On the 60-month cycle of multivariate ENSO index

Many point indices have been developed to describe El Niño/Southern Oscillation, but the multivariate El Niño Southern Oscillation (ENSO) index (MEI) is considered the most representative since it links six different meteorological parameters measured over the tropical Pacific. Spectral analysis with appropriate data reduction techniques of monthly values of MEI (1950–2008) has allowed the identification of a large 60-month cycle, statistically confident at a level larger than 99%. The highest values of MEI (typical of El Niño events) and the lowest values of MEI (typical of La Niña events) are concordant with respective maxima and minima values of the identified 60-month cycle.     

Late Holocene palaeoenvironmental evolution of the Roman harbour of <Emphasis Type="Italic">Portus</Emphasis>, Italy

We present a Holocene record of climate and environmental change in central New York (USA) inferred using lithologic and stable isotope data from two sediment cores recovered in Cayuga Lake. The record was divided into three intervals: (1) early Holocene (~11.6–8.8 ka), (2) Hypsithermal (~8.8–4.4 ka), and (3) Neoglacial (~4.4 ka to present). The early Holocene began abruptly, with rising lake level and relatively deep water. Between ~10.8 and 9.2 ka, cool and dry conditions prevailed at a time of maximum solar insolation. This anomaly has been referred to as the “post-Younger Dryas climate interval” and lasted ~1,600 years, the approximate length of one “Bond cycle.” The Hypsithermal was the warmest, wettest and most biologically productive interval of the Holocene in central New York. The Hypsithermal was characterized by centennial to multi-centennial-scale variability. The 8.2 ka event is one such variation. The Neoglacial was an interval of generally cooler and dryer conditions, falling lake levels, and several prominent climate anomalies. At approximately 2.4 ka, δ¹³C of bulk organic matter increased abruptly by 5‰ as lake level declined, and the lake flora was dominated by Chara sp. during the coldest interval of the Neoglacial. Numerous sediment variables display increased variability ~2.0 ka, which continues today. Archaeological data from the literature suggest that Native American populations may have been large enough to impact land cover by about 2.4 ka and we hypothesize that the “Anthropocene” began at about that time in central New York. We also found paleolimnological evidence for the Medieval Warm Period (~1.4–0.5 ka), which was warmer and wetter than today, and for the Little Ice Age (~500–150 years ago), a period with temperatures colder than today.     

Metazoan/microbial biostalactites from present‐day submarine caves in the Mediterranean Sea

Biostalactites formed by metazoan–microbialite associations from three submerged marine caves in the Plemmirio Peninsula (south of Syracuse, Ionian Sea) are randomly distributed and show different sizes and morphologies, as well as variations in surface roughness/smoothness. The biostalactites consist of crusts a few centimeters thick of small serpulids and other metazoans, associated with fine‐grained carbonate; the larger ones often include a nucleus of serpulid tubes (Protula). The metazoans include mainly serpuloideans, sponges, bryozoans and foraminifers but microbial carbonates are also significant components. The composition of both the living communities and thanatocoenoses on the outer surfaces, as well as the composition and fabric of the internal framework, were analysed and used to reconstruct the history of the caves. All of the identified sessile faunas mainly consist of cryptic and sciaphilic dwellers that reflect cave conditions and their variations through time. The distribution pattern, composition and abundance of the present‐day dwellers largely depend on the degree of roughness of the biostalactite surfaces and their positions within the caves. It has been suggested that the Protula specimens in the nuclei represent pioneer populations that formed aggregates during the early cave colonization phase, in response to relatively high food supply from seawater inflow and intruding continental waters. By contrast, the outer metazoan–microbialite carbonates reflect more confined conditions in the caves caused by Holocene sea‐level rises. Hypotheses are proposed for biostalactite growth, taking into account information about the growth rates of some constituents, and evidence of dissolution effects. Similarities and differences between these biostalactites and other Holocene deposits previously described from submarine caves in the Mediterranean Sea and in tropical reefs are discussed.     

Large‐scale modelling of channel flow and floodplain inundation dynamics and its application to the Pantanal (Brazil)

For large‐scale sites, difficulties for applying coupled one‐dimensional (1D)/2D models for simulating floodplain inundation may be encountered related to data scarcity, complexity for establishing channel–floodplain connections, computational cost, long duration of floods and the need to represent precipitation and evapotranspiration processes. This paper presents a hydrologic simulation system, named SIRIPLAN, developed to accomplish this aim. This system is composed by a 1D hydrodynamic model coupled to a 2D raster‐based model, and by two modules to compute the vertical water balance over floodplain and the water exchanges between channel and floodplain. Results are presented for the Upper Paraguay River Basin (UPRB), including the Pantanal, one of the world's largest wetlands. A total of 3965 km of river channels and 140 000 km² of floodplains are simulated for a period of 11 years. Comparison of observed and calculated hydrographs at 15 gauging stations showed that the model was capable to simulate distinct, complex flow regimes along main channels, including channel‐floodplain interactions. The proposed system was also able to reproduce the Pantanal seasonal flood pulse, with estimated inundated areas ranging from 35 000 km² (dry period) to more than 120 000 km² (wet period). Floodplain inundation maps obtained with SIRIPLAN were consistent with previous knowledge of Pantanal dynamics, but comparison with inundation extent provided by a previous satellite‐based study indicates that permanently flooded areas may have been underestimated. The results obtained are promising, and further work will focus on improving vertical processes representation over floodplains and analysing model sensitivity to floodplain parameters, time step and precipitation estimates uncertainty. Copyright © 2010 John Wiley & Sons, Ltd.     

Martian mud volcanism: Terrestrial analogs and implications for formational scenarios

The geology of Mars and the stratigraphic characteristics of its uppermost crust (mega-regolith) suggest that some of the pervasively-occurring pitted cones, mounds, and flows may have formed through processes akin to terrestrial mud volcanism. A comparison of terrestrial mud volcanism suggests that equivalent Martian processes likely required discrete sedimentary depocenters, volatile-enriched strata, buried rheological instabilities, and a mechanism of destabilization to initiate subsurface flow. We outline five formational scenarios whereby Martian mud volcanism might have occurred: (A) rapid deposition of sediments, (B) volcano-induced destabilization, (C) tectonic shortening, (D) long-term, load-induced subsidence, and (E) seismic shaking. We describe locations within and around the Martian northern plains that broadly fit the geological context of these scenarios and which contain mud volcano-like landforms. We compare terrestrial and Martian satellite images and examine the geological settings of mud volcano provinces on Earth in order to describe potential target areas for piercement structures on Mars. Our comparisons help to evaluate not only the role of water as a functional component of geological processes on Mars but also how Martian mud volcanoes could provide samples of otherwise inaccessible strata, some of which could contain astrobiological evidence.     

Understanding spatial and temporal dynamics of key environmental characteristics in a mesotidal Atlantic estuary (Douro,NW Portugal)

Ecosystem management and decision making process are dependent of a good knowledge of ecosystem functioning. Conceptual models allow knowledge organization through representation of relationships between variables and processes, facilitating management decisions. In this study, spatial and temporal characterization of key environmental variables, as well as relationships between them, was studied aiming the design of a conceptual model of the Douro estuary. This temperate mesotidal estuary is limited upstream by a hydroelectric power dam that controls freshwater inflow and prevents the propagation of the tide upstream, which, in turn, influences water circulation and biogeochemical dynamics of the system. During one year, from December 2002 to December 2003, water column data were collected monthly at 10 stations along the estuary, during ebb and flood tides. Spatial and temporal variability of water column salinity, temperature, nutrients, phytoplankton biomass, total particulate matter (TPM), phytoplankton primary production (PP), faecal coliform bacteria (FC) and community respiration (CR) were analysed. Salinity stratification was assessed by means of the Estuary Number (Ne) and variation of this index as well as other key characteristics with river flow was analysed. Freshwater discharge controlled salinity stratification and freshwater residence time. Ne indicated that the Douro was stratified for river flows <300 m³ s⁻¹, and freshwater residence time was >1 day for the same conditions. A decaying exponential relationship between PP and river flow was found, whereas nitrate and TPM increased logarithmically and linearly, respectively, with river flow. Regarding spatial distribution, nitrate and PP decreased downstream, showing that the river was a source of nutrients and phytoplankton, while the opposite trend was found for TPM, FC, ammonium and CR. The latter increase was probably due to untreated sewage discharge in the urbanized middle and lower estuarine stretches. Reduction of nitrate coming from the watershed and of bacterial contamination in the urban stretches of this highly modified water body, according to the European Water Framework Directive, emerges as the main water quality issues for this estuarine ecosystem.     

Fatty acids dynamics during embryonic development in genus Uca (Brachyura: Ocypodidae), from the mangroves of Inhaca Island,Mozambique

Variations in egg volume and fatty acid (FA) content through embryogenesis were evaluated in Uca species from Inhaca island, Mozambique. Egg volume increased 96.1%, 93.3%, 84.2%, 92.9%, 96.3%, respectively, in Uca annulipes, Uca inversa, Uca urvillei, Uca chlorophthalmus and Uca vocans (p < 0.05). Fatty acid content decreased through embryogenesis, showing its importance as fuel during embryonic development. Major fatty acids were 16:0, 18:0, 16:1n-7, 18:1n-9, 18:1n-7, 18:2n-6, 20:5n-3 and 20:4n-3. Unsaturated fatty acids (UFA) and saturated fatty acids (SFA) were used up at a similar rate for U. annulipes and U. inversa contrarily to the other three species. Within the UFA, MUFA were more consumed than PUFA for all species except U. chlorophthalmus. The high values detected for fatty acid trophic markers (essential C₁₈ and C₂₀ PUFAs) and odd-numbered fatty acid suggest that Uca species occupy medium trophic level, primarily omnivores and scavengers/detritivores consuming algae common in the intertidal habitats. The fatty acid consumption pattern during embryonic development was essentially similar between species with some variation as expected, as FA content varies within species mainly due to female feeding ecology, nutritional and physiological conditions, differential demands on resource allocation and geographic and seasonal variations in embryonic development.     

Land use changes due to energy policy as a determining factor for morphological processes in fluvial systems in São Paulo State,Brazil

The number of hydroelectric dams used for energy production and the cultivation of sugar cane crops for ethanol production have increased significantly in the southeastern region of Brazil. These land use/land cover changes (LULCC) associated with energy policy can affect landscape changes over a range of temporal and spatial scales. This article focuses on how human–landscape interactions have influenced geomorphological dynamics in the lower course of the Piracicaba River for two different scenarios that represent pre‐dam and post‐dam conditions in 1962 and 2007, respectively, and the expansion of sugar cane crops after 1975. This assessment was performed by mapping land use and geomorphological changes in the study area in the 1962 and 2007 scenarios, in addition to quantifying the sedimentation rates upstream from the Barra Bonita Reservoir using ²¹⁰Pb. The main land uses identified for the 1962 scenario were pastures, meadows, annual crops and forests. However, the main land use change was the expansion of sugar cane cropland from 4 to 39%. In the 1962 scenario, the lower course of the Piracicaba River had a predominantly meandering pattern, and there were pronounced alluvial plains in the region. In the 2007 scenario, oxbow lakes were not mapped, and the river terraces were reduced in area due to construction of the Barra Bonita Reservoir. The changes in the sedimentation rates indicate an association between the construction of the Barra Bonita Reservoir and the expansion of sugar cane crops. It was therefore not possible to assess the specific influences of each anthropogenic change on the sedimentation processes, reinforcing that the human–landscape systems in São Paulo State associated with energy policy are complex. Copyright © 2017 John Wiley & Sons, Ltd.