Simple hydrological models, such as the Seasonal Water Yield Model developed by the Natural Capital Project (InVEST SWYM), are attractive as data requirements are relatively easy to satisfy. However, simple models may produce unrealistic results when the underlying hydrological processes are inadequately described. We used the variation in performance of the InVEST SWYM across watersheds to identify correlates of poorly modeled outcomes of InVEST SWYM. We grouped 749 watersheds from across North America into five bioclimatic regions using nine environmental variables. For each region, we compared the predicted flow patterns to actual flow conditions over a 15-year period. The correlation between the modeled and actual flows was highly dispersed and relatively poor, with 92% of r2 values less than 0.5 and 42% less than 0.1. We linked cryospheric variables to model performance in the bioclimatic region with the poorest model performance (the Low elevation Boreal Sub-humid region—LeBSh). After incorporating cryospheric conditions into the InVEST SWYM, predictions improved significantly in 30% of the LeBSh watersheds. We provide a relatively straightforward approach for identifying processes that simple hydrological models may not consider or which need further attention or refinement.

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Free fatty acids (FFAs) are non-competitive antagonists of the nicotinic acetylcholine receptor (AChR). Their site of action is supposedly located at the lipid-AChR interface. To elucidate the mechanism involved in this antagonism, we studied the effect that FFAs with a single double-bond at different positions (ω6, ω9, ω11 and ω13 cis-18:1) have on different AChR properties. Electrophysiological studies showed that only two FFAs (ω6 and ω9) reduced the duration of the channel open-state. The briefest component of the closed-time distribution remained unaltered, suggesting that ω6 and ω9 behave as allosteric blockers. Fluorescence resonance energy transfer studies indicated that all FFAs locate at the lipid-AChR interface, ω6 being restricted to annular sites and all others occupying non-annular sites. The perturbation of the native membrane order by FFAs was evaluated by DPH (1,6-diphenyl-1,3,5-hexatriene) and Laurdan fluorescence polarization studies, with the greatest decrease observed for ω9 and ω11. AChR conformational changes produced by FFAs present at the lipid bilayer were evaluated by fluorescence quenching studies of pyrene-labeled AChR and also using the AChR conformational-sensitive probe crystal violet. All cis-FFAs produced AChR conformational changes at the transmembrane level, but only ω9, ω11 and ω13 perturbed the resting state. Thus, the position and isomerism of the torsion angle of unsaturated FFAs are probably a key factor in terms of AChR blockage, suggesting that FFAs with a unique cis double bond at a superficial position inside the membrane directly inhibit AChR function by perturbing a potential conserved core structure for AChR gating at that level.

Studies based on continuous monitoring of diel changes in dissolved oxygen concentration allow the estimation of ecosystem metabolism and provide a measure of the overall trophic processes of an ecosystem. In this study, net ecosystem production (NEP), community/ecosystem respiration (R), and gross primary production (GPP) rates were estimated in relation to physicochemical and climatic variables for 18 months in La Salada, a saline shallow lake. Net autotrophic conditions prevailed during the study period (NEP: 64.05 ± 44.22 mmol O 2 m -2 day -1 ). GPP and R were positively correlated and were synchronized on a daily timescale, with GPP typically greater than R. Principal component analysis revealed that monthly rates of GPP, R, and NEP responded, as expected, to temperature and light seasonal patterns. Water level and conductivity fluctuations, because of evapoconcentration and water management, were relevant as a driver of the physicochemical and biological characteristics of the lake. In saline lakes as La Salada, an adequate management of water resources will be relevant to maintain the ecosystem equilibrium and the quality of its resources.

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Watershed land use affects nutrient and sediment export, particularly through streambank erosion, which can add to P export and contribute to eutrophication in downstream waterbodies. We characterized P of soils from four different land uses (32 sites) along streams in the Missisquoi River basin (Vermont, USA)—silage corn (Zea mays L.), hay meadow, emergent wetlands, and forest—and their corresponding streambanks. We measured total P (TP), pH 4.8 NH4–acetate P, degree of P saturation (DPS), and soluble P. The latter three measurements were used as predictors of potential P bioavailability. Forest soils were relatively low in TP, whereas soils in corn, hay, and wetland were elevated (>1000 mg kg−1). With the exception of forests, the TP of the corresponding streambanks of each land use was statistically significantly lower than in the interior of the land use, while still higher than those in forests, suggesting a possible influence of land use on its adjacent streambank. The pH 4.8 NH4–acetate P was low in nonagricultural land uses and all streambanks of different land uses, but higher than optimum for soils in cornfields and hayfields. The DPS averaged 36% in the cornfields, but <21% in all of the streambanks. Mean soluble P was 0.14 mg kg−1 for corn‐ and hay‐associated streambanks with a DPS <10% but was as high as 3.2 mg kg−1 in the agricultural fields. The combination of low bioavailable P measurements indicates that most streambank soils are likely low contributors to P enrichment downstream. However, the elevated TP in some agricultural streambank soils suggests an accumulation of legacy P. Core Ideas Soil P concentrations varied widely among four watershed land uses. Agriculture and wetland streambank soils had less P than adjacent land uses. Streambank soils from the four different land uses had low P release potential.

An evaporitic environment is characterized by having high salinity, climatic, and hydrological factors that promote a negative water balance; however, biological factors may also influence their development. Modern coastal flat Paso Seco (40°33′S; 62°14′W) is located in a semi-arid region with low precipitation and dry winds coming mainly from the NW. The site is an old tidal channel, which nowadays behaves like a shallow coastal saline-like basin, separated from the sea by a sand barrier, which the sea periodically overcomes, flooding the flat with eventual water evaporation. Microbial mats of up to 1 cm thick colonize the sandy sediments of this evaporitic environment. Water samples were taken during five field trips (2017-2018) from interstitial water of the flat, a tidal creek that crosses the flat, and two shallow tidal depressions (TDs) within the flat with different degrees of evaporation. In comparison to the sea, the maximum salinity values measured in Austral spring (September 2017) in the tidal creek were doubled, tripled in interstitial water, and 5.9 to 8 times higher in TDs. Ionic concentration denotes that evaporite chemical divides are followed as water evaporates, corresponding to the presence of CaCO 3 , gypsum and halite found in TDs. On-site permeability of microbial mat-covered surfaces presented semi-pervious properties. Microbial mat presence is condition for CaCO 3 , gypsum, and halite precipitation as they allow for water retention and its consequent evaporation due to the impermeability they confer to the sedimentary surface. Thus, microbial mats are a biological factor affecting the development of an evaporitic environment.

Land use can significantly alter soil P forms, which will influence P loss in runoff. Organic P (P o ) compounds are an important component of soil P, but their forms and cycling in soils with different land uses are still poorly understood. In addition, streambanks are potential sources of P loss; P forms and concentrations in streambank soils may vary with land use, affecting potential P loss to water. This study used solution 31 P nuclear magnetic resonance spectroscopy to characterize and quantify P in interior and streambank soils (0-10 cm) under duplicate sites from four different land uses along streams in the Missisquoi River basin (VT, USA): silage corn, hay meadow, emergent wetlands, and forest. Orthophosphate monoesters were the dominant P compound class regardless of land use or landscape position. Forest soils had the lowest P o concentrations, less labile P forms than other soils, and significantly lower concentrations of total inositol hexakisphosphates and total orthophosphate monoesters compared with corn soils. Riparian buffer zones for agricultural soils lowered P concentrations in streambank soils for many soil P pools relative to interior soils. The wetland soils of this study had P concentrations and P forms that were similar to those for interior agricultural soils and generally showed no reduction in P concentrations in streambank soils relative to interior soils. This is consistent with the role of wetlands as P sinks in the landscape but also suggests these wetlands should be carefully monitored to minimize P accumulation, especially in streambank soils.Abbreviations: BMP, best management practice; DPS, degree of phosphorus saturation; FW, floodwater; IHP, inositol hexaphosphate; M/D ratio, ratio of orthophosphate monoesters to orthophosphate diesters (corrected for degradation); MRP, molybdate-reactive phosphorus; NETP, total P in NaOH-EDTA extracts; P i , inorganic phosphorus; P-NMR, solution 31 P nuclear magnetic resonance spectroscopy; P o , organic phosphorus; TP, total phosphorus; TP o , total organic phosphorus.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.