Spatial patterns in community structure of motile epibenthic fauna in coastal habitats along the Skagerrak – Baltic salinity gradient     

Emma Nohrén  Leif Pihl  Håkan Wennhage 《Estuarine, Coastal and Shelf Science》2009

Patterns in community structure and functioning of motile epibenthic fauna were investigated in shallow (0–1 m) sediment habitats along the Skagerrak–Baltic estuarine gradient (salinity range from 4 to 34). The study area was divided into five regions, reflecting different sea-basins along the 1260 km coastline, and fauna was collected at six sites within each region. Ten replicate samples of motile epibenthic fauna were taken randomly at each site with a portable drop trap (bottom area 1 m²) in June and September in 2004.  相似文献   

Contrasts between estuarine and river systems in near-bed turbulent flows in the Zhujiang (Pearl River) Estuary, China   总被引：5，自引：0，他引：5  

Huan Liu  Chaoyu Wu  Weiming Xu  Jiaxue Wu   《Estuarine, Coastal and Shelf Science》2009,83(4):591-601

A bottom-mounted instrumental tripod was deployed in the tidally energetic Zhujiang (Pearl River) Estuary to examine the contrasting properties of the bottom boundary layer (BBL) flows between estuarine and tide-affected river systems. Three aspects of the BBL flows were investigated to understand the mechanism of the turbulence responses to the large-scale ambient forcing: the flow structures (profile, anisotropy, and spectra), shearing strains and stresses, and the balance of turbulent kinetic energy (TKE). Single log-law profiles and turbulence anisotropy predominated in the two systems, but the non-log regime and stronger anisotropy occurred more frequently at the slack tide in the estuary. The ADV-based turbulence intensities and shearing strains both exceeded their low-frequency counterparts (frictional velocities and mean shears) derived from the logarithmic law. On the contrary, the ADV-based Reynolds stresses were smaller than the log profile-derived bottom stresses, so the hypothesis of a constant stress layer cannot be well satisfied, especially in the river. The bandwidth of the inertial subrange in the river was of one decade larger than in the estuary. The balance between shear production and viscous dissipation was better achieved in the straight river. This first-order balance was significantly broken in the estuary and in the meandering river, by non-shear production/dissipation due to wave-induced fluctuations or salinity/sediment stratification. All these disparities between two systems in turbulence properties are essentially controlled by the anisotropy induced by the large-scale processes such as secondary currents, density stratification. In conclusion, the acceleration of unsteady flows determines the profile structure of the BBL flow, and turbulence anisotropy results in the invalidation of the phenomenological relations such as the constant stress hypothesis and the first-order TKE balance.  相似文献   

Limno-tolerant bacteria govern nitrate concentration in Mandovi Estuary,India     

Baby Divya  Sheryl O. FernandesG. Sheelu  Shanta Nair  P.A. Loka BharathiD. Chandramohan 《Estuarine, Coastal and Shelf Science》2009

The spatial and temporal abundances of limno-tolerant and halo-tolerant bacteria were investigated in the tide-dominated Mandovi estuary along the west coast of India. These investigations were carried out in relation to various environmental parameters on a monthly basis at three fixed stations for a year. On an annual basis, the estuary showed an average salinity of 28.2, 17.4, and 12.6 at the mouth, midstream and upstream region. Halo-tolerant retrievable count (HTRC) and limno-tolerant retrievable count (LTRC) of bacteria were in the order of 10⁶ L⁻¹. Among the environmental parameters, a strong negative relationship between salinity and nitrate (r = −0.806; p < 0.001) suggested that 64% of the variation could be due to fresh water influence in the estuary. The limno-tolerant retrievable count (LTRC) brought about 23% variations in nitrate concentration. This influence was maximum during the monsoon (r = 0.522; p < 0.05) especially in the surface waters (r = 0.624; p < 0.001) suggesting nitrate reduction by LTRC. Measurements of nitrate reducing activity (NRA) in whole-water samples along the salinity gradient in the estuary also revealed higher reduction rates at lower salinity upstream. This was further confirmed by culture experiments where the limno-tolerant bacteria showed higher NRA than halo-tolerant forms. It is therefore suggested that LTRC is more actively involved in the variation of nitrate that enters the Mandovi estuary particularly during the monsoon.  相似文献   

Determination of fish trophic levels in an estuarine system     

S. Pasquaud  M. Pillet  V. David  B. Sautour  P. Elie 《Estuarine, Coastal and Shelf Science》2010

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Horizontal distribution and population dynamics of the dominant mysid Hyperacanthomysis longirostris along a temperate macrotidal estuary (Chikugo River estuary, Japan)     

Keita W. Suzuki  Kouji Nakayama  Masaru Tanaka 《Estuarine, Coastal and Shelf Science》2009,83(4):516-528

The estuarine turbidity maximum (ETM) that develops in the lower salinity areas of macrotidal estuaries has been considered as an important nursery for many fish species. Mysids are one of the dominant organisms in the ETM, serving as a key food source for juvenile fish. To investigate the horizontal distribution and population dynamics of dominant mysids in relation to the fluctuation of physical conditions (temperature, salinity, turbidity, and freshwater discharge), we conducted monthly sampling (hauls of a ring net in the surface water) along the macrotidal Chikugo River estuary in Japan from May 2005 to December 2006. Hyperacanthomysis longirostris was the dominant mysid in the estuary, usually showing peaks of density and biomass in or close to the ETM (salinity 1–10). In addition, intra-specific differences (life-cycle stage, sex, and size) in horizontal distribution were found along the estuary. Larger males and females, particularly gravid females, were distributed upstream from the center of distribution where juveniles were overwhelmingly dominant. Juveniles increased in size toward the sea in marked contrast with males and females. The findings suggest a possible system of population maintenance within the estuary; gravid females release juveniles in the upper estuary, juveniles grow during downstream transport, young males and females mature during the upstream migration. Density and biomass were primarily controlled by seasonal changes of temperature, being high at intermediate temperatures (ca. 15–25 °C in late spring and fall) and being low at the extreme temperatures (ca. 10 °C in midwinter and 30 °C in midsummer). High density (up to 666 ind. m⁻³) and biomass (up to 168 mg dry weight m⁻³) of H. longirostris were considered to be comparable with those of copepods in the estuary.  相似文献   

Composition and fluxes of particulate organic matter in a temperate estuary (Winyah Bay, South Carolina, USA) under contrasting physical forcings     

Miguel A. Goi  George Voulgaris  Yong H. Kim 《Estuarine, Coastal and Shelf Science》2009,85(2):273-291

To understand the role that physical processes play on the biogeochemical cycles of estuaries, we conducted intense field studies of the turbidity maximum region within a partially mixed estuary (Winyah Bay, SC, USA) under contrasting conditions of river discharge, tides and wind. Water samples and hydrographic data were collected at different depths and locations along the main channel over several tidal cycles during several cruises to Winyah Bay. Tidal variations in current speed, salinity, total suspended solid concentrations were measured within each cruise and were consistent with estuarine circulation processes. Salinity and total suspended solid concentrations ranged from 0 to 32 and from 20 to over 500 mg L⁻¹, respectively, with the highest salinity and total suspended solid values measured during periods of low river discharge. In fact, comparison of tidally averaged salinity and total suspended solid concentrations revealed marked differences among cruises that were negatively correlated to river discharge and SW wind speed. Moreover, significant contrasts in the chemical compositions of suspended particles were evident among periods of contrasting river discharge and wind regime. For example, the weight percent organic carbon content of suspended particles ranged from 1 to over 6% and displayed a positive correlation with river discharge. Similarly, both the molar carbon to nitrogen ratios (10 to 20 mol:mol) and stable carbon isotopic compositions (−25 to −29%) of the suspended organic matter varied significantly as a function of discharge and wind. Such trends indicate that in Winyah Bay low river discharge and steady SW winds promote resuspension of bed sediments from shallow regions of the estuary. These materials contain highly altered organic matter and their incorporation into the water column leads to the observed trends in suspended particle concentrations and compositions. Furthermore, these conditions result in net landward fluxes of salt, sediment and particulate organic matter throughout most of the water column, promoting efficient trapping of materials within the estuary. Our results illustrate the fundamental connection between physical forcings, such as discharge and wind, sediment transport processes and the cycling of biogeochemical materials in estuarine environments.  相似文献   

Metal pollution of estuarine sediments caused by leaching of acid sulphate soils     

Linda Nordmyr  Mats Åström  Pasi Peltola 《Estuarine, Coastal and Shelf Science》2008

This study tracks changes in metal distribution in estuarine sediments as a result of leakage from acid sulphate (AS) soil landscapes in the Boreal Zone (Finland). The main objective was to identify the impact of these nasty soils on sediment geochemistry in a biologically sensitive and shallow brackish-water estuary. In order to do this four sediment cores were sampled in a profile extending seawards from the mouth of the Vörå River, which is one of the most heavily AS soil-impacted rivers in Finland and Europe. Two of the cores were rather deep (2.5 m and 4.0 m) and the others were shallow (0.4 m and 0.8 m). The results showed that an appreciable amount of aluminium (Al), cobalt (Co), cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni) and zinc (Zn) were elevated in the surface and sub-surface of the sampled bottom sediments compared to the deeper sediment background levels. These metals are all known to be abundantly leached from the AS soils. At the site approximately 4 km away from the river mouth, the concentrations of Cd, Co, Mn, Ni and Zn were elevated 5–100 times as compared to the background levels and showed an intriguing cyclic pattern, most likely reflecting seasonal leaching dynamics in the AS soil landscapes. In contrast, metals that are not abundantly leached from AS soils, i.e. chromium (Cr), iron (Fe) and vanadium (V) had consistently low concentrations throughout all sediment cores. The elevated metal concentrations in the top layers of the sediments in the estuary are alarming. The continuous land uplift of the region combined with the episodic rapid declines in pH may result in short and long term extensive release of metals. This, in turn, may have significant effects on the trace-metal contents in the Gulf of Bothnia and the entire Baltic Sea.  相似文献   

Processes controlling cobalt distribution in two temperate estuaries,Sagami Bay and Wakasa Bay,Japan     

Hyoe Takata  Tatsuo AonoKeiko Tagami  Shigeo Uchida 《Estuarine, Coastal and Shelf Science》2010

Concentrations of cobalt (Co) in surface waters from the Sagami River to northern Sagami Bay and from the Yura River to southwestern Wakasa Bay in Japan were determined in order to investigate the factors governing the distribution of this metal during estuarine mixing. Dissolved (<0.2 μm) and particulate (>0.2 μm) Co showed non-conservative mixing behavior with low or mid-salinity maxima within those two estuarine regions, indicating benthic remobilization and/or sewage input apart from riverine input during the estuarine mixing. These results are supported by a suite of complementary measurements of other parameters, such as manganese, phosphate, and suspended particulate matter concentrations. In addition, the concentration ratio of dissolved Co to total Co (dissolved plus particulate) increased along the salinity gradient, implying the potential for desorption of this metal from suspended particulate matter on estuarine mixing.  相似文献   

从海岸地貌学看河海划界的可操作性     

高抒 《海洋学研究》2009,27(Z1)

根据河海划界的可操作性的要求,探讨了海岸地貌学指标在河口区划分中的作用,并通过对河口区与河流、海洋之间的动态联系的阐述,提出河口区管理方式的建议.河口是海岸带陆海相互作用的典型环境,具有物理、化学、地质、生物和环境等多种复杂动力学过程,每一个河口都是高度个性化的.在为数不多的体现河口共性的参数中,海岸地貌学指标可用来确定河口区的内、外边界.根据河流水力学特征和河口过程的可容空间范围特征,河口-河流的分界点可用B-L曲线(B为河岸宽度,L为距离原点沿河流轴线的累积长度)上的拐点位置来表示.而按照河口为"半封闭水域"的定义,河口-海洋分界线可采用围封河口水域的海岸线的包络线.河口水域受到河流和海洋的双重影响,且河口区的自然演化和人类开发活动也会影响河流和海洋.因此,在我国河口区管理上应建立海洋和其他管理部门之间的协调机制.  相似文献   

Stable isotopes in juvenile marine fishes and their invertebrate prey from the Thames Estuary,UK, and adjacent coastal regions     

Chris D.B. Leakey  Martin J. Attrill  Simon Jennings  Mark F. Fitzsimons 《Estuarine, Coastal and Shelf Science》2008

Estuaries are regarded as valuable nursery habitats for many commercially important marine fishes, potentially providing a thermal resource, refuge from predators and a source of abundant prey. Stable isotope analysis may be used to assess relative resource use from isotopically distinct sources. This study comprised two major components: (1) development of a spatial map and discriminant function model of stable isotope variation in selected invertebrate groups inhabiting the Thames Estuary and adjacent coastal regions; and (2) analysis of stable isotope signatures of juvenile bass (Dicentrarchus labrax), sole (Solea solea) and whiting (Merlangius merlangus) for assessment of resource use and feeding strategies. The data were also used to consider anthropogenic enrichment of the estuary and potential energetic benefits of feeding in estuarine nursery habitat.  相似文献