Are increased nutrient inputs responsible for more outbreaks of crown-of-thorns starfish? An appraisal of the evidence

The cause(s) of primary outbreaks of the coral-eating crown-of-thorns starfish (Acanthaster planci) are still subject to scientific controversy. The possibility of primary outbreaks being linked to terrestrial runoff has been postulated a number of times, suggesting that enhanced nutrient supply is critical for enhanced A. planci larval development. This paper examines the evidence for such a cause, focussing particularly on the Great Barrier Reef (GBR). Nutrient discharges from rivers have increased at least four-fold in the central GBR over the last century, and concentrations of large phyto-plankton (>2 microm) of the inshore central GBR shelf in the wet season when A. planci larvae develop, is double that of other places and times. Larval development, growth and survival increase almost ten-fold with doubled concentrations of large phyto-plankton. This and other lines of evidence suggest that frequent A. planci outbreaks on the GBR may indeed be a result of increased nutrient delivery from the land.     

Elemental distribution of coastal sea and stream sediments in the island-arc region of Japan and mass transfer processes from terrestrial to marine environments

A total of 49 elements have been identified in 338 coastal sea sediment samples collected from an area situated off the Ise-Tokai region of Japan for a nationwide marine geochemical mapping project. The spatial distribution patterns of the elemental concentrations in coastal seas along with the existing geochemical maps in terrestrial areas were used to define the natural geochemical background variation, mass transport, and contamination processes. The elemental concentrations of coastal sea sediments are determined primarily by particle size and regional differences. Most elemental concentrations increase with a decrease in particle size. Some elements such as Ca, Mn, and Yb are found to exist in large quantities in coarse particles containing calcareous shells, Fe–Mn oxides, and felsic volcanic sediments. Regional differences reflect the mass transfer process from terrestrial areas to coastal seas and the influence of the local marine geology. An analysis of variance (ANOVA) reveals that for many elements, the particle size effect is predominant over regional difference. The mean chemical compositions of coastal sea sediments are similar to those of stream sediments in adjacent terrestrial areas and in the upper crust of Japan. This observation supports the fact that coastal sea sediments have certainly originated from terrestrial materials. However, the spatial distributions of elemental concentrations are not always continuous between the land and coastal seas. The scale of mass movement observed in marine geochemical maps occurs at a distance of 20 km from the river mouth. A detailed examination of the spatial distribution patterns of K (K₂O) and Cr concentrations suggests that terrestrial materials supplied through rivers are deposited near the shore initially, and then gravity-driven processes shift the sediments deeper into the basin. Contamination with heavy metals such as Zn, Cd and Pb was observed in coastal bays surrounded by urban and industrial areas. It is noteworthy that the areas with the highest concentration of these elements usually do not occur near the shore (not near the contamination source) but at the center of the bay. Unexpected low concentrations of Zn, Cd and Pb near shore may either be due to a decreased anthropogenic load in the most recent sediments or to dilution by unpolluted flood sediments.     

RbSr whole-rock ages of Precambrian metamorphic rocks in the Kamiaso conglomerate from central Japan

Whole-rock samples of metamorphic and granitic cobbles and boulders from the Kamiaso conglomerate in central Japan yield well-defined RbSr isochron ages of 1985 ± 25 my and 1820 ± 40 my. These ages are the oldest yet obtained for rocks in the Japanese Islands, and provide key evidence for the middle Precambrian metamorphic and igneous events in the provenance of these rocks. The age of 1985 my defined by six samples of quartzo-feldspathic gneiss may be the time of emplacement of the original granitic rocks. The 1820 my age indicates the time of extensive regional metamorphism and igneous activity. Precambrian episodes in the provenance of the Kamiaso conglomerate are summarized as follows: (1) 2000 my — formation of granitic rocks, (2) 1800–1600 my — high grade metamorphism accompanied by igneous activity, (3) 1200–1000 my — some significant thermal event.Judging from rock types and geochronological data, it can be said that metamorphic rocks in the Kamiaso conglomerate are remarkably similar to those of the Matenrei and Nangnim systems in North Korea. The Precambrian complex from which the metamorphic and granitic rocks were derived, was exposed to the north not far from the present site of the Kamiaso conglomerate in the late Paleozoic time, and it was probably a part of the large Precambrian continent in East Asia.     

Some clinopyroxenes from ultramafic inclusions in Dreiser Weiher,Eifel

Eight clinopyroxenes from wehrlites and clinopyroxenites and three clinopyroxenes of crystal lapilli in tuff of Dreiser Weiher in Eifel, Germany, have been separated and chemically analysed. One hornblende and two phlogopites from a wehrlite and clinopyroxenites have also been analysed. The rocks enclosing these inclusions are alkali basalts of basanite composition. The analysed clinopyroxenes contain considerable amounts of Al₂O₃ (3.87–10.84 wt%). The calculated Tschermak's component ranges from 5.9 to 18.4 mol per cent. All of the analysed clinopyroxenes are clearly different from chromian diopsides in lherzolite inclusions in basaltic rocks in Dreiser Weiher and other localities; the former has higher contents of total FeO, CaO and TiO₂ and lower contents of MgO and Cr₂O₃ than the latter. Two clinopyroxenes separated from apatite-bearing clinopyroxenites show high contents of Fe₂O₃ with about 2 per cent of Na₂O, indicating the presence of considerable amounts of acmite component in addition to Tschermak's component. The relative proportions of Al in the tetrahedral site and that in the octahedral site in the analysed clinopyroxenes are clearly different from those of the common igneous clinopyroxenes and eclogites, and similar to those of the clinopyroxenes from other inclusions in basaltic rocks and granulites. It is suggested that all the analysed clinopyroxenes and their host inclusions have crystallized from alkali basalt magmas in relatively deep levels of the continental crust.     

一种新型潜浮式深海地震仪的设计与试验

鉴于国内外海洋地震台网的缺乏, 本文介绍了一种面向全球海域应用的漂浮式海底地震接收系统(mobile earthquake recording in marine areas by independent divers, MERMAID)。针对潜浮式地震仪MERMAID浮标的研发过程, 建立了浮标的总体设计要求与典型工作循环流程, 设计了液压式浮力调节系统、机械结构等, 并对比分析了不同转速及负浮力下潜过程, 最后进行了实验室压力检测和千岛湖湖试。试验结果表明, 该浮标能在15MPa压力下保持良好的密封性与稳定性, 利用水听器可以有效地采集到天然地震纵波(P波), 同时计算各模块单个周期的能耗, 以验证设计指标。     

Photosynthesis-irradiance relationship of phytoplankton and primary production in the vicinity of Kuroshio warm core ring in spring

The light-saturated maximum value (P ^B _max) and initial slope (α) of the photosynthesis-irradiance (P-E) curve were examined in a warm streamer, a cold streamer and a warm core ring off the Sanriku area in the subarctic western North Pacific Ocean during an ADEOS/OCTS Sanriku field campaign in early May 1997. BothP ^B _max and α were within the ranges of temperate populations. A regional difference was apparent inP ^B _max: populations in the warm streamer tended to show higher value ranging between 1.92 and 4.74 mgC (mgChla)⁻¹h⁻¹ than those in the cold streamer and the warm core ring (1.35–2.87 mgC (mgChla)⁻¹h⁻¹). A depth variation was also observed in α in both the warm streamer and the warm core ring: shallow populations tended to have lower α than deep populations. The depth variations in bothP ^B _max and α resulted in a lower light intensity of the light saturation in a deeper population than that of a shallower one. These depth-related variations in the P-E parameters were likely a manifestation of “shade-adaptation” of photosynthesis. Photoinhibition was not observed over in situ surface light intensity varying below ca 1600 μmol photon m⁻²s⁻¹. Water-column primary productivity was biooptically estimated to be 233 to 949 mgC m⁻²d⁻¹ using vertical distributions of the P-E parameters, chlorophylla, phytoplankton light absorption and underwater irradiance. Applicability of surface data sets for estimation of water-column productivity is discussed.     

Sea Beam,SeaMARC II and ALVIN-based studies of faulting on the East Pacific Rise 9°20′ N–9°50′ N

A study of Sea Beam bathymetry and SeaMARC II side-scan sonar allows us to make quantitative measures of the contribution of faulting to the creation of abyssal hill topography on the East Pacific Rise (EPR) 9°15 N–9°50 N. We conclude that fault locations and throws can be confidently determined with just Sea Beam and SeaMARC II based on a number of in situ observations made from the ALVIN submersible. A compilation of 1026 fault scarp locations and scarp height measurements shows systematic variations both parallel and perpendicular to the ridge axis. Outward-facing fault scarps (facing away from the ridge axis), begin to develop within 2 km of the ridge and reach their final average height of 60 m at 5–7 km. Beyond these distances, outward-dipping faults appear to be locked, although there is some indication of continued lengthening of outward-facing fault scarps out to the edge of the survey area. Inward-facing fault scarps (facing toward the ridge axis), initiate 2 km off axis and increase in height and length out to the edge of our data at 30 km, where the average height of inward fault scarps is 60–70 m and the length is 30 km. Continued slip on inward faults at a greater distance off axis is probable, but based on fault lengths, 80% of the lengthening of inward fault scarps occurs within 30 km of the axis (>95% for outward faults). Along-strike propagation and linkage of these faults are common. Outward-dipping faults accommodate more apparent horizontal strain than inward ones within 10 km of the ridge. The net horizontal extension due to faulting at greater distances is estimated as 4.2–4.3%, and inward and outward faults contribute comparably. Both inward- and outward-facing fault scarps increase in height from north to south in our study area in the direction of decreasing inferred magma supply. Average fault spacing is 2 km for both inward-dipping and outward-dipping faults. The azimuths of fault scarps document the direction of ridge spreading, but they are sensitive to local changes in least compressive stress direction near discontinuities. Both the ridge trend and fault scarp azimuths show a clockwise change in trend of 3–5° from 9°50 N to 9°15 N approaching the 9° N overlapping spreading center.     

Evolution of the East Pacific Rise at 16°–19° S since 5 Ma: Bisection of overlapping spreading centers by new,rapidly propagating ridge segments

Nearly complete side-scan, bathymetry and magnetic coverage documents the evolution of the geometry of the East Pacific Rise (EPR) between 16° and 19° S since 5 Ma. Lineaments visible in SeaMARC II, H-MR1 and Sea Beam 2000 side-scan data correspond dominantly to normal fault scarps which have developed in the axial region perpendicular to the least compressive stress. Except near overlapping spreading centers (OSCs), the lineament orientations are taken to represent the perpendicular to the instantaneous Pacific-Nazca spreading direction. Their dominant orientation in the axial region is 012°, in good agreement with the prediction of the current model of relative plate motion (DeMets et al., 1994). However, the variations of the lineament azimuths with age show that there has been a small (3°–5°) clockwise change in the Nazca-Pacific relative motion since 5 Ma. There is also a distinct population of lineaments which strike counterclockwise to the ambient orientation. These discordant lineaments form somewhat coherent patterns on the seafloor and represent the past migration tracks of several left-stepping OSCs. Concurrent analysis of these discordant zones and the magnetic anomalies, reveals that up to 1 Ma, the EPR was offset by a few large, left-stepping OSCs. These OSCs were bisected into smaller OSCs by new spreading segments forming within their overlap basins. The smaller OSCs proceeded to migrate rapidly and were further bisected by newly spawned ridge segments until the present staircase of small, left-stepping OSCs was achieved. By transferring lithosphere from one plate to the other, these migration events account remarkably well for the variable spreading asymmetry in the area. Between 16° and 19° S, the present EPR is magmatically very robust, as evidenced by its inflated morphology, the profuse volcanic and hydrothermal activity observed from submerisbles and towed cameras, the geochemistry of axial basalts, and seismic and gravity data. Since 1 Ma, all the OSCs have migrated away from the shallowest, most robust section of the ridge between 17° and 17°30 S, which was previously offset by a large OSC. We propose that the switch from a presumed starved magmatic regime typically associated with large OSCs to the presently robust magmatic regime occurred when the EPR overrode a melt anomaly during its westward migration relative to the asthenosphere. The resulting increase in melt supply at 17°–17°30 S has fed the migration of axial discontinuities for this section of the southern EPR since 1 Ma.     

efa②对Con-A诱导的小鼠肝脏损伤模型的保护作用研究

目的：探讨efa^{②对刀豆蛋白（con-A）诱导的自身免疫性肝炎小鼠模型的保护作用及其可能的作用机制。方法：将50只昆明种小鼠随机分为正常对照组、con-A自身免疫性肝炎模型组及样品efa②高（0.04mL/20g）、中（0.02mL/20g）、低（0.01mL/20g）剂量组,分别给予0.9%氯化钠注射液或相应浓度的efa②样品灌胃,每天1次,连续7d。本次灌胃结束禁食1晚后,尾静脉注射Con-A,断头取血测生化指标,并取肝右叶组织作病理切片,对肝脏组织中的CYP5A1、CYP2E1和CYP3A进行蛋白分析。结果：efa②能使自身免疫性肝炎模型小鼠血清中IL-10升高以及IFN-γ、TNF-α、PGE1活性降低。结论：efa②具有调节肝炎模型小鼠血清各细胞因子及ALT的水平,并显著改善肝脏组织病理变化的作用,其保护机制可能与CYP2E1相关。}