Response of Meiofauna to Immediate Benthic Disturbance in the Central Indian Ocean Basin

Abstract

Twenty-four stations (12 each, during pre- and postdisturbance studies) 5300 to 5330 m deep between 10°01' and 10°03'S latitude and between 75°59' and 76°02'E longitude were sampled to study the effect of benthic disturbance on the distribution of meiofauna in the Central Indian Ocean. Bottom-sampling was conducted with a box corer. Total meiofauna density ranged from 35 to 45 organisms per 10 cm² of bottom area during the predisturbance period and 21 to 32 organisms per 10 cm² during the postdisturbance period in the test and reference sites. Differences between pre- and postdisturbance study results were statistically significant (P < 0.05). Nematoda was the most abundant meta-zoan group, on an average representing >55% of the meiofaunal population. The abundance of nematodes and harpacticoid copepods as well as total meiofauna showed marked decreases during postdisturbance sampling. Vertical distribution of meiofauna in the sediment cores revealed that 75% to 90% of the metazoan population was confined to the top 2-cm layer of the sediment. Recolonization experiments suggest that harpacticoid copepods may take more time for recolonization than the nematodes and are more sensitive to the physical disturbance. These findings suggest that nematodes and harpacticoid copepods can be used as indicator organisms in recolonization experiments.     

The Structure of Coral Communities at Hurghada in the Northern Red Sea

Abstract. The community structure of hard and soft corals, with an emphasis on hard corals, was determined by means of line-transects on 9 on-and off-shore reefs of different type and different wave exposure in the Northern Red Sea near Hurghada in Egypt. Coral communities were found to differentiate along a horizontal wind- and wave-exposure gradient. Exposed communities were dominated by Acropora species, sheltered communities by Porites species, and semi-exposed communities by Millepora species. Also, vertical within-reef zonations following a depth gradient were observed; these were unique for each exposure-determined community type. Average transect diversity was highest on semi-exposed reefs, lowest on sheltered reefs. Reef slopes were more diverse than other reef zones. The observed community structure was compared with data from the literature, and widely distributed, roughly comparable hard and soft coral communities were identified.     

Paleoecological Relations of Foraminifera in a Desert-Enclosed Sea -The Gulf of Aqaba (Elat), Red Sea

Abstract. Planktonic and benthonic foraminifera live in the desert-enclosed, hypersaline and oligotrophic Gulf of Aqaba and northernmost Red Sea near the edge of their ecological tolerance. Marked changes in foraminiferal abundance patterns in the past, resulting from hydrological shifts related to global climatic fluctuations, facilitate a high-resolution ecostratigraphic subdivision of deep-sea records covering the last 150,000 years. Of particular significance are the foraminiferal plankton/benthos ratios, the presence/absence pattern of such species as Globigerinoides sacculifer , as well as the frequency variation of Globigerina bulloules-falconensis, Buliminacea, Miiiolacea and various "rotaliform" species. Paleoceanographic interpretation of the shifts in assemblage composition and of stable oxygen isotope data obtained on planktonic foraminifera and pteropods indicates that during glacial intervals - because of global cooling, lowered sea-level and reduced water exchange at the straits of Bab-el-Mandeb - the temperature of the upper waters fell by about 4–6 ^oC (to 15–17 ^oC), salinity rose by about 10%o to more than 50%₀ while residence time of the water became longer and the input/output ratio of nutrients became higher. As a consequence, fertility of the photic zone was higher, the organic content of the sediments increased and oxygen levels in the deep basin became reduced. Thus, sea level-oscillations and strait-dynamics played a major role in the foraminiferal paleoecology of the Red Sea.     

Benthic mucilaginous aggregates in the Mediterranean Sea: Origin, chemical composition and polysaccharide characterization

Benthic mucilaginous aggregates are frequently formed in various parts of the Mediterranean basin, as in the Tyrrhenian and Adriatic Seas. Notwithstanding their wide spatial distribution, the role played by these aggregates in the biogeochemical cycling of organic matter is still largely unknown.The characteristics of the benthic aggregates examined in the present study showed that they are different from other mucilaginous aggregates, such as the “pelagic” ones that can form in the same areas in the water column and subsequently sediment to the seafloor. The aggregates are usually formed of structures of the filamentous macroalgae Acinetospora crinita, Chrysonephos lewisii and Nematochrysopsis marina. The elemental composition of the aggregates showed a marine macrophyte origin on the basis of the bulk organic matter content of the aggregates. Carbohydrates and proteins account for 26.6 to 55.9% of the organic carbon in the mucilage, respectively. Monosaccharide composition of exopolysaccharides in the mucilage aggregates revealed a characteristic pattern, with galactose, xylose or mannose and fucose as the major components. The relatively high content of deoxysugars is another distinctive feature. The abundant sulphate and uronic groups present in the polysaccharides in addition to their macromolecular dimensions and elongation contribute to inter-chain aggregation. Electron microscopic observations suggest that the polysaccharide fraction is the main macromolecular component in the formation of the persistent gel network in the aggregates.     

Descriptive Analysis and Classification of Benthic Communities in Some Mediterranean Coastal Lagoons (Central Italy)

Abstract. Benthic samples were taken seasonally at 32 stations in five coastal lagoons of Central Italy (Fogliano, Monaci, Caprolace, Fondi, and Lungo) during a two-year period (1982–1984). Composition and distribution of benthic populations in each lagoon as well as seasonal trends of species richness, density, diversity, and redundancy are presented and discussed.
The faunal differentiation appeared to be mainly due to the different degree of water exchange, both with marine and continental systems.     

Circulation in the Gulf of Aqaba (Red Sea) during winter—spring

This study is devoted to oceanographic features of the semi-enclosed Gulf of Aqaba, Red Sea. The data were recorded in winter—spring 1999 on the R/V Meteor cruise leg 44/2. Temperature and salinity profiles were measured at six positions (I—VI). The shipboard NarrowBand Acoustic Doppler Current Profiler (NB ADCP) 150 kHz continuously recorded current profiles down to 350 m en route. The research revealed that the current near the Strait of Tiran front (position VI) represents a semidiurnal signal of an internal tide wave (∼12 h period; 0.2 ms⁻¹ amplitude) that might be generated by the barotropic tide at the sill of the Strait. A sequence of cyclonic and anticyclonic eddy pairs is found along the axis of the Gulf of Aqaba during winter-spring seasons. These sub-mesoscale signals are dominant above the main thermocline and might be caused by wind forcing and the narrowness of the Gulf; it might remain in other seasons with different dimensions in relation to the depth of thermocline. The total diameter of each pair was twice the baroclinic Rossby radius (R ≈ 10 km). A single anti-cyclonic eddy was observed in the upper 300 m in the northern tip of the Gulf with a diameter of about 5–8 km.     

Distribution of Deep-Sea Benthos in the Proposed Mining Area of Central Indian Basin

Abstract

During the first stage of the project work on the Indian Deep-Sea Environment Experiment (INDEX), the abundance and distribution of deep-sea benthos were surveyed in the Central Indian Basin for the collection of baseline data. The deep-sea community of the sediment was characterized by a moderately high standing crop and diverse fauna. The macrofaunal component was dominated by polychaetes (100% prevalence) and peracarid crustaceans, whereas the meiofauna was dominated by nematodes and harpacticoid cope-pods. The results of this study conform to the general distribution reported elsewhere. The macrofaunal abundance showed an inverse relation to the abundance of polymetallic nodules. However, the relation between meiofaunal vertical distribution and the vertical profile of the total organic matter and total labile matter was positive.     

Extension of Satellite Altimetry Jason-2 Sea Level Anomalies Towards the Red Sea Coast Using Polynomial Harmonic Techniques

Satellite altimetry data are facing big challenges near the coasts. These challenges arise due to the fundamental difficulties of correction and land contamination in the foot print, which result in rejection of these data near the coast. Several studies have been carried out to extend these data towards the coast. Over the Red Sea, altimetry data consist of gaps, which extend to about 30–50 km from the coast. Two methods are used for processing and extending Jason-2 satellite altimetry sea level anomalies (SLAs) towards the Red Sea coast; Fourier Series Model (FSM), and the polynomial sum of sine model (SSM). FSM model technique uses Fourier series and statistical analysis reflects strong relationship with both the observation and AVISO data, with strong and positive correlation. The second prediction technique, SSM model, depends on the polynomial sum of sine, and does not reflect any relationship with the observations and AVISO data close to the coast and the correlation coefficient (CC) is weak and negative. The FSM model output results in SLA data significantly better and more accurate than the SSM model output.     

Food Selection in Two Corallivorous Butterflyfishes, Chaetodon austriacus and C. trifascialis, in the Northern Red Sea

Abstract. Using an in situ observational approach, the food preferences among hard corals were examined for the two obligate coral‐feeding butterflyfishes Chaetodon austriacus and C. trifascialis in the Northern Red Sea, Gulf of Aqaba, Egypt. Chaetodon austriacus is a generalist coral feeder that feeds mainly on three genera of abundant hard corals (Acropora, Porites and Pocillopora). In contrast, C. trifascialis is a specialist coral feeder on Acropora spp. and Pocillopora verrucosa. In general, C. austriacus had a lower feeding rate than C. trifascialis (both species in the Northern Red Sea reefs had high feeding rates compared with other reefs). Ivlev's electivity index was calculated for the two species. This index shows that C. austriacus prefers Montipora and Pocillopora, and avoids Lobophyllia and Favites. On the other hand, C. trifascialis prefers Acropora valida and avoids Porites solida. Thus, the feeding preference and avoidance of these chaetodontids depend on both biting rate and food availability in the environment rather than on biting rate alone.     

A fossil record of shell boring: Possible evidence for sea level changes in the Red Sea

An aggregation of fossil shells of the Indo-Pacific muricid snails Chicoreus ramosus was found in the northern part of the island of Tiran, Red Sea. The site was 7 m above the present mean sea level. Radiocarbon dating of these shells indicated an age of 1570±80 years BP. Some of these shells bore-drilled holes, most of them uncompleted. Biological study revealed that such holes were probably drilled by conspecifics in the absence of alternative food after they had been disconnected from the sea. Since there is no evidence of human activity in this part of Tiran, I suggest that such conditions could be caused only by a physical process that changed the relative water level. In accordance with the character of the drilled holes and the short period which muricids maintain reproductive aggregates, I also postulate that such a physical process must have been a relatively rapid one.     

深海极端环境深部生物圈微生物学研究综述

20世纪下半叶是人类进行自然探索最为活跃的一段时期。新发现、新技术和新概念层出不穷，大大拓展了人们对宇宙和生命的视野和认识。在海洋学领域，深海热液喷口化能自养(chemolithoautotrophy)系统的发现大大激发了人们对洋底生物多样性及生命形式、过程、起源和进化的兴趣和热情(Baross et al.，1985)。最近30年相继开展的国际深海钻探计划(deep sea drilling project，DSDP)和大洋钻探计划(ocean drilling program，ODP)为我们揭示了一个以前未曾想象到的埋藏在海底沉积物和上部洋壳中的海底深部生物圈(subseafloor deep biosphere)微生物世界。近期研究表明， 深海热液系统中的嗜热和极端嗜热古菌据推测就来源于海底深部生物圈(Delaney et al.，1998;Summit et al.，2001)，由此推断，生命的真正起源就发生在地球深部生物圈内。巨大的深度和广度，使得海底深部生物圈容纳了大量的微生物生物量和新颖独特的代谢潜力(Whitman et al.，1998)。由于洋壳板块运动而产生的海底地质构造和过程的异质性、洋壳地球化学过程的复杂性，以及在漫长地质年代中的气候变迁和海洋真光层颗粒物沉降输出的历史和地理差异性，埋藏在海底沉积物和上部洋壳中的生命赖以维持和繁衍的能量供给形式具有高度的多样性， 海底深部生物圈蕴育着丰富多样的代谢形式和新颖的生理生化机制(IPSC，2001)。海洋深部生物圈内的古菌群落将作为特定地质微生物标志(geomicrobiological signature)，用来指示过去和现代海洋的地球化学变化和地质环境变迁(inagaki et al.，2001)。海洋微生物生态学研究在最近的20年中取得了一些重要进展，与全球海洋地质历史、地质事件、地质过程和地质作用相关的深海微生物生态学研究，已发展成为一门具有独特魅力的新兴学科，即海洋“地质微生物学”(geomicrobiology)。在46亿年的地球历史中，地圈和生物圈的协同进化过程主要是在微生物的作用下完成的，微生物在海洋沉积物和洋壳中的生物地球化学作用，既是微生物的生态学，又是沉积地质过程和洋壳蚀变的动力学，许多原来以为“无机” 的地质过程，其实都是生命活动的结果(汪品先，2003)。在过去的10年中，分子、遗传、生化和基因组学等现代生物技术被引入地质微生物学的研究中，不但揭示了许多地质环境的微生物多样性，而且阐明了微生物在生物地球化学过程中所发挥的独特作用及环境和生态功能(Newman et al.，2002)。海洋深部生物圈微生物的研究已成为新世纪海洋领域中地学和生物学交叉互补、综合研究前沿的一个新热点和生长点，被列入刚刚启动的国际综合大洋钻探计划(Integrated Ocean Drilling Program，IODP)研究项目的首选(IPSC，2001；中国大洋钻探学术委员会，2003)。尽管这一领域的研究才刚刚起步，却已显示了旺盛的生命力和发展应用前景。     

Bathymetric patterns of deep-sea gastropod species diversity in 10 basins of the Atlantic Ocean and Norwegian Sea

Bathymetric patterns of macrofaunal species diversity are best documented in the western North Atlantic where diversity is a unimodal function of depth, peaking in the mid-bathyal zone and being depressed in the upper slope and abyss. There are few inter-basin studies of diversity-depth trends that are controlled for taxonomy, sampling gear, and diversity measures. In this paper, we compare gastropod diversity gradients in the North American Basin of the Atlantic to estimates of diversity in 9 other regions: the Norwegian Sea, West European Basin, Guiana Basin, Gambia Basin, Equatorial Mid-Atlantic, Brazil Basin, Angola Basin, Cape Basin and Argentine Basin. All samples were collected with epibenthic sleds, and diversity calculated by the Sanders-Hurlbert normalized expected number of species. While sampling in other regions is generally less complete than in the western North Atlantic, results indicate that a unimodal pattern is not universal. Diversity can increase, decrease or show no relationship with depth. The level of diversity also varies among basins relative to the western North Atlantic, being depressed in the Norwegian Sea, at bathyal depths in the eastern North Atlantic, and below an oxygen minimum zone in the Cape Basin, and generally elevated at tropical latitudes and in abyssal regions where food supply is high. Associations between gastropod diversity and the ecology and geology of basins suggest that productivity, oxygen concentration, hydrographic disturbance and evolutionary-historical processes may be implicated in shaping bathymetric diversity gradients, but specific causes are difficult to discern. Much more intensive sampling, analyses of other major taxa, and more detailed ecological data are necessary to understand deep-sea biogeography at within- and between-basin spatial scales.     

Benthic community and biological trait composition in respect to artificial coastal defence structures: A study case in the northern Adriatic Sea

Biological Traits Analysis (BTA) is a method for addressing ecological functioning based on traits exhibited by members of biological assemblages. This study explores and compares species and biological trait patterns on either side (landward and seaward) of coastal breakwater structures in northwestern Adriatic Sea (Italy), with the aim of giving insights and knowledge for management of sandy beach systems affected by coastal development. Eight ecological traits of 96 benthic species were considered. Taxon composition evidenced differences in benthic assemblages across time and exposure: landward and seaward communities shared less than 50% of the total number of species. BTA suggested a no-management effect in the functioning of benthic assemblages. Dominant traits modalities were deposit-feeding, short life, small body size, short life span, iteroparity, gonocorism, with plankto-planktotrophic larvae. The results of BTA highlighted similarities and stability in trait composition contrary to species composition, suggesting a possible persistence in benthic functioning despite the occurrence of species replacements. To best of my knowledge, this study is one of the first attempts to investigate the effects of a management measure (submerged shore-parallel barriers with groynes) in a shallow marine system by means of BTA.     

Benthic macrofauna and productivity regimes in the Barents Sea — Ecological implications in a changing Arctic

Benthic faunal assemblages were analysed from 47 stations in the central and southern parts of the Barents Sea, together with sedimentary and water column parameters, daily ice records and modelled integrated primary productivity. Sampling spanned areas influenced by Atlantic Water (AW) to those lying under Arctic Water (ArW), and included stations with mixed water masses. Ice cover suppressed water column productivity in the northern areas. Three main faunal groups were identified, based on similarity of numerical faunal composition. The northern and southern faunal groups were separated by the northernmost penetration of AW in the bottom water and the third group, the Hopen group, was influenced by modified bank water. Faunal abundances were significantly higher within the southern faunal group relative to the northern group, but the numbers of taxa present were similar. The particularly rich fauna of the Hopen group reflected sediment heterogeneity and tight pelagic–benthic coupling. These results suggest that a retreat and thinning of the ice cover in the Barents Sea likely will result in the northern parts of the Barents Sea becoming more Atlantic in character, with a higher productivity at the sea floor.     

黄海北部近岸鱼类资源数量分布与群体结构

通过 1998 年 6 月和 9 月共 24 个站位的底拖网调查,分析了黄海北部近岸渔获物的组成,其结果表明,该海域鱼类资源量指数较低,为 17.068 kg / 网·h,鱼类资源经济品质结构低值化,鱼类资源群体结构小型化、低龄化更加突出,一些个体小、价值不高的种类如青鳞鱼、鳀鱼、斑鰶等占据了春季渔获量的主要部分,秋季捕获的经济鱼类如兰点马鲛、鲐鱼等全部是当年生幼鱼。     

Large Eddy Simulation of Open Ocean Deep Convection with Application to the Deep Water Formation in the East Sea (Japan Sea)

Various important features could be found on the open ocean deep convection and the subsequent deep water formation from large eddy simulation (LES), and the results were applied to the East Sea (Japan Sea). It was found that under a strong cold wind outburst with the heat flux of 1000 Wm⁻² for 5 days generates a deep convection which can penetrate to the depth 1500 m, but under the continuous cooling with the heat flux of 250 Wm⁻² the growth of a mixed layer is suppressed at 700 m. The effects of the spatial and temporal variations of the surface forcing were investigated with regard to the penetrative depth of convection, the generation of baroclinic eddies, the volume of the water mass formation, and the intensity of the rim current. The deep water formations in the intermediate and deep layer of the East Sea were explained in terms of the simulation results, and the intensity of the consequent circulation and the volume of water mass formation were compared with the observation data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Macrofauna Communities in the Eastern Mediterranean Deep Sea

Abstract. During two expeditions with RV ‘Meteor’ in summer 1993 and winter 1997/98 the structural and functional diversity of the benthic system of the highly oligotrophic eastern Mediterranean deep sea was investigated. The macrofauna communities were dominated by polychaetes even at the deepest stations. The fauna at shallow stations was dominated by surface deposit feeders, whereas subsurface deposit feeders and predators generally increased with depth. A high percentage of suspension‐feeding Porifera was found in the Levantine Basin. Mean abundance and number of taxa of both expeditions were significantly correlated to depth and distance to the nearest coast as well as to the total organic carbon (TOC) content in sediments. Numbers of taxa and abundance decreased generally with depth, although lowest numbers were not found at the deepest stations but in the extremely oligotrophic Levantine and Ierapetra Basin. Biomass measured during the second cruise was extremely low in the Ierapetra Basin and comparable to other extreme oligotrophic seas. The significant correlations found for TOC contents and macrofauna with distance to coast during both expeditions apparently reflect the role of hydrographically governed transport of organic matter produced in coastal regions into greater and extreme depths of the Mediterranean Sea. Seasonal differences in macrofauna communities due to seasonal differences in food supply were not found. However, recent large‐scale hydrographic changes (Eastern Mediterranean Transient, EMT) might change the oligotrophy and, thus, the structure of the benthic communities in the Eastern Mediterranean deep sea.     

2012年楚科奇海及其邻近海域浮游植物现存量和初级生产力粒级结构研究

通过2012年夏季第五次北极科学考察期间在楚科奇海及其邻近海域现场调查所获得的数据分析研究了海域的粒度分级叶绿素a浓度和初级生产力。结果表明,叶绿素a浓度和初级生产力的高值均出现在楚科奇海陆架区,并且远高于深海区。去程时调查海域水层平均叶绿素a浓度的变化范围为0.32~15.66mg/m3,平均(2.77±3.96)mg/m3,高值区出现在南部邻近白令海峡海域、北部阿拉斯加巴罗近岸和冰缘区;初级生产力的范围为50.11~943.28mg/(m2d),高值出现在冰缘水华区。返程时水层平均叶绿素a浓度的变化范围为0.07~1.52mg/m3,平均(0.41±0.40)mg/m3,高值仍出现在陆架区,但比去程时低了一个数量级;初级生产力的分布范围为12.31~41.35mg/(m2d),高值出现在陆架区。浮游植物粒度分级测定结果表明,在生物量较低的深海区,叶绿素a浓度和初级生产力的粒级结构以微微型浮游生物(Pico级份)占优势(其贡献率分别为46.1%和56.9%),小型(Net级份)和微型(Nano级份)对总叶绿素a浓度的贡献差异极小,分别为26.6%和27.3%,对总初级生产力的贡献分别为23.8%和19.3%;而在生物量较高的水深小于200m的陆架区,Net级份叶绿素a浓度所占百分比最高,Pico级份次之,Nano级份最低,分别为59.8%、27.9%和12.3%,初级生产力的粒级结构中叶绿素a浓度所占百分比由高到低同样是Net、Pico和Nano,所占百分比分别为60.6%,32.2%和7.2%。