Spatial and temporal variation of the nekton and hyperbenthos from a temperate European estuary with regulated freshwater inflow

The aquatic macrofauna of the Guadalquivir estuary were sampled (1 mm mesh persiana net) at 5 sampling sites located along the entire (except the tidal freshwater region) estuarine gradient of salinity (outer 50 km). A total of 134 fish and macroinvertebrate species was collected but only 62 were considered common or regularly present in the estuary. Univariate measures of the community structure showed statistically significant differences among sampling sites: species richness, abundance, and biomass decreased in the upstream direction, being positively correlated with the salinity. Temporal differences of these three variables were also statistically significant. While a clear seasonal pattern (minimum densities in winter and maximum in spring-summer) was observed for abundance and biomass, no such pattern existed for the number of species. Mysids was the most dominant group throughout the estuary (96% to 99% of abundance; 49% to 85% of biomass), although fish biomass was also important at the outer estuary (36% to 38%). Multivariate analyses indicated highly significant spatial variation in the macrofaunal communities observed along the salinity gradient. These analyses suggest that the underlying structure was a continuum with more or less overlapping distributions of the species dependent on their ability to tolerate different physicochemical conditions. There were also significant temporal (intermonthly + interannual) variation of the estuarine community; the relative multivariate dispersion indicated that monthly variation was more considerable (relative multivariate dispersion >1) at the outer part of the estuary during the wet year (last 20 km) and was higher in the inner stations during the dry year (32 to 50 km from the river mouth). Since a clear negative exponential relationship was observed between the freshwater input (from a dam located 110 km upstream) and water salinity at all sampling stations, it is concluded that the human freshwater management is probably affecting the studied estuarine communities. While the higher seasonal (long-term) stability of the salinity gradient, due to the human control of the freshwater input, may facilitate the recruitment of marine species juveniles during the meteorologically unstable early-spring, the additional (short-term) salinity fluctuations during the warm period may negatively affect species that complete their lifecycle within the estuary.     

Local dynamical equivalence of certain food webs

An important challenge in theoretical ecology is to find good coarse-grained representations of complex food webs. Here, we use the approach of generalized modeling to show that it may be possible to formulate a coarse-graining algorithm that conserves the local dynamics of the model exactly. We show examples of food webs with a different number of species that have exactly identical local bifurcation diagrams. Based on these observations, we formulate a conjecture governing which populations of complex food webs can be grouped together into a single variable without changing the local dynamics. As an illustration, we use this conjecture to show that chaotic regions generically exist in the parameter space of a class of food webs with more than three trophic levels. While our conjecture is at present only applicable to relatively special cases, we believe that its applicability could be greatly extended if a more sophisticated mapping of parameters were used in the model reduction.     

Potential for localized groundwater contamination in a porous pavement parking lot setting in Rhode Island

The control of polluted surface runoff and the assessment of possible impacts on groundwater is a concern at the local and regional scale. On this background, a study investigates possible impacts of organic and inorganic pollutants (including bacteria) originating from a permeable asphalt parking lot on the water quality immediately beneath it. The functioning of the permeable pavement, including clogging and restricted vertical percolation, was also evaluated. Four nested sample ports (shallow and deep) were installed below low- and high-traffic areas, including one port outside the parking lot. At least initially there was a good hydraulic connection between the parking surface and the shallow sample ports. The presence of a geotextile layer at the base of the parking lot structure, however, was identified in lab tests as one factor restricting vertical percolation to the deeper ports. Clogging of the permeable surface was most pronounced in heavy traffic areas and below snow pile storage areas. Corroborated by high electric conductivity and chloride measurements, sand brought in by cars during winter was the principal cause for clogging. No bacteria or BOD were found in percolating water. Polycyclic aromatic hydrocarbons (PAH) were present at concentrations near minimum detection limit. Nutrients (nitrate and phosphate) were being leached into the ground via the permeable parking lot surface at annual flux rates of 0.45–0.84 g/m²/year. A multi-species tracer test demonstrated a retention capacity of the permeable parking lot structure of >90% for metals and 27% for nutrients, respectively.     

Direct and Indirect Validation of Potential Fishing Zone Advisory off the Coast of Uttara Kannada,Karnataka

The technique of predicting Potential Fishing Zone using satellite derived sea surface temperature and chlorophyll is becoming an important aspect for the fishermen. In the present study an attempt has been made to compare fish density/catch per unit effort in the areas predicted by Satellite imagery and available to fishermen via electronic display boards at the fish landing centers of Uttara Kannada district, Karnataka with those of non predicted areas. Direct and Indirect validation was done. Direct method means comparing the catch using fishing vessels simultaneously in the notified region with that of catch from non notified region. And in indirect method by comparing catch data from landing centers on notified days with that of non notified days. Direct validation off Karwar showed that catch was significantly higher in notified (PFZ) area with high densities as compared to non notified (non PFZ) regions. When comparisons of landing center data of Karwar, Tadadi and Bhatkal are done it is evident that in all the centers during the period under study, higher catches were observed on notified days than non notified days except in Bhatkal centre in 2009–10. There by validating the accuracy of PFZ predictions and economic gains to fishermen.     

Stratigraphic relations and habitat of the Bende fish teeth,southeastern Nigeria

The age and habitat of the Bende fish fossils have remained a matter of controversy with interpretations ranging between the Paleocene Imo Formation and the Eocene Ameki Formation. Outcrop-based sequence stratigraphic analysis presented in this work shows that the Imo and Ameki Formations together include three laterally extensive estuarine central basin/offshore mud rock units that are associated with the 59.7, 58.1, and the 56.8 ma maximum flooding surfaces, respectively. Field evidence and stratigraphic analysis show that the Bende fossil bones are hosted by the mud rock unit containing the 58.1 ma maximum flooding surface, while the Ameke bone fossils are contained within the condensed section associated with the 56.8 ma maximum flooding surface. Apart from highlighting the relevance of sequence stratigraphy in paleobiological interpretations, this study shows that the Bende fish fauna which Arua first assigned to the Eocene Ameki Formation indeed belongs to the Paleocene Imo Formation.     

Spatial and temporal variability of mesozooplankton and tintinnid ciliates in a seasonally hypersaline estuary

The zooplankton community of Mission Bay, San Diego, California, was monitored over two years, to study spatial and temporal patterns and the response of zooplankton species composition to environmental variation. Data were collected every two weeks from six stations and included hydrographic parameters, dissolved nutrient concentrations, and phytoplankton and zooplankton species composition. Hydrography varied seasonally, along a spatial gradient from the mouth to the back of the bay, and between the two years around the influence of rainfall. Spatially, Mission Bay could be divided into three regions during this study based on hydrography and zooplankton species composition. Zooplankton species composition followed a predictable seasonal progression, with different groups of species being characteristic to particular times of the year. Variability in zooplankton species composition was also evident between years, as certain species were more common in one or the other year of the study. Spatial patterns were more consistent than temporal ones, and related to distance from the mouth of the bay during much of the year and distance from freshwater inlets during the relatively short rainy season. Multivariate analysis revealed that variation in zooplankton species composition was best related to measured abiotic factors (temperature, salinity, rainfall, and tidal velocity).     

Flow and transport predictions during multi-borehole tests in fractured chalk using discrete fracture network models

Multi-borehole pumping and tracer tests on the 10 to 100-m scale were conducted in a fractured chalk aquitard in the Negev Desert, Israel. Outcrop and core fracture surveys, as well as slug tests in packed-off intervals, were carried out at this site to obtain the parameters needed for construction of a stochastic discrete fracture network (DFN). Calibration of stochastic DFNs directly to the multiple borehole test data was inadequate. Instead, two equivalent deterministic DFN flow models were used: the vertical-fractures (VF) model, consisting of only vertical fractures, and the fractures’ intersections (INT) model, consisting of vertical and horizontal fractures with enhanced transmissivity at their intersections. Both models were calibrated against the multi-borehole response of one pumping test and their predictions were tested against three other independent pumping tests. The average accuracies of all transient drawdown predictions of the VF and INT models were 65 and 66%, respectively. In contrast to this equality in average drawdown predictions of both models, the INT model predicted better important breakthrough curve features (e.g., first and peak arrival times), than the VF model. This result is in line with previously assumed channeled flow, derived from analytical analysis of these pumping and tracer tests. Ronit Nativ, deceased, may her memory be blessed.     

Numerical simulation of physical and dynamical characteristics associated with the severe thunderstorm on April 5, 2015 at Kushtia and Jhenaidah

The paper deals with the study of the physical and dynamical characteristics of a severe thunderstorm, which had occurred on April 5, 2015, at about 2100 UTC in the southwestern Bangladesh with location around 23.3–23.7N and 89.0–89.4E within the upazilas (sub-districts) of Kumarkhali and Shailkupa under the districts of Kushtia and Jhenaidah, respectively. The thunderstorm was associated with numerous hails of large size. More than 5000 birds which used to live in the bird sanctuary at Shailkupa and 22,011 birds in Chhaglapara Bird Sanctuary of Kumarkhali died as they were hit by the hails. Large hails also damaged crops, houses and forests over the thunderstorm hit areas. The evolution of the thunderstorm is studied by the WRF model, which is initialized using the National Centers for Environmental Prediction Final reanalysis data of 0000 UTC of April 5, 2015. The simulated results provide a basis to study the physical and dynamical characteristics of the thunderstorm, which are generally not identified by the meteorological observations which are too sparse. The model has captured a micro-low over Kumarkhali and its neighborhood, which favored the occurrence of the severe thunderstorm. The model simulated rainfall is about 26 mm near the place of occurrence, which matches well with the area where the reflectivity of hydrometeor is maximum. The convective available potential energy is found to be 1600 J kg^?1 at 1730 UTC near the place of occurrence of the thunderstorm; this indicates high atmospheric instability over the thunderstorm location for the formation of the thunderstorm. The vertical velocity, convergence, cloud water mixing ratio and the ice water mixing ratio and their vertical extensions are found to be satisfactory and responsible for the occurrence of large hails associated with the thunderstorm.     

Geochemical Characteristics of Gold Polymetallic Deposits as Exemplified by the Laozuoshan Deposit,Heilong jiang,China

From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent.