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1.
Extensive areas of methane-derived authigenic carbonate (MDAC) have been mapped in the Irish Sea. In the Irish Sector, 23
seabed mounds associated with the Codling Fault Zone were identified by multi-beam echo sounder mapping. Inspection by ROV-mounted
video showed that these mounds are rocky features rising 5–10 m above the normal seabed; sampling showed that they are comprised
of quartz grains bound together by carbonate cement, probably MDAC. Two separate locations have been mapped in the UK Sector.
At Texel 11, seabed mounds and a 6–8 m high cliff were mapped geophysically (MBES, SSS and seismic profiler surveys). Video
surveys showed that both the mounds and the cliff are rocky reefs colonised by a prolific fauna. Samples proved to be carbonate-cemented
sediments, and carbon isotope analysis (δ13C −41 to −46% PDB) showed that the cement was MDAC. Similar surveys of the Holden’s Reefs area proved the presence of similar
rocky reefs which are also cemented by MDAC. The total area covered by these two MDAC occurrences is estimated to be >500,000 m2. These MDAC occurrences are comparable in nature and formation to the ‘bubbling reefs’ of the Kattegat. As the bubbling reefs
are “seabed features formed by leaking gas”, one of the marine habitats identified by the European Commission’s Habitats Directive
as being sensitive and worthy of protection, it is suggested that the Irish Sea carbonate reefs should also be considered
as special habitats. 相似文献
2.
Sarah J.M. Harper C. Richard Bates Hector M. Guzman James M. Mair 《Ocean & Coastal Management》2010,53(10):615-623
The purpose of this study was to investigate, characterize and map areas of the seabed of Las Perlas Archipelago (LPA), Republic of Panama using swath-bathymetry acoustic sonar techniques and to assess these methods as tools for feeding information into management zoning policy. In 2007 the LPA was granted conservation protection under national legislation. However, detailed management plans are still pending. Seabed mapping plays a fundamental role in identifying areas which should be prioritized within the management framework. Visual representation of habitat maps provides an effective medium for involving stakeholders in a co-management arena. In this survey, acoustically mapped areas of the seabed were ground-truthed using a combination of benthic grab samples, drop-down video and diver observations. The resulting mapped areas were then incorporated into a Geographic Information System (GIS) for further analysis. The output was a physical characterization of the seabed at three locations selected for being areas of high rugosity (habitat complexity) and, therefore, their potential importance as valuable fish aggregation sites. The rocky reefs and rhodolith beds identified in this survey represent particularly important fish aggregation and nursery habitats which should be considered priorities for protection under the management plans. This survey demonstrated the use of acoustic techniques to spatially resolve topographic features and physical characteristics of the seabed, illustrating their potential value as tools for fisheries management and marine reserve zoning in Las Perlas Archipelago and elsewhere. 相似文献
3.
Alexander Callaway Jennifer Smyth Craig J. Brown Rory Quinn Matthew Service David Long 《Estuarine, Coastal and Shelf Science》2009,84(3):409-422
The Irish Sea, like many marine areas, is threatened by anthropogenic activities. In particular the Pisces Reef system, a series of smothered rocky reefs are subject to fishing pressures as a result of their position within a Nephrops norvegicus fishery. In an area of sediment deposition and retention the reefs modify the environment by increasing the energy of near-bottom currents which results in localised scouring. This is the first study to attempt to characterise and investigate the ecological functioning of the Pisces Reef system. A multidisciplinary approach was essential for accurate investigation of the area. To facilitate more effective management of the benthic habitats of the Reef system, this study integrates acoustic, seismic, grab sampling and video ground-truthing methods for benthic habitat discrimination. Orientation of the scour hollows also suggest that seabed features could be used to infer dominant flow regimes such as the Irish Sea Gyre. The data revealed significant geology–benthos relationships. A unique biotope was described for the reef habitat and it was demonstrated that scouring may influence community composition through disturbance mechanisms. This study provides preliminary information required for management of a unique habitat within a uniform region. 相似文献
4.
Multibeam imagery of siliceous sponge reefs (Hexactinellida, Hexactinosida) reveals the setting, form, and organization of five reef complexes on the western Canadian continental shelf. The reefs are built by framework skeleton sponges which trap clay-rich sediments resulting in a distinctive pattern of low intensity backscatter from the reefs that colonize more reflective glacial sediments of higher backscatter intensity. Bathymetry and backscatter maps show the distribution and form of reefs in two large complexes in the Queen Charlotte Basin (QCB) covering hundreds of km2, and three smaller reef complexes in the Georgia Basin (GB). Ridges up to 7 km long and 21 m in height, together with diversely shaped, coalescing bioherms and biostromes form the principal reef shape in the QCB whereas chains of wave-form, streamlined mounds up to 14 m in height have developed in the GB. Reef initiation is dependent on the distribution of high backscatter-intensity relict glacial surfaces, and the variation in reef complex morphology is probably the result of tidally driven, near seabed currents. 相似文献
5.
相位差测深声呐(Phase Differencing Bathymetric Sonar,PDBS),也被称作干涉式声呐(Interferometric Sonar),可以同步采集水深点云数据和双频侧扫声呐图像,完全适用于大范围的近海人工鱼礁探测。本文采用基于PDBS原理的Edge Tech 6205地形地貌一体化测量设备对莱州湾某海域海洋牧场投礁区进行全覆盖探测,获取了高精度水深数据以及双频侧扫声呐图像。对水深数据进行地形特征变量计算,精细刻画了研究区的微地形地貌特征,并结合侧扫声呐图像通过多数据融合实现了对鱼礁边界的精准识别。在此基础上利用地理信息系统中的空间分析方法对人工鱼礁的水下物理参数进行计算和统计,并探讨了研究区地形地貌的成因及其演化模式,最后论证了基于PDBS的近海人工鱼礁探测技术具有高效率、低成本、高精度等诸多优势。研究结果表明,研究区水深介于4.1~7.3 m,鱼礁分布区有较大的海底起伏且在礁体周围存在明显的沉降和冲刷现象;鱼礁总占地面积约占研究区的14.04%,总空方量共计2 528.22 m3,鱼礁高度介于1.26~3.63 m且呈正态分布。本研究为近海人工鱼礁探测提供了数据和技术支撑,具有较强的实践意义。 相似文献
6.
The purpose of this paper is to describe the status and general faunal composition of sponge reefs in the Georgia Basin (GB), British Columbia, Canada. Fourteen distinct deep-water glass sponge (Hexactinellid) reefs have been mapped using multibeam bathymetry and sidescan sonar in the GB. Seven of these have been surveyed visually using video from remotely operated vehicles (ROVs). Analysis of video data indicated that three reefs were undamaged, two were damaged and the other two were damaged but potentially recovering. The nature of the damaged reefs, with large areas of scattered dead sponge skeleton fragments and few live reef-building sponges (Aphrocallistes vastus and Heterochone calyx), as well as video evidence of tracks suggest they were damaged mechanically by mobile fishing gear.Relative abundance of the megafauna associated with the reefs is discussed in the context of oceanographic conditions, such as sediment accumulation and organic flux, as well as overall reef status. Of particular interest for fisheries conservation efforts in the area was the fact that one undamaged reef in the southern GB showed higher taxonomic richness and abundance of rockfish (Sebastes spp.), both adult and juvenile, compared to an adjacent damaged reef. This result suggests that undamaged reefs may act as refugia for these endangered stocks. 相似文献
7.
Despite substantial survey effort and a large body of literature on abiotic and biotic factors in temperate reef ecosystems, knowledge of the complex and interactive effects of environmental variables on those communities is limited. Various survey methods have been developed to study environmental predictors of biodiversity, but there remains a gap in our understanding of how survey results are influenced by environmental factors. Here, we surveyed the fish assemblage associated with southeastern U.S. temperate marine reefs with simultaneous, paired trap, and camera gears throughout a ~50,000 km2 area during 2011–2013 and assessed the influence of environmental variables on the trap‐ and video‐surveyed assemblages. Predictor variables in the multivariate general linear models included depth, temperature, month, year, location, substrate relief, percent sessile biota, biota type, and turbidity. Depth and latitude had the greatest influence on the fish assemblage for both gears. The influence of habitat variables differed between methods and percent biota explained more variation in the fish assemblage when assessed by traps, while substrate relief and biota type explained more variation in the fish assemblage when assessed by video. In general, habitat complexity was positively related to the abundance of fishes in the video survey, but there was a negative relationship in the trap survey. Differences between gears were species‐specific and the influences of environmental variables were similar for some species such as Haemulon plumierii and Hyporthodus niveatus. The methods presented here can be used to assess method‐dependent differences in fish assemblages, which is a necessary precursor to assess the effect of environmental variables on the accuracy of surveys. 相似文献
8.
人工鱼礁礁体与不同粒径底质间最大静摩擦系数的试验研究 总被引：2，自引：0，他引：2
通过平面拉动法分别测量了5种不同开口比人工鱼礁礁体模型对5种不同粒径大小底质间的最大静摩擦系数,分析了不同粒径底质以及礁体不同开口比的最大静摩擦系数变化规律。试验研究表明:最大静摩擦系数与底质粒径大小呈强负相关(r=-0.964,P<0.01);控制底质粒径时,最大静摩擦系数与礁体质量呈弱负相关(r=-0.265,P<0.01),与礁体开口比呈弱正相关(r=0.245,P<0.01);礁体本身的设计属性如开口比是最大静摩擦系数的主要影响因子。对于新设计礁型在进行礁体稳定性校核时,应根据礁体开口比和实际海域底质泥沙的粒径组成,选取适当的最大静摩擦系数。 相似文献
9.
Gassy sediments in the Ría de Arousa are preferentially distributed in areas of muddy seabed sediments. The close relationship between seabed sediment parameters and gas distribution is here studied in detail to establish better constraints on the presence of gas. Discriminant analysis was applied to the textural and compositional characteristics of 303 seabed sediment samples to classify gas-related and gas-free areas in the Ría de Arousa. The parameters considered in the classification were: particle size data (percentages of clay, silt, sand and gravel), the total inorganic carbon and the total organic carbon contents of the samples. The samples were initially classified in two groups according to the presence or absence of acoustic turbidity in the seismic profiles, shallower than 150 cm below seabed. Of the total known cases, 85.5% were correctly classified using these variables. Applying the Wilks’ lambda criterion, the most influential textural discriminating variables were the percentage of clay and the percentage of coarse fraction (gravel and sand) in the sediment sample. Discriminant analysis has achieved good differentiation between gas-related and gas-free sediments using near-seabed sediment information. The application of the discriminant method has enabled the estimation of the total area covered by gassy sediments in the Ría de Arousa. The area calculated based on the seismic data (30 km2) is a minimum estimate that is constrained by the limits of the existing seismic data. Based on the sediment information obtained from seabed samples, the statistical method estimates a total area of gassy sediments of 39 km2. The new gassy areas recognized are located around the gas field at the inner ría, and the gas field west of Arousa Island, which increase in area by 8.3 and 0.4 km2 respectively. 相似文献
10.
11.
对于大面积的大比例尺珊瑚礁遥感制图而言,SPOT5数据是一种高性价比卫星遥感资料.以Quickbird2数据对东沙环礁珊瑚礁的分类、解译的矢量结果作为该区域实际的珊瑚礁分布,以此为基础分析SPOT5数据的珊瑚礁遥感制图能力.SPOT5只有两个水体穿透信道,从基于光谱数据的分类角度看,以XS1通道为准的珊瑚礁信息提取易将高反射的沙底质归为珊瑚礁;以XS2通道为准的珊瑚礁分布制图存在提取不足问题.由于空间分辨率提高,对潟湖淤泥质中的珊瑚礁提取能力较强,要优于ETM数据.结合ETM数据及PCA融合后的SPOT5的遥感解译结果,能提高SPOT5数据的制图能力. 相似文献
12.
María Lourdes Jaubet María de los Ángeles Sánchez María Silvia Rivero Griselda Valeria Garaffo Eduardo Alberto Vallarino Rodolfo Elías 《Marine Ecology》2011,32(2):188-197
The rocky intertidal zone around the city of Mar del Plata (SW Atlantic, 38° S–57° W) is characterized by dense mussel beds of Brachidontes rodriguezii. This intertidal community develops on natural and artificial hard substrates, including abrasion platforms in sewage‐impacted areas. A monitoring program, designed to assess the effect of sewage discharge on intertidal macrobenthic communities, has been conducted since 1997. During the spring season of 2008, a new spionid polychaete (Boccardia proboscidea) was found near the sewage outfall, forming large biogenic reefs. This is the first report of biogenic reefs being built by a non reef‐forming spionid polychaete in areas organically impacted by sewage discharges. The aim of this work was to evaluate the spatial–temporal dynamics (% cover and density of B. proboscidea) of these reefs. These biogenic reefs covered almost the entire impacted site, reaching a density of 650,000 ind·m?2. This phenomenon is unique in that there is no other record available worldwide of any other biogenic polychaete reefs that could be sewage‐induced. The presence and stability of these biogenic reefs is discussed in relation to increased organic contamination as a structuring factor. 相似文献
13.
We present four new high-resolution multibeam bathymetry datasets from the shelf edge of the northern Great Barrier Reef (GBR). Analysis of these data, combined with Chirp sub-bottom profiles and existing submersible observation data provides a fresh insight into the detailed morphology and spatial distribution of submerged reefs and terraces at the shelf edge. An extensive and persistent line of drowned shelf edge reefs exist on the GBR margin in about 40 to 70 m. They appear as barrier reefs up to 200 m wide and comprising twin parallel ridges of rounded pinnacles. Subtle yet consistent terrace and step features lie between 78 and 114 m seaward of the shelf edge reefs in the southern study area. Submersible observations confirm that the drowned reefs now provide a favorable hard substrate for live soft corals and algae. They form a consistent and extensive seabed habitat that extends for possibly 900 km along the GBR shelf edge. The submerged reef and terraces features may reflect a complex history of growth and erosion during lower sea-levels, and are now capped by last deglaciation reef material. 相似文献
14.
宣德环礁作为我国南海诸岛礁开发利用程度最高的岛礁之一, 其周围海域地质灾害对岛礁基础工程建设及人类活动具有重大危害。为适应南海岛礁可持续发展的需要, 文章采用广州海洋地质调查局2018年采集的单道地震数据, 对宣德环礁东部斜坡带海域灾害地质因素进行综合解释和分析。结果表明, 研究区主要发育有海底滑坡、海底陡坎和断层3类地质灾害。海底滑坡是研究区主要灾害地质因素, 规模大小不一, 海底陡坎和断层为次要地质灾害。海底陡坎根据成因可分为礁体陡坎和滑坡陡坎, 礁体陡坎为礁盘形成过程中受海平面上升控制形成, 滑坡陡坎为海底滑坡导致。通过分析认为陡峭的地形和峡谷水道的侵蚀搬运作用是研究区地质灾害发育的主控因素。这些地质灾害对海洋工程建设及管线铺设均有不利的影响, 应尽量避开。 相似文献
15.
《Marine Policy》2017
Coral reefs provide important ecological services such as biodiversity, climate regulation, and cultural benefits through recreation and tourism. However, many of the world's reefs are declining, with Caribbean reefs suffering a significant decline in living corals over the past half century. This situation emphasizes the need to assess and monitor reef conditions using a variety of methods. In this study, a new method for assessing reef conditions to inform management using participatory mapping by coral reef “experts” in the U.S. Virgin Islands (USVI) is described. Occupational SCUBA divers were recruited (n=87) to map coral reef conditions, uses, and threats (stressors) using an internet-based mapping website. The data reveal an uneven geographic distribution of reef conditions in the USVI with the most frequently mapped perceived healthy reef characteristics being: large amount of physical reef structure (n=872 markers); endangered or threatened species present (n=721); and large amount of live coral cover (n=615). The greatest perceived threats were: invasive species (n=606); water pollution (n=234); and unsustainable fishing (n=200). Areas of important reef characteristics, perceived threats to reefs, and perceived recovery potential were plotted to identify areas requiring critical management attention. The authors found that perceptions of healthy reef conditions outnumbered perceptions of reef threats for nine of the ten most familiar coral reefs; the most frequent activity type within the coral reefs was tourism diving; and for the most familiar coral reefs, the divers perceived a high recovery potential. Given the novelty of participatory mapping methods to assess coral reefs, the strengths and weaknesses of the method is evaluated. The authors further propose a management typology for categorizing reef areas to inform their future management. In the absence of primary data, or, as a supplement to underwater surveys and remotely-sensed data on reef condition, participatory mapping can provide a cost-effective means for assessing coral reef conditions while identifying place-specific reef locations requiring management attention. 相似文献
16.
The relationship between acoustic backscatter, sediment characteristics and benthic habitat is examined using high-resolution sidescan sonar data collected at the Loch Linnhe artificial reef site on the west coast of Scotland. The site is typical for the continental shelf of NW Europe, with a mix of seabed environments from muddy to coarse, stony substrata on a 10–100 m length scale. A sidescan sonar mosaic was produced and classified according to derived backscatter parameters (mean, median and standard deviation of the backscatter values) using an unsupervised classification procedure. The accuracy of the final classified map was assessed by comparison with a ground-truthing survey in which the biological habitat was derived from underwater video footage. The sidescan correctly predicted seabed surface characteristics of observed biological habitat with 78% accuracy. A second, and more challenging test of the acoustic data to correctly predict biological habitat was made by comparing it with data from 21 grab sampling stations. These stations were divided into three groups using multivariate statistical techniques based on their backscatter properties. Benthic assemblage structure was found to be significantly distinct between the high and low, and the medium and low backscatter stations. There was a low to moderate but significant correlation between the multivariate patterns of acoustic backscatter, benthic assemblage structure, and particle size distribution. The work shows that even in areas with subtle and gradational changes in substratum, the sidescan was able to predict biological community with an acceptable accuracy. 相似文献
17.
Connell SD 《Marine environmental research》2001,52(2):115-125
There remains little understanding of the relationship between the ecologies of urban habitats (pilings and pontoons) and natural habitats (rocky reef) for sessile plants and animals (epibiota) living on urbanised coasts. This study describes the structure of subtidal assemblages of epibiota among pilings, pontoons and adjacent rocky reef in Sydney Harbour, Australia. I tested the prediction that the experimental provision of substrata of the same age and composition in all three habitats would produce assemblages that: (1) differed among all three habitats; and (2) differed most on floating pontoons relative to the two fixed habitats (pilings and reef). As predicted, the results suggested that both pilings and pontoons, particularly the latter, create novel habitats for epibiotic assemblages independent of age and composition of substratum. It is not fully understood why these urban structures act as such different habitats from natural rocky reefs. The important point is that they are different and we are yet to understand the implications of this for the ecology of coastal areas subject to urbanisation. 相似文献
18.
基于WorldView-2和GF-2遥感影像的赵述岛礁坪底质变化研究 总被引：1，自引：1，他引：0
以西沙群岛海域赵述岛礁坪为研究区域,应用2010年的WorldView-2和2015年的GF-2两期高分辨率卫星遥感影像数据,结合现场水下珊瑚礁照片和视频资料,建立了赵述岛礁坪底质类型遥感分类体系,分别构建了针对WorldView-2遥感影像和GF-2遥感影像的珊瑚礁底质分类决策树模型,并通过对两期遥感影像的底质类型提取结果的变化分析,完成了赵述岛礁坪退化区域的提取。结果表明:(1)WorldView-2影像的分类决策树具有91%的总体分类精度和0.89的Kappa系数,GF-2影像的分类决策树具有更高的分类精度;(2)6年期间研究区大约1/4的珊瑚礁分布区发生了退化;(3)最突出的自然变化是礁前区大面积的珊瑚丛生区转变成藻脊,结合相关资料认为东北季风、热带气旋和温度上升的综合影响是驱动因素;(4)赵述岛西侧的藻脊、珊瑚沉积区大面积转化为珊瑚砂和深水区域,原因是航道和码头的开发活动。研究分析了6年间赵述岛礁坪底质的退化状况,并分析原因,为珊瑚礁底质分类提供方法,并为西沙群岛的珊瑚礁监测和保护提供了有效资料和手段。 相似文献
19.
西沙群岛生物碳酸盐的成因和沉积:来自活体仙掌藻的证据 总被引：1，自引：0，他引：1
A recent island survey reveals that the Xuande Atoll and the Yongle Atoll in the Xisha Islands can be classified into one of two systems: the depleted atoll system and growth atoll system; the survey also indicates that the decreased area of several shoals is an unbearable burden for the Xisha Islands, of which the largest island area is 2.13 km2 and the minimum elevation is 1.4 m. According to a survey on the ecological characteristics of Halimeda in the Laolongtou breaker zone of Shidao Island in the Xisha Islands, the green and white living Halimeda are collected,the isotopic ages of 14 C contained in the Halimeda are shown to be 27 years and 55 years, respectively, and carbonate mainly occurs in five types, i.e., luster, segment, sand, sand grain, and marl in the formation. The Halimeda segments mainly provide the carbonate sediments of long-term biogenic deposits in the reef environment and the annual productivity per area is 60–100 g/m2; the characteristics of the microstructure of the Halimeda are analyzed, the aragonite raphide carbonate is deposited and enriched in the cortexes, medullas and cysts, and the Halimeda generally contain major elements such as C, O, Ca, Cl, Mg, K, Na, S and Al, and are rich in trace elements such as tellurium(Te), rhodium(Rh) and strontium. It is believed that the Halimeda grow slowly,including the biotic community of reef corals in the reef areas, thus they possess an environmental remediation capacity, but it takes much time to remedy the environment, and it is necessary to make the law to protect the diversity and vulnerability of the Xisha marine ecology, the ecology of the reef community and the island environment in a scientific way. As indicated in the survey, under the background of global warming and sea-level rise, the discovery of large amounts of Halimeda in the Laolongtou sea area is significant for the natural increase of the depleted atoll system of the Xuande Atoll, while the Halimeda segments represent the primary form of the fossil Halimeda, of which the species can be identified and preserved in great numbers under geological conditions. The Miocene was discovered in large amounts in the Xichen-1 well, therefore the study on the characteristics and mechanism of Halimeda carbonate sediments plays a pivotal role in the formation and construction of organic reefs in the South China Sea as well as oil and gas exploration. 相似文献
20.
Characteristics and distribution patterns of reef complexes on the carbonate platform margin in deep water areas: the western South China Sea 总被引：2，自引：1，他引：1
CHEN Ping LI Xushen WANG Yahui LU Yongchao ZHONG Zehong CHEN Lei ZUO Qianmei MA Yiquan WANG Chao DU Xuebin 《海洋学报(英文版)》2015,34(10):71-80
As a potential oil and gas reservoir, reef complexes have been a research focus from petroleum geologists for a long time. There are favorable conditions for the development of reef complexes in the South China Sea; however, their internal structures, evolution and distribution are still poorly understood. Based on 2D and 3D seismic data, the internal structures and evolution patterns of the reef complexes on the carbonate platform margin in the deep water areas over the western South China Sea were studied in detail. The result shows that two types of reef complexes, i.e., fault controlling platform margin reef complexes and ramp reef complexes have been developed in the study area. The reef complexes have independent or continuous mound or lenticular seismic reflections, with three internal structures (i.e., aggrading, prograding and retrograding structures). There are different growth rates during the evolution of the reef complexes, resulting in the formation of catch-up reefs, keep-up reefs and quick step reefs. The study also reveals that different platform margin reef complexes have different internal structures and distributions, because of the different platform types. These results may be applied to the exploration and prediction of carbonate platform margin reef complexes in other areas that are similar to the study area. 相似文献