Phytoplankton ecology of a barrier island estuary: Great South Bay,New York

The phytoplankton ecology of Great South Bay, New York, was studied over a 1-year period. The study area, a large barrier island estuary (coastal lagoon with estuarine circulation), was characterized by high levels of inorganic nutrients, high turbidity and a shallow euphotic zone (<2 m). Net annual primary production by phytoplankton was high—450 g C m^?2 year^?1—and accounted for approximately 85% of the total ecosystem primary production. Chlorophyll a-specific productivity was dependent on mean photic zone light intensity in areas of the bay <1 m in depth from September 1979 through June 1980; 65–95% of the total light extinction in those areas was attibutable to suspended solids. Nitrogenous nutrient concentration did not limit phytoplankton productivity. Diatom and dinoflagellate cell densities varied greatly over time, while cryptomonad and chlorophyte species were abundant throughtout the year. Chlorophytes of 2–4 μm (‘small forms’) were numerically dominant, and contributed approximately half of the total phytoplankton biomass. Dilution of bay water by intruding ocean water appeared to control the spatial distribution of chlorophyll a on the south side of the bay; in other areas, growth appeared to exceed the rate of dilution by flushing. Waters entrained in eelgrass beds were significantly higher in salinity and mean photic zone light intensity, and had lower phytoplankton standing stock and depth-integrated primary production than control areas; waters in the sediment plume of active clamdigging boats were statistically similar to control areas with respect to water quality and phytoplankton community characteristics.     

Uptake of nitrogenous nutrients by phytoplankton in a barrier Island estuary: Great South Bay,New York

The uptake of urea, nitrate and ammonium by phytoplankton was measured using ¹⁵N isotopes over a one-year period in Great South Bay, a shallow coastal lagoon. The bay is a unique environment for the study of nutrient uptake since ambient concentrations of $\text{NO}{}_3{}^{\mathrm{?}}\text{NH}{}_4{}^{\mathrm{+}}$ and urea remain relatively high through the year, and phytoplankton are probably never nutrient limited. Urea nitrogen averaged 52% of the total assimilated, while ammonium represented 33% and nitrate 13%. High rates of ammonium uptake occurred only at low urea concentrations (ca< 1-μg-atom urea l^?1). Over the sampling period urea was present in relatively high concentrations, averaging 5·35 μg-atom N l^?1, while means for ammonium and nitrate averaged 1·94 and 0·65 μg-atom N l^?1, respectively. Total N uptake measured with ¹⁵N averaged about 3·3 times the calculated (from elemental ratios and ¹⁴C productivity measurements) N needs of the phytoplankton population. Highest nitrogen uptake occurred in the summer and coincided with the primary production maximum.     

淤积型海湾整治修复效果综合评价——以厦门湾为例

淤积型海湾整治修复属于海域空间整治工作中较为典型的整治形式,有着目标多重、手段多样、效果多面的综合性特点。本研究在分析海湾淤积环境问题成因机理的基础上,系统梳理了淤积型海湾整治修复工程效果评价的流程和技术方法,形成淤积型海湾整治修复效果综合评价技术指标体系,建立了评价模型,并以厦门海域清淤整治工程为例进行应用。研究表明,海湾淤积问题成因、整治措施和修复目标是评价指标体系的关键因素。厦门海域清淤整治工程的效果综合评价指数为84. 2,达到了较好的整治效果。     

Microbial biogeochemistry and bioturbation in the sediments of Great Bay, New Hampshire

The influence of bioturbation on certain aspects of the biogeochemistry of sulfur and iron was examined in shallow-water sediments of Great Bay Estuary, New Hampshire. A bioturbated (JEL) and non-bioturbated (SQUAM) site were compared. Annual sulfate reduction measured with ³⁵S, was 4·5 times more rapid at JEL. A significant portion of this difference was attributed to rapid rates which occurred throughout the upper 12 cm of sediment at JEL due to infaunal reworking activities. Sulfate reduction decreased rapidly with depth at SQUAM. FeS in the upper 2 cm at JEL increased in concentration from 3 to 45 μmol ml⁻¹ from early May to late July while only increasing from 3 to 8 μmol ml⁻¹ at SQUAM. Infaunal irrigation and reworking activities caused rapid and continous subsurface cycling of iron and sulfur at JEL. This maintained dissolved iron concentrations at 160–170 μM throughout the summer despite rapid sulfide production. Therefore, dissolved sulfide never accumulated in JEL pore waters. Although dissolved organic carbon (DOC) was generated during sulfate reduction, bioturbation during summer caused a net removal of DOC from JEL pore waters. Sulfate reduction rates, decomposition stoichiometry and nutrient concentrations were used to calculate turnover times of nutrients in pore waters. Nutrient turnover varied temporally and increased three-to five-fold during bioturbation. A secondary maximum in the abundance of recoverable sulfate-reducing bacteria occurred at 10 cm in JEL sediments only during periods of active bioturbation, demonstrating the influence of macrofaunal activities on bacterial distributions.     

Impact of microorganism degradation on hydrocarbon generation of source rocks: A case study of the Bozhong Sag,Bohai Bay Basin

The discovery of the Bozhong 19-6 gas field, the largest integrated condensate gas field in the eastern China in 2018, opened up a new field for the natural gas exploration deep strata in the Bohai Bay Basin, demonstrating there is a great potential for natural gas exploration in oil-type basins. The ethane isotope of the Bozhong 19-6 condensate gas is heavy, showing the characteristics of partial humic gas. In this paper, aimed at the source rocks of the Bozhong 19-6 gas field in the Bohai Bay Basin, the characteristics of the source rocks in the Bozhong 19-6 structural belt were clarified and the reason are explained from impact of microorganism degradation on hydrocarbon generation of source rocks why the condensate oil and gas had heavy carbon isotope and why it showed partial humic characteristics was explored based on the research of parent materials. The following conclusions were obtained: The paleontology of the Bozhong 19-6 structural belt and its surrounding sub-sags is dominated by higher plants, such as angiosperm and gymnosperm. During the formation of source rocks, under the intensive transformation of microorganism, the original sedimentary organic matter such as higher plants was degraded and transformed by defunctionalization. Especially, the transformation of anaerobic microorganisms on source rocks causes the degradation and defunctionalization of a large number of humic products such as higher plants and the increase of hydrogen content. The degradation and transformation of microorganism don’t transform the terrestrial humic organic matter into newly formed “sapropel” hydrocarbons, the source rocks are mixed partial humic source rocks. As a result, hydrogen content incrased and the quality of source rocks was improved, forming the partial humic source rocks dominated by humic amorphous bodies. The partial humic source rocks are the main source rocks in the Bozhong 19-6 gas field, and it is also the internal reason why the isotope of natural gas is heavy.     

Seasonal metal remobilization in the sediments of Great Bay,New Hampshire

Concentrations of dissolved iron, manganese, molybdenum, copper, and organic carbon (DOC) were measured in the pore waters from surficial sediments of a temperate estuary to delineate seasonal metal remobilization from 1978 through 1980. Iron and DOC data were collected for 31 months and covaried inversely and exponentially. Iron dissolution occurred during the spring and during periods of active bioturbation with concentrations as high as 18 mg 1^?1. Iron values were low during winter due to oxidation to ferric oxides. The lack of active bioturbation during the summer of 1978 allowed for the nearly complete removal of iron as a monosulfide precipitate. However, bioturbation resumed during the summer of 1979 and 1980 and dissolved iron concentrations as high as 10 mg 1^?1 were observed at those times. The iron and DOC data were a qualitative measure of bioturbation activity. Dissolved manganese, molybdenum, and copper data were collected for 18 months during 1978 and 1979. All three metals displayed spring maxima covariate with iron, suggesting that they behaved chemically like iron and/or were associated with iron- or manganese-rich phases during this time of the year. In general, manganese and molybdenum varied temporally with iron while copper concentrations mimicked iron variations only during the spring.     

The chemical, physical and structural properties of estuarine ice in Great Bay, New Hampshire

The purpose of this study was to provide general information on the chemical, physical and structural properties of estuarine ice and show how it compares with sea ice found at higher latitudes in order to determine whether the ice in Great Bay can be used as an analog in the study of arctic sea ice.Ice cores and water samples were collected during the 1983–1984 winter season at Adams Point in Great Bay, New Hampshire. Concentrations of chloride, nitrogen (as nitrate and nitrite), bromide, phosphate, sulfate and silicate were determined for samples chosen on the basis of identifiable stratigraphic layers (i.e. bubble size and shape, sediment layers, etc.).Similarities between ice formation in Great Bay and those in the arctic regions include the nature of the freezing process and the ice types produced. In addition, the distribution and concentration of chemical constituents were found to be similar to those observed in arctic sea ice. Factors affecting the chemistry of the ice in Great Bay include rainfall during the freezing season, the presence of sediment layers in the ice cores, the nature of incorporation of brine into the crystal structure of the ice and the drainage of brine.     

Modeling bed-load transport of coarse sediments in the Great Bay Estuary, New Hampshire

Current, sea level and bed-load transport are investigated in the Lower Piscataqua River section of the Great Bay Estuary, New Hampshire, USA—a well-mixed and geometrically complex system with low freshwater input, having main channel tidal currents ranging between 0.5 and 2 m s⁻¹. Current and sea level forced by the M₂M₄M₆ tides at the estuarine mouth are simulated by a vertically averaged, non-linear, time-stepping finite element model. The hydrodynamic model uses a fixed boundary computational domain and accounts for flooding–drying of tidal flats by making use of a groundwater component. Inertia terms are neglected in comparison with pressure gradient and bottom friction terms, which is consistent with the observed principal dynamic balance for this section of the system. The accuracy of hydrodynamic predictions in the study area is demonstrated by comparison with four tidal elevation stations and two cross-section averaged current measurements. Simulated current is then used to model bed-load transport in the vicinity of a rapidly growing shoal located in the main channel of the lower system. Consisting of coarse sand and gravel, the shoal must be dredged every five to eight years. Two approaches are taken—an Eulerian parametric method in which nodal bed-load flux vectors are averaged over the tidal cycle and a Lagrangian particle tracking approach in which a finite number of sediment particles are released and tracked. Both methods yield pathways and accumulations in agreement with the observed shoal formation and the long-term rate of sediment accumulation in the shoal area.     

历史遗留围填海生态保护修复工作探讨——以晋江盐场围填海项目为例

本研究以晋江盐场围填海项目为例,针对项目情况和区域环境特征,在收集现有资料和补充调查的基础上,分析评估了围填海工程建设的海洋生态影响,并提出了相应的生态保护修复方案。在此基础上,提出了今后工作的建议:(1)保护修复应推行整体保护、系统修复的有效机制,实现区域生态系统的恢复与良性发展。(2)围填多年已经形成相对稳定的生态系统的围填海项目,制定修复对策也应遵循现有的生态条件,充分考虑修复工程的成本与效益,增强修复方案的可操作性,做出最有利的决策。(3)生态修复模式应以自然恢复为主、人工修复为辅,最大程度恢复生态系统功能。本研究可为类似生态保护修复工作提供借鉴。     

Discontinuous hindcast simulations of estuarine bathymetric change: A case study from Suisun Bay,California

Simulations of estuarine bathymetric change over decadal timescales require methods for idealization and reduction of forcing data and boundary conditions. Continuous simulations are hampered by computational and data limitations and results are rarely evaluated with observed bathymetric change data. Bathymetric change data for Suisun Bay, California span the 1867–1990 period with five bathymetric surveys during that period. The four periods of bathymetric change were modeled using a coupled hydrodynamic-sediment transport model operated at the tidal-timescale. The efficacy of idealization techniques was investigated by discontinuously simulating the four periods. The 1867–1887 period, used for calibration of wave energy and sediment parameters, was modeled with an average error of 37% while the remaining periods were modeled with error ranging from 23% to 121%. Variation in post-calibration performance is attributed to temporally variable sediment parameters and lack of bathymetric and configuration data for portions of Suisun Bay and the Delta. Modifying seaward sediment delivery and bed composition resulted in large performance increases for post-calibration periods suggesting that continuous simulation with constant parameters is unrealistic. Idealization techniques which accelerate morphological change should therefore be used with caution in estuaries where parameters may change on sub-decadal timescales. This study highlights the utility and shortcomings of estuarine geomorphic models for estimating past changes in forcing mechanisms such as sediment supply and bed composition. The results further stress the inherent difficulty of simulating estuarine changes over decadal timescales due to changes in configuration, benthic composition, and anthropogenic forcing such as dredging and channelization.     

A case study: imaging OBS multiples of South China Sea

The subseafloor structure offshore South China Sea was imaged using first-order water-layer multiples from ocean-bottom seismometer data and the results were compared to conventional imaging using primary reflections. The mirror-imaging method employs a primaries-only reverse time pre-stack depth migration algorithm to image the receiver ghosts. The additional travel path of the multiples through the water layer is accounted for by a simple manipulation of the velocity model and processing datum: the receivers lie not on the sea floor but on a sea surface twice as high as the true water column. Migration results show that the multiple-migrated image provides a much broader illumination of the subsurface than the conventional image using the primaries, especially for the very shallow reflections. The resulting image from mirror imaging has illumination comparable to the vertical incidence surface streamer (single-channel) reflection data.     

A prominent colour front in False Bay, South Africa: Cross-frontal structure, composition and origin

Colour fronts are a frequent occurrence in False Bay, South Africa, and their occurrence has been the subject of previous study and anecdotal conjecture. The opportunity arose to make a cross-frontal study of this feature in November 2005. Photographs were taken and, subsequently, satellite imagery was obtained. Measurements were made of temperature, salinity, turbidity, dissolved oxygen, suspended solids, plant nutrients and chlorophyll a. Cross-frontal comparisons were also made on particulate material using a scanning electron microscope (SEM) and elemental dispersive x-ray (EDX) analysis. Frontal waters were milky white-green in colour, in stark contrast to the adjacent clearer, green-blue waters. The milky white-green water (MW-GW) was found to be warmer, (apparently) less saline, more turbid, richer in nitrate and silicate and had a higher chlorophyll a concentration. The dissolved oxygen signal was less pronounced, both water types being supersaturated. Paradoxically, in spite of the higher turbidity in the MW-GW, both water types had similar weights of suspended solids, although the MW-GW material was found to be more abundant and fragmentary when compared with its green-blue water (G-BW) counterpart. The MW-GW was rich in calcium whereas the G-BW was silicon enriched. The central findings of this study are that the strong southerly, onshore wind conditions prior to MW-GW formation introduced calcium-rich, fine particulates into the waters of the surf-zone. The sources of these particulates are thought to be the sea bed sediments and the sea/land interface. The particulates are close to neutral buoyancy enabling the MW-GW to persist over the time-scale of days. A mechanism reinforced by the warming of this water in the nearshore zone. The water was then advected by wind-forcing and subsequently, its own inertia around the north-west corner of False Bay, at which stage it was easily observed and sampled. It is suggested that the eventual collapse of the front was due to the slowing down of inertial movement in combination with the passive sinking of fine particulates and evaporative cooling resulting in downward convection.     

A Late Winter Hydrography in Hidaka Bay, South of Hokkaido, Japan

Hydrographic observations in Hidaka Bay, south of Hokkaido, Japan were carried out in late winter 1996 and 1997 to examine the spatial distributions and circulation features of two different water masses, i.e., Coastal Oyashio Water (COW) and Tsugaru Warm Water (TWW), and their modifications. It is known that COW is mostly composed of cold and low-salinity water of the melted drift ice coming from the Okhotsk Sea and flows into Hidaka Bay from winter to spring and TWW with high-salinity continuously supplies from the Tsugaru Strait to the North Pacific. Cold surface mixed layers (<26.2σ_θ, 0–100 m depth) were found mainly over the shelf slope, confirming that anti-clockwise flow of COW was formed. TWW was relatively high in salinity and low in potential vorticity, and had some patch-like water masses with a temperature and salinity maximum in the limited area in the further offshore at the deeper density levels of 26.6–26.8σ_θ. The fine structure of vertical temperature and salinity profiles appeared between TWW and COW is an indication of enhanced vertical mixing (double-diffusive mixing), as inferred from the estimated Turner angles. At a mouth of the Tsugaru Strait in late winter 1997, a significant thermohaline front between TWW and the modified COW was formed and a main path of TWW spreaded south along the Sanriku coast, probably as the bottom controlled flow. Hence, the patch-like TWW observed in late winter is isolated from the Tsugaru Warm Current and then rapidly modified due to a diapycnal mixing. This revised version was published online in August 2006 with corrections to the Cover Date.     

象山港滨海湿地互花米草入侵过程遥感监测与评估

互花米草在20世纪70年代后期作为海岸带生态防护工程物种引入我国,由于其超强的繁殖能力,目前已经对我国的滨海湿地生态环境健康与安全造成了严重的威胁,成为生长在中国沿海的一种典型生态入侵植物,引起了相关部门的高度重视。文章选择浙江象山港为重点研究区,通过遥感技术手段,基于2003年,2009年和2014年中分辨率Landsat系列遥感卫星数据,采用空间与光谱特征相结合的综合判读,提出了生境空间环境支持下的植物群落遥感自动识别方法,动态监测了互花米草在象山港的繁衍和入侵过程已经空间格局变化。研究结果表明:过去10年余年,互花米草在象山港呈现指数模型的爆炸性增长。2003年,整个象山港互花米草的分布面积约为590 hm²;2009年其分布面积达到1745 hm²;2014年互花米草在象山港的分布面积超过5715 hm²。2003-1014年10年间互花米草在该区域分布面积翻了近10倍,几乎占据了海岸带所有的泥质海滩,成为象山港滨海湿地区的主导型盐生植被和区域优势种,对附近农田,尤其是淡水水域构成巨大的威胁。而在快速扩张的驱动要素方面,研究认为强劲的自我繁殖性能是互米花草在区域能够快速扩张的主要原因;人类围垦活动促进了这一快速扩张进程。以上研究结论可为区域互花米草的综合治理提供数据支持和遥感监测提供技术参考。     

Environmental controls on phytoplankton production in coastal ecosystems: A case study from Tokyo Bay

Phytoplankton biomass and primary production were examined in their environmental context, for a semi-enclosed bay (Tokyo Bay, Japan) using data from monthly samples collected over a three-year period. Heavy precipitation and high surface temperatures in the late spring and summer gave rise to a highly-stratified water-column and stimulated a series of phytoplankton blooms, whereas during the winter, a weakly-stratified and deeply-mixed water-column led to a rapid decline in phytoplankton biomass under light-limited growth conditions. By incorporating pigment, photophysiological and optical data into a primary production model we show that daily, water-column primary production ranges from ∼160 mg C m⁻² d⁻¹ to 7600 mg C m⁻² d⁻¹. High water turbidity and deep vertical mixing, both separately and in concert, limit the light available for algal growth over much of the year. Annual primary production varied from 370 to 580 g C m⁻² y⁻¹. The relative influences of nutrient limitation and light limitation are assessed. A model is developed that describes this in an explicit manner using photophysiological parameters.     

Jamaica Bay studies VII: Factors affecting the distribution and abundance of ducks in a New York estuary

The abundance and distribution of ducks (Anatini, Cairinini, Aythyini, Mergini, Oxyurini) were examined at Jamaica Bay Wildlife Refuge, a coastal estuary on Long Island, New York. The refuge contains a variety of tidal habitats as well two freshwater impoundments. The largest concentrations of diving ducks were present in March and April, and from October through December; while the largest concentrations of dabbling ducks were present from June through December. Thus, diving ducks used the refuge on migration whereas dabbling ducks used the refuge during and following the breeding season. Time of year was thus the most significant factor affecting distribution and abundance. Some species were present all year, including Black Duck Anas rubripes, Mallard A. platyrhynchos, Gadwall A. strepera, and Ruddy Duck Oxyura jamaicensis. Although both dabblers and divers used all areas of the bay, dabblers used both ponds while divers used only the East Pond. Dabbling ducks concentrated in the bay at low tide, and on the ponds at high tide. There were more divers on the bay on a falling tide although tide direction did not influence the abundance or distribution of dabblers. Temperature and wind variables influenced the distribution of all ducks: they used the bay at low temperatures, and rafted in large flocks on the bay in intermediate, Northwest winds. Only the numbers and distribution of dabblers were significantly influenced by cloud cover. We conclude that abiotic factors influence the abundance and distribution of ducks on Jamaica Bay Wildlife Refuge, and that tidal factors should be considered when managing migratory or wintering populations of ducks.     

Monitoring benthic biodiversity restoration in Lyme Bay marine protected area: Design,sampling and analysis

Long-standing concerns about the effects of scallop dredging and demersal trawling on high diversity mudstone reef and cobble habitats in Lyme Bay, southwest England, were addressed by the exclusion of bottom towed fishing gear from a 206 km² area in July 2008. A consortium led by Plymouth University Marine Institute was funded by the UK Department of Environment, Food and Rural Affairs to design and implement a study (initially funded for 3 years) to examine the effects of the closure on both nekton and epibenthos. This paper provides a detailed account of the methodology employed from survey design to data analysis to provide a protocol for future MPA monitoring programmes. Information on historical fishing effort, substrate distributions and current and previous closure boundaries was overlaid using GIS to locate suitable monitoring sites. Non-destructive and cost-effective techniques, including a towed high-definition video array and static baited video, were used to quantify changes in relative abundances of epibenthos and nekton over three years at sites previously fished but now closed to bottom towed fishing compared to both fished and un-fished reference sites. The monitoring programme as described provides a model for robust, cost-effective evaluation of the efficacy of policy instruments for feedback into the adaptive management cycle.     

Using a GIS to Examine Changes in the Bathymetry of Borrow Pits and in Lower Bay, New York Harbor, USA

Standard analyses with geographic information systems (GIS) and the publicly available GEODAS database were used to highlight bathymetric changes in the Lower Bay complex of New York Harbor. Dredging operations have deepened much of the Lower Bay complex. Approximately 6,580 hectares, or 20% of the bay bottom surveyed in 1934, was deeper in 1979/1982 than during 1934. Half of this deepening, 3,219 hectares or 10% of the bay bottom surveyed during 1934, was deeper by at least 2 m. Surveys conducted by the U.S. Army Corps of Engineers of three borrow pits in the central part of the Lower Bay complex were used to examine sedimentation over a 16-year period from 1979 to 1995. Results were consistent with studies conducted during the 1970s and 1980s that show the pits function as sediment traps. Between 1979 and 1995, sediment accumulated at rates of 6 to 12 cm per year in many portions of the borrow pits.     

Using a GIS to Examine Changes in the Bathymetry of Borrow Pits and in Lower Bay,New York Harbor,USA

Standard analyses with geographic information systems (GIS) and the publicly available GEODAS database were used to highlight bathymetric changes in the Lower Bay complex of New York Harbor. Dredging operations have deepened much of the Lower Bay complex. Approximately 6,580 hectares, or 20% of the bay bottom surveyed in 1934, was deeper in 1979/1982 than during 1934. Half of this deepening, 3,219 hectares or 10% of the bay bottom surveyed during 1934, was deeper by at least 2 m. Surveys conducted by the U.S. Army Corps of Engineers of three borrow pits in the central part of the Lower Bay complex were used to examine sedimentation over a 16-year period from 1979 to 1995. Results were consistent with studies conducted during the 1970s and 1980s that show the pits function as sediment traps. Between 1979 and 1995, sediment accumulated at rates of 6 to 12 cm per year in many portions of the borrow pits.