Phytoplankton driven distribution of dissolved and particulate lipids in a semi-enclosed temperate sea (Mediterranean): Spring to summer situation

The relationship between changes in lipid classes and phytoplankton composition and abundance in the northern Adriatic was studied during spring and summer 2008 at two stations with different nutrient levels, i.e. at the western mesotrophic and eastern oligotrophic areas. Changes in the phytoplankton community depended on temporal surface nutrient depletion and bottom accumulation; that is, microphytoplankton, mainly diatoms Pseudo-nitzschia sp., developed at nutrient richer surface layers of the mesotrophic area in spring and at deeper layers of the oligotrophic site in late summer. In other periods nanophytoplankton dominated. Dissolved organic carbon (DOC) and lipid content were comparable for the two stations, while particulate organic carbon (POC) was richer at the mesotrophic side. Total lipid concentrations varied in the range from 8.0 to 92.2 μg l⁻¹ and from 16.9 to 76.9 μg l⁻¹ in the dissolved and particulate fractions, respectively. DOC and POC contents were in the ranges from 0.77 to 1.58 mg l⁻¹ and from 0.06 to 0.56 mg l⁻¹, respectively. Lipid and organic carbon distribution did not follow phytoplankton progression, indicating decoupling between organic matter production and decomposition throughout the investigation period. The main sources of lipids were marine phytoplankton and bacteria. Low nutrient conditions caused increased biosynthesis of lipids. Also, increasing oligotrophy led to an increasing number of phytoplankton taxa. The synthesis and accumulation of glycolipids by the developed taxa were enhanced during nutrient exhaustion, contributing in late summer, on average, 20.2 and 22.0% at the mesotrophic and oligotrophic stations, respectively, in the particulate fraction. The distribution of bacterial lipids and lipid breakdown products implies that bacterial lipid degradation was significant in spring, while very probably lipid abiotic degradation took place during summer.     

The impact of topography on social factors,a case study of Montenegro

Relationships between environmental and social factors have long been studied by geographers.Nowadays,GIS-aided statistical analysis provides new tools to explore these relationships.In order to detect the impact of topography on social factors,we selected the country of Montenegro as a case example due to its high topographic variability.We compared the spatial pattern of population,settlements and ethnic minorities to physical geographic factors,especially to topography,but lithology and land cover data were also taken into consideration.We found that certain factors are closely correlated,e.g.the settlement density linearly decreases with elevation,while the characteristic settlement area shows an exponential increase upwards.The population density is not related to absolute elevation,but it is in close correlation with height（i.e.elevation relative to the local minimum）.Population change and illiteracy are also topography-related social factors.On the contrary,the variable ethnic pattern of Montenegro is influenced by historical,political and economic effects rather than by environmental factors or topographic features.As a conclusion we state that in the scale of a country or a region,the environment can strongly impact some social factors.     

Application of piezoelectric transducers in simulated rainfall erosivity assessment

Abstract

Rainfall simulators have often been used to mimic natural rainfall for studies of various land-surface and water interaction processes. The characteristics of the simulated rainfall are the main indicators used to judge the performance of the rainfall simulators. The aim of this study is to investigate the potential of piezoelectric transducers for measuring and evaluating a dripper-type simulated rainfall drop-size distribution (DSD) and kinetic energy (KE). The directly measured KE was significantly correlated with the estimated KE using the drop-size distribution and empirical rain drop fall velocity relationships. This result emphasizes the potential use of the piezoelectric sensor to directly measure and evaluate rainfall kinetic energy. Also, the relationship between rainfall intensity and KE showed good patterns of agreement between simulated rainfall and natural rainfall.

Citation Abd Elbasit, M. A. M., Yasuda, H. & Salmi, A. (2011) Application of piezoelectric transducers in simulated rainfall erosivity assessment. Hydrol. Sci. J. 56(1), 187–194.     

Regional sea-surface temperatures explain spatial and temporal variation of summer precipitation in the source region of the Yellow River

ABSTRACT

The summer precipitation (June–September) in the source region of the Yellow River accounts for about 70% of the annual total, playing an important role in water availability. This study divided the source region of the Yellow River into homogeneous zones based on precipitation variability using cluster analysis. Summer precipitation trends and teleconnections with global sea-surface temperatures (SST) and the Southern Oscillation Index (SOI) from 1961 to 2010 were investigated by Mann-Kendall test and Pearson product-moment correlation analysis. The results show that the northwest part (Zone 1) had a non-significantly increasing trend, and the middle and southeast parts (zones 2 and 3) that receive the most precipitation displayed a statistically significant decreasing trend for summer precipitation. The summer precipitation in the whole region showed statistically significant negative correlations with the central Pacific SST for 0–4 month lag and with the Southern Indian and Atlantic oceans SST for 5–8 month lag. Analyses of sub-regions reveal intricate and complex correlations with different SST areas that further explain the summer precipitation variability. The SOI had significant positive correlations, mainly for 0–2 months lag, with summer precipitation in the source region of the Yellow River. It is seen that El Niño Southern Oscillation (ENSO) events have an influence on summer precipitation, and the predominant negative correlations indicate that higher SST in equatorial Pacific areas corresponding to El Niño coincides with less summer precipitation in the source region of the Yellow River.

Editor Z.W. Kundzewicz; Associate editor D. Gerten     

Third-order geomorphometric variables (derivatives): definition,computation and utilization of changes of curvatures

Third-order geomorphometric variables (based on third derivatives of the altitudinal field) have been neglected in geomorphometry, but their application to the delimitation of surface objects will lead to their increasing significance in future. New techniques of computation, presented and evaluated here, facilitate their use. This paper summarizes recent knowledge concerning definition, computation and geomorphologic interpretation of these variables. Formulae defining various third-order variables are unified based on the physical definition of slope gradient. Methods for their computation are compared from the point of view of method error and error generated by digital elevation model (DEM) inaccuracy. For exact mathematical test surfaces, the most natural and simple variant of the method of central differences (CD2) shows a method error 2–3 times smaller than the other methods used recently in geomorphometry. However, success in coping with DEM inaccuracy depends (for a given grid mesh) on the number and weighting of points from which the derivative is computed. This was tested for surfaces with varying degrees of random error. Here least squares-based methods are the most effective for mixed derivatives (especially for finer grids and less accurate DEMs), while a variant of the CD method, that repeats numerical evaluation of first derivatives (CD1), is the most successful for derivatives in cardinal directions. The CD2 method is generally the most successful for coarser grids where the method error is dominant.

Utilization of third-order variables is documented from examples of terrain feature (ridge, valley and edge) extraction and from a first statistical test of the hypothesis that real segments of the land surface have a tendency to a constant value of some morphometric variable. For detection of (sharp) ridges and valleys, it is shown that the rate of change of tangential curvature is inadequate: rate of change of normal curvature is also required. A basic confirmation of the constant-value tendency is provided.     

Vehicle-derived emissions and pollution on the road autovia 2 investigated by rock-magnetic parameters: A case study from Argentina

In this work, we carried out a preliminary study of traffic-derived pollutants from primary sources (vehicles), and on roads (paved area), road borders and surroundings areas. The study is focussed on the identification, distribution and concentration of pollutants and magnetic carriers. Magnetic parameters and their analyses suggest that the magnetic signal of vehicle-derived emissions is controlled by a magnetite-like phase. Magnetic grain size estimations reveal the presence of fine particles (0.1–5 μm) that can be inhaled and therefore are dangerous to human health. Magnetic susceptibility results (about 175 × 10⁻⁵ SI) show a higher magnetic concentration — magnetic enhancement — in the central area of the tollbooth line that is related to higher traffic. In addition, magnetic susceptibility was computed on several roadside soils along a length of 120 km and used to generate a 2-D contour map, which shows higher magnetic values (100–200 10⁻⁵ SI) near the edge of the road. The observed distribution of magnetic values indicates that magnetic particles emitted by vehicles are accumulated and mainly concentrated within a distance of several meters (1–2 m) from the edge of the road. In consequence, the magnetic susceptibility parameter seems to be a suitable indicator of traffic-related pollution. Non-magnetic studies show an enrichment of some trace elements, such as Ba, Cr, Cu, Zn and Pb, that are associated with traffic pollution. Furthermore, statistical correlations between the content of toxic trace metals and magnetic variables support the use of magnetic parameters as potential proxies for traffic-related pollution in this study area.     

Fate and tidal transport of butyltin and mercury compounds in the waters of the tropical Bach Dang Estuary (Haiphong, Vietnam)

In this work, two field campaigns were performed in July 2008 (wet season) and March 2009 (dry season) to produce original data on the concentration, partition and distribution of mercury and butyltin compounds along the tropical Bach Dang Estuary located in North Vietnam (Haiphong, Red River Delta). The results demonstrate that mercury and butyltin speciation in the surface waters of this type of tropical estuary is greatly affected by the drastic changes in the seasonal conditions. During high river discharge in the wet season, there was a large estuarine input of total Hg and tributyltin, while the longer residence time of the waters during the dry season promotes increasing MMHg formation and TBT degradation. Although most of the Hg and TBT is transported into the estuary from upstream sources, tidal cycle measurements demonstrate that this estuary is a significant source of TBT and MMHg during the wet (～3kgTBT/day) and dry (～3gMMHg/day) seasons.     

Inter-model variability of projected sea level changes in the western North Pacific in CMIP3 coupled climate models

We investigate sea level changes in the western North Pacific for twenty-first century climate projections by analyzing the output from 15 coupled models participating in the Coupled Model Intercomparison Project phase 3 (CMIP3). Projected changes in the wind stress due to those in sea level pressure (SLP) result in the projected sea level changes. In the western North Pacific (30?50°N, 145?170°E), the inter-model standard deviation of the sea level change relative to the global mean is comparable to that based on the multi-model ensemble (MME) mean. Whereas a positive SLP change in the eastern North Pacific (40?50°N, 170?150°W) induces a large northward shift of the Kuroshio Extension (KE), a negative SLP change in this region induces a strong intensification of the KE. Large inter-model variability of the SLP projection in the eastern North Pacific causes a large uncertainty of the sea level projection in the western North Pacific. Models with a larger northward shift (intensification) of the KE exhibit a poleward shift (an intensification) of the Aleutian Low (AL) larger than that for the MME mean. However, models that exhibit a larger intensification of the AL do not necessarily show a larger intensification of the KE. Our analysis suggests that the SLP change that induces an intensification of the KE is associated with a teleconnection from the equatorial Pacific, and that the SLP change that induces a northward shift of the KE is characterized by a zonal mean change.     

Manmade Vulnerability of the Cancun Beach System: The Case of Hurricane Wilma

Climate change and resultant coastal erosion and flooding have been the focus of many recent analyses. Often these studies overlook the effects of manmade modifications to the coastline which have reduced its resilience to storm events. In this investigation, we integrate previous reports, historical photo analysis, field work, and the application of numerical models to better understand the effects of Wilma, the most destructive hurricane to affect Cancun, Mexico. Huge waves (of significant height, >12 m), long mean wave periods (>12 s), devastating winds (>250 km/h), and powerful currents (>2 m/s) removed >7 million cubic meters of sand from the Cancun beach system, leaving 68% of the sub‐aerial beach as bedrock, and the rest considerably eroded. Numerical simulations show that the modifications to the barrier island imposed by tourist infrastructure have considerably increased the rigidity of the system, increasing the potential erosion of the beach under extreme conditions. If there were no structural barriers, a series of breaches could occur along the beach, allowing exchange of water and alleviating storm surge on other sections of the beach. If the effects caused by anthropogenic changes to Cancun are ignored, the analysis is inaccurate and misleading.