Biodiversity,ecological structure,and change in the sponge community of different geomorphological zones of the barrier fore reef at Carrie Bow Cay,Belize

Changes in the relative abundance of benthic groups on the barrier fore reef at Carrie Bow Cay, Belize, point to a significant reduction of corals and an expansion of the sponge community in 1995–2009. Fifty‐one species are now present in the four geomorphological zones of this reef: the low‐relief spur‐and‐groove zone, the inner reef slope, the outer ridge, and the fore‐reef slope (to a depth of 30 m). Five species are new additions to the sponge fauna reported for Belize, and six species account for 42.6% of the total assemblage: Niphates erecta (9.60%), Aiolochroia crassa (8.8%), Niphates digitalis (6.9%), Callyspongia plicifera (6.63%), Aplysina archeri (5.37%) and Xestospongia muta (5.37%). Species richness, average density, diversity and evenness indexes are statistically similar in these four zones but some species appear to be more dominant in certain areas. In the same 30 years, coral cover has decreased by more than 90%, while the octocoral cover has greatly increased (by as much as 10‐fold in the low‐relief spur‐and‐groove zone). Thus the Carrie Bow fore reef appears to be undergoing a transition from coral dominance in the late 1970s to algae dominance today, with other benthic groups such as sponges and octocorals showing signs of gradual recovery.     

Depth distribution of algal species on the deep insular fore reef at Lee Stocking Island,Bahamas

Deep-water benthic algal composition and cover were studied with a submersible on the deep fore reef of Lee Stocking Island, Bahamas, from 45 to 150 m. Algal cover decreased from 57% to 16% over this depth range. Although there was substantial overlap in depth distributions, different species or groups of species dominated benthic cover at different depths. Lobophora and Halimeda copiosa co-dominated the fore reef from 45 to 60 m. A Corallinales/Peyssonnelia group was abundant from 60 to 120 m. The Corallinales/Peyssonnelia group shared dominance with Ostreobium between 90 and 120 m. Ostreobium was the only alga observed below 150 m and remained abundant below 200 m. Movement of sand down the fore reef is recognized as having substantial influence on algal cover.     

Optical monitoring of coastal waters: Photic depth estimates

Measurements of underwater irradiance, transparency and Secchi disc depth were carried out in Liverpool Bay during 1974. The depth of the photic zone measured in the green portion of the spectrum ranged from 5 m to 50 m, depending on location and season. Inshore values of photic depth were smaller than those encountered offshore. By mid-summer the depth of the photic zone had reached or exceeded the depth of the sea bed over the whole study area.Consideration was given to the error terms associated with the optical measurements and to the problems of using standard optical relationships in coastal waters. The relationship between Secchi disc depth and the depth of the photic zone could not be taken as constant but was a function of the absorption and scattering properties of the water mass.     

Nematode Community Structure Along a Mediterranean Shelf-slope Gradient

Abstract. Nematode assemblages along a Mediterranean depth transect (160–1220 m) and vertically in the sediment were investigated. The station at the edge of the continental shelf (160 m) was distinctly different from those situated on the continental slope (280–1220 m). On the slope, nematode communities in the upper centimetre differed significantly from communities in the deeper sediment layers, which were dominated by fewer and larger species. Vertical segregation could be a factor explaining the coexistence of several species belonging to the genus Sabatieria , with larger species penetrating deeper into the sediment. Clear differences in buccal morphology suggest food resource partitioning as the dominant factor promoting coexistence of several species belonging to the other dominant genus, Acantholaimus .     

Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data

A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat, providing the first multibeam imaging of the seafloor across the entire gulf head spanning both Israeli and Jordanian territorial waters. Analyses of the seafloor morphology show that the gulf head can be subdivided into the Eilat and Aqaba subbasins separated by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin is influenced by the Aqaba Fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive drainage basins of the Arava Valley (Wadi ’Arabah) and Yutim River to the north–northeast. These sediments and those entering from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the Evrona Fault zone to the west and the Ayla Fault zone to the east. The shelf–slope break that lies along the 100 m isobath in the Eilat subbasin, and shallower (70–80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water depths line the southwest margin of the gulf. These terraces are truncated by faulting along their northern end. Fossil coral reefs, which have a similar morphological appearance to the present-day, basin margin reefs, crop out along these deeper submarine terraces and along the shelf–slope break. One fossil reef is exposed on the shelf across the Ayla high at about 60–63 m water depth but is either covered or eroded in the adjacent subbasins. The offshore extension of the Evrona Fault offsets a fossil reef along the shelf and extends south of the canyon to linear fractures on the deep basin floor.     

The statistical structure of synoptic variability ocean currents at the continental slope of the Laptev Sea and features of their generation by anemobaric forces

Based on vector-algebraic analysis of random processes, we study the statistical structure of the synoptic variability of currents measured by an ADCP in the upper mixed layer in the central part of the continental slope of the Laptev Sea in 2006–2007. The results of statistical analysis show that in some cases the synoptic currents in the surface layer of the sea are signs of wind drift currents. This is indicated by the high correlation between the tangential friction of wind and currents, as well as the reversal of the depth of current vectors and the major axes of the ellipses of the mean-square deviation of the Ekman spiral. Due to the large variability of wind flows and stratification of water masses, the penetration depth of these currents is small and varies from 6 to 30 m, with pronounced seasonal variation. In deeper layers, no relationship between the currents and anemobaric forces is traced. It is concluded that the fluctuations of synoptic scale currents in the area of the continental slope of the Laptev Sea represent a superposition of Ekman drift currents and movements associated with free baroclinic Kelvin waves. These currents are the dominant contributor in the upper 30-m layer of the ocean, while waves play a key role in deeper waters.     

Substrate Effects on the Bioeroding Demosponge Cliona orientalis.2. Substrate Colonisation and Tissue Growth

Abstract Sponge bioerosion is a result of tissue expansion of endolithic sponges in calcium carbonate substrates. The efficiency of erosion by the sponges can be affected by substrate features, which are thus also likely to influence the way in which the sponge will grow. A field experiment was conducted, in which sponge tissue was grafted to biogenic blocks cut from the corals Goniopora tenuidens, massive Porites sp., Astreopora listeri, Favites halicora, Favia pallida, Goniastrea retiformis and Cyphastrea serailia, and the clam Tridacna squamosa, to investigate colonisation capabilities and growth patterns of Cliona orientalis Thiele, 1900 after 9 months of the experiment. C. orientalis is not substrate‐specific. It invaded > 90 % of the different substrate blocks and penetrated them to varying depths, but usually only down to slightly more than 1 cm. Lateral penetration clearly exceeded depth penetration. Enlargement of surface area versus restricted depth penetration benefits the symbiotic zooxanthellae located in the sponge's surface. Structural irregularities and barriers such as coral dissepiments temporarily deflected the direction of tissue growth and created characteristic tissue patch patterns in different substrates. Tissue growth may be more pronounced in substrates of higher density and lower pore volume, but evidence was only slight. Protection against predation is better in denser materials, which may stimulate the sponge's tissue growth especially in shallower substrate depth. In more porous substrates, favoured by grazers and corallivores, relatively more tissue was located in deeper layers.     

南沙永暑礁表层珊瑚年代结构及其环境记录

南沙群岛永暑礁7个表层礁坪原生块状珊瑚的高精度TIMS U-Th和12个常规^14C测年结果表明,永暑礁表层礁坪形成于现代,与钻探研究结果吻合。全新世永暑礁系从约7300aBP开始,以现代礁坪面以下17m左右的晚更新世礁灰岩为基底连续发育至今,因此,与南海周边地区的珊瑚礁不同,南沙群岛珊瑚礁的表层块状珊瑚不能够提供全新世高海平面的证据。由于现代珊瑚礁的堆积速率大于地壳沉降速率,可能会形成更多的灰沙洲或灰沙岛。     

Winter Oceanographic Conditions in the Southwestern Part of the Okhotsk Sea and Their Relation to Sea Ice

In the southwestern part of the Okhotsk Sea, oceanographic and sea-ice observations on board the icebreaker Soya were carried out in February 1997. A mixed layer of uniform temperature nearly at the freezing point extending down to a depth of about 300 m was observed. This is much deeper than has previously been reported. It is suggested that this deep mixed layer originated from the north (off East Sakhalin), being advected along the shelf slope via the East Sakhalin Current, accompanied with the thick first-year ice (average thickness 0.6 m). This vertically uniform winter water, through mixing with the surrounding water, makes the surface water more saline (losing a characteristic of East Sakhalin Current Water) and the water in the 100–300 m depth zone less saline, colder, and richer in oxygen (a characteristic of the intermediate Okhotsk Sea water). The oceanographic structure and a heat budget analysis suggest that new ice zone, which often appears at ice edges, can be formed through preconditioning of thick ice advection and subsequent cooling by the latent heat release due to its melting. This revised version was published online in August 2006 with corrections to the Cover Date.     

东山岛以东近岸海域水下沙丘及其环境

1990～1991年，我所对东山岛海域进行海底地形、底质调查、水文泥沙测验时发现：1）沿东山岛一古雷半岛的NNE、NE向断裂在海域呈现为落差可达20m左右“V”字型深糟；2）在东山岛东部10m等深线以东海域发育众多的水沙丘群，水深15m左右有一地形坡折线，水深20～25m海底为水下一级阶地。据底质粒度、石英电镜扫描、重矿物、地球化学指标等分析表明，水下沙丘群分布区的沉积为准残留沉积，水下一级阶地及水下沙丘为早期滨岸的准残留地貌作，又受到后期现代水动力的改造。     

基于多时相多光谱遥感影像的珊瑚礁面积估算方法研究

准确计算珊瑚礁的面积是评估其资源、环境效应的基础,但我国迄今对南海珊瑚礁的面积估算仍缺乏共识,缺少可靠的估算方法是导致这一现象的重要原因。针对这一问题,本文以西沙群岛羚羊礁为例,提出了一种利用多时相多光谱遥感影像低成本半自动化估算珊瑚礁面积的方法。首先快速目视确定地貌带分界线的粗略位置,然后利用基于梯度向量场的主动轮廓线模型（Gradient Vector Flow-Snake, GVF-Snake）实现这些分界线位置的自动精化,最后将不同时相的瞬时分界线转换为面要素进行多时相的融合,从而得到珊瑚礁的面积。基于53景Sentinel-2 多光谱成像仪（MSI）影像的实验表明,羚羊礁的总面积为17.22 km2（Landsat 8 陆地成像仪（OLI）用于方法稳定性的验证,得到的羚羊礁面积为17.29 km2）,其中礁前斜坡、礁坪?潟湖坡、潟湖的面积分别为1.76 km2、10.29 km2、5.17 km2。该数值与实测数据具有较好的一致性。具体地,该方法获得的地貌带分界点与实测水深所指示分界点的位置偏差能控制在0.2～4.9 m的范围内（不超过0.5个像素）,珊瑚礁最外轮廓线与30 m等深线的位置偏差亦在1个像素大小内（5.7～9.5 m）,而估算面积与高分辨率WorldView-2影像解译得到的面积差异为0.02%。同时,该方法获得的珊瑚礁边界线的完整度、正确度、提取质量精度能够由单时相平均的60%、64%和54%分别提高至84%、83%和72%。此外,该方法能够减小基于不同遥感数据源的珊瑚礁面积估算结果的差异,即6景以上的多时相Sentinel-2 MSI和Landsat 8 OLI影像提取的珊瑚礁面积标准差分别不超过0.01 km2和0.05 km2,仅相当于珊瑚礁总面积的0.2%和0.5%。总而言之,该方法能够用低成本的10 m分辨率Sentinel-2 MSI和30 m分辨率Landsat 8 OLI影像获得接近1.8 m分辨率WorldView-2影像的面积估算精度,且具有良好的稳定性和可靠性。     

江苏小庙洪牡蛎礁的地貌-沉积特征

利用卫星影象和野外实地勘察资料对江苏小庙洪牡蛎礁的地貌-沉积特征进行分析。结果表明，该牡蛎礁发育在强潮淤泥质潮坪上，造礁牡蛎主要是近江牡蛎和长牡蛎，表层的鲜活牡蛎为褶牡蛎。牡蛎礁区海水属盐度较高(27—30)的半成水，含沙量较大，为0．2—0．3g／L。活体牡蛎堆积体顶面高于周围潮间下带滩面1．0—1．5m。潮流较强，多在0．5—2．0m／s。海岸剖面可分为4个带，即礁后潮间带、潮沟、礁体生长带及礁前斜坡带。由于处于海岸侵蚀段，礁后潮坪缺失潮上带和大部分的潮间上带。礁后潮坪主要以粗粉砂为主，礁后潮沟冲淤变化较大，故礁体生长带时而为一沙洲，时而又与岸滩相连。礁体生长带分布在潮间下带，可看到独立的斑状礁体、带状礁体和大面积环状礁体群。环状礁的微地貌可以划分为礁塘(泻湖)、塘口和塘沟、塘口三角洲、礁墙和礁平台等。     

Polychaete Depth Distribution in a Posidonia oceanica Bed (Rhizome and Matte Strata) and Neighbouring Soft and Hard Bottoms

Abstract. The study was carried out in a Posidonia oceanica bed and in the neighbouring sandy and rocky bottoms, at Ponza Island (Central Tyrrhenian Sea), in order to investigate the distributional pattern of the polychaete community at different depths. A total of 15232 individuals of polychaetes belonging to 218 species was collected and three new species of Syllidae were found. The polychaete community of the matte can be clearly distinguished from the neighbouring communities; this is due to the high species richness in Posidonia , which is related to the heterogeneity of the biotope. In the Posidonia bed the shallow stations (1 m and 5 m depth) were the richest in terms of species numbers and individuals due to the high shoot density of the seagrass bed. In the shallow waters polychaete community structure changed according to the different exposure to water movement. Rocky bottom species, which preferentially inhabit crevices, were more abundant in the matte exposed to water movement (5–10 m depth). In contrast, soft-bottom species were more abundant in the sheltered zone (1 m depth) as well as in the deeper zone due to the reduction of the Posidonia bed.     

Light and substrate concentration relationships with marine ammonium assimilation and oxidation rates

Relationships between light intensity and substrate concentration and rates of assimilation and oxidation of ammonium by microorganisms were investigated at four stations off the Washington coast and three stations in the Southern California Bight. Ammonium oxidation rates were negatively correlated with light in the photic zone at all stations; light inhibition of nitrifying bacteria forms an important control over the depth distribution of ammonium oxidation activity. Both assimilation and oxidation were positively correlated with ammonium concentration at the Washington coast stations, where ambient ammonium concentrations were high. Light and ammonium assimilation rate were positively correlated at the Southern California Bight stations (within the photic zone; i.e., excluding depths greater than 150m), but unrelated at the Washington coast stations. Assimilation and oxidation have nearly opposite distribution patterns with depth in the water column, but phytoplankton and nitrifying bacteria probably compete for ammonium at depths near the bottom of the photic zone.     

Les recifs coralliens Au-Vent de l'ile Maurice (Archipel des Mascareignes,Océan Indien): Geomorphologie et Bionomie de la pente externe

The outer slope of the eastern reefs of Mauritius shows: from 0 to 15 m depth, a spurs-and-grooves zone of coral morphogenesis, sometimes replaced by a flagstone of coral morphogenesis (down to 20 m) or a spurs-and-grooves zone of volcanic morphogenesis; from 20 to 50 m, a volcanic flagstone with a thin coral-built layer and a buttresses-and-valleys zone of volcanic morphogenesis. The living cover of the upper part (0–15 m) is also quite similar to the cover of the leeward side. On the contrary, the volcanic basement in the lower part is poorly covered by reef-building organisms, while soft or slightly calcified algae are of widespread occurrence.     

基于类海啸波型的岛礁水动力特性数值模拟研究

基于非静压单相流模型NHWAVE建立了高精度二维数值波浪水槽,采用日本2011年实测真实海啸波型系统研究了海啸波在岛礁上传播变形的规律,并且分析了波高、礁坪淹没水深和礁前斜坡坡度等因素对孤立波和真实海啸传播变形的影响。结果表明,相比孤立波,类海啸波的波长明显大于孤立波波长,在测点处引起的水面变化持续时间更长,同等波高情况下真实海啸波型比孤立波能够携带更多的能量,与岛礁的相互作用也更为复杂,在礁坪上形成的淹没水深约为孤立波的两倍。礁前斜坡坡度和礁坪淹没水深均对类海啸波的反射和透射系数有显著影响。随着礁前斜坡坡度的增加,反射系数和透射系数均逐渐增加。随着礁坪淹没水深的增加,反射系数逐渐减小,而透射系数逐渐增大。但是,反射系数和透射系数均随着入射波高的增加而逐渐减小。     

Monterey Bay cold-seep biota: Assemblages,abundance, and ultrastructure of living foraminifera

Although there is a growing body of evidence indicating benthic foraminifera inhabit hydrocarbon and cold seep environments, biochemical and ultrastructural data on seep foraminiferal communities are not available. Therefore, sediments collected from cold seeps in Monterey Bay, CA (900–1000 m), were examined for the presence of live benthic foraminifera. Results from three independent methods (ATP assay, ultrastructural analysis, rose Bengal staining) indicate that certain species inhabit the Clam Flat and Clam Field seeps. Abundances in our seep samples were lower than in comparable non-seep sites, although not atypical for these bathyal depths. Of 38 species represented at these two seep sites by cytoplasm-containing specimens, only Spiroplectammina biformis was restricted to the seep environment. However, because S. biformis is also known from non-seep sites in other areas, it should not be considered as endemic to seeps. Ultrastructural studies show abundant peroxisomes in seep specimens, which may allow inhabitation of such environments. One specimen of Uvigerina peregrina had prokaryotes nestled in test pores, suggesting that bacteria may play a role in the survival of foraminifera in this seep environment.     

Interactions between sediment chemistry and frenulate pogonophores (Annelida) in the north-east Atlantic

The small frenulate pogonophores (Annelida: Pogonophora a.k.a. Siboglinidae) typically inhabit muddy sediments on the continental slope, although a few species occur near hydrothermal vents and cold seeps. We present data on the distribution and habitat characteristics of several species on the European continental shelf and slope from 48°N to 75°N and show how the animals interact with the chemistry of the sediments. The environments inhabited include: shallow (30 m), organic-rich, fjord sediments; slope sediments (1000–2200 m) and methane seeps at 330 m depth. All the species studied obtain nutrition from endosymbiotic bacteria. They take up reduced sulphur species, or in one case, methane, through the posterior parts of their tubes buried in the anoxic sediment. We conclude that most species undertake sulphide ‘mining’, a mechanism previously demonstrated in the bivalves Lucinoma borealis and Thyasira sarsi. These pogonophores participate in the sulphur cycle and effectively lower the sulphide content of the sediments. Our results show that the abundance of frenulate pogonophores increases with increasing sedimentation and with decreasing abundance of other benthos, particularly bioturbating organisms. The maximum sustainable carrying capacity of non-seep sediments for frenulate pogonophores is limited by the rate of sulphate reduction.     

Morphologie et sedimentologie de la pente externe de la partie nord du Grand Recif ed Tulear (SW de Madagascar). Nature et repartition des elements organogenes libres. (Morphology and sedimentology of the outer slope of the northern part of the “Grand Recif” of tulear (Madagascar). Nature and distribution of free organic elements.)

The Tuléar area lies on the southwest coast of Madagascar. The Tropic of Capricorn runs across the center of the Bay of Tuléar which is closed by a barrier reef called the “Grand Récif”. Other reef tracts can be found in this bay: fringing reefs, inner reefs, coral islets, coral banks.This paper is the result of a study of the outer side of the area called the “shipwreck sector”, which extends just in front of the city of Tuléar, in the northern part of the Grand Récif. The investigations were made by diving as deep as 50 m and below this depth by dredging down to 150 m. The outer slope consists of several zones, the succession of which forms the elements of a morphological model.The numerical values of sedimentological indices and sedimentary facies were obtained by means of an I.B.M. 360/44 or a C.I.I. computer; they do not vary independently but derive from each other. A sedimentary sequence is defined as a precise succession of facies which continues to be modified during the transfer of sediments inside the sedimentary sequence. The numerical values of the indices of a given facies show coherent variations which point to the evolution of the sediments during their transfer. The successions and relations of different sequences form the sedimentological model. The combination of terms in the morphological and sedimentological models allows the morpho-sedimentary model to be defined. This model can be integrated into one elaborated for the Tuléar area as a whole.Generally, two sequences extend on the outer slope. The first one is the spur and groove sequence that starts with an accumulated facies of gravel in the surf zone. The shifting facies of sands in which a very evolved material is included, mark the transition to the stable facies of accumulation. In this sequence wave action plays a central part. The second sequence is formed by sedimentary deposits of the coral flagstone (deep coral flagstone forward the reef). They are characterized by the presence of free or loose organic elements. These elements derive from calcareous algea. They are chiefly made of rhodolite nodules, rhodolite pseudonodules and Lithothamnion particles mixed with sand very rich in Foraminifera.The nature, distribution and percentage of these elements were studied as a function of the depth where they were found and, therefore, of the distance from the reef front. These free organogenic elements are typical of the outer slope of coral-reef tracts beaten by heavy swells.     

Evolution history and trend of the modern Huanghe River Delta

The evolvement history of modern Huanghe River Delta tidal flat, coastline and underwater terrain were studied based on the analysis of remote sensing images and water depth data. Based on the analysis of seafloor terrain evolution on different historical stages, a formula simulating the erosion and deposition evolvement model of subaqueous Huanghe River Delta slope was proposed, and the evolvement trend of the subaqueous delta terrain was predicted. The result shows that the equilibrium transition zone is near the water depth of 12 m with seabed erosion in shallower water and accumulation in deeper water during the first 150 a after the river channel was deserted. In the meantime, the underwater slope became gentler and the coastal erosion rate became slow gradually. Then, the subaqueous delta slope changed to up concave from upper convex, and the shape of subaqueous delta disappeared. The coast type changed to silt-mud coast about 100-150 a after the river course was deserted. The erosion depth in the foot of the seawall is calculated based on the formula.