Horizontal Distribution Patterns Research Articles

Localisation of Nursery Areas Based on Comparative Analyses of the Horizontal and Vertical Distribution Patterns of Juvenile Baltic Cod (Gadus morhua)

Knowledge of the spatial distribution of juvenile cod is essential for obtaining precise recruitment data to conduct sustainable management of the eastern and western Baltic cod stocks. In this study, the horizontal and vertical distribution and density patterns of settled juvenile 0- and 1-group Baltic cod are determined, and their nursery areas are localised according to the environmental factors affecting them. Comparative statistical analyses of biological, hydrographic and hydroacoustic data are carried out based on standard ICES demersal trawl surveys and special integrated trawl and acoustic research surveys. Horizontal distribution maps for the 2001–2010 cohorts of juvenile cod are further generated by applying a statistical log-Gaussian Cox process model to the standard trawl survey data. The analyses indicate size-dependent horizontal and distinct vertical and diurnal distribution patterns related to the seabed topography, water layer depth, and the presence of hydrographic frontal zones (pycnoclines) as well as intraspecific patterns in relation to the presence of adult cod. The extent of the nursery areas also depends on the cod year class strength. Juvenile cod (≥3 cm) are present in all areas of the central Baltic Sea (CBS), showing broad dispersal. However, their highest density in the Baltic Basins is found at localities with a 40–70 m bottom depth in waters with oxygen concentrations above 2 ml O2.l−1 and temperatures above 5°C. The smallest juveniles are also found in deep sea localities down to a 100 m depth and at oxygen concentrations between 2–4 ml O2.l−1. The vertical, diurnally stratified and repeated trawling and hydroacoustic target strength-depth distributions obtained from the special surveys show juvenile cod concentrations in frontal zone water layers (pycnocline). However, the analyses indicate that in the CBS, juvenile cod of all sizes do not appear to aggregate in dense schooling patterns, which differs from what has been reported from the North Sea.

Variability of temperature and chlorophyll of the Iberian Peninsula near costal ecosystem during an upwelling event for the present climate and a future climate scenario

Understanding the importance and the implication of the climate changes on coastal areas may be one of the major issues for this and next centuries. Climate changes may, indeed, impact the nearshore marine ecosystem, as coastal areas are very sensitive to the strength and the variability of the meteorological forcings.The main purpose of this work is to study temperature and phytoplankton distributions along the Portuguese near coastal zone during upwelling events in the present climate conditions and in a future climate scenario. The SRES-A2 IPCC scenario has been considered.We have used a three-dimensional model for coastal and shelf seas, including the following sub-models: hydrodynamical/physical, biological, sediment and contaminant. The forcings are provided by the interactions at the air–sea, considering the wind intensity and direction with the help of the WRF model (Weather Research and Forecast Model) and the coupled atmosphere–ocean model ECHAM5/MPI-OM.Results show that, for the future climate scenario, there is a reinforcement of the southward wind. The responses of the coastal ecosystem corresponds to the reinforcement of both, the southward (up to 10cm/s) and the westward (up to 6cm/s) induced upwelling currents. This, in turn generates an enlargement of the near coast upwelled cold layer, extending up to 60km, as well as the rise of the warm layer temperature (up to 2.0°C) and the spreading of the phytoplankton offshore. Significant changes in both the Chl-a vertical and the horizontal distribution patterns have been observed, as the nutrient supply to the upper layers depends on the strength of the upwelling, the bottom topography and orography of the coastal. These results confirm that changes in the strength and eventually the frequency of the upwelling favourable wind impact the phytoplankton distribution, which can have significant effect in the distribution and population of the upper level of the trophic chain of the coastal ecosystem.

Ants of Three Adjacent Habitats of a Transition Region Between the Cerrado and Caatinga Biomes: The Effects of Heterogeneity and Variation in Canopy Cover

Habitat heterogeneity and complexity associated with variations in climatic conditions are important factors determining the structure of ant communities in different terrestrial ecosystems. The objective of this study was to describe the horizontal and vertical distribution patterns of the ant community associated with three adjacent habitats in a transition area between the Cerrado and Caatinga biomes at the Pandeiros River, state of Minas Gerais, Brazil. We tested the following hypotheses: (1) the richness and composition of ant species and functional group structure changes between different habitats and strata; (2) habitats with higher tree species richness and density support higher ant species richness; and (3) habitats with lower variation in canopy cover support higher ant species richness. Sampling was conducted in three adjacent habitats and at three vertical strata. Ant species richness was significantly different among vertical strata. Ant species composition was different among both habitats and vertical strata and functional group structure was divergent among habitats. Partitioning of the diversity revealed that the diversity for the three components was statistically different from the one expected by the null model; α and β 2 were higher and β 1 was lower than the values expected by chance. Tree density and variation in canopy cover negatively affected ant species richness. The occurrence of different species and the changing of functional group structures in different habitats and strata suggest an ecological-evolutionary relationship between ants and their habitats and emphasize the need to implement local conservation strategies in the ecotones between biomes.

Active moss biomonitoring of small-scale spatial distribution of airborne major and trace elements in the Belgrade urban area

In urban environments, human exposure to air pollutants is expected to be significantly increased, especially near busy traffic streets, street canyons, tunnels, etc. where urban topography and microclimate may additionally cause poor air conditions giving rise to pollution hotspots. As a practical and cost-effective approach, active moss biomonitoring survey of some major and trace element air pollution was performed in the Belgrade street canyons and city tunnel in 2011 with the aim to evaluate possibility of using Sphagnum girgensohnii moss bags for investigation of the small-scale vertical and horizontal distribution patterns of the elements. In five street canyons, the moss bags were hung at heights of about 4, 8 and 16 m, during 10 weeks, and also, for the same time, the moss bags were exposed in the tunnel, in front of and out of it. After the exposure period, the concentrations of Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V and Zn in the moss were determined by inductively coupled plasma optical emission spectrometry. According to the results, in all street canyons, the vertical distribution patterns of the moss elements concentration (Al, Ba, Co, Cr, Cu, Ni, Pb, Sr, V and Zn) showed statistically significant decrease from the first to the third heights of bags exposure. In the tunnel experiment, from inner to out of the tunnel, for Al, Ba, Cd, Co, Cr, Cu, Fe, K and Zn, decreasing trend of concentrations was obtained. Significantly higher concentration of the elements was pronounced for the tunnel in comparison with the street canyons. The results indicate that the use of S. girgensohnii moss bags is a simple, sensitive and inexpensive way to monitor the small-scale inner city spatial distribution of airborne major and trace element content.

SPATIAL AND TEMPORAL DISTRIBUTION PATTERN OF SUSPENDED SEDIMENT IN THE JINGHAI BAY AND ADJACENT WATERS, SHANDONG PENINSULA

Suspended sediment concentration(SSC),as the basis for sediment flux balance,is an important parameter in marine sedimentology.Based on the survey and hydrological observations at 10 stations in the Jinghai Bay and its adjacent waters,SSC in different layers is calculated,and the SSC horizontal and vertical distribution patterns and the transportation of suspended sediment are analyzed.Data show that SSC changes with the variation of tide current and runoff,and increases from the surface to the bottom and from southwest to northeast.The mechanism of longitudinal suspended sediment transport shows that sediments move toward the land and Wuleidao Bay where flood tide dominates,but move towards the sea near the Changhuikou area where ebb tide dominants.

Spatial and Temporal Variation in PBL Height over the Korean Peninsula in the KMA Operational Regional Model

Spatial and temporal variations in planetary boundary layer height (PBLH) over the Korean Peninsula and its surrounding oceans are investigated using a regional grid model operated at the Korea Meteorological Administration (KMA). Special attention is placed on daily maximum mixing height for evaluation against two radiosonde observation datasets. In order to construct a new high-resolution PBLH database with 3-hour time and 10 km spatial resolution, short-term integrations with the regional model are carried out for a one-year period from June 2010 to May 2011. The resulting dataset is then utilized to explore the seasonal patterns of horizontal PBLH distribution over the peninsula for one year. Frequency distributions as well as monthly and diurnal variations of PBLH at two selected locations are examined. This study reveals specific spatiotemporal structure of boundary layer depth over the Korean Peninsula for the first time at a relatively high-resolution scale. The results are expected to provide insights into the direction for operational tuning and future development in the model boundary layer schemes at KMA.

Peculiarities of the Messel fish fauna and their palaeoecological implications: a case study

General aspects and some peculiarities of the Lake Messel fish fauna are presented and discussed with special focus on the palaeoenvironmental framework. The overall composition of that fauna is analysed including details such as age and growth. Palaeopathological information is derived from scale regeneration, and selected aspects of mortality and taphonomy are also investigated. Special emphasis is placed on analyses of the horizontal and vertical distribution patterns of the fishes in comparison with those of plant and arthropod records on the one hand and the orientation patterns of fish carcasses on the other hand. In this context, long- and short-term, and also local, differences and modifications are discussed. All results indicate a very particular environmental scenario. Lake Messel cannot have been steadily isolated from external water bodies during the period of time that is represented by the investigated fossils. There must instead have been various opportunities for a renovation of the lake’s fish fauna. Probably, the peculiarities of that fauna were predominantly triggered by a selective influx, which also changed during more extended periods of time. The selection could have taken place during active immigration events and by modified interactions with different types of external catchment areas. There need not necessarily have been locally fixed inlets and outlets. It is probable that there were more flexible control mechanisms, like an exchange of water with other bodies of water during occasional high water periods, and in places with a partial (or complete) erosion of the tephra wall shelter. The latter may also have varied as a function of the intensity of the respective high water events.

Horizontal distribution of megalopae of Brachyura (Crustacea, Decapoda) in a South American tropical estuary

The available information on the larval phase of estuarine crabs in tropical habitats is scarce, despite its importance for the population dynamics of these crustaceans. The goal of the present study was to evaluate patterns of spatial distribution of megalopae along a gradient in the Ubatumirim River estuary, Ubatuba region, state of São Paulo, Brazil. Samples were taken periodically during neap and spring tides in April and November 2005. The megalopae were collected on passive collectors made from an organic substrate, at 10 sampling sites equally spaced along the two river channels of the Ubatumirim estuary. At the laboratory, larvae were identified according to available literature. Sesarmid and ocypodid crabs predominated in the samples. Megalopae settled differently in neap- and spring-tide periods, with a tendency toward increased settlement during high-amplitude tides. The highest density of megalopae was recorded at the sites near the river mouth. The observed horizontal distribution pattern probably results from the influence of seawater or from mechanisms to avoid predation and/or competition for resources. Despite problems in identifying taxa to species level, the results of the present study contribute to increase knowledge about overall trends in the horizontal distribution of megalopae in estuarine systems.

Different patterns of stage-specific horizontal distribution between two sympatric oligohaline copepods along a macrotidal estuary (Chikugo River, Japan): implications for life-history strategies

Stage-specific horizontal distribution was compared between two sympatric oligohaline copepods to elucidate their life-history strategies related to reproduction: free-spawning Sinocalanus sinensis and egg-carrying Pseudodiaptomus inopinus. Copepods were sampled by vertical hauls of a 100-mm mesh plankton net along the macrotidal Chikugo River estuary in southwestern Japan from 2005 to 2006. Sinocalanus sinensis dominated throughout the year except for the warm season, when P. inopinus outnumbered S. sinensis. The spatiotemporal correspondence of peak densities with the estuarine turbidity maximum was evident for S. sinensis but ambiguous for P. inopinus. Nauplii of S. sinensis were always distributed on average downstream from copepodids and adults, whereas P. inopinus usually showed the opposite pattern of stage-specific horizontal distribution. During large freshwater discharges, S. sinensis was more subject to washout from the estuary. In addition, the potential vulnerability of S. sinensis to droughts was suggested by low tolerance for high salinities. Consequently, egg-carrying P. inopinus has higher flexibility to live under varying estuarine conditions especially during the warm season. In contrast, ecological specializations, such as tidal vertical migration and detritivorous feeding, are considered to underlie the dominance of the free-spawning S. sinensis under the conditions prevailing in the macrotidal environment.

Reliability of determining the parameters of Gutenberg-Richter distribution for weak Earthquakes in Garm, Tajikistan

The behavior of the Gutenberg-Richter distribution (the frequency-magnitude relation for the earthquakes) in response to advancing the system of seismic observations and applying various methods for estimation of the Gutenberg-Richter b value is studied. The long highly accurate time series of seismological measurements at the Garm geophysical testing site in Tajikistan is an input for the study. We analyzed the data from the detailed catalogue of earthquakes with magnitude M = 0–5 that occurred within the test site from 1955 through 1992. It is shown that the changes in the design of measurements both as to the number of observation sites and as to the measurement capacities during the development of the seismic network in 1955–1966 have strongly affected the content of the catalogue. Our study revealed spatiotemporal changes in the minimum magnitude of completeness, which were associated with advancing the design of observations. We have analyzed the accuracy of the calculation of the b value as a function of the reliability of determining the actual minimal magnitude of completeness (the cutoff magnitude) for the catalogue (Mc), the method of calculation of the b value, and the volume of the spatial sample of the earthquakes used. It is established that the pattern of horizontal distribution of the b value is closely correlated to the tectonic structure of the test area, while its vertical distribution distinctly reflects the crustal waveguide at a depth of 9–17 km, which has been previously revealed approximately in this depth interval according to other seismological data. This suggests that, in the first approximation, the lateral and vertical variations in the b value observed in our study are caused by the changes in the strength properties of the crustal material, namely, by the increased plasticity of the rocks within a thick sedimentary layer and in the waveguide.

Spatial distribution of phosphorus in marsh soils of a typical land/inland water ecotone along a hydrological gradient

Profile samples from 0 to 70 cm depth were collected in five plant zones along a hydrological gradient in a typical land/inland water ecotone, Northeast China. Total phosphorous (TP), organic phosphorous (OP), inorganic phosphorous (IP) and available phosphorous (AP) were measured to study their horizontal and vertical distribution patterns in the land/inland water ecotone, as well as their important influencing factors such as soil organic carbon (SOC) and water level. Our results demonstrated that the levels of TP, OP, IP and AP were generally higher in the flooding zone (zone A), the over-wetted zone (zone B) and the drying and wetting zone (zone C), but the drying zones (zones D and E) contained lower P concentrations. Soil P was mainly concentrated in upper soils (0–30 cm) and the P levels decreased with depth, except for small accumulative peaks in the 50 to 70 cm soil increment for TP and OP in zone C and for IP and AP in zone A. Surface soils in zones D and E had a lower mean SOC:OP ratio than zones A, B and C, reflecting the higher probability of OP mineralization in the drying zones. However, higher mean values of the IP:OP and AP:TP ratios were found in zone A ( P < 0.05), indicating that increasing soil moisture may be the most important agent determining IP release rate and biological availability. The significantly positive correlations with soil organic matter (SOM) and clay content would contribute to P retention in zones A, B and C ( P < 0.01) where the soils contained relatively high organic matter and clay content. The results obtained in this study suggest that the distributions and dynamics of P forms in soil, especially in the land/inland water ecotone, can be significantly impacted by various biogeochemical and environmental factors (i.e., soil moisture, SOM, and clay content). ► The drying zones contain lower soil P levles compared to the wetting zones. ► Soil P mainly concentrates in the top 30cm soils and decreased with depth. ► Soils of the flooding zone shows higher mean values of the IP:OP and AP:TP ratios. ► SOM and clay content can contribute to P retention in zones A, B and C. ► The relative altitude and distance related to water tables can influence IP levels.

Sour orange fine root distribution after seventeen years of atmospheric CO2 enrichment

Long-term (more than 15 years) effects of elevated CO2 on belowground responses of trees have received limited attention in the literature. We report on a study in which sour orange trees (Citrus aurantium L.) grown in an Avondale loam in Phoenix, AZ, were exposed to ambient and elevated (ambient+300μmolmol−1) levels of atmospheric CO2 for 17 years. At study termination, soil cores were collected to determine how long-term CO2 enrichment affected horizontal (0.5, 1.0, 1.5, and 2.0m from each tree) and vertical (0–105cm in 15cm increments) standing crop fine root dry weight and length. Overall, elevated CO2 increased both root length (35.6%) and root dry weight (39.1%) densities. There was no effect of CO2 concentration on horizontal root distribution patterns. However, significant CO2 by depth interactions were noted for both root length and root dry weight densities with differences occurring only in the top two depths. Elevated CO2 increased fine root length density by 64.5 and 57.2% at the 0–15 and 15–30cm depths. Respective increases for root dry weight were 80.3 and 82.8%. These large responses occurred under water and nutrient supplies typical of orchard conditions and suggest that long-term citrus productivity can be enhanced under future levels of atmospheric CO2.

Distribution and variations of phosphorus speciation in Lake Chenghai on plateau, Yunnan Province

采用GPS定位,在程海设置了3个断面9个采样点,对各种形态磷进行了为期1 a的研究,分析了高原深水湖泊程海磷形态分布和变化.结果表明:程海中总磷含量范围为0.008~0.155 mg/L,年平均值为0.046 mg/L,含量水平已经较高.存在形态是颗粒态总磷占54.35%;溶解态有机磷占19.56%;溶解态无机磷占26.09%.各形态磷时间分布和变化与水生生物特别是浮游植物生命活动和周期变化密切相关;水平分布格局受浮游生物活动、湖流风动等综合影响;由水表层-亚底层垂直分布比较均匀,湖底层含量不同程度升高.;Nine sampling sites along three sections in Lake Chenghai were established by Global Positioning System for a study on phosphorus forms in a period of a year. The characteristics of the distribution and variations of phosphorus forms in deep lake on plateau are analyzed. The results indicate that the total phosphorus content is between 0.008 and 0.155 mg/L, and the annual average content is 0.046 mg/L. The percent of existent state of phosphorus forms is 54.35% particulate total phosphorus, 19.56% dissolved organic phosphorus, 26.09% dissolved inorganic phosphorus. The characteristics of the distributions and variations of phosphorus forms are closely related to vital processes and cycles of phytoplankton. The horizontal distribution pattern is easily affected by the composites effects of biological processes of plankton, and movement and feeding of lake water. The distribution of phosphorus is relatively homogenous from the surface layer to the sub-bottom layer, and increase with various degrees at the bottom layer.

李肖叶甲成虫数量及三维空间格局动态

对合肥地区李肖叶甲成虫数量动态及三维空间格局进行研究,结果表明该成虫5月下旬初见,6月4日至7月16日为发生高峰期,9月上旬仍有零星虫口。6月4日至9月10日种群增长模型为<em>y</em>=1692.2258e^{-0.0545<em>t</em>},6月4日至8月27日树冠上部部位增长模型为<em>y</em>=205.60e^{-0.0523<em>t</em>},树冠西部部位的增长模型为<em>y</em>=257.13e^{-0.0505<em>t</em>}。样地中的李肖叶甲5月21日至8月13日半变异函数方程是<em>y</em>=0.0709<em>x</em>³-10.479<em>x</em>²+391.67<em>x</em>-300.71、<em>y</em>=-0.0122<em>x</em>³+1.1201<em>x</em>²-19.781<em>x</em>+317.84、<em>y</em>=-0.0013<em>x</em>³+0.1613<em>x</em>²-4.4862<em>x</em>+67.363、<em>y</em>=-0.0016<em>x</em>³+0.9177<em>x</em>²-11.495<em>x</em>+551.94、<em>y</em>=-0.0029<em>x</em>³+0.3034<em>x</em>²-7.5906<em>x</em>+103.37和<em>y</em>=-0.0002<em>x</em>³+0.0172<em>x</em>²-0.4975<em>x</em>+13.691,变程在20.3938-65.0289之间,均为聚集格局,聚集强度指标表明也均为聚集格局;树冠东、西、南、北方位的水平分布5月21日至8月13日的<em>C</em>值均大于1,I值均大于0,C_A值均大于0,Iw值均大于1,为聚集格局;树冠上、中、下方位的垂直分布6月4日至8月13日的<em>C值均大于1,I</em>值均大于0,<em>C_A</em>值均大于0,<em>Iw</em>值均大于1,为聚集格局;5月21日至8月13日的树冠东、南、西、北、上、中、下部位的<em>C</em>值均大于1,I值均大于0,C_A值均大于0,Iw值均大于1,三维分布均为聚集格局。用Iwao公式计算的结果与聚集强度指标分析的结果一致。6月4日-8月13日林间李肖叶甲的种群聚集均数λ值均大于2,聚集是李肖叶甲本身的行为所致。;To analyze quantitative dynamics of adult population and 3-D spatial pattern of <em>Ceoporus variabilis</em> (Baly), from March 26 to September 24, 2006, we investigated the adult population occurrence of <em>Ceoporus variabilis</em> (Baly) in the Redleaf Cherry Plum trees in the Apricot Blossom Park of Hefei city (117°12' E,31°52' N). The results showed that <em>Ceoporus variabilis</em> (Baly) was firstly seen on May 21, the high peak period of their occurrence was from June 4 to July 16, and only scattered adult numbers appeared in early September. The population growth model of <em>Ceoporus variabilis</em> (Baly) was <em>y</em>=1692.2258e^{-0.0545<em>t</em>} between June 4 and September 10. Similarly, the population growth model of <em>Ceoporus variabilis</em> (Baly) in the top part and the western part of the tree crown was <em>y</em>=205.60e^{-0.0523<em>t</em>} and <em>y</em>=257.13e^{-0.0505<em>t</em>}, respectively, between May 4 and July 27. These results indicate that the adult numbers of <em>Ceoporus variabilis</em> (Baly) in both horizontal and vertical direction all presented exponential decline form after the high peak period of their occurrence. The geostatistics analysis showed that the semivariable function equation of space distribution of <em>Ceoporus variabilis</em> (Baly) in May 21, June 4, June 18, July 2, July 16, July 30 and August 13, respectively, was <em>y</em> = 2E-05<em>x</em>³ - 0.024<em>x</em>² + 0.0727<em>x</em>+0.142, <em>y</em> = 0.0709<em>x</em>³-10.479<em>x</em>²+391.67<em>x</em>-300.71, <em>y</em> = -0.0122<em>x</em>³ + 1.1201<em>x</em>² - 19.781<em>x</em> + 317.84, <em>y</em> = -0.0013<em>x</em>³ + 0.1613<em>x</em>² - 4.4862<em>x</em> + 67.363, <em>y</em> = -0.0016<em>x</em>³ + 0.9177<em>x</em>² -11.495<em>x</em>+551.94, <em>y</em> = -0.0029<em>x</em>³ + 0.3034<em>x</em>² - 7.5906<em>x</em> +103.37</em> and <em>y</em> = -0.0002<em>x</em>³+0.0172<em>x</em>²-0.4975<em>x</em>+13.691. The range of spatial dependence of adult population of <em>Ceoporus variabilis</em> (Baly) in the seven periods was from 20.3938 to 65.0289. The above results revealed that the spatial pattern of adult population of <em>Ceoporus variabilis</em> (Baly) was aggregated distribution from May 21 to August 13. Moreover, our results demonstrated that aggregation indices of horizontal distribution pattern of <em>Ceoporus variabilis</em> (Baly) in the eastern, western, northern and southern part of the tree crown, respectively, have <em>C</em> value＞1, <em>I</em> value＞0, <em>C_A</em> value＞0 and Iw value＞1, indicating that the spatial pattern of their horizontal distribution was aggregated pattern from May 21 to August 13. Consistently, the spatial pattern of their vertical distribution in upper, middle and lower part of the tree crown, respectively, was aggregated pattern with all <em>C</em>＞1, <em>I</em>＞0, <em>C_A</em>＞0 and <em>Iw</em>＞1 from June 4 to August 13. The further analysis indicated that the spatial pattern in the eastern, western, northern, southern, upper, middle and lower part of the tree crown, respectively, presented also aggregated pattern with all <em>C</em>＞1, I＞0, <em>C_A</em>＞0 and <em>Iw</em>＞1 from May 21 to August 13. In addition, our results showed that the <em>λ</em> values of <em>Ceoporus variabilis</em> from June 4 to August 13 were all more than 2, implying that their aggregation behaviors were caused by theirself features.

Distribution and feeding of chaetognaths in the epipelagic zone of the Lazarev Sea (Antarctica) during austral summer

This study seeks to determine the effects of local hydrography on the distribution, abundance and feeding of chaetognaths in the Lazarev Sea, an area strongly controlled by physical processes which has been held responsible for initiating the Weddell Polynya. Zooplankton samples were taken at 39 stations on four transects located between 6°W and 3°E and from 60°S to 70°S between surface and 350 m. The dominant species, Eukrohnia hamata, accounted for 86.5% of all chaetognaths, followed by Sagitta gazellae (8.1%) and Sagitta marri (5.4%). These three species showed distinct vertical and horizontal distribution patterns. While E. hamata and S. marri had maximum abundances below 250 m depth, S. gazellae showed a narrow distribution band in the upper 150 m depth. The distribution pattern was strongly modified at the Greenwich meridian with an upward transport of a high abundance of deep dwelling organisms (S. marri and E. hamata) and a displacement of S. gazellae to the surface, likely coupled with the rise of the warm, saline halo around the Maud Rise. Small copepods were the main prey of all three chaetognath species. Feeding rates (FR) varied among species and depth. Sagitta marri showed the highest FR with 0.38 prey d−1, followed by S. gazellae and E. hamata (0.22 and 0.07 prey d−1). Feeding rates were usually highest in the 25–80-m stratum. Size distribution and maturity of E. hamata revealed a dominance of small and immature organisms along all depths and stations, suggesting that this area might be acting as an important source of recently spawned organisms to the surface.

Spatio-Temporal Variability of Soil Salinity in Alluvial Plain of the Lower Reaches of the Yellow River—A Case Study

Soil salinity and hydrologic datasets were assembled to analyze the spatio-temporal variability of salinization in Fengqiu County, Henan Province, China, in the alluvial plain of the lower reaches of the Yellow River. The saline soil and groundwater depth data of the county in 1981 were obtained to serve as a historical reference. Electrical conductivity (EC) of 293 surface soil samples taken from 2 km × 2 km grids in 2007 and 40 soil profiles acquired in 2008 was analyzed and used for comparative mapping. Ordinary kriging was applied to predict EC at unobserved locations to derive the horizontal and vertical distribution patterns and variation of soil salinity. Groundwater table data from 22 observation wells in 2008 were collected and used as input for regression kriging to predict the maximum groundwater depth of the county in 2008. Changes in the groundwater level of Fengqiu County in 27 years from 1981 to 2008 was calculated. Two quantitative criteria, the mean error or bias (ME) and the mean squared error (MSE), were computed to assess the estimation accuracy of the kriging predictions. The results demonstrated that the soil salinity in the upper soil layers decreased dramatically and the taxonomically defined saline soils were present only in a few micro-landscapes after 27 years. Presently, the soils with relatively elevated salt content were mainly distributed in depressions along the Yellow River bed. The reduction in surface soil salinity corresponded to the locations with deepened maximum groundwater depth. It could be concluded that groundwater table recession allowed water to move deeper into the soil profile, transporting salts with it, and thus played an important role in reducing soil salinity in this region. Accumulation of salts in the soil profiles at various depths below the surface indicated that secondary soil salinization would occur when the groundwater was not controlled at a safe depth.

Patterns of distribution and abundance of larval phosichthyidae (actinopterygii, stomiiformes) in southeastern Brazilian waters

Horizontal and vertical distribution patterns and abundance of larval phosichthyids were investigated from oblique and depth-stratified towns off Southeastern brazilian waters, from São Tomé cape (41ºW.; 22ºS.) to São Sebastião island (45ºW.; 24ºS.). The sampling was performed during two cruises (January/2002 -summer; August/2002 -winter). Overall 538 larvae of Phosichthyidae were collected during summer and 158 in the winter. Three species, Pollichthys mauli, Vinciguerria nimbaria and Ichthyioccoccus sp. occurred in the area, but Ichthyioccoccus sp. was extremely rare represented by only one specimen, caught in the oceanic region during the summer. Geographically, larval were concentrated in the oceanic region, and vertically distributed mainly between the surface and 80 m depth in the summer and winter. Larvae were more abundant during the night, performing a diel vertical migration in the water column. The results suggest that the meandering and eddies of Brazil Current play important role on the transport and distribution patterns of larval phosichthyids over the oceanic and neritic area in the Southeastern Brazil.

Within-plant distribution of cotton aphids,Aphis gossypiiGlover (Hemiptera: Aphididae), in Bt and non-Bt cotton fields

Knowledge of the vertical and horizontal distribution of Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified cotton plants over time could help optimize decision-making in integrated cotton aphid management programs. Therefore, the aim of the present study was to determine the vertical and horizontal distribution of A. gossypii in non-transgenic Bt cotton and transgenic Bt-cotton over time during two cotton seasons by examining plants throughout the seasons. There was no significant interaction between years and cotton cultivar treatments for apterous or alate aphids. Considering year-to-year data, analyses on season-long averages of apterous or alate aphids showed that aphid densities per plant did not differ among years. The number of apterous aphids found per plant for the Bt transgenic cultivar (2427 apterous aphids per plant) was lower than for its isoline (3335 apterous aphids per plant). The number of alate aphids found per plant on the Bt transgenic cultivar (12.28 alate aphids per plant) was lower than for the isoline (140.56 alate aphids per plant). With regard to the vertical distribution of apterous aphids or alate aphids, there were interactions between cotton cultivar, plant age and plant region. We conclude that in comparison to non-Bt cotton (DP 4049), Bt cotton (DP 404 BG (Bollgard)) has significant effects on the vertical, horizontal, spatial and temporal distribution patterns of A. gossypii, showing changes in its distribution behaviour inside the plant as the cotton crop develops. The results of our study are relevant for understanding the vertical and horizontal distribution of A. gossypii on Bt cotton cultivar (DP 404 BG (Bollgard)) and on its isoline (DP 4049), and could be useful in decision-making, implementing controls and determining the timing of population peaks of this insect.

Distribution and behavior of Argentine hake larvae: Evidence of a biophysical mechanism for self-recruitment in northern Patagonian shelf waters

It has been proposed that vertical movements of planktonic organisms coupled to a horizontally or vertically stratified circulation pattern could describe a retention mechanism, with ecological advantages such as favoring recruitment success. The Patagonian stock of the Argentine hake Merluccius hubbsi spawns mainly from January to February in relation to a highly productive tidal frontal system. Although retention of fish eggs and larvae has been previously hypothesized for this system, it has not been fully proven and its mechanisms have not yet been proposed for hake early stages. To better understand the physical and biological processes involved in the survival and distribution of hake larvae, we focused on transport features and associated larval behavior governing the retention of larvae in the spawning area and their subsequent distribution to settlement and nursery grounds. To test this hypothesis at appropriate spatial and temporal scales, we analyzed acoustic records to describe vertical and horizontal distribution patterns of hake larvae, discrete plankton samples to confirm the identity of acoustic targets, and outputs from a numerical circulation model to estimate current patterns in the region during the hake spawning months. Coinciding with the development of a functional swimbladder, hake larvae of 4 mm and larger showed a strong vertical distribution pattern associated with a sound scattering layer migrating from the thermocline during the night to near-bottom depths during the day. This diel vertical migration pattern was associated with the circulation structure, equivalent to a two-layer flow, indicating a recirculation pattern in the vertical plane. The retention of early larval stages in the spawning area was evident from the acoustic data, indicating a persistent location for the bulk of hake larvae at the main spawning ground during summer months. The distribution extends to the rest of the nursery grounds as the breeding season advances in agreement with the general pattern of middle shelf bottom circulation vectors produced by the numerical model. The results are discussed within the framework of Bakun’s fundamental triad, identifying its elements. In addition, a conceptual model for the main biophysical coupling processes during the early life history of M. hubbsi is proposed in order to gain insight about the recruitment mechanism of this species.

Small-mammal community structure in a South American deciduous Atlantic Forest

We investigated how the small-mammal community is structured in a deciduous forest in southern Brazil, analysing the patterns of vertical and horizontal distribution. We used 12 transect lines, with 180 live-traps distributed on the ground and in the understory, and 12 pitfall traps in total. During six field sessions, we captured 510 individuals belonging to 12 small-mammal species. The combination of different methods of capture resulted in a relative high species richness for the area, although the presence of additional species cannot be ruled out. The forest complexity plays an important role allowing the coexistence of cursorial, scansorial and some arboreal species in this community. The structural variables, liana and bamboo, were the most important ones for species richness. However, the dominant species, Akodon montensis was associated to sites with dense vegetation at ground level such as ferns, bamboos, and shrubs.