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

J Kantoussan  JM Ecoutin  R Laë  OT Thiaw  L Tito de Morais 《African Journal of Marine Science》2018,40(2):175-185

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.  相似文献   

Classification of marine bioregions on the east coast of South Africa     

T-C Livingstone  JM Harris  AT Lombard  AJ Smit  DS Schoeman 《African Journal of Marine Science》2018,40(1):51-65

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.  相似文献   

Evaluating sources of uncertainty and variability in rock glacier inventories     

Francesco Brardinoni  Riccardo Scotti  Rudolf Sailer  Volkmar Mair 《地球表面变化过程与地形》2019,44(12):2450-2466

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Filling the gap: The geospatial skills shortage in New Zealand     

Mairéad de Róiste 《New Zealand geographer》2014,70(3):179-189

Geospatial technologies span governmental, academic and private commercial sectors, and their potential for growth is considerable. The USA and Australia have trouble meeting demand for geospatial skills. This paper reports on a national survey of 157 organisations that identified a similar geospatial shortage in New Zealand. The paper also details dimensions of the shortage and the current frameworks for meeting the shortfall of skilled professionals. Arising from this skills gap, key challenges facing both the geography and geospatial communities are identified and discussed: raising student numbers, gaining experience, up‐skilling current professionals and raising awareness of the value of the geospatial skillset.  相似文献   

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

KL Strachan  TR Hill  JM Finch 《African Journal of Marine Science》2017,39(4):409-422

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.  相似文献   

High-pressure synthesis,long-term stability of single crystals of diboron trioxide,B<Subscript>2</Subscript>O<Subscript>3</Subscript>, and an empirical electronic polarizability of <Superscript>[3]</Superscript>B<Superscript>3+</Superscript>     

Manfred Burianek  Johannes Birkenstock  Philipp Mair  Volker Kahlenberg  Olaf Medenbach  Robert D. Shannon  Reinhard X. Fischer 《Physics and Chemistry of Minerals》2016,43(7):527-534

Single crystals of B₂O₃ are needed for the precise determination of the refractive indices used to calculate the electronic polarizability α of 3-coordinated boron. The α(B) values in turn are used to predict mean refractive indices of borate minerals. Since the contribution of boron to the total polarizability of a mineral is very low, the synthetic compound B₂O₃ represents an ideal model system because of its high molar content of boron. Millimeter-sized crystals were synthesized at 1 GPa in a piston-cylinder apparatus. The samples were heated above the liquidus (800 °C), subsequently cooled at 15 °C/h to 500 °C and finally quenched. The refractive indices were determined by the immersion method using a microrefractometer spindle stage. The refractive indices n _o = 1.653 (3) and n _e = 1.632 (3) correspond to a total polarizability for B₂O₃ of α = 4.877 Å³. These values were used to determine the electronic polarizability of boron of α(B) = 0.16 Å³. Although the surface of the B₂O₃ crystals was coated with a hydrous film immediately after being exposed to air, its bulk crystallinity is retained for a period of at least 2 months.  相似文献   

The invasive Asian green mussel Perna viridis in South Africa: all that is green is not viridis     

JM Micklem  CL Griffiths  N Ntuli  M Mwale 《African Journal of Marine Science》2016,38(2):207-215

The Asian green mussel Perna viridis is an invasive Indo-Pacific species recently reported from South African harbours. To verify the invasion, a phylogenetic (and morphological) analysis of green-shelled mussels (n = 39), found in six South African harbours, was conducted using the mitochondrial cytochrome c oxidase subunit I gene (COI). Estimates of genetic distances using the neighbour-joining analysis identified P. viridis only from Durban Harbour. All other green mussels were more than 3.2% divergent from P. viridis and were identified as green-shelled variants of indigenous P. perna. The only reliable morphological differences distinguishing the two species were the poorly developed mantle papillae and the wavy pallial line in P. viridis. The confirmed occurrence of P. viridis in a South African harbour suggests that there is a possible threat of the species becoming established and then spreading onto the open coast and competing with indigenous P. perna.  相似文献   

Petrology of contact metamorphic metapelites from the southern rim of the Permian Brixen Granodiorite (South Tyrol, italy)     

S. Wyhlidal  W. F. Th?ny  P. Tropper  R. Kaindl  C. Hauzenberger  V. Mair 《Mineralogy and Petrology》2012,106(3-4):173-191

The Brixen Granodiorite is part of the Permian calc-alkaline plutonic association (Brixen Granodiorite, Ifinger Granite, Kreuzberg Granite, Cima d’Asta Granitoid) that intruded the Variscan Southalpine metamorphic basement. The Brixen Granodiorite is located to the south of the Periatriatic Lineament in the eastern part of the Southalpine basement complex and comprises a series of tonalitic, granitic and granodioritc intrusions, which were emplaced during the Permian (280?Ma) into the country rocks of the Brixen Quarzphyllites. The depth of these Southalpine granodioritic intrusions was less than 10?km (P?≤?0.3?GPa) and solidus temperatures were 670–720?°C (Visona, Mem Sci Geol 47:111–124, 1995; Acquafredda et al., Miner Petrogr Acta XL:45–53, 1997; Wyhlidal et al., Austr J Earth Sci 102:181–192, 2009). Only a small, about 200?m wide, contact aureole formed at the southern rim of the Brixen Granodiorite near the village Franzensfeste/Fortezza (South-Tyrol, Italy). Within the contact aureole four different zones can be distinguished based upon mineralogical, mineral chemical and textural features. Approximately 200?m from the granite contact zone I occurs. The rocks from this zone are macroscopically still quartzphyllites and are characterized by two texturally and chemically different generations of micas (muscovite, biotite) and the appearance of cordierite. Zone II is characterized by quartzphyllites containing pseudomorphs of cordierite + biotite after garnet. The inner contact aureole (zone III) starts approximately 50?m from the granite contact and shows already typical hornfels textures. This zone is characterized by the first occurrence of andalusite. In the innermost area (zone IV), ca 10?m from the granite contact, spinel and corundum occur. Geothermometry (two-feldspar-, Ti-in-biotite) yielded an increase in temperature from 540?°C in the outermost aureole (zone I) to <740?°C in the innermost aureole (zone IV). Pseudosection modelling of hornfelses from zones III and IV also resulted in similar P-T conditions of <0.28?GPa and <620?°C. This contact aureole represents one of the few well-developed remaining areas of Permian contact metamorphism in the Southalpine domain, which are otherwise mostly obliterated by late-stage hydrothermal alteration in the course of the Alpine tectonic overprint.  相似文献   

新疆阿尔泰铁木尔特铅锌矿床流体包裹体研究及地质意义   总被引：6，自引：3，他引：3  

耿新霞  杨富全  杨建民  黄承科  刘锋  柴凤梅  张志欣 《岩石学报》2010,26(3):695-706

铁木尔特中型铅锌矿是阿尔泰山南缘克兰盆地内的重要VMS型矿床。矿床赋存于上志留统-下泥盆统康布铁堡组上亚组第二岩性段,容矿岩石为大理岩、绿泥石英片岩、变钙质粉砂岩、夕卡岩。矿体呈似层状和透镜状。矿床的形成经历了喷流沉积期、叠加改造期和表生期。石英、长石、方解石和石榴子石中包裹体类型主要为液体包裹体,在石英中另出现了气体包裹体、纯气体包裹体、含子矿物多相包裹体、含液体CO2的三相包裹体和两相CO2包裹体。喷流沉积期成矿流体均一温度变化于150～330℃,其峰值是165℃和285℃,成矿流体盐度(NaCleq)为4%～16%,流体密度为0.77～0.97g/cm3,流体阳离子主要以Na+为主,次之为K+,阴离子以Cl-为主,其次是SO42-,气相成分主要是H2O和CO2。叠加改造期均一温度范围是150～480℃,峰值为285℃,盐度(NaCleq)为2.2%～17.08%和33.93%～47.2%,流体密度变化于0.61～1.03g/cm3之间,流体阳离子主要以Na+为主,次为K+、Mg2+、Ca2+,阴离子以Cl-为主,其次是SO42-,气相成分主要是H2O和CO2,其次为N2、CH4,含有少量C2H6。  相似文献   

A simple method to combine snow height and meteorological observations to estimate winter precipitation at sub-daily resolution     

E. Mair  G. Leitinger  S. Della Chiesa  G. Niedrist  U. Tappeiner  G. Bertoldi 《水文科学杂志》2013,58(11):2050-2060

ABSTRACT

Measuring winter solid and liquid precipitation with high temporal resolution in remote or higher elevation regions is a challenging task because of undercatch and power supply issues. However, the number of micro-meteorological stations and ultrasonic height sensors in mountain regions is steadily increasing. To gain more benefit from such stations, a new simple approach for EStimating SOlid and LIquid Precipitation (ESOLIP) is presented. The method consists of three main steps: (1) definition of precipitation events using micro-meteorological data, (2) quantification of solid and liquid precipitation using wet-bulb temperature and filtered snow height and (3) calculation of fresh snow density. ESOLIP performance was validated using data from a heated rain gauge, snow pillow and daily manual observations both for single precipitation events and over three winter seasons. Results proved ESOLIP as an effective approach for precipitation quantification, where snow height observations and basic meteorological measurements (air temperature, solar radiation, wind speed, relative humidity), but no reliable rain gauges are available.  相似文献