Contribution of occult precipitation to the water balance of páramo ecosystems in the Colombian Andes

Páramos are high‐altitudinal neotropical ecosystems located in the upper regions of the northern Andes. Their hydrology is characterized by an extraordinarily high run‐off ratio. One major contributing mechanism is thought to be fog occurrence, which is common in the páramos and occurs by the cooling of near‐surface moist air, as it is forced to higher elevations by topography. However, field‐based observations and quantification of this flux are rare. We present results of monitoring of occult precipitation, understood as the combination of fog and drizzle inputs, combined with meteorological and soil moisture monitoring for periods between 7 to 17 months in 6 sites distributed over 3 páramos catchments in Colombia: three sites in Romerales (Quindío), two in Chingaza (Cundinamarca), and one in Belmira (Antioquia). Occult precipitation inputs were measured with cylindrical fog gauges with a cover on top. We estimate occult precipitation inputs to add between 7% and 28% to rainfall inputs in the study sites. Our results also show that occult precipitation has a large temporal and spatial variability, both within one site and between sites, which make it difficult to upscale and quantify at a catchment scale. Nevertheless, occult precipitation can be important for downstream water supply given that these inputs are especially concentrated during periods with low rainfall. Lastly, we also find evidence for an increase in soil moisture related to occult precipitation during a dry period in Romerales páramo.     

Rural property size drives patterns of upland and riparian forest retention in a tropical deforestation frontier

Deforestation in Brazilian Amazonia accounts for a disproportionate global scale fraction of both carbon emissions from biomass burning and biodiversity erosion through habitat loss. Here we use field- and remote-sensing data to examine the effects of private landholding size on the amount and type of forest cover retained within economically active rural properties in an aging southern Amazonian deforestation frontier. Data on both upland and riparian forest cover from a survey of 300 rural properties indicated that 49.4% (SD = 29.0%) of the total forest cover was maintained as of 2007, and that property size is a key regional-scale determinant of patterns of deforestation and land-use change. Small properties (≤150 ha) retained a lower proportion of forest (20.7%, SD = 17.6) than did large properties (>150 ha; 55.6%, SD = 27.2). Generalized linear models showed that property size had a positive effect on remaining areas of both upland and total forest cover. Using a Landsat time-series, the age of first clear-cutting that could be mapped within the boundaries of each property had a negative effect on the proportion of upland, riparian, and total forest cover retained. Based on these data, we show contrasts in land-use strategies between smallholders and largeholders, as well as differences in compliance with legal requirements in relation to minimum forest cover set-asides within private landholdings. This suggests that property size structure must be explicitly considered in landscape-scale conservation planning initiatives guiding agro-pastoral frontier expansion into remaining areas of tropical forest.     

Animal thermal comfort index for the state of Paraíba,Brazil: trend,influencing factors,and mitigating measures

Theoretical and Applied Climatology - The present work had the objective to determine the tendency and the influence percentage of climatic variables on the Temperature and Humidity Index (THI) in...     

Exudates of different marine algae promote growth and mediate trace metal binding in Phaeodactylum tricornutum

Phaeodactylum tricornutum was grown in filtered natural seawater enriched with nitrate, phosphate, and silicate only (control) or with exudates from itself, from Emiliania huxleyi (a coccolithophore micro-alga), Porphyra spp. (a red macro-alga) or Enteromorpha spp. (a green macro-alga). Cathodic (and anodic) stripping voltammetry (C(A)SV) were used to determine the concentrations of trace metals, both in the medium and in the algae, as well as total Cu-complexing organic ligands in the medium and, among these, some thiols (compounds identified as cysteine- or as glutathione by CSV). Exudates of different marine micro- and macro-algae could cause allelopathic effects in P. tricornutum cultures. Cell yield of P. tricornutum was increasingly promoted by exudates of E. huxleyi >Porphyra >Enteromorpha. Although exudates strongly complex Cu (and probably other metals), their presence promoted Cu uptake. Significant changes of Ni, Cd, Fe, Zn and Mn uptake by P. tricornutum were also observed in the presence of exudates of different algal species. In addition, both intensity of production and nature of exudates released by P. tricornutum were markedly influenced by the presence of exudates of other algae, the allelopathic effects being very specific (variable from one species to another). Allelopathy will probably also occur in the aquatic environment, although to a lesser extent than in cultures, particularly during bloom events and may have effects on both chemical speciation and bioavailability of chemicals to phytoplanktonic species. Such changes might cause the predominance of some species over other species. Therefore, in future in vitro culture studies with the purpose of using them as models of the real environment, more attention should be paid to the role of algal exudates, in order to improve the environmental relevance and significance of the results.     

Bioenergetics of parental investment in two polychaete species with contrasting reproductive strategies: The planktotrophic Boccardia chilensis and the poecilogonic Boccardia wellingtonensis (Spionidae)

The level of parental investment for larval nutrition may determine the life cycle in marine invertebrate species laying egg masses or capsules, where the food available for enclosed individuals would determine time and developmental stage of hatching. Most species show a unique type of larval development. However, few species are poecilogonous and combine more than one development type. Poecilogony, although scarcely studied, allows comparing different patterns of parental reproductive investment, without the phylogenetic effect of the species ancestral modes of development (phylogenetic inertia), to help to understand the factors determining life strategy evolution in marine invertebrates. The poecilogonous polychaete worm Boccardia wellingtonensis encapsulates and incubates its offspring, which then hatches as either planktotrophic larvae or benthic juveniles; while Boccardia chilensis shows a non-poecilogonous reproductive type, producing only planktotrophic larvae. In this work, we estimated the bioenergetic and biochemical composition of brooding and non-brooding females of B. wellingtonensis and B. chilensis to compare the costs of reproduction in these two species. Results showed that glucose, protein, lipid, and energy content were significantly higher in non-brooding than in brooding females of B. wellingtonensis; but also contained significantly more glucose, protein, and lipid than females of B. chilensis (in absolute and relative dry weight values). The poecilogonous species showed higher energy content previous to laying offspring. Our results support the idea that the evolution of a certain reproductive and life history traits in marine invertebrates is related to adaptations in the female's reproductive investment.     

Sedimentation within and among mangrove forests along a gradient of geomorphological settings

Coastal wetlands provide important ecological services to the coastal zone, one of which is sediment retention. In this study we investigated sediment retention across a range of geomorphological settings and across vegetation zones comprising coastal wetlands. We selected six coastal wetlands dominated by mangroves over a gradient from riverine to tidal settings in Southeast Queensland, Australia. Each site was comprised of three distinct vegetation communities distributed as parallel zones to the coast line: seaward fringe mangroves, landward scrub mangroves and saltmarsh/ cyanobacteria mat of the high intertidal zone. We measured suspended sediment retention and sedimentation rates. Additionally, in order to assess the origin of sediment transported and deposited in the mangroves, glomalin, a novel terrestrial soil carbon tracer, was used. Our results show a mean average sedimentation of 0.64 ± 0.01 mg cm⁻² spring tide⁻¹, which was variable within sites, regardless of geomorphological setting. However, geomorphological setting influenced spatial patterns of sediment deposition. Riverine mangroves had a more homogeneous distribution of sediments across the intertidal zone than tidal mangroves, where most sedimentation occurred in the fringe zone. Overall, the fringe zone retained the majority of sediment entering the coastal wetland during a tidal cycle with 0.90 ± 0.22 mg cm⁻² spring tide⁻¹, accounting for 52.5 ± 12.5% of the total sedimentation. The presence of glomalin in suspended sediments, and thus the relative importance of terrigenous sediment, was strongly influenced by geomorphological setting, with riverine mangroves receiving more glomalin in suspended solids than tidal mangroves. Glomalin was also differentially deposited within the vegetation zones at different geomorphological settings: primarily at the fringe zone of tidal mangroves and within the scrub zone of riverine mangroves. The differences we observed in the spatial distribution of sedimentation and the difference in the origin of the sediment deposited in riverine and tidal mangroves are likely to have an impact on ecological processes.     

Long-term Regional Dynamic Sea Level Changes from CMIP6 Projections

Anthropogenic climate forcing will cause the global mean sea level to rise over the 21st century.However,regional sea level is expected to vary across ocean basins,superimposed by the influence of natural internal climate variability.Here,we address the detection of dynamic sea level(DSL)changes by combining the perspectives of a single and a multimodel ensemble approach(the 50-member CanESM5 and a 27-model ensemble,respectively,all retrieved from the CMIP6 archive),under three CMIP6 projected scenarios:SSP1-2.6,SSP3-7.0 and SSP5-8.5.The ensemble analysis takes into account four key metrics:signal(S),noise(N),S/N ratio,and time of emergence(ToE).The results from both sets of ensembles agree in the fact that regions with higher S/N(associated with smaller uncertainties)also reflect earlier ToEs.The DSL signal is projected to emerge in the Southern Ocean,Southeast Pacific,Northwest Atlantic,and the Arctic.Results common for both sets of ensemble simulations show that while S progressively increases with increased projected emissions,N,in turn,does not vary substantially among the SSPs,suggesting that uncertainty arising from internal climate variability has little dependence on changes in the magnitude of external forcing.Projected changes are greater and quite similar for the scenarios SSP3-7.0 and SSP5-8.5 and considerably smaller for the SSP1-2.6,highlighting the importance of public policies towards lower emission scenarios and of keeping emissions below a certain threshold.     

European Climatic Response to Millennial-Scale Changes in the Atmosphere–Ocean System during the Last Glacial Period

Pollen, foraminifer, dinocyst, and coarse lithic high-resolution analyses and δ¹⁸O measurements have been carried out for the last-glacial section of marine core MD95-2042 located near the southwestern margin of the Iberian Peninsula. The pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period, suggesting a climatic variability very similar to that of the Dansgaard-Oeschger cycles recorded by the Greenland ice cores. The detailed direct correlation of the terrestrial and marine proxy data from core MD95-2042 indicates a three-phase pattern of Heinrich events in land and ocean environments. The first and last phases of the H5 and H4 events are characterized by a mild and humid climate in southwestern Europe, probably associated with the European origin of the ice-rafted detritus. The middle phase exhibits a cold and dry climate in Iberia linked with the maximum input of ice-rafted detritus. This phase seems to correspond with the Laurentide ice-sheet surges. Between the Heinrich events, several cold and dry periods on land are correlated with stades of the Dansgaard-Oeschger cycles. The impact of the Dansgaard-Oeschger stades in southwestern Europe seems to be preferentially connected to the cold winter air masses reaching this mid-latitude region.     

Moment tensors of acoustic emissions in shear faulting under plane-strain compression

The study of localized failure under controlled conditions can be accomplished within a laboratory setting with the University of Minnesota plane-strain compression apparatus. The device provides an opportunity to observe shear faulting and to compare displacements from acoustic emission (AE) sources with global measurements. A biaxial compression test on a sandstone specimen was performed with monitoring of AE. The plane-strain test showed that the shear fault was not formed until after peak load. Compaction of the shear fault was observed from the axial and lateral measurements of displacement and the orientation of the failure plane. The AE events were modeled as displacement discontinuities. The complicated deconvolution process for the transducer transfer function was eliminated by using a simplified calibration procedure. The sources of the postpeak events were characterized as being caused predominantly by slip in the direction of the global failure plane, although components of displacement associated with closing were identified. To provide an order of magnitude estimate of the slip, the field observation of a 10⁻⁴ strain drop over the seismic area was assumed. The tangential displacement from 110 AE events was estimated to be 0.01 mm. During the same period of time, the displacement along the shear fault from global measurements was 0.03 mm.     

Cu and Fe associated with humic acids in sediments of a tropical coastal lagoon

The amount of Cu and Fe associated with humic acids was estimated in five sediment cores from a tropical coastal lagoon (Piratininga Lagoon, Rio de Janeiro, Brazil). Core samples were analysed for humic acid contents, total Fe and Cu content. Fe and Cu associated with humic acids were also measured. Results show amounts of humic acids ranging from 0.7 to 21.7% of the dry weight of sediment (average 4.6%, standard deviation 4.4%). Concentrations of Fe and Cu ranged from 0.3 to 6.0% (average 2.2%, S.D. 1.2%) and from <1.0 to 65.0 μg g⁻¹ (average 28.6 μg g⁻¹, S.D. 16.4 μg g⁻¹), respectively. The results of strongly bound metals show that while humic acids are the main carrier for Cu, Fe does not seems to be significantly associated with this organic matter.