A turbidity survey of Narragansett Bay

A turbidity survey of Narragansett Bay, Rhode Island, was made during the summer months of 1971 and included measurements of the attenuation function for scalar irradiance for daylight and the volume attenuation function for white tungsten light at various depths. One hundred and three stations were made at 17 different locations. Variations in the optical parameters were large, one standard deviation at any given location ranging from 7 to 23 per cent of the mean value. This variation was only slightly dependent on the state of the tidal currents, depth of the location, or weather factors. The magnitude of turbidity variations was almost 4-fold over a north-south range of 31 km within the estuary, with clearest water at the southern mouths of the Bay. A good correlation exists between turbidity parameters and Autumn values of suspended-material concentration found by Morton (1967), with both data sets showing highest turbidity and suspended concentrations in the West Passage of the Bay. “Wedges” and “bulges” of clear water were detected throughout the Bay but were most evident at the southern (Atlantic Ocean) end.Although it was not possible to fully define the parameters producing these temporal and geographic variations in estuarine turbidity, it is suggested that knowledge of these parameters can assist those concerned with the physical and biological state of an estuary, as well as divers and photographers plying their trades within its boundaries.     

A marine magnetic survey off southern Iceland

Total-intensity magnetic anomalies observed in a 1973 survey reflect contrasts in the structure of the southern Iceland shelf respectively west and east of 20°W. The western part, which is wider and more evenly sloping than the eastern part, has subdued magnetic relief indicating basement (basalt) depth of at least 400 m. On the eastern part of the shelf there occur pronounced edge anomalies, apparently due to a basement step of at least 1 km mean thickness and of mean width 3–4 km. The distance from the upper edge of this basement step to the bathymetric shelf edge increases from 5–8 km at 19°W to 12–14 km at 14°30W. The basement has alternating magnetic polarities. Linear magnetic anomalies are indistinct or absent in the surveyed region. It is speculated that the sharp basement step represents the trace of the maximum southerly extent of the eastern volcanic zone of Iceland.     

Sea ice,hydrological, and biological processes in the Churchill River estuary region,Hudson Bay

A conceptual scheme for the transition from winter to spring is developed for a small Arctic estuary (Churchill River, Hudson Bay) using hydrological, meteorological and oceanographic data together with models of the landfast ice. Observations within the Churchill River estuary and away from the direct influence of the river plume (Button Bay), between March and May 2005, show that both sea ice (production and melt) and river water influence the region's freshwater budget. In Button Bay, ice production in the flaw lead or polynya of NW Hudson Bay result in salinization through winter until the end of March, followed by a gradual freshening of the water column through April–May. In the Churchill Estuary, conditions varied abruptly throughout winter–spring depending on the physical interaction among river discharge, the seasonal landfast ice, and the rubble zone along the seaward margin of the landfast ice. Until late May, the rubble zone partially impounded river discharge, influencing the surface salinity, stratification, flushing time, and distribution and abundance of nutrients in the estuary. The river discharge, in turn, advanced and enhanced sea ice ablation in the estuary by delivering sensible heat. Weak stratification, the supply of riverine nitrogen and silicate, and a relatively long flushing time (∼ 6 days) in the period preceding melt may have briefly favoured phytoplankton production in the estuary when conditions were still poor in the surrounding coastal environment. However, in late May, the peak flow and breakdown of the ice-rubble zone around the estuary brought abrupt changes, including increased stratification and turbidity, reduced marine and freshwater nutrient supply, a shorter flushing time, and the release of the freshwater pool into the interior ocean. These conditions suppressed phytoplankton productivity while enhancing the inventory of particulate organic matter delivered by the river. The physical and biological changes observed in this study highlight the variability and instability of small frozen estuaries during winter–spring transition, which implies sensitivity to climate change.     

Sources, pathways and sinks of particulate organic matter in Hudson Bay: Evidence from lignin distributions

Hudson Bay is a large, estuarine, shelf-like sea at the southern margin of the Arctic, where changes in seasonal ice cover and river discharge appear already to be underway. Here we present lignin data for dated sediments from eleven box cores and evaluate sources of terrigenous carbon, transport pathways, and whether terrigenous organic matter has been influenced by recent environmental change. Lignin yields (0.04 to 1.46 mg/100 mg organic carbon) decreased from the margin to the interior and from south to north, broadly reflecting the distribution of river inputs. Lignin compositional patterns indicated distinct regional sources with boreal forest (woody gymnosperm) vegetation an important source in the south, vs. tundra (non-woody angiosperm) in the north. Lignin patterns suggest redistribution of a fine-grained, mineral-associated fraction of the southern-derived terrigenous carbon to the northeast part of the Bay and ultimately into west Hudson Strait with the Bay's cyclonic coastal circulation. A small component of the carbon makes it to the central basins of Hudson Bay but most of the terrigenous organic material in that area appears to derive from resuspension of older, isostatically-rebounding coastal and inner shelf deposits. Most modern plant debris appears to be retained near river mouths due to hydrodynamic sorting, with the exception of the southwest inner shelf, where these materials extend > 30 km from shore. Temporal changes in the composition of terrigenous organic carbon recorded in most of the southern Hudson Bay cores perhaps reflect increases in erosion and cross-shelf transport from coastal deposits, possibly mediated by change in ice climate. In contrast, temporal changes in the northwest may relate to changes in the supply of modern plant debris under recent warmer conditions. On the western shelf, changes may relate to ice climate and the distribution of northern coastal water and/or changes in the delivery of materials by the Churchill River due to water diversion. Although the cores show evidence of change related to the ice climate, there is little evidence that ice itself transports terrigenous organic carbon within the system.     

An approach to ecological monitoring in the rocky intertidal: A survey of Bantry Bay and Dunmanus Bay,Ireland

The methodology of a monitoring study of the fauna and flora of the rocky intertidal zone in Bantry Bay and Dunmanus Bay in southwest Ireland is described and some representative results are presented. Five shores, four in Bantry and o one in Dunmanus Bay, were visited monthly from May, 1978 to June, 1980, and more limited monitoring is continuing. On each visit to each shore, four research programmes were undertaken—transect studies, recolonisation of cleared areas, barnacle studies and limpet studies. The transect methods are discussed in relation to other methods in current use. Combining community and key species approaches is shown to be most useful in monitoring programmes. The increased effectiveness of continuous shore monitoring when compared with one-off or before and after impact-type studies is stressed.     

A shipborne wave-recording system with digital data processing

A shipborne wave-recording system which consists of a sonic wave gauge, accelerometers, gyroscopes and a computer system is described. Signals from the measuring apparatus are fed directly into a shipborne digital computer system at a prescribed sampling rate. The time series of wave heights and the acceleration are transformed into Fourier series using an algorithm of Fast Fourier Transform. Errors contained in the observed wave heights due to ship motion are corrected in the Fourier series by using the Fourier coefficients for the vertical acceleration. Power spectra and waveforms can also be calculated in a short time with this system from Fourier coefficients. Examples of the observational results obtained in the central part of the East China Sea in 1969 are presented.     

基于船载雷达图像的海上船只检测方法

随着雷达成像技术和高分辨率光栅显示技术的发展和应用,基于船载雷达图像的船只检测成为可能.海上船只检测的主要困难之一是雷达图像中包含固有的海面背景杂波.传统的雷达船只检测方法,如恒虚警率法(CFAR),以杂波分布模型为基础,计算待检测窗口中的信号统计分布来确定自适应阈值,取得了一些成果.但是,当海面背景杂波和船只目标的回波强度在同一数量级,甚至船只目标淹没在海面背景杂波中时,就难以确定一个有效的阈值将船只目标从雷达图像中提取出来.在分析海面背景杂波和船只目标的相关差异性基础上,提出了一种基于船载雷达序列图像的海上船只快速检测方法.该方法首先对相邻两幅图像进行互相关性分析,在两幅图像中的同一位置提取一定尺寸的移动窗口,计算其互相关函数值,窗口移动一个步长,重复操作直至遍布整幅图像,形成一幅由灰度图像互相关函数值组成的相关图像.然后使用概率神经网络模型(PNN模型)来估计相关图像背景杂波的灰度概率密度分布函数(PDF),应用CFAR技术,使用二分法求解一个区分船只和背景噪声的自适应整体阈值,并根据阈值将相关图像二值化,其中大于阈值的像元作为候选的船只目标信息,小于阈值的像元则为海面背景杂波.最后使用连通性8-邻域准则统计各个候选船只目标区域的像元数,并与预先定义的最小船只目标像元数进行比较,偏小的候选船只目标区域作为虚警去除,保留下来的候选船只目标区域即为船只检测结果.研究显示,如果图像序列中没有船只目标信息,则三维相关图像比较平整.相反,如果图像序列中含有船只目标信息,则三维相关图像上有峰值被检测出,通过测量峰值的高度,就能判断存在可能的船只目标.运用X波段船载雷达序列图像对本文提出的海上船只检测方法进行了测试.测试结果表明,该检测方法具有很好的船只检测效果,得到的船只检测结果与目视判别的结果一致.而且该检测算法原理简单,计算速度快,易于实时处理,具有广阔的应用前景.     

Temporal and spatial variations in the biogeochemical cycling of cobalt in two urban estuaries: Hudson River Estuary and San Francisco Bay

Despite the fact that Co is an essential trace element for the growth of marine phytoplankton, there is very limited information on the cycling of this trace metal in the marine environment. We report here the distribution of dissolved (<0.4 μm) and particulate (>0.4 μm) Co in surface waters of the Hudson River Estuary (HRE) and San Francisco Bay (SFB). Samples were collected during several cruises (from 1990 to 1995 in SFB and from 1995 to 1997 in the HRE) along the whole salinity gradient. Dissolved Co concentrations (mean±1 standard deviation) were nearly identical in magnitude in both estuaries despite differences in climate, hydrography, riverine-flow conditions and land-usage (HRE=0.91±0.61 nM; SFB=1.12±0.69 nM). Dissolved Co levels in each system showed non-conservative distributions when plotted as a function of salinity, with increasing concentrations downstream from the riverine end-members. Desorption from suspended particulates and sewage inputs, therefore, seems to be the major processes responsible for the non-conservative behavior of Co observed. Mass balance estimates also indicated that most of the estuarine Co is exported out of both estuaries, indicating that they and other estuarine systems are principal sources of this essential trace element to the open ocean.     

一种船载水深测量数据均匀性分布研判方法

针对联合船载水深测量数据和海面重力信息构建海底地形模型时,判断测区水深测量数据分布均匀性主要依靠目视判别方法,致使效率较低缺点,借鉴图像处理领域特征点分布均匀性评价方法,结合船载水深数据抽稀简化技术,给出了描述船载水深测量测区数据均匀性分布量化指标方法.首先以4'网格边长为划分依据,将密集的船载水深测量数据抽稀简化;计...     

杭州湾跨海大桥桥位地形测绘中的潮位改正

在杭州湾跨海大桥桥位地形测绘中,采用三角分带解析法进行潮位改正计算,结果表明:合理布设潮位站、合理安排测量时间,可以提高地形测量精度,正确地进行潮位计算。一般应在高平潮前后3h时间内施测,可保证浅滩不出现测量空白区。地形测绘过程中还应布设不少于主测线数量的5%的检查线,以检查其测量精度。在所测的河口湾两岸潮位明显不等时,采用三角分带解析法进行潮位改正计算,其结果合理、正确,可达到规范的要求。     

A Comprehensive Lagrangian Transport Study in A Long-Narrow Bay,Xiangshan Bay,China

Study on the transport and mixing in coastal waters is of great concern to the ocean resources exploitation and ecological system protection. Lagrangian methods are direct and effective of researching mass transport. Two Lagrangian tools were adopted and combined to describe water transport in a long-narrow bay, Xiangshan Bay,China. Based on the fields of tidal velocity simulated from the 3-D hydrodynamic model, Lagrangian Coherent Structures(LCSs) and synoptic Lagrangian maps(SLMs) were calculated in the study area. Through comparison of the results, the features and relation of the two tools were discussed. The results show that the LCSs act as the separatrix of the water regions with different transport characteristics and can identify the water areas with different transport time scales. The comprehensive application of the Lagrangian tools is helpful to obtain more insight into the water transport process.     

Community based fishery management within the Menai Bay conservation area: A survey of the resource user

Management strategies are challenging to implement in Zanzibar's fisheries because the local people depend upon these resources for basic subsistence. This difficulty epitomizes the vital need for sustainable management: the more people need a fishery, the harder it is to limit fishing to allow regeneration. Comparing fisheries management strategies in two coastal villages in Unguja, the largest island of Zanzibar, Tanzania, this paper confirms the results of existing scholarship that communitybased strategies provide the most promising solutions to this challenge. Interviews with officials from the Department of Fisheries and Marine Resources, Village Fishermen Committees, and 51 fishermen in the villages of Kizimkazi Dimbani and Jambiani reveal the efficacy of strategies where local fishermen are centrally involved. The fishermen interviews reveal ignorance of existing fishing regulations and a lack of enforcement while fishermen at both sites noted that many illegal methods of fishing are still in use and expressed concern that such methods damage fish stocks. The Village Fishermen Committees, a recently implemented community-based initiative, are well attended by fishermen, and constitute a management strength that this paper concludes should be the foundation of future policy. To be successful, these committees need additional educational and financial resources.     

2003年胶州湾红岛海域生物的初步研究Ⅲ——底栖生物的初步调查与研究

根据2003年10月底和11中旬对红岛海域的大面积调查资料，对该海域的底栖生物现状进行了初步研究。调查结果表明，远岸海域底栖生物样品的多样性指数低于3。生物种间个体数分布比较均匀，优势种不明显，造成这种现象的原因有待进一步调查研究。     

A carbon budget in Tokyo Bay

Organic carbon flux from eutrophicated Tokyo Bay to the Pacific Ocean is estimated as 260 ton C day^–1 based on the horizontal gradient of COD and the dispersion coefficient at the bay mouth. Also, carbon flux from the air or from the open ocean to Tokyo Bay is estimated as 156 ton C day^–1. If we suppose that five percent of the coastal seas in the world might be eutrophicated as Tokyo Bay and the organic carbon flux from the shelf to the open ocean in other coastal seas might be one third of that in Tokyo Bay, 1.12 G tons year^–1 would be transported from the eutrophicated coastal seas to the open ocean and such carbon flux may account for the missing sink in the global carbon budget.     

RTK技术在杭州湾跨海大桥桥位地形测绘中的应用

介绍了RTK技术在杭州湾跨海大桥桥位地形测绘中的应用,并对其定位结果进行了精度比较与分析,结果表明:RTK定位测量的点位精度可达厘米级,各点位之间不存在误差积累,与全站仪等测量手段取得的结果符合得较好,可以用来代替二三级导线控制测量和等外水准等测量方法;流动站与基准站的距离在10km范围以内时,应用RTK技术对近岸水下地形进行测量具有方便、快捷、精度高等特点,但当此距离超过10km时,其精度则难以保证。杭州湾跨海大桥施工时应用RTK技术进行定位、高程测量,可提高工作效率和成果的质量。     

高分辨率遥感技术在厦门海湾生态环境调查中的应用

对于局部区域研究，高分辨率卫星遥感及其影像的智能化处理技术是获取信息的新手段．本文以IKONOS遥感影像在厦门海湾的应用为例，探讨高分辨率遥感卫星影像应用于海湾生态环境调查与分析的应用技术．通过分析高分辨率影像地物特征，提出高分辨率遥感影像的重要处理技术：采用不同缩放尺度进行分类和利用空间特征及纹理结构进行专题信息提取。     

Walrus foraging marks on the seafloor in Bristol Bay, Alaska: a reconnaissance survey

A reconnaissance sidescan sonar survey in Bristol Bay, Alaska revealed extensive areas of seafloor with features related to walrus foraging. They are similar to those seen in areas such as the outer Bering Sea and Chukchi Sea. Two types of feature were observed: (a) small (≪1 m diameter) shallow pits, often in clusters ranging in density from 5 pits per hectare to 35 pits per hectare; and, (b) more abundant, narrow, sinuous furrows, typically 5 to 10 m long with some reaching 20 m or more. Most foraging marks were in less than 60 m water depth in areas of sandy seafloor that were smooth, hummocky or characterized by degraded bedforms; the absence of foraging marks in other areas may be related, in part, to their more dynamic nature. The distribution of foraging marks was consistent in a general way with walrus locations from satellite telemetry studies.     

Early Diagenesis of Plant Pigments in Hudson River Sediments

Plant pigment concentrations were measured using high performance liquid chromatography in Hudson River sediments. Sedimentation rates and mixing characteristics were determined from depth profiles of the naturally occurring radionuclides ⁷Be, ²¹⁰Pb. Previous estimates of the mean-lives (1/λ) of plant pigments (chlorophylls a and b, fucoxanthin) from laboratory experiments, indicate a range of c. 20-40 days. However, in the field, we observed that these pigments decreased less rapidly with depth and penetrated deeper than ⁷Be (mean-life 77 days) in Hudson sediments 95% of the time. Assuming similar mixing processes for particles carrying ⁷Be and pigments, this indicates that pigment decay rates in the field are slower than the 0·013 day^-1 decay rate of ⁷Be, hence, more than 2-fold slower than the derived laboratory rates. We believe that high inputs of vascular plant detritus in the Hudson may increase the complexation of humic substances with pigments resulting in slower decay rates.While most pigments showed an exponential decrease with sediment depth, lutein concentrations generally increased with depth. This pattern of decay resistance is in agreement with laboratory experiments which show that lutein is the most decay resistant among dominant pigments. These data along with other studies demonstrate that the carotenoids lacking the 5,6-epoxide group (i.e., lutein) are more decay resistant than pigments that contain it (i.e., fucoxanthin).