An experimental marine ecosystem study of the pelagic biogeochemistry of pentachlorophenol     

M. B. Yunker 《Marine environmental research》1990,30(4)

The marine biogeochemistry of pure pentachlorophenol was studied relative to a control treatment at a scale which provided a good model for the pelagic planktonic environment (70 m³ polyethylene bags). Pentachlorophenol that was dispersed at concentrations of 10 and 100 μg/litre showed identical relative rates of decrease over 25 days to concentrations 32·8% and 31·1%, respectively, of the initial concentrations. No bioaccumulation by phytoplankton or zooplankton was observed and pentachlorophenol removal by adsorption (by particulates, zooplankton or the enclosure walls) was insignificant. The log of the pentachlorophenol concentration was significantly correlated to the hours of bright sunshine up to Day 18, after which the photolysis efficiency decreased as the proportion of pentachlorophenol exposed to sunlight decreased. The results imply a long residence time for pentachlorophenol in deeper waters outside the photolysis zone. A persistent reduction in the primary production and production per unit carbon was observed at 100 μg/litre and, when coupled to the reproducible demise of the centric diatom Skeletonema costatum in culture and the spiked enclosures, suggests that pentachlorophenol inhibits phytoplankton growth.  相似文献   

Tephrostratigraphy and paleo-environmental implications of Late Quaternary sediments and interstitial water in the western Ulleung Basin, East/Japan Sea     

M. H. Park  J. H. Kim  I. S. Kim  B. J. Ryu  K. M. Yu 《Geo-Marine Letters》2005,25(1):54-62

Two piston cores, collected from the western Ulleung Basin of the East/Japan Sea, were used to investigate the Late Quaternary tephrostratigraphy, lithology, and mineralogy of the sediments, as well as the elemental composition of both sediments and interstitial water, and their paleo-environmental implications. The cores show two lapilli tephra layers and one rhyolitic ash layer at the boundaries between sedimentary lithofacies units I, II, and III. These layers can be correlated with the well-known Ulleung-Oki (ca. 9.3 ka; boundary of units I/II), Ulleung-Yamato (ca. 25–33 ka), and Aira-Tanzawa (ca. 25.1 ka; boundary of units II/III) layers, respectively. These data suggest that the cores cover the period from the middle stage of marine isotope stage (MIS) 3 to the Holocene. In each core, a so-called dark laminated mud (DLM) layer in unit II commonly has high contents of Si and Al, suggesting that the DLM layer generally contains significant amounts of fine-grained silicates and/or aluminosilicates. In addition, these DLM layers are enriched in Fe relative to Mn, iron being predominantly bound in framboidal pyrite. The size distribution of pyrite in the DLM layers suggests that these have formed under anoxic (euxinic) conditions at times of reduced water circulation in the basin during sea-level lowstand (euxinic environment). The C/N ratios [5–12] suggest that sedimentary organic matter in the cores is predominantly of marine origin. Total organic carbon (TOC) contents increased shortly before Termination I. This could have been caused by an increased flux of marine organic matter in association with sea-level rise. The C and S values of units II and III (Late Pleistocene sediments; C: <2.0%; S: 0.5–2.1%) suggest a more euxinic environment than that of unit I (Holocene sediments; C: 1.0–3.5%; S: <1.0%). Concentrations of SO₄^2– in the interstitial water decrease with increasing burial depth, whereas CH₄ concentrations show the reverse trend. Therefore, it seems that sulfate reduction, probably related to microbial activity, predominates in the upper core sections (<5 m), shifting to methanogenesis in the lower core sections.  相似文献   

Structure of the Wave Bottom Boundary Layer over Smooth and Rough Bottoms     

V. M. Kushnir 《Physical Oceanography》2005,15(6):370-382

The comparison of six well-known models of the wave bottom boundary layer shows that they are identical in the case of a smooth bottom but exhibit serious differences for the other types of conditions. The thickness of the wave bottom boundary layer and the coefficient of vertical diffusion of momentum are studied by using the relations of the k-ε-model. The validity of these estimates is checked by comparing the measured and computed values of the friction velocity. This comparison demonstrates fairly good agreement between the results characterized by a coefficient of correlation equal to 0.851. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 54–67, November–December, 2005.  相似文献   

Environmental change and oyster colonization within the Hudson River estuary linked to Holocene climate   总被引：4，自引：0，他引：4  

S.?M.?CarbotteEmail author  R.?E.?Bell  W.?B.?F.?Ryan  C.?McHugh  A.?Slagle  F.?Nitsche  J.?Rubenstone 《Geo-Marine Letters》2004,24(4):212-224

Geophysical mapping and sampling data provide a record of changing environmental and faunal conditions within the Hudson River estuary during the mid- to late Holocene. On the shallow, broad marginal flats of the mesohaline Hudson, fossil oyster beds (Crassostrea virginica) are found exposed on the river bottom and buried by sediment. The shallowest beds are well imaged in chirp sub-bottom and side-scan sonar data and form discrete flow-perpendicular bands, 0.6–1.0 km wide and up to 3 km long, which cover 30% of the river bottom. Radiocarbon-dated sediment cores indicate oysters thrived within two time periods from ~500–2,400 and ~5,600–6,100 cal. years b.p. Sediment and physical property data indicate a changing depositional regime consistent with the oyster chronology. Similar changes in oyster presence are found in local shell midden sites of the Lower Hudson Valley as well as elsewhere along the Atlantic coast, and may reflect climatic controls associated with warm–cool cycles during the Holocene. Oysters flourished during the mid-Holocene warm period, disappeared with the onset of cooler climate at 4,000–5,000 cal. years b.p., and returned during warmer conditions of the late Holocene. The most recent demise of oysters within the Hudson at 500–900 cal. years b.p. may have accompanied the Little Ice Age.  相似文献   

Changing anthropogenic influence on the Santa Monica Bay watershed     

Dojiri M  Yamaguchi M  Weisberg SB  Lee HJ 《Marine environmental research》2003,56(1-2):1-14

Santa Monica Bay is an open coastal embayment located directly seaward of Los Angeles, California. The Bay provides vital economic value through its water-dependent activities, such as swimming, diving, boating, and fishing. An increase from 100,000 residents in 1900 to 10 million in 2000 has imposed numerous environmental stressors on the Bay, including urbanization of the watershed. Pollutant discharges into the Bay increased throughout the early part of the century, but declined following passage of the Clean Water Act in 1972. Since that time, the predominant source of pollutant inputs has changed from point sources to non-point urban runoff. To assess how present-day and historical pollution interact to affect the environmental quality of Santa Monica Bay, three organizations collaborated on a multi-disciplinary study in 1997, towards which this volume is focused. This paper details the temporal patterns of anthropogenic influence on Santa Monica Bay to provide context for the papers that follow.  相似文献   

Co–rich Mn crusts from the Magellan Seamount cluster: the long journey through time     

Geoffrey P. Glasby  Xiangwen Ren  Xuefa Shi  Irina A. Pulyaeva 《Geo-Marine Letters》2007,27(5):315-323

The Magellan seamounts began forming as large submarine shield volcanoes south of the equator during the Cretaceous. These volcanoes formed as a cluster on the small Pacific plate in a period when tectonic stress was absent. Thermal subsidence of the seafloor led to sinking of these volcanoes and the formation of guyots as the seamounts crossed the equatorial South Pacific (10–0°S) sequentially and ocean surface temperatures became too high for calcareous organisms to survive. Guyot formation was completed between about 59 and 45 Ma and the guyots became phosphatized at about 39–34 and 27–21 Ma. Ferromanganese crusts began formation as proto-crusts on the seamounts and guyots of the Magellan Seamount cluster towards the end of the Cretaceous up to 55 Ma after the formation of the seamounts themselves. The chemical composition of these crusts evolved over time in a series of steps in response to changes in global climate and ocean circulation. The great thickness of these crusts (up to 15–20 cm) reflects their very long period of growth. The high Co contents of the outer parts of the crusts are a consequence of the increasing deep circulation of the ocean and the resulting deepening of the oxygen minimum zone with time. Growth of the Co-rich Mn crusts in the Magellan Seamount cluster can be considered to be the culmination of a long journey through time.  相似文献   

Casualties in dry bulk shipping (1963–1996)     

Stephen E. Roberts  Peter B. Marlow 《Marine Policy》2002,26(6)

In recent years, bulk carriers have been identified with high risks of catastrophic structural failure and foundering, and with heavy loss of human life. This study, based upon Lloyd's of London casualty records, identified four risk factors that had significant, independent effect upon the likelihood of a bulk carrier foundering. The risk of foundering increased with the age of the ship, and was related to the ship's flag of registration. Most importantly, however, increased risks were found for heavy cargoes of iron ore and scrap steel or iron, and for trading routes to the Far East and from Europe to North America. Additional safety measures, in particular regarding ship design and high-risk trades, may well be necessary to reduce the high casualty rates.  相似文献   

Primary productivity in the western tropical Pacific and equatorial warm waters   总被引：1，自引：0，他引：1  

Chen Xingqun  Zhang Ming  Chen Qihuan 《海洋学报(英文版)》2001,20(1):117-129

ＩＮＴＲＯＤＵＣＴＩＯＮＢｙｓｔｕｄｙｉｎｇｃｈｌｏｒｏｐｈｙｌｌａｎｄｐｒｉｍａｒｙｐｒｏｄｕｃｔｉｖｉｔｙｉｎｏｃｅａｎ ,ｅｉｔｈｅｒｉｎｔｈｅｂｉｇ ｓｃａｌｅｏｒｉｎｔｈｅｓｍａｌｌｓｃａｌｅ ,ｔｈｅｐｒｏｄｕｃｔｉｖｉｔｙｄｉｓｔｒｉｂｕｔｉｏｎａｎｄｖａｒｉａｔｉｏｎｏｆｍａｒｉｎｅｏｒｇａｎｉｃｍａｔｅｒｉａｌｉｎｔｈｅｔｅｍｐｏ ｒａｌａｎｄｓｐａｔｉａｌｃａｎｂｅｕｎｄｅｒｓｔｏｏｄ .Ｔｈｅｓｅａａｒｅａｓ ,ｓｉｔｕａｔｉｎｇｉｎｔｈｅｗｅｓｔｅｒｎｔｒｏｐｉｃａｌＰａｃｉｆｉｃ…  相似文献   

Geochemical variation in ferromanganese nodules and associated sediments from the Pacific Ocean     

S.E. Calvert  N.B. Price 《Marine Chemistry》1977,5(1):43-74

The major and minor element compositions of a suite of abyssal sea-floor ferromanganese nodules and associated sediments from the eastern central Pacific have been used to examine inter-element relationships and the mineralogy of the nodules, the relationship between the composition of nodules and their associated sediments and regional variations in composition with respect to likely modes of formation of such deposits. Apart from Mn and Fe, significant proportions of the total Ti, Ca, Mg, K, Ba, Sr, Th and Y and almost all the P, As, Ce, Co, Cu, Mo, Ni, Pb, Zn and Zr are present in the oxide fractions of the nodules. The Mg, Ba, Cu, Mo, Ni and Zn contents are significantly correlated with the Mn content, while Ti, P, As, Pb, Sr, Y and Zr are similarly correlated with the total Fe content.Nodules from the northeastern tropical Pacific have Mn/Fe ratios higher than those in the oxide fractions of their associated sediments, todorokite as the principal Mn phase and relatively high concentrations of minor elements associated with Mn. Nodules from the south central Pacific have Mn/Fe ratios similar to those in the oxide fractions of the associated sediments, δ-MnO₂ as the only Mn-phase, and relatively high concentrations of minor elements associated with Fe. There appears to be a smooth gradation in composition in the tropical Pacific between these two end members.The regional compositional variation is interpreted as a reflection of different sources of metals for, and different growth mechanisms of, sea-floor nodules. The oxide precipitate from sea water consists of δ-MnO₂, has a relatively low Mn/Fe ratio and minor element contents related to the total Fe and Mn(δ-MnO₂) content. The oxide precipitate forming in areas of very low sedimentation as a result of diagenetic remobilisation in the surface sediment consists of todorokite, and has a high Mn/Fe ratio and enhanced metal content in the Mn-(todorokite)phase. Available information on the morphology and compositional variation of individual nodules from the tropical Pacific corroborates these contrasting metal sources and suggests that they can be resolved on the scale of an individual oxide concretion.  相似文献   

Co60γ射线对海带幼孢子体的影响     

方宗熙  李家俊  陈登勤 《海洋科学集刊》1964,(6):27-32

近几年来,有关X射线对海带配子体和幼孢子体的影响以及Co60γ射线对海带配子体的影响都有过报导。本实验在于观察Co60γ射线对海带幼孢子体的影响和目前条件下可能看到的作用机制。正如Gray(1959)所指出：尽管X射线对活细胞的作用问题已有60多年的研究,但对有关的机制还是所知极少。本实验所能探讨的只是一些可见的、也就是属于细胞水平的机制。  相似文献