Seabirds drastically transform the environmental conditions of the sites where they establish their breeding colonies via soil, sediment, and water eutrophication (hereafter termed ornitheutrophication). Here, we report worldwide amounts of total nitrogen (N) and total phosphorus (P) excreted by seabirds using an inventory of global seabird populations applied to a bioenergetics model. We estimate these fluxes to be 591 Gg N y−1 and 99 Gg P y−1, respectively, with the Antarctic and Southern coasts receiving the highest N and P inputs. We show that these inputs are of similar magnitude to others considered in global N and P cycles, with concentrations per unit of surface area in seabird colonies among the highest measured on the Earth’s surface. Finally, an important fraction of the total excreted N (72.5 Gg y−1) and P (21.8 Gg y−1) can be readily solubilized, increasing their short-term bioavailability in continental and coastal waters located near the seabird colonies.

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The determination of optical properties of organic matter using spectroscopic techniques is a powerful tool for the characterization of humic substances (HS) in soils and sediments because of sensitivity, specificity and sample throughput. However, basic spectroscopic techniques have practical limitations because of the similarity in the optical properties of many HS. To improve resolution, the combination of excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) was applied for characterizing fulvic acid (FA) and humic acid (HA) fractions from soils and sediments of two estuarine environments in Spain. Five fluorescent components were identified by EEM-PARA-FAC and were found in both FA and HA fractions, consistent with the new paradigm of HS as supramolecular associations as well as the ubiquity of the HS components in the environment. Their contribution was, however, different between the FA and HA fractions. Two different, humic-like, fluorescent components were representative of FA and HA fractions, respectively. The spectral characteristics of these components were similar to previously reported PARAFAC components in dissolved organic matter (DOM) in a wide range of environments, suggesting their applicability in assessing OM quality and environmental dynamics. A microbial humic-like component was much more abundant in FA than in HA fractions. Furthermore, principal component analysis clarified that the two identified protein-like components, were enriched in sediment HA compared to soil HA, suggesting a larger contribution of refractory algaenan in sediment HA. The results of the present study demonstrate that EEM-PARAFAC is a useful technique for the biogeochemical characterization of soil and sedimentary HS.

Wildfires frequently threaten water quality through the transfer of eroded ash and soil into rivers and reservoirs. The ability to anticipate risks for water resources from wildfires is fundamental for implementing effective fire preparedness plans and post-fire mitigation measures. Here we present a new approach that allows quantifying the amount and characteristics of ash generated under different wildfire severities and its respective water contamination potential. This approach is applied to a wildfire in an Australian dry sclerophyll eucalypt forest, but can be adapted for use in other environments. The Balmoral fire of October 2013 affected 12,694 ha of Sydney's forested water supply catchment. It produced substantial ash loads that increased with fire severity, with 6, 16 and 34 Mg ha(-1) found in areas affected by low, high and extreme fire severity, respectively. Ash bulk density was also positively related to fire severity. The increase with fire severity in the total load and bulk density of the ash generated is mainly attributed to a combination of associated increases in (i) total amount of fuel affected by fire and (ii) contribution of charred mineral soil to the ash layer. Total concentrations of pollutants and nutrients in ash were mostly unrelated to fire severity and relatively low compared to values reported for wildfire ash in other environments (e.g. 4.0-7.3mg As kg(-1); 2.3-4.1 B mg kg(-1); 136-154 P mg kg(-1)). Solubility of the elements analysed was also low, less than 10% of the total concentration for all elements except for B (6-14%) and Na (30-50%). This could be related to a partial loss of soluble components by leaching and/or wind erosion before the ash sampling (10 weeks after the fire and before major ash mobilisation by water erosion). Even with their relatively low concentrations of potential pollutants, the substantial total ash loads found here represent a water contamination risk if transported into the hydrological network during severe erosion events. For example, up to 4 Mg of ash-derived P could be delivered into a single water supply reservoir.