An unusual kind of diurnal streamflow variation
Cuevas, J. G., Arumí, J. L., Zúñiga-Feest, A., & Little, C.
During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing season). The end of this DSS coincided with a sustained rain event in autumn, which deeply affected stream and meteorological variables. A survey along the stream revealed that the DSS maximum and minimum values appeared 6 and 4 hours earlier, respectively, at headwaters located in the mountain forests/ plantations than at the control point in the swamp forest. Et in the swamp forest was higher in the morning and in the late afternoon, but this process could not influence the groundwater stage. Trees in the mountain headwaters reached their maximum Ets in the early morning and/or close to midday. Our results suggest that the DSS is a wave that moves from forests high in the mountains towards lowland areas, where Et is decoupled from the DSS. This signal delay seems to convert the link between streamflow and Et in an apparent, but spurious positive relationship. It also highlights the role of landscape heterogeneity in shaping hydrological processes.
Palabras claves: Evapotranspiration; Groundwater; Riparian zones; Streamflow; Swamp forests
Late Quaternary environmental dynamics in the Atacama Desert reconstructed from rodent midden pollen records
De Porras, M. E., Maldonado, A., Pol‐Holz, D., Latorre, C., & Betancourt, J. L.
In the past two decades, much has been learned about the late Quaternary climate history of the Atacama Desert with some details still unclear about the seasonality, timing and extent of wet and dry phases. Modern climate studies reveal that, far from exhibiting a unique pattern, seasonal precipitation originates from many sources and mechanisms. For the last 16 ka, we attempt to sort out these complexities in pollen records from four fossil rodent midden series spanning 22°–25°S in northern Chile. Widespread wet conditions prevailed during the late Pleistocene and early Holocene, particularly between 13 and 9 ka, evidenced by <400 m lowering of pollen zones (plant communities) compared to today. Regional differences in the timing and magnitude of this displacement may be related to the prevailing source (tropical/extra‐tropical) or mode (NNW/SE) of tropical precipitation through time. Wet conditions persisted well into the early Holocene, lasting ∼1–1.5 ka longer than previously suggested. The pollen record suggests extreme drying ∼8 ka, possibly associated with a northward shift of the Inter Tropical Convergence Zone, tracking minimum insolation values at subtropical latitudes during the austral summer. The establishment of conditions similar to today happened ∼4 ka. Copyright © 2017 John Wiley & Sons, Ltd.
Palabras claves: Atacama Desert, Late Pleistocene–Holocene, Paleoclimate, Pollen, Rodent middens
Temporal stability and mixed-stock analyses of humpback whales (Megaptera novaeangliae) in the nearshore waters of the Western Antarctic Peninsula
Albertson, G. R., Friedlaender, A. S., Steel, D. J., Aguayo-Lobo, A., Bonatto, S. L., Caballero, S., Constantine, R., Cypriano-Souza, A.L., Engel, M.H., Garrigue, C., Flórez-González, R., Johnston, D.W., Nowacek, D.P., Olavarría, C., Poole, M.M., Read, A.J., Robbins, J., Sremba, A.L., & Baker, C.S.
Southern Hemisphere humpback whales breed in tropical waters and migrate to Antarctica to forage. While the breeding grounds are well defined, the population structure on Antarctic feeding grounds is poorly described. The Western Antarctic Peninsula (WAP) is of particular interest, where rapidly changing environmental conditions could alter prey distribution or migration pathways. To examine changes in the population of whales around the WAP, we used mitochondrial DNA (mtDNA) and 15 microsatellite loci. We compared our WAP dataset to a dataset collected 18 years earlier, and identified new haplotypes for the region, but found no significant difference between the datasets. We compared whales from the WAP to breeding populations in Oceania, Colombia, and Brazil. We used an Analysis of Molecular Variance to confirm significant genetic differentiation between the WAP and each breeding ground (overall F ST = 0.035/0.007 mtDNA/microsatellite, p < 0.001) except Colombia. Bayesian mixed-stock analyses showed a large apportionment to Colombia (mtDNA 93.0%; CL 91–99%; microsatellites 86%; CL 72–93%) and a small apportionment to French Polynesia/Samoan Islands (mtDNA 2.9%; CL 0.0–11.5%; microsatellites 8.9%; CL 0–22%), supporting the strong connection between Colombia and the WAP. Assignment tests allocated 81 individuals to Colombia and two to French Polynesia/Samoan Islands. No other breeding grounds had significant apportionments. Direct connectivity of French Polynesia to the WAP was confirmed with the first genotype match of French Polynesia to a feeding area. Continued genetic monitoring will highlight the complex patterns of humpbacks in this rapidly changing climate. Our results serve as a baseline for humpback whale population structure, illustrate mixed-stock analysis as a useful tool for migrating wildlife, and aid in future management considerations for humpbacks.
Palabras claves: Humpback whales, Population structure, Climate change, Mixed-stock analysis, DNA markers, Antarctic Peninsula
Molecular characterization and protein localization of the antimicrobial peptide big defensin from the scallop Argopecten purpuratus after Vibrio splendidus challenge
González, R., Brokordt, K., Cárcamo, C. B., de la Peña, T. C., Oyanedel, D., Mercado, L., & Schmitt, P.
Big defensins are antimicrobial peptides (AMPs) that are proposed as important effectors of the immune response in mollusks, chelicerates and chordates. At present, only two members of the big defensin family have been identified in scallop. In the present work, a cDNA sequence encoding a new big defensin homologue was characterized from the scallop Argopecten purpuratus, namely ApBD1. ApBD1 cDNA sequence comprised 585 nucleotides, with an open reading frame of 375 bp and 5'- and 3′-UTRs of 41 and 167 bp, respectively. The deduced protein sequence contains 124 amino acids with a molecular weight of 13.5 kDa, showing characteristic motifs of the big defensin family and presenting 76% identity with the big defensin from the scallop A. irradians. Phylogenetic analysis revealed that ApBD1 is included into the cluster of big defensins from mollusks. Tissue-specific transcript expression analysis by RT-qPCR showed that ApBD1 was present in all tissues tested from non-immune challenged scallops but it was most strongly expressed in the mantle. The transcript levels of ApBD1 were significantly up-regulated in gills at 24 and 48 h post-injection with the heat-attenuated bacteria Vibrio splendidus. Additionally, immunofluorescence analysis using a polyclonal anti-ApBD1 antibody showed that this protein was abundantly located in epithelial linings of gills and mantle; and also in digestive gland showing ApBD1-infiltrating hemocytes from immune challenged scallops. This is the first time that a big defensin is detected and located at the protein level in a mollusk. These results suggest an important role of ApBD1 in the mucosal immune response of A. purpuratus.
Palabras claves: Antimicrobial peptides, Big defensin, Innate immunity, Mucosal immunity, Scallops
Migratory preferences of humpback whales between feeding and breeding grounds in the eastern South Pacific
Acevedo, J., Aguayo‐Lobo, A., Allen, J., Botero‐Acosta, N., Capella, J., Castro, C., Dalla-Rosa, L., Denkinger, J., Félix, F., Flórez-González, L., Garita, F., Guzmán, H.M, Haase, B., Kaufman, G., Llano, M., Olavarría, C., Pacheco, A.S., Plana, J., Rasmussen, K., Scheidat, M., Secchi, E.R., Silva, S., & Stevick, P.T.
Latitudinal preferences within the breeding range have been suggested for Breeding Stock G humpback whales that summer in different feeding areas of the eastern South Pacific. To address this hypothesis, humpback whales photo‐identified from the Antarctic Peninsula and the Fueguian Archipelago (southern Chile) were compared with whales photo‐identified from lower latitudes extending from northern Peru to Costa Rica. This comparison was performed over a time span that includes 18 austral seasons. A total of 238 whales identified from the Antarctic Peninsula and 25 whales from the Fueguian Archipelago were among those photo‐identified at the breeding grounds. Our findings showed that humpback whales from each feeding area were resighted unevenly across the breeding grounds, which suggests a degree of spatial structuring in the migratory pathway. Humpback whales that feed at the Antarctic Peninsula were more likely to migrate to the southern breeding range between northern Peru and Colombia, whereas whales that feed at the Fueguian Archipelago were more likely to be found in the northern range of the breeding ground off Panama. Further photo‐identification efforts and genetic sampling from poorly sampled or unsampled areas are recommended to confirm these reported connectivity patterns.
Palabras claves: Megaptera novaeangliae, Migratory destinations, Breeding Stock G, Photo‐identification, Feeding ground, Antarctic Peninsula, Fueguian Archipelago
Seasonal variation of carrageenans from Chondracanthus chamissoi with a review of variation in the carrageenan contents produced by Gigartinales
Véliz, K., Chandía, N., Rivadeneira, M., & Thiel, M.
Seasonal and geographic variations in carrageenan biosynthesis influence the commercial value and industrial applications of these phycocolloids due to the variation in yield and quality. This study examined the effects of season and seaweed origin on the carrageenans produced by the isomorphic phases of the red alga Chondracanthus chamissoi collected during winter and summer from two localities in the SE Pacific Ocean (northern-central Chile). Results were compared with those from other carrageenan-producing seaweeds, and a random forest analysis was carried out with the carrageenan contents reported for Gigartinales in order to determine the principal variables influencing carrageenan yields. The mean carrageenan contents of C. chamissoi ranged from 15.2 to 42.1% DW. Higher yields were observed in gametophytes than in tetrasporophytes, and in samples collected in summer than in winter. Seaweeds from the site close to a local upwelling center had more carrageenans than those from a more distant site. The chemical composition of the carrageenans of C. chamissoi varied only between phases. Carrageenan contents reported for Gigartinales vary from 5.4 to 75.5% DW. The random forest model showed a large accuracy explaining variation in carrageenan yields (pseudo-r 2 = 0.63), where genus was ranked as the most important factor, followed by biogeographical origin, solar radiation, nitrate concentrations, and temperature. Considering that the understanding of the genetic basis of carrageenan biosynthesis is limited, our analysis highlights the need for experimental studies examining the effects of taxon and geographical origin in these polysaccharides as a strategy for improving both carrageenan quality and quantity through strain selection.
Palabras claves: Carrageenans, Gigartinales, Chondracanthus chamissoi, Chile
Assessment of transboundary river basins for potential hydro-political tensions.
De Stefano, L., Petersen-Perlman, J. D., Sproles, E. A., Eynard, J., & Wolf, A. T.
This paper presents a systematic, global assessment of transboundary watersheds that identifies regions more likely to experience hydro-political tensions over the next decade and beyond based upon environmental, political, and economic indicators. The development of new water infrastructure in transboundary basins can strain relationships among fellow riparians as the impacts of new dams and diversions are felt across borders. Formal arrangements governing transboundary river basins, such as international water treaties and river basin organizations, provide a framework for dialogue and negotiation, thus contributing to assuaging potential disputes. Our study examines these two issues in tandem − the stresses inherent in development and the mitigating impact of institutions − and maps the risk of potential hydro-political tensions that exist where basins may be ill-equipped to deal with transboundary disputes triggered by the construction of new dams and diversions. We also consider several factors that could exacerbate those hydropolitical tensions in the near future, including changes in terrestrial water storage, projected changes in water variability, per capita gross national income, domestic and international armed conflicts, and recent history of disputes over transboundary waters. The study points to the vulnerability of several basins in Southeast Asia, South Asia, Central America, the northern part of the South American continent, the southern Balkans as well as in different parts of Africa, where new water infrastructure is being built or planned, but formal transboundary arrangements are absent. Moreover, in some of these regions there is a concomitance of several political, environmental and socioeconomic factors that could exacerbate hydropolitical tensions. This study contributes to the understanding of how the recent proliferation of development accompanied with unfavourable socio-economic and environmental indicators may influence global hydropolitical resilience.
Palabras claves: Transboundary,Treaty, Assessment, Dispute, Cooperation, Conflict
Genetic differentiation between humpback whales (Megaptera novaeangliae) from Atlantic and Pacific breeding grounds of South America
Cypriano‐Souza, A. L., Engel, M. H., Caballero, S., Olavarría, C., Flórez‐González, L., Capella, J.,Steel D., Sremba, A., Aguayo, A., Thiele, D., Baker, S., & Bonatto, S.L
Humpback whales wintering in tropical waters along the Atlantic and Pacific coasts of the South American continent are thought to represent distinct populations or “stocks.” Here we present the first analysis of genetic differentiation and estimates of gene flow between these breeding stocks, based on both mitochondrial DNA (mtDNA) control region sequences (465 bp) and 16 microsatellite loci from samples collected off Brazil (n = 277) and Colombia (n = 148), as well as feeding areas near the western Antarctic Peninsula (n = 86). We found significant differentiation between Brazilian and Colombian breeding grounds at both mtDNA (FST = 0.058) and microsatellite (FST = 0.011) markers and corroborated previous studies showing genetic similarity between humpbacks from Colombia and those from Antarctic Peninsula feeding areas. Estimates of long‐term gene flow between Brazil and Colombia were low to moderate, asymmetrical, and mostly mediated by males. Assignment procedures detected some cases of interchange and individuals of admixed ancestry between breeding grounds, indicating limited mixing of individuals between these stocks. Overall, results highlight the differentiation of humpback whale breeding populations with adjacent feeding grounds. This appears to be a remarkable example of fidelity to seasonal habitat in the absence of any contemporary barriers.
Palabras claves: Megaptera novaeangliae, Population genetic structure, Microsatellites, mtDNA, Migration, Individual assignment
Spatial and short-term variability of larval, post-larval and macrobenthic assemblages associated with subtidal kelp forest ecosystems in Central Chile
Carrasco, S. A., Vandecasteele, L., Rivadeneira, M. M., Fernández, M., & Pérez-Matus, A.
Identifying patterns of spatial and temporal variability in the composition of communities associated with kelp forests is critical to understand the functioning of this productive, yet vulnerable ecosystem. We used a suite of sampling methods (light attraction and airlift devices) to evaluate the variability of larval, post-larval and macrobenthic assemblages associated with kelp forests (Lessonia trabeculata) in Central Chile (30° to 33°S). Pelagic collections identified two assemblages: early-life stages and emerging macrobenthos, with the later contributing three quarters to the total abundance regardless of the source of illumination (permanent or flashing). Field experiments showed that moon phases affected the structure and composition of the samples. Surveys carried out during new moon showed the highest abundances and taxonomic richness of emergent assemblages. However, species composition varied in both assemblages depending on the moon phase. Although the pelagic assemblages collected at sites with contrasting upwelling intensity did not show differences in community structure, differences in composition were evident for early-life stages. The relationship between pelagic and benthic collections indicated that four decapod crustaceans were represented at both larval and early juvenile stages; however, only the high abundances and densities of Paraxanthus barbiger allowed for estimations of benthic-pelagic coupling. For this species, larval abundances and benthic juvenile densities demonstrated contrasting local and regional patterns, suggesting a decoupling between pelagic and benthic environments. These findings highlight the differential variability in smaller components of kelp forests, but also suggest that post-settlement processes may be driving biological interactions through these highly productive and complex environments.
Palabras claves: Larval supply, Emerging macrobenthos, Invertebrate, Fish, Recruitment, Upwelling
Context‐dependent functional dispersion across similar ranges of trait space covered by intertidal rocky shore communities
Valdivia, N., Segovia‐Rivera, V., Fica, E., Bonta, C. C., Aguilera, M. A., & Broitman, B. R.
Functional diversity is intimately linked with community assembly processes, but its large‐scale patterns of variation are often not well understood. Here, we investigated the spatiotemporal changes in multiple trait dimensions (“trait space”) along vertical intertidal environmental stress gradients and across a landscape scale. We predicted that the range of the trait space covered by local assemblages (i.e., functional richness) and the dispersion in trait abundances (i.e., functional dispersion) should increase from high‐ to low‐intertidal elevations, due to the decreasing influence of environmental filtering. The abundance of macrobenthic algae and invertebrates was estimated at four rocky shores spanning ca. 200 km of the coast over a 36‐month period. Functional richness and dispersion were contrasted against matrix‐swap models to remove any confounding effect of species richness on functional diversity. Random‐slope models showed that functional richness and dispersion significantly increased from high‐ to low‐intertidal heights, demonstrating that under harsh environmental conditions, the assemblages comprised similar abundances of functionally similar species (i.e., trait convergence), while that under milder conditions, the assemblages encompassed differing abundances of functionally dissimilar species (i.e., trait divergence). According to the Akaike information criteria, the relationship between local environmental stress and functional richness was persistent across sites and sampling times, while functional dispersion varied significantly. Environmental filtering therefore has persistent effects on the range of trait space covered by these assemblages, but context‐dependent effects on the abundances of trait combinations within such range. Our results further suggest that natural and/or anthropogenic factors might have significant effects on the relative abundance of functional traits, despite that no trait addition or extinction is detected.
Palabras claves: Community assembly, Desiccation, Environmental filtering, Functional beta‐diversity, Functional traits, Marine, Mesoscale, Seasonal