The coastal ocean off Oregon from 1961 to 2000: is there evidence of climate change or only of Los Niños?

A zonal hydrographic section along 44.65°N, from the coast of Oregon to 300 km offshore, was occupied regularly (at least seasonally) from 1961 to 1971 and then sporadically until recently. Regular monitoring of this section to 160 km offshore resumed in July 1997 as part of the GLOBEC Long Term Observational Program; the recent data provide observations in Oregon coastal waters of El Niño 1997–98 and La Niña conditions that followed. The complete seasonal data from the decade 1961–1971 provide a basis for comparison with the recent temperature and salinity sections, steric height profiles, geostrophic velocity, and water mass characteristics. These data, and sporadic observations in intervening years, allow us to compare conditions during several ENSO events with the recent event and to search for evidence of climate change. The PFEL Coastal Upwelling Index, sea level from the University of Hawaii Sea Level Center, the Multivariate ENSO Index (MEI), the Pacific Decadal Oscillation (PDO), and outflow from the Columbia River are used to distinguish local and remote causes of variability in physical oceanographic conditions off Oregon. The sequence of El Niño/La Niña/El Niño in 1963–66, during a cool phase of PDO, provides a comparison to El Niño/La Niña of 1997–2000. El Niño in 1982–83 and 1997–98, during a warm phase of PDO, caused the largest oceanographic anomalies in the 40 years. The comparison indicates warming of the coastal ocean off Oregon and suggests a modulation of ENSO effects by PDO. Such modulation would mask evidence for secular climate change in our 40-year oceanographic data series.     

Life Cycle,Growth and Secondary Production in a Brackish-Water Population of the Polychaete Notomastus latericeus (Capitellidae) in the Mediterranean Sea

Abstract. Three years of observations on a population of Notomastus latericeus Sars from Acquatina lagoon (Lecce, Italy) are reported. The population dynamics, life cycle, and reproduction were investigated in order to explain periodic density variations of this species. Some physical parameters of the water column were measured and sediment analyses were performed to characterize the environment. Secondary production was also estimated as part of a functional study of the benthic system in the Acquatina lagoon. The species is opportunistic; its density is apparently correlated to variation in salinity, but its presence in the lagoon is dependent on recruitment success and competition with other polychaete species.     

Hierarchical procedure for creating local typologies for riparian zone research and management based on biophysical features

Riparian systems have been included as a key component in ecosystem management because of their role in buffering the impact of land-use activities on fluvial systems. Riparian knowledge can be enhanced with a typology that reflects the multiple relationships occurring throughout the landscape. We propose a hierarchical procedure based on biophysical aspects for building local to regional typologies for guiding research and management, using the Cuitzmala River Basin as a case study. The variables involved were obtained from geospatial databases, water balances, and topographic profiles. The levels and variables are context (altitude, geoform [mountains/hills/plains], and runoff coefficient), structure (stream order, longitudinal slope, hydroperiod, and segment length), and microstructure (lateral slope, bankfull width, and length-to-width ratio). We consider humidity and functional gradient along the basin to identify groups of streams and fluvial networks. Inside each network, we described structural and microstructural features associated with riparian functions, linking them with management decisions. Therefore, the proposed hierarchical procedure can help in making riparian heterogeneity visible, focusing research and management goals, and allowing the recognition of a spatial dimension of the processes being studied.     

Late pleistocene and holocene loess deposits of the Southeastern Buenos Aires province,Argentina

The Late Pleistocene and Holocene loess deposits of the SE Buenos Aires province are composed of four allostratigraphic units that represent four episodes of loess deposition. The first and the second episodes occurred in Late Pleistocene times. The second episode was followed by a soil forming interval (Early Holocene to Mid-Holocene times). The third episode took place at about 5000 yr BP, after the Holocene sea-level maximum when marine regression began. The fourth episode constitutes a historical event of only local significance.Loess shows a fairly constant granulometric and mineralogical composition. The modal fraction consists of very fine sand and coarse silt (3 to 5 phi). They are classified as sandy silts or silty sands. Three grain-size subpopulations are differentiated: coarse, medium and fine. The medium-size subpopulation, which is the most important, consists of most of the very fine sand and coarse silt. It is thought to be transported by modified saltation and short-term suspension during local dust-storms.The mineralogical composition of loess consists of a volcaniclastic assemblage derived mainly from reworked pyroclastic deposits, primary tephras and volcaniclastic sediments. The source area of these materials was located in the lower Colorado river valley about 400 km SW of the studied area. There was also a direct supply by volcanic ash falls.     

First Images of Impulsive Millimeter Emission and Spectral Analysis of the 1994 August 18 Solar Flare

We present here the first images of impulsive millimeter emission of a flare. The flare on 1994 August 18 was simultaneously observed at millimeter (86 GHz), microwave (1-18 GHz), and soft and hard X-ray wavelengths. Images of millimeter, soft and hard X-ray emission show the same compact ( 8) source. Both the impulsive and the gradual phases are studied in order to determine the emission mechanisms. During the impulsive phase, the radio spectrum was obtained by combining the millimeter with simultaneous microwave emission. Fitting the nonthermal radio spectra as gyrosynchrotron radiation from a homogeneous source model with constant magnetic field yields the physical properties of the flaring source, that is, total number of electrons, power-law index of the electron energy distribution, and the nonthermal source size. These results are compared to those obtained from the hard X-ray spectra. The energy distribution of the energetic electrons inferred from the hard X-ray and radio spectra is found to follow a double power-law with slope 6–8 below 50 keV and 3–4 above those energies. The temporal evolution of the electron energy spectrum and its implication for the acceleration mechanism are discussed. Comparison of millimeter and soft X-ray emissions during the gradual phase implies that the millimeter emission is free-free radiation from the same hot soft X-ray emitting plasma, and further suggests that the flare source contains multiple temperatures.     

Suspended sediment transport analysis in two Italian instrumented catchments

Suspended sediment transport in streams is an effective indicator of soil erosion at the watershed scale. This process was studied using the data obtained from two continuous monitoring stations installed in Italian watersheds, the Rio Cordon and Torrente Carapelle. The catchments have substantially different climatic, morphological and land use characteristics. The Rio Cordon, a small Alpine watershed, has been monitored since 1986, while in the Torrente Carapelle, a medium-size Mediterranean watershed, the monitoring station has provided data since 2007. Several flood events with suspended sediment transport were isolated in the two catchments, excluding those determined by snowmelt in the Rio Cordon as this process does not affect the Carapelle watershed. Analysis of the events showed different behavior in terms of hysteresis loop trends between water discharge (m³ s^-1) and suspended sediment concentration (g l^-1) values, as the Rio Cordon confirms clockwise relationships most frequently, while counter-clockwise trends represent the majority of cases for the Carapelle Torrent. The different behavior of the two watersheds was further analyzed by evaluating relationships between the main hydrological parameters related to suspended sediment transport. Runoff controls the total sediment budget in both catchments. In contrast, it was noted that the runoff process does not interfere in the magnitude of the suspended sediment transport in the Rio Cordon catchment, while variations due to the larger size of the catchment area characterize the events in the Carapelle watershed. Lastly, a flow peak threshold that determines the advance or delay of the hydrograph peak with respect to the sedigraph peak was established for the Carapelle Torrent, while it was not reported in the Rio Cordon.     

Seagrass tolerance to herbivory under increased ocean temperatures

Climate change is acknowledged as a major threat to marine ecosystems, but the effect of temperature on species interactions remains poorly understood. We quantified the effects of long-term warming on plant-herbivore interactions of a dominant seagrass, Zostera muelleri. Growth, herbivory and tolerance to damage were compared between a meadow warmed by the thermal plume from a power station for 30 years (2–3 °C above background temperatures) and three control locations. Leaf growth rates and tissue loss were spatially variable but unrelated to temperature regimes. Natural herbivory was generally low. Simulated herbivory experiments showed that the tolerance of Z. muelleri to defoliation did not differ between warm and unimpacted meadows, with damaged and undamaged plants maintaining similar growth rates irrespective of temperature. These results suggest that the ability of temperate Z. muelleri to tolerate herbivory is not strongly influenced by warming, and this species may be relatively resilient to future environmental change.     

Taxonomic distinctness in Mediterranean marine nematodes and its relevance for environmental impact assessment

Taxonomic distinctness has been applied successfully for the exploration of biodiversity patterns, yet its relevance in environmental impact assessment is far from being unquestioned. In this study, we assessed the potential of taxonomic distinctness to discern perturbed and unperturbed sites by analysing Mediterranean nematode assemblages. Geographic and habitat-related effects on the performance of the index were also explored. Above all, our findings do not corroborate the conjecture that taxonomic distinctness could be largely unaffected by natural variability, habitat features, and biogeographic context, casting doubts on potential generalization concerning its application as an indicator of environmental stress. Taxonomic distinctness represents an excellent metric to identifying taxonomic properties of ecological systems but, as for other ecological indices, it should be viewed as a complementary tool in environmental impact assessment, due to its sensitiveness to specific environmental features of systems being investigated.     

An integrative physical,mineralogical and ichnological approach to characterize underfilled lake-basins

Lakes are particularly sensitive to environmental fluctuations, which are recorded in their facies and stratigraphy. Ephemeral lakes reveal their sensitivity to palaeoenvironmental changes in the overprinting of the sedimentary features in every single bed. Tetrapod-track taphonomic-modes and ichnological taphonomic-pathways can be used as sensitive indicators of environmental conditions of the track-bearing beds during deposition and imprinting. The Middle Triassic Cerro de las Cabras succession (Cuyana Basin, Argentina) provides an excellent opportunity to these environmental indicators in an underfilled palaeolake. A model of ichnological preservation for underfilled lake systems is proposed and the role of the ichnology record in the sequence stratigraphy analysis is evaluated, based on the integration of tetrapod-track modes, taphonomic-pathways of playa-lake ichnofauna, mineralogy and physical data. Soft-ground suites include those dominated by invertebrate grazing traces and arthropod locomotion traces (Suite 1), and those overprinted by horizontal-vertical dwelling burrows with tetrapod tracks preserved in taphonomic modes B and C (Suite 2). The firm-ground suite (Suite 3) comprises tetrapod-tracks with the best preservation styles (modes A and B) along less abundant invertebrate dwelling and feeding traces as found in Suite 2. Clay mineralogy (dominated by illite with subordinate smectite) suggests low plasticity of the layers, in agreement with low-relief deformation structures observed in tetrapod-track taphonomic-modes. The well-preserved track tetrapod features documented in the Cerro de las Cabras succession, together with the absence of pedogenic disturbance, trampling obliterating the footprints, and/or evidence of strong disturbance by wind, desiccation and/or precipitation, supports short periods of exposure of the imprinted surface particular to this succession. An integrated multiproxy approach is proposed to evaluate the evolutionary interpretation and identification of autogenic versus allogenic controls in underfilled lake-basin histories. The observed aggradational-trend suggests an equilibrium between rates of accommodation change and sediment supply, and that the basin-centre did not experience prolonged sediment-starved conditions.