Macrobenthic infaunal communities associated with deep‐sea hydrocarbon seeps in the northern Gulf of Mexico

There are thousands of seeps in the deep ocean worldwide; however, many questions remain about their contributions to global biodiversity and the surrounding deep‐sea environment. In addition to being globally distributed, seeps provide several benefits to humans such as unique habitats, organisms with novel genes, and carbon regulation. The purpose of this study is to determine whether there are unique seep macrobenthic assemblages, by comparing seep and nonseep environments, different seep habitats, and seeps at different depths and locations. Infaunal community composition, diversity, and abundance were examined between seep and nonseep background environments and among three seep habitats (i.e., microbial mats, tubeworms, and soft‐bottom seeps). Abundances were higher at seep sites compared to background areas. Abundance and diversity also differed among microbial mat, tubeworm, and soft‐bottom seep habitats. Although seeps contained different macrobenthic assemblages than nonseep areas, infaunal communities were also generally unique for each seep. Variability was 75% greater within communities near seeps compared to communities in background areas. Thus, high variability in community structure characterized seep communities rather than specific taxa. The lack of similarity among seep sites supports the idea that there are no specific infauna that can be used as indicators of seepage throughout the northern Gulf of Mexico, at least at higher taxonomic levels.     

Ophiuroid fauna of cobalt-rich crust seamounts in the Northwest Pacific Ocean

Seamounts are vulnerable ecosystems in the deep sea and can be heavily impacted by human activities, such as bottom fishing and deep-sea mining. The species composition and distribution patterns of benthic fauna is key information for the designation of marine protected areas and environmental management plans. Three contracts for cobalt-rich crust exploration have been granted to China, Japan and Korea in the Northwest Pacific Ocean by the International Seabed Authority. However, our knowledge ...     

北冰洋水体对格陵兰海混合增密对流的可能影响分析

格陵兰海内发生的等密度混合后产生的增密对流是重要的对流现象之一。北冰洋正在发生快速变化,其内水团变性以及环流系统的改变都将使格陵兰海等密度混合对流发生明显变化,继而对全球气候变化产生影响。以往关于等密度混合对流的研究很少,大都集中在对流发生海域。由于等密度混合的主体是大西洋回流水与北冰洋流出水体,本文目的是探讨北极内部不同海域的水体会对混合增密对流造成的可能影响。文中定义了有效对流速度,强调水平温度梯度和垂向层化强度是影响有效对流速度的决定性因素;水平温度差越大,垂向层化越弱,产生的对流越强。发生在东格陵兰极锋处的有效对流都是大西洋的水体,一部分是在格陵兰海回流的大西洋回流水;一部分是在北冰洋潜沉并回流的北极大西洋水,该水体在北冰洋循环的时间越长,温度差越大,产生的有效对流越强。而横越北冰洋的太平洋水因密度过低而不能参与等密度混合对流,加拿大海盆主盐跃层之上的水体也都不能参与对流。北冰洋几个海盆深层水的温度差异明显,有可能与格陵兰海深层水形成有效对流;但是,由于深层水流速低、湍流混合弱、水平温度梯度小,是否可以产生有效对流尚不清楚。     

The Arctic Ocean halocline and its interannual variability from 1997 to 2008

As a key structure to understand the role of the ocean on the sea ice mass balance, the Arctic Ocean halocline and its spatiotemporal variability require serious attention. In this paper, we are proposing a new definition of the halocline, which is based on the salinity gradient structure, taking into account both the salinity amplitude and the thickness of the halocline. The Brunt Vaisala frequency is used as the halocline stratification index. CTD data collected from 1997 to 2008 and coming from various sources (icebreaker cruises, drifting buoys, etc.) are used to determine the halocline, and its time and space variability during three time periods, with a special focus on three main regions of the Arctic Ocean: the Canada basin, the Makarov basin and the Amundsen basin. Observations reveal that the halocline in the Amundsen basin was always present and rather stable over the three time periods. In contrast, the Canada and Makarov basins' halocline became more stratified during the IPY than before, mainly because of surface water freshening. In addition, observations also confirmed the importance of the halocline thickness for controlling the stratification variability. Observations suggest that both large scale and small scale processes affect the halocline. Changes in surface salinity observed in the Makarov basin are more likely due to atmospheric variability (AO, Dipole Anomaly), as previously observed. More locally, some observations point out that salt/heat diffusion from the Atlantic water underneath and brine rejection during sea ice formation from above could be responsible for salt content variability within the halocline and, as a consequence, being influential for the variability of the halocline. In spite of the existence of interannual variability, the Arctic Ocean main stratification, characterized by a stable and robust halocline until now, suggested that the deep ocean had a limited impact on the mixed layer and on sea ice in actual conditions. The drastic changes observed in Arctic sea ice during this period (1997-2008) cannot be attributed to a weakening of the halocline that could trigger an enhanced vertical heat flux from the deep ocean.     

The economics of mining seabed manganese nodules: A case study of the Indian Ocean nodule field

Abstract

Because of ever-growing demand for strategic metals, the focus of the international community has fallen on deep sea manganese nodules occurring at a water depth of more than 4500?m. We present an economic appraisal and strategy for mining of nodules from the Indian Ocean Nodule Field- one of the four economically potential areas in the world oceans. In contrast to the prevailing perception of non-viability of nodule mining, our analysis indicates a fair degree of economic feasibility and commercial sustainability to mine the deep-sea manganese nodules.     

Biostratigraphic Analysis of the Top Layer of Sediment Cores from the Reference and Test Sites of the INDEX Area

Radiolarian fossil study in the sediment cores collected during the pre- and postdisturbance cruises of the Environmental Impact Assessment (EIA) Indian Ocean Experiment (INDEX) program of deep sea mining in the Central Indian Ocean Basin suggests a pronounced directional deposition of fossil radiolarians exhumed during the deep sea benthic disturbance experiment. The relative occurrences of the Stylatractus universus species that became extinct ~0.425 million years before present were mostly confined to the older and deeper strata of the sediment of the disturbance tract in the southwestern direction. This pattern is remarkable and suggests that the disturbance plume has been preferentially redeposited in the southwestern direction. This observation is in concurrence with the prevailing southwestern abyssal current during the disturbance experiment in the Central Indian Basin.     

Deep‐Sea Diversity: Overlooked Messages from Shallow‐Water Sediments

Abstract. Much of the discussion of high deep‐sea diversity has assumed that asymmetric inter‐specific competition will rapidly lead to the elimination of many species unless restrained by extensive differentiation of niches, or the action of predation and/or environmental disturbance. This is true for some habitats, including rocky shores. However, experimental studies indicate that marine soft sediment communities do not function like this. In shallow‐water sediments, competition is usually symmetric and relatively weak. Asymmetric competition that leads to the elimination of one species by another on time scales shorter than one generation is rare, apart from interactions that involve large‐scale modification or disturbance of the sediment. Competition is therefore relatively unimportant as a process structuring communities and the impact of predation is usually to reduce rather than enhance diversity. These results have been largely ignored by the literature on deep‐sea diversity. If deep‐sea communities function in similar ways, coexistence of many species within small areas on short time scales does not need further explanation. We do , however, need to explain why abundances of all species remain bounded on large spatial scales and time scales of several generations. The model of diversity maintenance proposed by Huston (1979) and applied to the deep sea by Rex (1983) achieves this by implicit intra‐specific, density‐dependent processes that increase the population growth rate of species that have become locally rare. This would give robust maintenance of diversity, but there is no evidence for density dependence of this type in the deep sea, and no plausible mechanisms by which it could occur. Alternative models require either spatial heterogeneity on a scale much larger than that envisaged by the grain‐matching hypothesis or the placing of a cap on the abundance of common species, perhaps by frequency‐dependent predation. Arbitrating between these possibilities will require assessments of the population dynamics and spatial distribution of individual species on spatial and temporal scales much greater than those usually considered in the deep sea.     

Halokinetic deep‐seated slumping on the mediterranean slope of northern Sinai and southern Israel

Abstract

The continental margin of northern Sinai and Israel consists of a seaward‐inclined wedge, made up predominantly of foreset beds of mainly Nile‐derived clastics. They overlie seaward‐thickening Messinian (Upper Miocene) evaporites. Detailed bathymetric and seismic surveys reveal large areas of sea floor disturbances off northern Sinai and in several places off Israel, expressed by a complex block topography of the outer continental shelf and slope. These disturbed areas appear to be gigantic, deep‐seated, compound rotational slumps over down‐slope flowing evaporites. Many of the disturbances are above landward lobes of evaporites which fill buried Late Miocene erosion channels of the pre‐Messinian retreat of the sea. Flowage of the evaporites was presumably caused by excessive pore pressures, generated by the Pliocene‐Quaternary overload, in confined layers of the elastics interbedded within the evaporites.     

Erosion and Accretion of a Placer Mining Beach of SW Indian Coast

The erosion/accretion pattern in a placer mining beach on the southwest Indian coast was monitored for five years to study the role of different driving forces. The beach has maximum width during the fair weather months and least in the rough monsoon months. Apart from hydrodynamic processes, sand mining and presence of sea wall are found to be the driving forces for erosion/accretion. Impact of sand mining is not felt on the beach when the mining is within an optimum level, equivalent to the natural replenishment. It is concluded that, though sand mining will cause erosion in the innershelf, the time taken for a measurable impact can be long if the mining volumes are much less than the annual volume changes.     

“桑吉”号泄漏物质扩散与漂移数值模拟预测

基于ROMS(Regional Ocean Modeling System)模式,对西北太平洋海域进行了水平分辨率高达4km的水动力环境数值模拟,该分辨率可以很好地分辨我国东海陆架环流以及中尺度涡旋等过程,此外模式考虑了8个分潮,模式结果很好地再现了黄、东海陆架环流等。基于模式结果,对"桑吉"号泄漏物质可能的扩散和迁移轨迹进行了数值模拟分析。在"桑吉"号沉船位置的表、底Ekman层内,释放拉格朗日粒子和示踪物来示踪"桑吉"号泄漏物质的可能影响范围。拉格朗日粒子和示踪物模拟结果表明:在未来3个月,"桑吉"号泄漏物质对我国黄海的影响较小,其主要随着对马暖流进入日本海和随着黑潮进入日本九州以南的太平洋海域。随着冬、春的季节转换,三个月后,北风会减弱,减弱风场的试验表明,风场减弱会减少泄漏物质向黄海的输送。5月份后黄海冷水团逐渐形成,由于斜压效应,在黄海深层水中会逐渐建立起气旋式环流,从而进一步阻碍了"桑吉"号泄漏物质向黄海的输送,该气旋式环流有利于"桑吉"号泄漏物质通过对马海峡向日本海的输送,而会抑制底层泄漏物质向我国黄海西侧的输送。     

Peripheral communities of the Eastern Lau Spreading Center and Valu Fa Ridge: community composition,temporal change and comparison to near‐vent communities

Western Pacific hydrothermal vents will soon be subjected to deep‐sea mining and peripheral sites are considered the most practical targets. The limited information on community dynamics and temporal change in these communities makes it difficult to anticipate the impact of mining activities and recovery trajectories. We studied community composition of peripheral communities along a cline in hydrothermal chemistry on the Eastern Lau Spreading Center and Valu Fa Ridge (ELSC‐VFR) and also studied patterns of temporal change. Peripheral communities located in the northern vent fields of the ELSC‐VFR are significantly different from those in the southern vent fields. Higher abundances of zoanthids and anemones were found in northern peripheral sites and the symbiont‐containing mussel Bathymodiolus brevior, brisingid seastars and polynoids were only present in the northern peripheral sites. By contrast, certain faunal groups were seen only in the southern peripheral sites, such as lollipop sponges, pycnogonids and ophiuroids. Taxonomic richness of the peripheral communities was similar to that of active vent communities, due to the presence of non‐vent endemic species that balanced the absence of species found in areas of active venting. The communities present at waning active sites resemble those of peripheral sites, indicating that peripheral species can colonize previously active vent sites in addition to settling in the periphery of areas of venting. Growth and mortality were observed in a number of the normally slow‐growing cladorhizid stick sponges, indicating that these animals may exhibit life history strategies in the vicinity of vents that differ from those previously recorded. A novel facultative association between polynoids and anemones is proposed based on their correlated distributions.     

Biostratigraphic Analysis of the Top Layer of Sediment Cores from the Reference and Test Sites of the INDEX Area

Abstract

Radiolarian fossil study in the sediment cores collected during the pre- and postdisturbance cruises of the Environmental Impact Assessment (EIA) Indian Ocean Experiment (INDEX) program of deep sea mining in the Central Indian Ocean Basin suggests a pronounced directional deposition of fossil radiolarians exhumed during the deep sea benthic disturbance experiment. The relative occurrences of the Stylatractus universus species that became extinct ～0.425 million years before present were mostly confined to the older and deeper strata of the sediment of the disturbance tract in the southwestern direction. This pattern is remarkable and suggests that the disturbance plume has been preferentially redeposited in the southwestern direction. This observation is in concurrence with the prevailing southwestern abyssal current during the disturbance experiment in the Central Indian Basin.     

从ODP到IODP

大洋钻探计划（ODP）结束以后实施的整合大洋钻探计划（IODP）与以往钻探计划不同的是将以多个钻探平台为主，其航次将进入过去ODP无法进入的地区，将在古环境、海底资源（包括气体水合物）、地震机制、大洋岩石圈、海平面变化、深部生物圈等研究方面有所突破。从ODP到IODP有一过渡机构－ISAS，于2001年6月开始运作，到IODP开始实施时结束使命。ISAS将负责航次建议书的接受与评估、确保ODP与IODP的平稳过渡及负责与IODP有关的公共活动等工作。     

The coral assemblages of an off‐shore deep Mediterranean rocky bank (NW Sicily,Italy)

In this study we characterized the deep assemblages dwelling at 200–250 m depth on a large shoal off Capo St. Vito Promontory (Northwestern coast of Sicily, South Tyrrhenian Sea) by means of ROV‐imaging. Two assemblages of suspension feeders, dominated by the gorgonian Callogorgia verticillata and by the black coral Leiopathes glaberrima, together with a tanatocoenosis of the colonial yellow scleractinian coral Dendrophyllia cornigera, were examined. The three main species were significatively distributed into two areas corresponding to different habitat preferences: a more elevated hardground hosting black corals and a gently sloping, silted rocky bottom hosting the other coral species. The study area is subjected to a heavy pressure from the professional fishery, resulting in the mechanical damage of numerous colonies, some of which are then overgrown by various epibionts including a parasitic bioluminescent zoanthid, new for the Mediterranean fauna, and tentatively identified as Isozoanthus primoidus. In the Mediterranean Sea, these deep off‐shore rocky banks are widely known among recreational and professional fishermen due to their rich fish fauna. However, there has been still little effort into quantifying and characterizing the extent of the impact and its consequences on the benthic communities, which may represent, as in this case, only a partial picture of their original structure and extent.     

长江口及其邻近海区环流和温、盐结构动力学研究IV 盐度结构

盐度的数值模拟结果表明: 一年四季长江口及其邻近海区的盐度分布均为近岸低, 外海高,近岸与外海盐差大。冬季近岸和外海的上层盐度呈垂直均匀分布, 陡坡及外海的底层出现层化; 近岸特别是长江口及其以南近岸盐度的水平变化显著, 外海变化缓慢。春季在长江口以北, 近岸至外海的表层至近底层盐度呈垂直均匀分布, 近岸至外海的底层存在一个向北延伸的盐舌; 长江口及其以南近岸和外海的表层至次表层盐度呈垂直均匀分布, 在近岸稍远的表层至次表层形成盐跃层, 其强度自近岸至外海和自表层至底层逐渐减弱; 在陡坡区的底层盐度几乎呈均匀分布, 并保持高盐特征。夏季除长江口及其以南近岸浅水区盐度呈垂直均匀分布外, 其它区域盐度均出现剧烈分层, 在长江冲淡水区形成强盐跃层, 其强度自表层至底层迅速减弱, 陡坡至外海的底层盐度大致呈均匀分布且保持高盐特征。秋季长江口以北近岸浅水区表层盐度低且出现层化, 表层以下盐度高且呈垂直均匀分布; 近岸以远自表层至底层呈垂直均匀分布, 在外海上层盐度低且呈垂直均匀分布, 而底层盐度高并出现分层;长江口及其以南近岸浅水区盐度呈垂直均匀分布, 陡坡区出现层化, 其盐度为表层低, 底层高; 层化自表层至底层逐渐增强, 并随陡坡至外海的减弱, 上层又逐渐变为垂直均匀分布。     

Impact of a scallop drag on the sediment chemistry, microbiota, and faunal assemblages of a shallow subtidal marine benthic community

Scallops are usually obtained by means of a heavy metal dredge that is pulled over the sea bottom. Most studies of the impact of this gear type have shown that larger invertebrates, in particular, are severely disturbed. These studies, however, have been conducted on coarse sediments, ranging from sands to cobble, and have dealt only with faunal changes. In this paper the impact of a New England type scallop dredge on the fauna and sedimentary nutritional characteristics of a silty sand community is detailed. The site, in the Damariscotta River, Maine, USA, was sampled during the fall and winter prior to, then again immediately following, the dragging event, and twice more over the ensuing six months. Loss of surficial sediment, lowered food quality of the sediment (as measured by microbial populations, enzyme hydrolysable amino acids, and chlorophyll a), and changes in the faunal composition of the dragged site were observed. While some taxa returned to the drag track relatively quickly, others such as the cumaceans, phoxocephalid and photid amphipods, and nephtyid polychaetes, were not seen in abundances comparable to those of the adjacent undragged site until the food quality also recovered.     

天海达工程建设对附近海域水环境影响预测分析

运用三维海洋模型FVCOM(Finite-Volume Coastal Ocean Model),采用有限体积计算方法,引入了"干、湿"判断,建立了天海达工程附近海域的三维潮流和泥沙输移模型,预测分析了天海达工程建设后对附近海域水动力和地形冲淤的影响。结果表明工程建设后对其西侧潮流影响较大,东侧与南侧影响较小,且随着距离的增加,影响程度减小,在距离工程1200 m以外海域流速相对变化值大约在8%以内;工程建设前后,静风条件下,工程附近海域地形变化趋势基本一致,但由于岸线的改变,工程东西两侧500m范围内近岸海域淤积程度增大,淤积增大幅度范围为0.05～0.1 cm/a。     

Studying Indian ocean typical dynamical phenomena using TOPEX observations

TOPEX altimeter data of 1993 have been analyzed to study the following three types of oceanographic phenomena in the Indian Ocean: (1) sea level variability of the Indian Ocean (20⁼S to 25⁼N. 40⁼E to 100⁼E): (2) sea surface height signals of the Somali eddy; and (3) sea surface slope variations of the equatorial Indian Ocean (EIO) spanning 5⁼S to 5⁼N and 45⁼E to 95⁼E. Root‐mean‐square sea level variability revealed the presence of Rossby waves in the southern Indian Ocean. Fast Fourier technique analysis of a few passes near the Somali region is used to study the formation and dissipation of an anticyclonic eddy.     

The marine chemistry of dimethylsulfide

Dimethylsulfide (DMS) was determined in surface seawater and vertical hydrographic profiles in the Atlantic Ocean during two cruises from Hamburg to Montevideo (Uruguay), and from Miami (Florida) into the Sargasso Sea. These data cover most of the ecological zones of the Atlantic. DMS concentrations are related to the levels of marine primary production, in agreement with its release by marine phytoplankton in laboratory cultures. The vertical distribution of DMS in the euphotic zone follows that of primary production, with a maximum at or near the ocean surface and a decrease with depth. Below the level of 1% light penetration, DMS levels decline gradually, but DMS remains detectable even in the bottom waters. The mean DMS concentration in surface water is 84.4, and in deep water 3.2 ng S (DMS) 1^?1. No steep gradients of DMS exist near the sea surface on scales of centimeters to tenths of millimeters. At a drift station, DMS was observed to be diurnally variable, with an increase in concentration in the euphotic zone throughout the day. DMS is actively turned over in the surface ocean with a residence time of a few days, but it is apparently very stable in the deep sea. DMS is the major volatile sulfur compound in the ocean, and its transfer across the air-sea interface contributes significantly to the atmospheric sulfur budget.     

Relevance of Bathymetry for Tsunami Run‐up Modeling

Abstract

Marine positioning is relevant for several aspects of tsunami research, observation, and prediction. These include accurate positioning of instruments on the ocean bottom for determining the deep‐water signature of the tsunami, seismic observational setups to measure the earthquake parameters, equipment to determine the tsunami characteristics during the propagation phase, and instruments to map the vertical uplift and subsidence that occurs during a dip‐slip earthquake.

In the accurate calculation of coastal tsunami run‐up through numerical models, accurate bathymetry is needed, not only near the coast (for tsunami run‐up) but also in the deep ocean (for tsunami generation and propagation). If the bathymetry is wrong in the source region, errors will accumulate and will render the numerical calculations inaccurate. Without correct and detailed run‐up values on the various coastlines, tsunami prediction for actual events will lead to false alarms and loss of public confidence.