Wintertime rates of net primary production and nitrate and ammonium uptake in the southern Benguela upwelling system

The elevated levels of primary productivity associated with eastern boundary currents are driven by nutrient- rich waters upwelled from depth, such that these regions are typically characterised by high rates of nitrate-fuelled phytoplankton growth. Production studies from the southern Benguela upwelling system (SBUS) tend to be biased towards the summer upwelling season, yet winter data are required to compute annual budgets and understand seasonal variability. Net primary production (NPP) and nitrate and ammonium uptake were measured concurrently at six stations in the SBUS in early winter. While euphotic zone NPP was highest at the stations nearest to the coast and declined with distance from the shore, a greater proportion was potentially exportable from open-ocean surface waters, as indicated by the higher specific nitrate uptake rates and f-ratios (ratio of nitrate uptake to total nitrogen consumption) at the stations located off the continental shelf. Near the coast, phytoplankton growth was predominantly supported by ammonium despite the high ambient nitrate concentrations. Along with ammonium concentrations as high as 3.6 µmol l^–1, this strongly suggests that nitrate uptake in the inshore SBUS, and by extension carbon drawdown, is inhibited by ammonium, at least in winter, although this has also been hypothesised for the summer.     

根据天气类型划分欧洲中期天气预报中心的集合预报产品

该研究的主要目的是找出一种对集合预报产品进行释用的新方法。其基本假定是集合预报要素在一定程度上代表了未来可能发生的天气形势。为了解决天气尺度在中期预报的不可预报性问题 ,引入了天气类型的概念。对集合预报进行划分的方法是 Diday提出的动力模糊法 ,初始划分时的重心由天气类型定义 ,划分用到的距离是位移和最大相关方法。根据城市块 (City- Block)距离找出了影响中国的按冬夏两季划分的天气类型 ,初步划分结果表明 ,欧洲中期天气预报中心的集合预报系统可以预报出横槽转竖型天气类型的演变情况 ,在夏天的预报效果则没有冬天好。     

Runoff generation and routing on artificial slopes in a Mediterranean–continental environment: the Teruel coalfield,Spain

The aim of this study was to identify the mechanisms of runoff generation and routing and their controlling factors at the hillslope scale, on artificial slopes derived from surface coal mining reclamation in a Mediterranean–continental area. Rainfall and runoff at interrill and microcatchment scales were recorded for a year on two slopes with different substrata: topsoil cover and overburden cover. Runoff coefficient and runoff routing from interrill areas to microcatchment outlets were higher in the overburden substratum than in topsoil, and greater in the most developed rill network. Rainfall volume is the major parameter responsible for runoff response on overburden, suggesting that this substratum is very impermeable—at least during the main rainfall periods of the year (late spring and autumn) when the soil surface is sealed. In such conditions, most rainfall input is converted into runoff, regardless of its intensity. Results from artificial rainfall experiments, conducted 3 and 7 years after seeding, confirm the low infiltration capacity of overburden when sealed. The hydrological response shows great seasonal variability on the overburden slope in accordance with soil surface changes over the year. Rainfall volume and intensities (I₃₀, I₆₀) explain runoff at the interrill scale on the topsoil slope, where rainfall experiments demonstrated a typical Hortonian infiltration curve. However, no correlation was found at the microcatchment level, probably because of the loss of functionality of the only rill as ecological succession proceeded. The runoff generation mechanism on the topsoil slope is more homogeneous throughout the year. Runoff connectivity, defined as the ratio between runoff rates recorded at the rill network scale and those recorded at the interrill area scale in every rainfall event, was also greater on the rilled overburden slope, and in the most developed rill network. The dense rill networks of the overburden slope guarantee very effective runoff drainage, regardless of rainfall magnitude. Rills drain overland flow from interrill‐sealed areas, reducing the opportunity of reinfiltration in areas not affected by siltation. Runoff generation and routing on topsoil slopes are controlled by grass cover and soil moisture content, whereas on overburden slopes rill network density and soil moisture content are the main controlling factors. Copyright © 2002 John Wiley & Sons, Ltd.     

Evaluating restoration of man‐made slopes: a threshold approach balancing vegetation and rill erosion

The management of reclaimed slopes derived from industrial and civil activities (e.g. surface mining and road construction) requires the development of practical stability analysis approaches that integrate the processes and mechanisms that rule the dynamics of these ubiquitous emerging ecosystems. This work describes a new modelling approach focused on stability analysis of water‐limited reclaimed slopes, where interactive relationships between rill erosion and vegetation regulate ecosystem stability. Our framework reproduces two main groups of possible trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. Furthermore, this analytical approach allows the determination of threshold values for the state variables (i.e. vegetation cover and rill erosion) that drive the system's stability, facilitating the identification of critical situations that require specific human intervention (e.g. revegetation or, in very problematic cases, revegetation combined with rill network destruction) to ensure the long‐term sustainability of the restored ecosystem. The application of our threshold analysis framework in Mediterranean‐dry reclaimed slopes derived from surface coal mining (the Teruel coalfield in central‐eastern Spain) showed a good field‐based performance. Therefore, we believe that this model is a valuable contribution for the management of water‐limited reclaimed systems, including those associated with rill erosion, as it provides a tool for the evaluation of restoration success and can play an important role in decision‐making during ecosystem restoration in severely disturbed landscapes. Copyright © 2011 John Wiley & Sons, Ltd.     

Fe,Mn, P and S Speciation in Sediments from the Capivara Hydroelectric Dam Lake (Brazil) as an Indicator of Anthropogenic Influences

The conservation of large water resources is essential for the preservation of human life. The quantification and, more importantly, the speciation of chemical substances that indicate the presence of anthropogenic contamination in water resources are of great importance. This paper presents the results of analysis for the determination of organic, inorganic and total phosphorus, pseudo‐sulfur, and iron and manganese, in five fractions, in water sediments collected from the Capivara Hydroelectric Power Plant, Brazil. A study on the seasonal variation of these parameters was conducted, with data having been collected in the winter and in the summer, at two sites along the dam, 5 km apart, close to the city of Primeiro de Maio. Phosphorous was found in sediments and adjacent soil in the organic form (OP), and was used as an indicator of anthropogenic influence on the reservoir banks. Speciation of potentially toxic Mn showed that it is present in the exchangeable fraction of the 0–5 cm depth layer (sediment/water interface), making its transfer to the water column possible. Results from this study showed that domestic and industrial effluent treatment measures are needed for the preservation of the quality of aquatic environments.     

Bottlenose dolphin Tursiops truncatus group dynamics,site fidelity,residency and movement patterns in the Madeira Archipelago (North-East Atlantic)

The bottlenose dolphin Tursiops truncatus is one of the most frequently sighted cetacean species in the Madeira Archipelago (North-East Atlantic); however, little is known about its population ecology in these waters. Photo-identification undertaken during systematic, non-systematic and opportunistic surveys conducted between 2001 and 2012 was used to assess group dynamics, site fidelity, residency and movement patterns of bottlenose dolphins in the archipelago. Three different patterns of residency were assigned, based on individual sighting histories. Group size ranged between 2 and 90 individuals (median 12), with no significant monthly difference in group size. All resident dolphins formed a core, complex network with migrant and transient dolphins. In contrast, satellite clusters were formed exclusively by transient individuals. The lagged identification rate (LIR) model indicated that a dolphin remained in the area for an average of 90 days, whereas the average time an individual spent outside the study area was approximately 313 days. The Madeira Archipelago appears to be only a section of a much larger home range for this population, with the dolphins exhibiting three different patterns of occurrence that associate with each other. The information gained about this poorly studied population contributes to the overall knowledge of bottlenose dolphins in insular oceanic habitats.     

A multimetric-index approach using fisheries data to assess fish assemblage structure in relation to salinity gradient in a tropical West African estuary

This study examines the effects of increasing salinity on fish assemblage structure in the Casamance Estuary, Senegal, using a series of indices. The study data were derived from commercial fishery surveys conducted between April and July 2005. Analysis of within-trophic-group diversity in the Casamance Estuary shows a significant drop in the diversity of apex predators in the upper, more saline reaches of the estuary. By contrast, primary consumers adapted well to salinity changes and exhibited higher taxonomic diversity in the upper reaches of the estuary than in the lower reaches. The findings also indicate decreases in average sizes of the landed species and the trophic levels among fish catches in the direction of the upper reaches. However, the catch per unit effort (CPUE) was globally higher in the upstream area of the estuary as compared with the downstream area. This increasing CPUE trend from the lower towards the upper reaches is attributed to (i) the high primary productivity in the upper Casamance Estuary; (ii) the increasing abundance of euryhaline fish species in an upstream direction; and (iii) ‘telescoping’ of the food chain through the presence of mostly herbivorous fishes in the upper reaches. Such a situation likely facilitated high fish production in the upstream area of the estuary, though multimetric indices indicated unfavourable living conditions for many fish taxa in this area.     

Classification of marine bioregions on the east coast of South Africa

Marine bioregional planning requires a meaningful classification and spatial delineation of the ocean environment using biological and physical characteristics. The relative inaccessibility of much of the ocean and the paucity of directly measured data spanning entire planning regions mean that surrogate data, such as satellite imagery, are frequently used to develop spatial classifications. However, due to a lack of appropriate biological data, these classifications often rely on abiotic variables, which act as surrogates for biodiversity. The aim of this study was to produce a fine-scale bioregional classification, using multivariate clustering, for the inshore and offshore marine environment off the east coast of South Africa, adjacent to the province of KwaZulu-Natal and out to the boundary of the exclusive economic zone (EEZ), 200 nautical miles offshore. We used remotely sensed data of sea surface temperature, chlorophyll a and turbidity, together with interpolated bathymetry and continental-slope data, as well as additional inshore data on sediments, seabed oxygen and bottom temperature. A multivariate k-means analysis was used to produce a fine-scale marine bioregionalisation, with three bioregions subdivided into 12 biozones. The offshore classification was primarily a pelagic bioregionalisation, whereas the inshore classification (on the continental shelf) was a coupled benthopelagic bioregionalisation, owing to the availability of benthic data for this area. The resulting classification was used as a base layer for a systematic conservation plan developed for the province, and provided the methods for subsequent planning conducted for the entire South African EEZ. Validation of the classification is currently being conducted in marine research programmes that are sampling benthic biota and habitats in a sampling design stratified according to the biozones delineated in this study.     

Vertical distribution of living mangrove foraminifera from KwaZulu-Natal,South Africa

Modern foraminiferal assemblage zones can be used to reconstruct palaeo sea levels when applied to fossil foraminifera down a sediment core. Previous intertidal foraminiferal studies have predominantly focused on assemblages in surface sediments (0–1 cm), with the rationale that surface assemblages reflect the modern-day environment. Foraminifera live infaunally and therefore there is a need to document the infaunal vertical distribution of living foraminifera to fully capture the modern environment. Infaunal foraminiferal populations may compositionally differ from or be similar to those in the uppermost 1 cm of a core sample, but abundance is variable vertically, making it very complex to reconstruct and interpret past sea levels. This can have implications for the choice of assemblages to use as modern analogues for past sea-level reconstructions. This study documents the vertical infaunal distribution of living foraminifera, to allow for more informed interpretations of palaeo-reconstructions in mangrove environments. The down-core vertical distribution and abundance of living foraminifera, along with grain size and organic content, were documented using sediment cores along an elevational transect. Nine taxa were recorded as living at the time of collection, six of which were restricted to the top 4 cm. The majority of these were calcareous and found in the cores situated closer to the intertidal channel. Therefore, we argue that the diversity of living calcareous and agglutinated foraminifera could be restricted by grain size, with coarser grain sizes associated with lower species diversity. The findings suggest that foraminiferal species inhabiting the top 4 cm represent deeper living foraminiferal populations. Therefore, the top 4-cm interval can be used to establish a modern training set upon which reconstructions can be based. The findings from this study will provide guidance on the use of South African mangrove environments for future sea-level reconstructions.     

Study of the total lightning activity in a hailstorm

A thunderstorm that developed over northeastern Spain on 16 June 2006 is analyzed. This severe thunderstorm produced hailstones as large as 40 mm and had a lifetime of 3 h and 30 min. Radar cross-sections show strong vertical development with cloud echo tops reaching an altitude of 13 km. The specific characteristics of the lightning activity of this storm were: (i) a large amount (81%) of negative cloud-to-ground (−CG) flashes with very low peak currents (< 10 kA in absolute value), (ii) a very large proportion of intra-cloud (IC) flashes with an IC/CG ratio reaching about 400, (iii) a large number of “short” IC flashes (with only 1-VHF source according to SAFIR detection), (iv) a large increase of the −CG flash rate and of the CG proportion near the end of the storm. The rate of −CG flashes with a low peak current were observed to evolve similarly to the rates of IC flashes. Most of them have been assumed to be IC flashes misclassified by the Spanish Lightning Detection Network (SLDN). They have been filtered as it is usually done for misclassified +CG flashes. After this filtering, CG flash rates remained very low (< 1 min^− 1) with +CG flashes sometimes dominant. All the particular lightning activity characteristics similar to those observed in the Severe Thunderstorm Electrification and Precipitation Study (STEPS) campaigns support the hypothesis that this thunderstorm could have had an inverted-polarity or complex charge structure. The maximum IC flash rate (67 min^− 1) peaked 24 min before the presence of reflectivity higher than 60 dBZ. The IC activity abruptly decreased during the period when reflectivity was dramatically increasing. The time of maximum reflectivity observed by radar was consistent with the times of reported hail at the ground.