Spatial scale variability in shoot density and epiphytic leaves of Posidonia oceanica on Kerkennah Island (Tunisia) in relation to current tide effects

A study was undertaken of the patterns of spatial variability, epiphytic biomass and distribution of epiphytic fauna and flora of Posidonia oceanica. Samples were taken at four stations located approximately 4 km apart, exposed to different current conditions. Stations A and B, situated near the Oued Mimoun tidal channel with its relatively strong bi‐directional flows, were affected by high current tide. The other two stations, North Oued Mimoun (L1) and South Oued Mimoun (L2), were located further from the channel, in low current tide conditions. Sampling was conducted in the Attaya area of Kerkennah Island (Tunisia) in August 2009 at depths between 2 and 3 m, with the results indicating differences among the stations. Shoot density decreased when exposed to high levels of hydrodynamic activity generated by current tides whereas the epiphytic biomass of P. oceanica leaves decreased at sheltered stations located far from the channel. Epiphytic algae such as Heterokontophyta, Rhodophyta and Chlorophyta, and epiphytic fauna represented by Bryozoa, Hydrozoa, Annelida, Porifera and Tunicata, dominated the epiphytic assemblages and were abundant at the station most exposed to high current tide hydrodynamics. Cyanobacteria, however, were dominant in stations exposed to low current tide.     

海南岛冬季暴雨的时空分布及大尺度环流场特征分析

利用海南岛气象观测站逐日降水整编资料和欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts，ECMWF） ERA5再分析资料，分析了1991—2020年海南岛冬季暴雨的时空分布及环流特征。结果表明：海南岛冬季暴雨在月际分布（12月—次年2月）上存在较大差异性，降雨量级越大，差异越明显；在空间分布上也存在显著的地域性，东部地区发生频次最高，总体上呈现东多西少的分布特征。海南岛冬季暴雨的水汽输送主要以偏东方向为主，气流来自副高南侧的偏东气流和大陆冷高压东南侧的东北气流。海南岛冬季暴雨发生期间，相对气候平均态而言，偏东低空急流较为强劲，中南半岛南支槽形态明显，副高偏北偏西偏强，南亚高压西北向的出流偏强，且南海海域存在显著的海温正距平。     

居民对海岛旅游影响感知的实证研究

采用实地考察、问卷调查与访谈的方法对我国旅游型海岛东山岛进行调查发现,当地居民对旅游影响的正面感知较强,突出表现在旅游经济影响方面,反映了当地旅游业发展处于起步阶段;居民对旅游的负面影响感知较弱,反映了当地经济转型时期居民对旅游业的期望较高;居民人口统计学的差异对旅游影响感知总体差异不大,但在某些方面存在一定差异。     

First cosmogenic 10Be constraints on LGM glaciation on New Zealand's North Island: Park Valley,Tararua Range

We report the first direct ages for late Quaternary glaciation on the North Island of New Zealand. Mt Ruapehu, the volcanic massif in the North Island's centre, is currently glaciated and probably sustained glaciers throughout the late Quaternary, yet no numeric ages have been reported for glacial advances anywhere on the North Island. Here, we describe cosmogenic ¹⁰Be ages of the surface layers of a glacially transported boulder and glacially polished bedrock from the Tararua Range, part of the axial ranges of the North Island. Results indicate that a limited valley glaciation occurred, culminating in recession at the end of the last glacial coldest period (LGCP, ca. 18 ka). This provides an initial age for deglaciation on the North Island during the last glacial–interglacial transition (LGIT). It appears that glaciation occurred in response to an equilibrium‐line altitude (ELA) lowering of ～1400 m below the present‐day mean summer freezing level. Ages for glaciation in the Tararua Range correspond closely to exposure ages for the last glacial maximum (LGM) from the lateral moraines of Cascade Valley in the South Island, and in Cobb Valley, in northern South Island. The corollary is that glaciation in the Tararua Range coincided with the phase of maximum cooling during MIS 2, prior to the Antarctic Cold Reversal (ACR), during the LGCP. Copyright © 2008 John Wiley & Sons, Ltd.     

Slab melt as metasomatic agent in island arc magma mantle sources, Negros and Batan (Philippines)

Abstract Two new cases of association of adakites with ‘normal’ island arc lavas and transitional adakites are recognized in the islands of Batan and Negros in northern and central Philippines, respectively. The Batan lavas are related to the subduction of the middle Miocene portion of the South China Sea basin along the Manila trench; those of Negros come from the almost aseismic subduction of the middle Miocene Sulu Sea crust along the Negros trench. The occurrence of the Batan adakites is consistent with previous findings showing adakitic glass inclusions within minerals of mantle xenoliths associated with Batan arc lavas. The similarity of adakite ages (1.09 Ma) and that of the metasomatized xenoliths (1 Ma) suggests that both are linked to the same slab‐melting and metasomatic event. Earlier Sr, Pb and Nd‐isotopic studies, however, also reveal the presence of an important sediment contribution to the Batan lava geochemistry. Thus, the role played by slab melts, assumed to have mid‐ocean ridge basalts‐like (MORB) isotopic characteristics, in enriching the Batan subarc mantle is largely masked by the sediment input. The Negros adakites are present only in Mount Cuernos, the volcanic center nearest to the Negros trench. Batch partial melting calculations show that the Negros adakites could be derived from a garnet amphibolitic source with normal‐MORB (N‐MORB) geochemistry. This is supported by the MORB‐like isotopic characteristics of the Mount Cuernos lavas. The volcanic rocks from the other volcanoes consist of normal arc and transitional adakitic lavas that have slightly higher Sr‐ and Pb‐isotopic ratios, probably due to slight sediment input. Mixing of adakites and normal arc lavas to produce transitional adakites is only partly supported by trace element geochemistry and not by field evidence. The transitional adakites can be modeled as partial melts of an adakite‐enriched mantle. Trace element enrichment of non‐adakitic lavas could reflect the interaction of their mantle source with uprising slab melts, as metasomatic mantle minerals scavenge certain trace elements from the adakitic fluids. Therefore, in arcs beneath which thick (up to 2 km) continent‐derived detrital sediments are involved in subduction, like in Batan, the sediment signature can overwhelm the slab melt input. In arcs like Negros where slow subduction could cause a more efficient scraping of thinner (approximately 1 km) detrital sediments, the contribution of slab melts is easier to detect.     

Forearc deformation and tectonic significance of the ultramafic Molucca central ridge, Talaud islands (Indonesia)

Abstract The Molucca Sea is a narrow basin located south of Mindanao (Philippines) and underlined by a north-south ophiolitic ridge. This ridge represents the outer ridge of the Sangihe subduction zone and emerges by uplift in the central part of the basin, in the Talaud Islands. Field studies indicate that forearc sediments rest uncomformably on (i) a dismembered ophiolitic series and (ii) thick melanges. Structural analysis indicates two deformation events, one of which is oriented east-west coaxial with the present state of strain. We interpret the earlier (N20°E) direction as a thrusting event that affected an ophiolitic basement associated with the edge of the Celebes Sea. Thrusting within the oceanic crust and sediments also generated olistostromes (melanges). The style of deformation is characterized by flattened rhombs of peridotites which exists in situ in the upper section of the crustal sequence and were also found inside the melange. Incipient Sangihe subduction around 15 Ma uplifted the deformed crust and buried the melanges beneath the forearc sediments. Recent east-west shortening during subduction of the Snellius Plateau reactivated the melanges within thrusts cutting the forearc series.     

Report of Pontoniinae Shrimps (Crustacea: Decapoda) Collected by Joint Chinese-German Marine Biology Expeditions to Hainan Island, South China Sea. Ⅲ. Periclimenes

1　INTRODUCTIONInthefirstandsecondpapersofthisseries (LietLiu ,2 0 0 2 ,2 0 0 3) ,wereported 9genera 1 6speciesofPontoniinae ,collectedbytheJointChinese GermanMa rineBiologyExpeditionstoHainanIsland (winterof1 990andspringof 1 992 ) .ThepresentpaperreportsonthespeciesofgenusPericlimenesfromHainanIslandcollectedbytheexpedition.ThematerialsstudiedherearealldepositedintheInstituteofOceanology ,ChineseAcademyofSciences,Qingdao,China (IOCAS) .Inthispaper,“Materialexamined”and“RN…     

The deglaciation of Clyde Inlet,northeastern Baffin Island,Arctic Canada

The behaviour of ice sheets as they retreated from their Last Glacial Maximum (LGM) positions provides insights into Lateglacial and early Holocene ice‐sheet dynamics and climate change. The pattern of deglaciation of the Laurentide Ice Sheet (LIS) in arctic fiord landscapes can now be well dated using cosmogenic exposure dating. We use cosmogenic exposure and radiocarbon ages to constrain the deglaciation history of Clyde Inlet, a 120 km long fiord on northeastern Baffin Island. The LIS reached the continental shelf during the LGM, retreated from the coastal lowlands by 12.5 ± 0.7 ka (n = 3), and from the fiord mouth by 11.7 ± 2.2 ka (n = 4). Rapid retreat from the outer fiord occurred 10.3 ± 1.3 ka (n = 6), with the terminus reaching the inner fiord shortly after 9.4 ka (n = 2), where several moraine systems were deposited between ca. 9.4 and ca. 8.4 ka. These moraines represent fluctuations of the LIS during the warmest summers since the last interglaciation, and this suggests that the ice sheet was responding to increased snowfall. Before retreating from the head of Clyde Inlet, the LIS margin fluctuated at least twice between ca. 7.9 and ca. 8.5 ka, possibly in response to the 8.2 ka cold event. Copyright © 2006 John Wiley & Sons, Ltd.     

CHEMICAL CHARACTERISTICS OF THE COASTAL SEA OFF TIANHENG ISLAND

Chemical characteristics of the coastal sea off Tianheng Island were investigated from May 1990 toFebruary 1991 in this study which included distribution pattern,seasonal variability and the controlling fac-tors of oxygen,pH,nutrients.The rich nutrient salt content is suited for phytoplankton growth andmariculture.The coastal sea waters is of good quality based on the national standard of seawater qual-ity in terms of pH,oxygen,and nutrients,the main controlling factors for which in the investigated seaarea are hydrographic(salinity,temperature,river runoff,etc.),biological(photosynthesis of plankton),andanthrogenic(fertilizing in the nearby land and sea).     

南极乔治王岛菲尔德斯半岛西湖柱状剖面藻类化石与环境演变

根据西湖柱状岩芯样品中藻类化石的分布与含量变化,推测本区在3600年前仍为冰川覆盖;距今3600～3000年前为冰缘浅湖期;3000～1200年前湖水稳定,气候环境相对较好;距今1200年至现代气候略有波动。