural snowpack.

Vilmi, Annika Picazo Mota, Félix https://hdl.handle.net/10481/111697 2026-02-27T17:35:32Z

Dispersal–niche continuum index: a new quantitative metric for assessing the relative importance of dispersal versus niche processes in community assembly Vilmi, Annika; Picazo Mota, Félix Patterns in community composition are scale-dependent and generally difficult to distinguish. Therefore, quantifying the main assembly processes in various systems and across different datasets has remained challenging. Building on the PER-SIMPER method, we propose a new metric, the dispersal–niche continuum index (DNCI), which estimates whether dispersal or niche processes dominate community assembly and facilitates the comparisons of processes among datasets. The DNCI was tested for robustness using simulations and applied to observational datasets comprising organis- mal groups with different trophic level and dispersal potential. Based on the robustness tests, the DNCI discriminated the respective contribution of niche and dispersal pro- cesses in pairwise comparisons of site groups with less than 40% and 30% differences in their taxa and site numbers, respectively. In the observational datasets, the DNCI suggested that dispersal rather than niche assembly was the dominant assembly pro- cess which, however, varied in intensity among organismal groups and study contexts, including spatial scale and ecosystem types. The proposed DNCI measures the relative strength of community assembly processes in a way that is simple, easily quantifiable and comparable across datasets. We discuss the strengths and weaknesses of the DNCI and provide perspectives for future research.

Paparazzo, F. E. Crespi-Abril, A. C. Gonçalves, Rodrigo Javier Barbieri, E. S. Gracias Villalobos, L. L. Solís, M. E. Soria, G. https://hdl.handle.net/10481/111558 2026-02-26T08:30:36Z

Patagonian Dust as a Source of Macronutrients in the Southwest Atlantic Ocean Paparazzo, F. E.; Crespi-Abril, A. C.; Gonçalves, Rodrigo Javier; Barbieri, E. S.; Gracias Villalobos, L. L.; Solís, M. E.; Soria, G. The role of Patagonian wind-borne dust as a source of macronutrients to the surface waters of the Southwest Atlantic Ocean was evaluated for the first time. During spring 2016, a series of experiments with dust was conducted to evaluate the dynamics of macronutrient dissolution in seawater. The results showed a differential contribution of macronutrients to seawater depending on the dust source and the amount added. Addition of a conservative amount of Patagonian dust to the sea­water contributed nitrate (NO3−) and silicic acid (Si(OH)4), but not phosphate (PO43–). Additional dust input to the system resulted in higher macronutrient concentrations. Particles collected from a nearby burned field did not contribute any macronutrients to the seawater. Thus, each dust event may affect biological productivity differently, depending on the source of the particles. Dissolution experiments suggest that macronutrients from dust are available immediately after particle deposition on the sea surface. The study includes field measurements of macronutrient concentrations before and after a dust storm at three nearshore marine stations. The data are consistent with macronutrient increase after the storms. Dust storms could become a very important source of nutrients to the ocean in future global warming scenarios.

Durán-Romero, C. Villafañe, V. E. Valiñas, M. S. Gonçalves, Rodrigo Javier Helbling, E. W. https://hdl.handle.net/10481/111556 2026-02-26T08:29:46Z

Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification Durán-Romero, C.; Villafañe, V. E.; Valiñas, M. S.; Gonçalves, Rodrigo Javier; Helbling, E. W. The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll a fluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of the acclimation period. Mid-term effects (days) were evaluated as changes in taxonomic composition, growth rates and size structure of the community. Although the UVR-induced inhibition on ΦPSII decreased in both clusters, samples remained sensitive to UVR after the 5 days of acclimation. Also, under the future conditions, there was, in general, an increase in the phytoplankton carbon incorporation rates along the experiment as compared to the present conditions. Bacterioplankton sensitivity to UVR changed along the experiment from inhibition to enhancement of HBP, and future environmental conditions stimulated bacterial growth, probably due to indirect effects caused by phytoplankton. Those changes in the microbial loop functioning and structure under future global change conditions might have important consequences for the carbon pump and thus for the carbon sequestration and trophodynamics of Patagonian coastal waters.

Wang, Xinjie Feng, Xinqian Zhuang, Yang Lu, Jianghuan Wang, Yang Gonçalves, Rodrigo Javier Li, Xi Lou, Yongliang Guan, Wanchun https://hdl.handle.net/10481/111555 2026-02-26T08:28:25Z

Effects of ocean acidification and solar ultraviolet radiation on physiology and toxicity of dinoflagellate Karenia mikimotoi Wang, Xinjie; Feng, Xinqian; Zhuang, Yang; Lu, Jianghuan; Wang, Yang; Gonçalves, Rodrigo Javier; Li, Xi; Lou, Yongliang; Guan, Wanchun A batch culture experiment was conducted to study the interactive effects of ocean acidification (OA) and solar ultraviolet radiation (UVR, 280–400 nm) on the harmful dinoflagellate Karenia mikimotoi. Cells were incubated in 7-days trials under four treatments. Physiological (growth, pigments, UVabc) and toxicity (hemolytic activity and its toxicity to zebrafish embryos) response variables were measured in four treatments, representing two factorial combinations of CO2 (400 and 1000 μatm) and solar irradiance (with or without UVR). Toxic species K. mikimotoi showed sustained growth in all treatments, and there was not statistically significant difference among four treatments. Cell pigment content decreased, but UVabc and hemolytic activity increased in all HC treatments and PAB conditions. The toxicity to zebrafish embryos of K. mikimotoi was not significantly different among four treatments. All HC and UVR conditions and the combinations of HC*UVR (HC-PAB) positively affected the UVabc, hemolytic activity in comparison to the LC*P (LC-P) treatment, and negatively affected the pigments. Ocean acidification (OA) was probably the main factor that affected the chlorophyll-a (Chl-a) and UVabc, but UVR was the main factor that affected the carotenoid (Caro) and hemolytic activity. There were no significant interactive effects of OA*UVR on growth, toxicity to zebrafish embryos. If these results are extrapolated to the natural environment, it can be hypothesized that this strain (DP-C32) of K. mikimotoi cells have the efficient mechanisms to endure the combination of ocean acidification and solar UVR. It is assumed that this toxic strain could form harmful bloom and enlarge the threatening to coastal communities, marine animals, even human health under future conditions.