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The purple-tipped sea urchin, Psammechinus miliaris, was exposed to artificially acidified seawater treatments (pH(w) 6.16, 6.63 or 7.44) over a period of 8 days. Urchin mortality of 100% was observed at pH(w) 6.16 after 7 days and coincided with a pronounced hypercapnia in the coelomic fluid producing an irrecoverable acidosis. Coelomic fluid acid-base measures showed that an accumulation of CO(2) and a significant reduction in pH occurred in all treatments compared with controls. Bicarbonate buffering was employed in each case, reducing the resultant acidosis, but compensation was incomplete even under moderate environmental hypercapnia. Significant test dissolution was inferred from observable increases in the Mg(2+) concentration of the coelomic fluid under all pH treatments. We show that a chronic reduction of surface water pH to below 7.5 would be severely detrimental to the acid-base balance of this predominantly intertidal species; despite its ability to tolerate fluctuations in pCO(2) and pH in the rock pool environment. The absence of respiratory pigment (or any substantial protein in the coelomic fluid), a poor capacity for ionic regulation and dependency on a magnesium calcite test, make echinoids particularly vulnerable to anthropogenic acidification. Geological sequestration leaks may result in dramatic localised pH reductions, e.g. pH 5.8. P. miliaris is intolerant of pH 6.16 seawater and significant mortality is seen at pH 6.63. 相似文献
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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. 相似文献
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内蒙古西拉沐伦成矿带碾子沟钼矿床成矿流体地球化学特征 总被引：7，自引：3，他引：4
碾子沟钼矿床是内蒙古西拉沐伦钼多金属成矿带中石英脉型钼矿床的典型代表,矿体以石英大脉形式产于燕山期中粗粒黑云母二长花岗岩内,受断裂构造控制。流体包裹体研究发现包裹体均为气液两相,按照相比不同,可进一步分为WL型(5%～20%)和WV型(20%～50%)。Ⅰ阶段流体为低温(89.3～245.2℃)、中低盐度(2.07%～17.96%NaCleqv)流体;Ⅱ阶段流体具有中低温(134.4～458.8℃,峰值170℃～240℃)、中低盐度(0.53%～19.92%NaCleqv)特征;Ⅲ阶段流体为低温(134.9～202.4℃)、中低盐度(4.96%～14.97%NaCleqv)流体。流体成分均以H2O为主(96.1mol%),含少量挥发份CO2、N2、CH4、C2H6、Ar、H2S,阳离子以Na+为主,阴离子以SO42-、Cl-为主,属NaCl-H2O体系。各阶段成矿热液氢、氧同位素特征为:δ18OH2O介于-5.75‰～-1.90‰、δD介于-128.821‰～-109.234‰,说明成矿流体是岩浆热液与古大气降水混合而成。开放的断裂体系为流体混合创造了条件,流体的混合作用是造成碾子沟辉钼矿沉淀成矿的主要原因。这与斑岩型钼矿床的高盐度流体以及以沸腾为主的矿石沉淀机制具有显著区别。 相似文献
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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
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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
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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
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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
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
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M. Söffker K.A. SlomanJ.M. Hall-Spencer 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(8):818-825
The abundance and behaviour of fish on and around coral reefs at Twin Mounds and Giant Mounds, carbonate mounds located on the continental shelf off Ireland (600-1100 m), were studied using two Remotely Operated Vehicle (ROV) dives. We recorded 30 fish taxa on the dives, together with three species of Scleractinia (Lophelia pertusa, Madrepora oculata and Desmophyllum cristagalli) and a diverse range of other corals (Antipatharia, Alcyonacea, and Stylasteridae). Stands of live coral provided the only habitat in which Guttigadus latifrons was observed whereas Neocyttus helgae was found predominantly on structural habitats provided by dead coral. Significantly more fish were found on structurally complex coral rubble habitats than on flatter areas where coral rubble was clogged with sand. The most common species recorded was Lepidion eques (2136 individuals), which always occurred a few cm above bottom and was significantly more active on the reefs than on sedimentary habitats. Synaphobranchus kaupii (1157 indiv.), N. helgae (198 indiv.) and Micromesistius poutassou (116 indiv.) were also common; S. kaupii did not exhibit habitat-related differences in behaviour, whilst N. helgae was more active over the reefs and other structured habitats whereas M. poutassou was more active with decreasing habitat complexity. Trawl damage and abandoned fishing gear was observed at both sites. We conclude that Irish coral reefs provide complex habitats that are home to a diverse assemblage of fish utilising the range of niches occurring both above and within the reef structure. 相似文献
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Bayden D. Russell Sean D. Connell Sven Uthicke Nancy Muehllehner Katharina E. Fabricius Jason M. Hall-Spencer 《Marine pollution bulletin》2013
While carbon capture and storage (CCS) is increasingly recognised as technologically possible, recent evidence from deep-sea CCS activities suggests that leakage from reservoirs may result in highly CO2 impacted biological communities. In contrast, shallow marine waters have higher primary productivity which may partially mitigate this leakage. We used natural CO2 seeps in shallow marine waters to assess if increased benthic primary productivity could capture and store CO2 leakage in areas targeted for CCS. We found that the productivity of seagrass communities (in situ, using natural CO2 seeps) and two individual species (ex situ, Cymodocea serrulata and Halophila ovalis) increased with CO2 concentration, but only species with dense belowground biomass increased in abundance (e.g. C. serrulata). Importantly, the ratio of below:above ground biomass of seagrass communities increased fivefold, making seagrass good candidates to partially mitigate CO2 leakage from sub-seabed reservoirs, since they form carbon sinks that can be buried for millennia. 相似文献