Tropical Cyclone Impacts on Coastal Regions: the Case of the Yucatán and the Baja California Peninsulas,Mexico     

Luis M. Farfán  Eurico J. D’Sa  Kam-biu Liu  Victor H. Rivera-Monroy 《Estuaries and Coasts》2014,37(6):1388-1402

Tropical cyclones (TCs) are large-scale natural disturbances that generate strong winds and heavy rainfall, impacting coastal and inland environments. TCs also influence biogeochemical and hydrological cycles controlling aquatic primary productivity in tropical and subtropical coastal ecosystems. We assessed TC landfall activity and identified sites along the Mexican east and west coasts with high frequency in the period 1970–2010 and evaluated TCs with significant precipitation. Changes in chlorophyll-a (Chl-a) concentrations before and after storm impacts were estimated using remotely sensed ocean color. There were 1,065 named TCs with a wide diversity in tracks. Three states with the highest number of landfalls were identified: Baja California Sur and Sinaloa on the west coast and Quintana Roo on the east coast. While a relative increase in Chl-a values following TC landfalls in the Baja California and Yucatán Peninsula regions appeared to be strongly linked to TC strength, the intensity of precipitation, the spatial scales of the two peninsulas, and the relative movement of TCs appeared to have contributed to Chl-a variability. Satellite estimates of Chl-a in the nearshore coastal waters following TC passage were likely enhanced by coastal morphology and water discharge along with constituents such as suspended particulate, colored dissolved organic matter and nutrients from rivers, tributaries, and groundwater.  相似文献   

Stochastic seismic performance evaluation of tuned liquid column dampers     

Luis Esteva  Sonia E. Ruiz 《地震工程与结构动力学》1997,26(8):875-876

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Low densities of sea urchins influence the structure of algal assemblages in the western Mediterranean     

Cruz Palacín  Gonzalo Giribet  Susanna Carner  Luis Dantart  Xavier Turon 《Journal of Sea Research》1998,39(3-4)

Numerous studies of interactions between urchins and algae in temperate areas have shown an important structuring effect of sea urchin populations. These studies focused almost wholly on the effect of high urchin densities on laminarian forests. In contrast, algal communities below 5–6 m depth in the northwestern Mediterranean are characterised by low sea urchin densities (<5 ind m⁻²) and the absence of laminarian forests. No previous research has addressed sea urchin/algal interactions in this type of community. To determine the effect of the most abundant echinoid species, Paracentrotus lividus, on well-established algal communities in this area, we performed a removal–reintroduction experiment in rocky patches located between 13 and 16 m depth in the northwestern Mediterranean, where sea urchin densities ranged between 0.9 and 3.4 ind m⁻². After 6 months, the cover of non-crustose algae was significantly higher in the plots from which sea urchins had been removed than in control plots (84 vs 67% cover). These removal plots reverted to their original state upon reintroduction of sea urchins. The non-crustose algae consisted of turfing and frondose forms, with the former representing some 70% of the non-crustose algal cover. Change in the cover of turfing algae was responsible for the significant increase in algal development in the sea urchin removal plots. The response of frondose algae to the treatment varied between algal species. It is concluded that grazing by P. lividus exerts a significant effect on habitat structure, even in communities with low sea urchin densities, such as those found in vast areas of the Mediterranean sublittoral.  相似文献   

Assessing the factors driving the changes in the spatio-temporal distribution of Hepatus pudibundus (Decapoda,Brachyura) over a 20-year interval in a region under the influence of El Niño (ENSO)     

Jeniffer Natalia Teles  Fernando Luis Mantelatto  Antonio Leão Castilho  Adilson Fransozo  Giovana Bertini 《Marine Ecology》2020,41(6):e12617

This study aimed to compare the spatio-temporal distribution of demographic groups of Hepatus pudibundus in the Ubatuba Bay, São Paulo, Brazil, over a 20-year interval. Two 1-year samplings were conducted: the 1st period (P1) ran from September 1995 to August 1996 and the 2nd period (P2) ran from September 2016 to August 2017. Samples were taken from five stations that differed in depth (5, 10, and 15 m) and location (exposed area and sheltered area), aboard a shrimp fishing boat. Over the 20-year period, the percentage of fine sediment increased in all stations. In total, we captured 865 H. pudibundus individuals in the P1 and 4,222 in the P2. The higher abundance seen in the P2 may have been caused by the effects of an intense ENSO event in Ubatuba, as well as co-occurring protective actions against fisheries activities in the region. The spatial distribution also changed after 20 years: In the P1, H. pudibundus were more concentrated in the 15 m station and exposed area, but they shifted to the sheltered area in the P2. This change may be related to the increase of fine sediments in this area, and to the fact that it is naturally protected from fisheries. According to the correspondence analysis, the abundance of males and juveniles was correlated with spring and winter, respectively. In the P1, females were more abundant in spring, whereas in the P2 they were more abundant in summer, which may be explained by a higher nutrient availability to the larvae in the summer of the P2. Our comparisons over the 20-year interval revealed that the spatio-temporal distribution of H. pudibundus has changed and that the population is well established in Ubatuba Bay.  相似文献   

Metazoan parasite communities of Selar crumenophthalmus and Decapterus muroadsi (Pisces: Carangidae) from Mexican Pacific coasts     

Yesenia Gallegos-Navarro  Scott Monks  Sergio García-Ibáñez  Agustín A. Rojas-Herrera  José Luis Rosas-Acevedo 《新西兰海洋与淡水研究杂志》2019,53(3):377-396

Metazoan parasites communities of marine fishes can include both adults and larval stages of several endoparasite groups that use fishes as intermediate or paratenic hosts. The richness and abundance of parasite species larvae that harbour a fish species can therefore be a good indicator of that species’ role as an intermediate host to endoparasite species.

The parasite communities of two small carangid fishes (Selar crumenophthalmus and Decapterus muroadsi) from Mexican Pacific coasts were quantified and analysed. Five hundred sixty-three carangids (S. crumenophthalmus, n?=?402; and D. muroadsi, n?=?161) were collected between April 2014 and April 2018 from three locations. Twenty-four metazoan parasite species were identified in both hosts: five species of Monogenea (adults), eight of Digenea (7 adults and 1 metacercaria), two of Cestoda (larvae), two of Nematoda (one adult and one larva), two of Acanthocephala (adults), and five of Copepoda. Larval helminths numerically dominated the endoparasite communities of both hosts, suggesting that these carangids are important intermediate hosts for several parasite species. Component parasite community richness and species composition differed between hosts, locations, and sampling years. Variations in host feeding behaviour, and body size were considered as important factors influencing these differences.  相似文献   

Every single street? Rethinking full coverage across street‐level imagery platforms     

Sterling Quinn  Luis Alvarez Len 《Transactions in GIS》2019,23(6):1251-1272

Street‐level images taken by vehicles and pedestrians have found a role in various companies’ location‐based intelligence services. Some platforms collect their images using their own cars and drivers, while others rely on crowdsourcing; however, to what extent can we expect crowdsourced approaches to reach the imagery coverage levels obtained by paid drivers? Is capturing every single street a useful or obtainable goal? We use online coverage maps to compare Google Street View, Mapillary, and OpenStreetCam in 24 major world cities and 25 differently sized cities in Brazil. We find that Google has often taken an all‐or‐nothing approach to collecting coverage in world cities, whereas crowdsourced platforms have achieved a more even distribution of coverage across space. Extremely low‐ and high‐income neighborhoods are sometimes omitted due to visible and invisible barriers. Coverage patterns are influenced by how and why each company procures imagery, along with other social, economic, and geographic factors.  相似文献   

Estimating chlorophyll content of crops from hyperspectral data using a normalized area over reflectance curve (NAOC)     

Jesús Delegido  Luis AlonsoGonzalo González  José Moreno 《International Journal of Applied Earth Observation and Geoinformation》2010

The Normalized Area Over reflectance Curve (NAOC) is proposed as a new index for remote sensing estimation of the leaf chlorophyll content of heterogeneous areas with different crops, different canopies and different types of bare soil. This index is based on the calculation of the area over the reflectance curve obtained by high spectral resolution reflectance measurements, determined, from the integral of the red–near-infrared interval, divided by the maximum reflectance in that spectral region. For this, use has been made of the experimental data of the SPARC campaigns, where in situ measurements were made of leaf chlorophyll content, LAI and fCOVER of 9 different crops – thus, yielding 300 different values with broad variability of these biophysical parameters. In addition, Proba/CHRIS hyperspectral images were obtained simultaneously to the ground measurements. By comparing the spectra of each pixel with its experimental leaf chlorophyll value, the NAOC was proven to exhibit a linear correlation to chlorophyll content. Calculating the correlation between these variables in the 600–800 nm interval, the best correlation was obtained by computing the integral of the spectral reflectance curve between 643 and 795 nm, which practically covers the spectral range of maximum chlorophyll absorption (at around 670 nm) and maximum leaf reflectance in the infrared (750–800 nm). Based on a Proba/CHRIS image, a chlorophyll map was generated using NAOC and compared with the land-use (crops classification) map. The method yielded a leaf chlorophyll content map of the study area, comprising a large heterogeneous zone. An analysis was made to determine whether the method also serves to estimate the total chlorophyll content of a canopy, multiplying the leaf chlorophyll content by the LAI. To validate the method, use was made of the data from another campaign ((SEN2FLEX), in which measurements were made of different biophysical parameters of 7 crops, and hyperspectral images were obtained with the CASI imaging radiometer from an aircraft. Applying the method to a CASI image, a map of leaf chlorophyll content was obtained, which on, establishing comparisons with the experimental data allowed us to estimate chlorophyll with a root mean square error of 4.2 μg/cm², similar or smaller than other methods but with the improvement of applicability to a large set of different crop types.  相似文献   

MERLIN: a flood hazard forecasting system for coastal river reaches     

Fraga  Ignacio  Cea  Luis  Puertas  Jerónimo 《Natural Hazards》2020,100(3):1171-1193

Natural Hazards - This study presents MERLIN, an innovative flood hazard forecasting system for predicting discharges and water levels at flood prone areas of coastal catchments. Discharge...  相似文献   

Effects of foundation embedment during building–soil interaction     

Javier Avils  Luis E. Prez-Rocha 《地震工程与结构动力学》1998,27(12):1523-1540

A numerical solution for evaluating the effects of foundation embedment on the effective period and damping and the response of soil–structure systems is presented. A simple system similar to that used in practice to account for inertial interaction effects is investigated, with the inclusion of kinematic interaction effects for the important special case of vertically incident shear waves. The effective period and damping are obtained by establishing an equivalence between the interacting system excited by the foundation input motion and a replacement oscillator excited by the free-field ground motion. In this way, the use of standard free-field response spectra applicable to the effective period and damping of the system is permitted. Also, an approximate solution for total soil–structure interaction is presented, which indicates that the system period is insensitive to kinematic interaction and the system damping may be expressed as that for inertial interaction but modified by a factor due to kinematic interaction. Results involving both kinematic and inertial effects are compared with those obtained for no soil–structure interaction and inertial interaction only. The more important parameters involved are identified and their influences are examined over practical ranges of interest. © 1998 John Wiley & Sons, Ltd.  相似文献   

250 years of sardine and anchovy scale deposition record in Mejillones Bay, northern Chile   总被引：2，自引：1，他引：1  

Jorge Valds  Luc Ortlieb  Dimitri Gutierrez  Luis Marinovic  Gabriel Vargas  Abdel Sifeddine 《Progress in Oceanography》2008,79(2-4):198

Marine oxygen-deficient environments with high sedimentation rates and high primary productivity can provide relevant information regarding variations of ocean–climatic conditions in the past. In the Humboldt current ecosystem, which now hosts huge populations of pelagic fishes (mainly anchovy and sardine), fish scale abundance in the sedimentary record may be useful indicators of environmental change. Here we assess such a proxy record in a 42 cm-long sedimentary core collected from 80 m in Mejillones Bay (23°S, northern Chile). We also analyse fish remains in surface sediment sampled along a bathymetric transect (from 10 to 110 m water depth) in the same bay. In the core-top record, the fluctuations of sardine and anchovy scale deposition rates (SDR) agreed with those of industrial catches for these two species in northern Chile, tending to validate the SDR as a proxy of local fish biomass when bottom anoxic conditions prevail. However, apparent SDR for records prior to 1820 have probably been influenced by dissolution processes linked to the oxygenation of the bottom environment of Mejillones Bay, as suggested by other proxy records. After 1820, the fluctuations in the relative abundance of sardine and anchovy scales point to alternating warm and cold conditions during about 30 years and then a progressively cooler period. Since ca. 1870, marked fluctuations of SDR of both species are observed, probably as a consequence of the onset of a different oceanographic regime characterized by intensified upwelling, stronger subsurface oxygen deficiency, higher primary productivity, and enhanced “ENSO-like” interdecadal variability. While anchovy SDR fluctuated in periods of 25–40 years, only two peak periods of sardine SDR occurred (late 19th century and late 20th century), suggesting that sardine abundance depends on other ocean–climatic factors.  相似文献