Magellanic penguin mortality in 2008 along the SW Atlantic coast

Magellanic penguins migrate from Patagonia reaching northern Argentina, Uruguay, and southern Brazil on their winter migration, in parallel with the seasonal pulse of anchovy spawning. In 2008, Magellanic penguins went further north than usual. Many died and a few swam nearly to the Equator. Twelve groups surveyed 5000 km of coastline encountering 3371 penguins along the coast. Most penguins arrived in northern Brazil (68.4%) without petroleum (2933, 87%). Almost all penguins without petroleum were juveniles (2915, 99%) and 55% were alive when found. Penguins were dehydrated, anemic, hypothermic, and emaciated. Of the penguins with petroleum, 13% arrived in the southern half of Brazil, showing that petroleum pollution remains a problem along the SW Atlantic coast. The mortality occurred in the winter of 2008 when sea surface temperature were unusually cold perhaps reducing the prey for penguins.     

Gamma-ray bursts with peculiar temporal asymmetry

Based on Link & Epstein's study of temporal asymmetry of 631 gamma-ray bursts from the BATSE 3B catalogue, we identify the population of bursts with rising times that are longer than their decays, thus showing atypical profiles. We analyse their sky distribution, morphology, time–space clustering and other average properties and compare them with those associated with the bulk of the bursts. We show how most of the peculiar bursts analysed are consistent with recent fireball models, but a fraction of bursts (∼4 per cent of the total sample) appear to be inconsistent.     

Flood hazard mapping in Southern Brazil: a combination of flow frequency analysis and the HAND model

The Itajaí River basin is one of the areas most affected by flood-related disasters in Brazil. Flood hazard maps based on digital elevation models (DEM) are an important alternative in the absence of detailed hydrological data and for application in large areas. We developed a flood hazard mapping methodology by combining flow frequency analysis with the Height Above the Nearest Drainage (HAND) model – f2HAND – and applied it in three municipalities in the Itajaí River basin. The f2HAND performance was evaluated through comparison with observed 2011 flood extent maps. Model performance and sensitivity were tested for different DEM resolutions, return periods and streamflow data from stations located upstream and downstream on the main river. The flood hazard mapping with our combined approach matched 92% of the 2011 flood event. We found that the f2HAND model has low sensitivity to DEM resolution and high sensitivity to area threshold of channel initiation.     

Influence of beach morphodynamics on the bivalve Donax hanleyanus and Mesodesma mactroides populations in Argentina

Five exposed microtidal sandy beaches of North-eastern Buenos Aires (Argentina) were analysed to evaluate the influence of coastal dynamics on the abundance of the intertidal clams Donax hanleyanus and Mesodesma mactroides over a 1-year period. The physical characterisation of each beach was performed using 15 environmental variables and six morphodynamic indices. The population densities of both clam species were estimated by the number of individuals per strip-transect. Analysis of similarities revealed a significant multivariate environmental difference among beaches, which could be aggregated into a northern and a southern group. The former group was characterised by an intermediate morphodynamic state and by having, in general, high density values for both clam species. The latter was composed of beaches with an intermediate reflective state and showed, in general, low density values. Beach Index and Area showed the lowest temporal variation. Total density values, as well as density values of recruits and adults of D. hanleyanus and M. mactroides did not follow a north–south latitudinal gradient. Spatial and temporal fluctuations of density values were best explained by changes in individual physical variables rather than by changes in composite indices.     

Comparison of the spatio-temporal distribution of the roughneck shrimp Rimapenaeus constrictus (Stimpson, 1874) (Crustacea,Penaeoidea) from monthly samples collected 20 years apart: Effects of a marine protected area in southeastern Brazil

This study was motivated by the data about a Rimapenaeus constrictus population from Ubatuba Bay, obtained in the 1990s, and by the establishment of a marine protected area (MPA) in the same region in 2008. We obtained comparable data about the distribution and abundance of this species collected 20 years apart, to evaluate the effectiveness of the MPA, for its preservation and possible changes in the populational profile. Biotic and abiotic data were obtained monthly, in September 1995–August 1996 (period 1 = 1ºP), and in September 2016–August 2017 (period 2 = 2ºP), from five transects within Ubatuba Bay. In total, 710 and 2,362 individuals were caught in the 1^oP and 2^oP, respectively. Despite this increase in abundance, aspects of the spatial distribution did not change substantially. The high abundance recorded at 5 m of depth was probably due to the creation of the MPA and to the accumulation of detritus at this depth. The high abundance seen in the transect sheltered from waves may be related to sediment heterogeneity, which was higher in this transect, and to the fact that this area is naturally protected from fisheries. In the 1ºP, the highest abundances were recorded in spring and summer, whereas in the 2ºP, they occurred in autumn and winter. This change may be explained by the entrance of the South Atlantic Central Water (SACW), which drives shrimps towards shallower areas. During the 2ºP, a fishing ban occurred in autumn (March 1st until May 31st), which is also when the SACW retreats and water temperature and salinity increase. These two factors combined may have been responsible for the increased shrimp abundance. In conclusion, both conservation practices (MPA and fishing ban) along with the existence of an area naturally protected from fisheries seem to have positively affected the population of R. constrictus, leading to an increase in abundance over the 20-year interval.     

Spectral classification of water masses under the influence of the Amazon River plume

The large amount of dissolved and particulate material discharged by the Amazon River into the Equatorial Atlantic Ocean cause distinct spectral response of its waters as compared to the nearby ocean waters. This paper shows the application of K-means clustering algorithm for classifying water masses in the region under the Amazon River plume influence according to their spectral behavior. Salinity and temperature data from 67 oceanographic stations were related to Sea-viewing Wide Field-of-view Sensor (SeaWiFS) remote sensing reflectances values and the following bio-optical products:(i) chlorophyll-a concentration, (ii) water attenuation coefficient and (iii) absorption coefficient for dissolved and detrital material. Four different water masses were identified such as:(1) oceanic water, (2) intermediate oceanic water, (3) intermediate river plume water and (4) Amazon River plume water. The spectral behavior of these water masses allowed concluding that the main active optical component of the waters in the region is the colored dissolved organic matter originated mostly from the Amazon River.     

Uniform fragility spectra for the performance‐based seismic design of structures considering variabilities in structural properties

This paper presents a new methodology based on structural performance to determine uniform fragility design spectra, i.e., spectra with the same probability of exceedance of a performance level for a given seismic intensity. The design spectra calculated with this methodology provide directly the lateral strength, in terms of yield‐ pseudo‐accelerations, associated with the rate of exceedance of a specific ductility characterizing the performance level for which the structures will be designed. This procedure involves the assessment of the seismic hazard using a large enough number of seismic records of several magnitudes; these records are simulated with an improved empirical Green function method. The statistics of the performance of a single degree of freedom system are obtained using Monte Carlo simulation considering the seismic demand, the fundamental period, and the strength of the structure as uncertain variables. With these results, the conditional probability that a structure exceeds a specific performance level is obtained. The authors consider that the proposed procedure is a significant improvement to others considered in the literature and a useful research tool for the further development of uniform fragility spectra that can be used for the performance‐based seismic design and retrofit of structures.     

Changes in snowmelt runoff timing in the contiguous United States

Changes in timing of snowmelt-fed streamflow have great importance for water supply, flood management, and ecological processes, as well as being a common indicator of climate change. In this study, snowmelt runoff timing change in the contiguous United States between 1957 and 2016 was investigated by analysing data from 97 streamflow gages. The annual snowmelt runoff timing shift was identified using ‘Center Time (CT)’ and ‘Spring Pulse Onset (SPO)’ methods, jointly with the monthly fractional streamflow (MFS) analysis, conducted between January and June. Since snowmelt-derived streamflow timing change is mainly induced by regional meteorological factors, such as air temperature and precipitation, their trends and relationship with CT were also examined. Shifts toward earlier snowmelt runoff timing were found by both methods, CT (8.3 days on average) and SPO (8.5 days on average). Although the results of the CT change are stronger than the SPO change, both outcomes are mostly correlated, particularly in the central and northwestern parts of the country. MFS trends support the outcomes of CT and SPO. In January, February, and especially March, a higher number of the stations indicated increasing trends in MFS. In April, May, and June, their number decreased and the number of gages with diminishing trends rose sharply. The timing difference is highly related to temperature change. Annual average temperature and temperature in the melting period increase considerably. The annual average temperature is significantly negatively correlated with CT in the vast majority of the regions. Although precipitation is not as effective as the temperature, its trends have impacts on snowmelt runoff timing change depending on the region and elevation. These results demonstrate the importance of the impacts of snowmelt runoff timing changes due to global warming on the regional and large-scale hydrology in the contiguous United States.