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501.
Copepod feeding in a coastal area of active tidal mixing: diel and monthly variations of grazing impacts on phytoplankton biomass 总被引:1,自引:0,他引:1
This study examined monthly feeding rates and grazing impact on phytoplankton biomass, as well as diel feeding rhythms of four key copepod species in a tidally well mixed estuary (Asan Bay, Korean Peninsula). Monthly ingestion rates estimated based on gut pigment analysis were closely associated with their peak densities, but not with phytoplankton biomass, implying high ingestion may be related to reproductive output for population growth. The three smaller copepods, Acartia hongi, Acartia pacifica and Paracalanus parvus, showed feeding preference for smaller phytoplankton (<20 μm) with higher clearance rates, whereas the larger Calanus sinicus preferred larger phytoplankton. Acartia pacifica and P. parvus showed distinct increased nocturnal feeding rates as measured with gut fluorescence, whereas A. hongi showed no significant day–night differences. Copepod diel feeding patterns were not associated with food quantity, and endogenous physiological rhythm might be hypothesized as responsible for the observed diel feeding patterns. Grazing impact on phytoplankton biomass by the four copepods in the estuary was on average 8% (range 0.2–29.8%) of the phytoplankton standing stock, similar to values reported in other coastal waters. Very high copepod abundances but low daily carbon ration (<20% for all copepods) provided by feeding on phytoplankton indicate that copepods also grazed on other non‐phytoplankton foods in Asan Bay. 相似文献
502.
503.
渤海莱州湾表层沉积物中金属元素分布及环境质量 总被引:3,自引:1,他引:2
利用X-射线荧光光谱仪、等离子质谱仪或原子荧光光度计测定了莱州湾表层沉积物中金属元素的含量,探讨了它们的分布特征、来源及污染程度,结果表明,沉积物中铜、锌、铅、镉、砷、镍、铬、钴、钒、钪、铁、锰的含量由近岸向湾内递减,莱州湾北部海域的含量大于南部的。银含量高的沉积物主要分布在莱州湾中部偏西南的环流中心区。沉积物中砷和镍含量超过ERL值,潜在生态风险较高。富集系数和主成分分析显示,沉积物中铁、铜、锌、镉、砷、铬、镍、钴、锰、钒和钪为无富集,砷为轻度富集,铅和银为中度富集。铁、铜、锌、镉、铬、镍、钴、锰、钒、砷和钪主要来源于自然源,铅既有岩石和土壤风化产物硅酸盐矿物等自然源的贡献,又受到了人为活动的影响,银主要受人为活动的影响。聚类分析表明,可把莱州湾沉积物分为4类,其中黄河口西北缘沉积物中砷和镍污染生态风险最高,其次是莱州湾中部和北部。 相似文献
504.
The equation most commonly used to describe the bay planform was proposed by Hsu and Evans (1989) and it was obtained through empirical analysis of sand beach planforms.In the last decade interest in gravel sediments increased owing to their greater stability on beaches, compared with sand sediments. Due to the differences between the morphodynamics of sand and gravel beaches, which is strictly influenced by their different hydraulic characteristics, it was necessary to create a predictive instrument for this beach type as well.Therefore, in this study the standard Hsu and Evans equation (1989) was modified in order to make it applicable not only to sand beaches but also to gravel beaches. The shoreline was computed according to a parabolic model in polar coordinates whose coefficients are considered linearly dependent on the wave direction and related to the beach type. The estimation of the free parameters of the model was performed according to a statistical analysis of a shorelines data set of Mediterranean sand and gravel embayed beaches. 相似文献
505.
使用电感耦合等离子体质谱仪对采自莱州浅滩表层沉积物悬浮组分进行研究, 从地球化学角度分析了6 种常量元素质量分数、24 种微量元素质量比特征及它们与黄河细粒沉积物的联系。研究表明:莱州浅滩所取的7 个样品东西两侧略有差异, 元素质量分数的变异系数较小, 样品间变化不明显, 同源性和整体性显著。同黄河沉积物相比, 莱州浅滩细粒泥沙Al, Fe, Ca, K, Mg 和部分金属元素Cu, Zn质量分数略高, 大多数微量元素质量比略低, 两者大多数元素的判别系数绝对值较低, 标准偏差比值也较小, 经过Al 标准化处理后, 各元素对比值变化趋势较一致, 表现出较强的相似性。黄河细颗粒沉积物可以通过余流、环流扩散迁移至整个渤海, 而莱州浅滩所处地理位置及水文环境为黄河悬浮泥沙提供了良好的沉积条件, 黄河泥沙的沉积使浅滩细粒沉积物表现出了黄河沉积物的元素特征, 而两者细微差异可能与附近河流输沙、元素迁移方式及人类活动影响有关。通过莱州浅滩表层沉积物与黄河样各元素地球化学特征对比分析可以为探索黄河的入海悬浮组分在海域中的混合及扩散提供参考。 相似文献
506.
青岛唐岛湾的形成机制与海岸演化 总被引:1,自引:0,他引:1
通过野外地质调查,结合区域地质背景,探讨分析了青岛唐岛湾的形成机制与海岸演化过程。结果表明,唐岛湾的
形成机制主要涉及三个方面:NNE-NE向断裂的活动奠定构造格局并控制其岸线的延伸方向;第四纪冰川的侵蚀作用塑造
中间低洼、两岸较高的基底地形;约10 ka BP 前的大规模海侵使海水突破口门的阻挡进入湾内,唐岛湾正式形成。其海岸
形态自全新世以来可分为三个演化阶段,主控因素为海平面变化、海浪和潮汐作用,宋代时刘家岛与石岭子之间连岛沙坝
的形成标志着唐岛湾成为半封闭性海湾,清代时其海岸形态接近现今面貌。 相似文献
507.
《China Geology》2019,2(1):16-25
There are three transgression-regression events and evolutions of the sedimentary environment by sea level changes since the Pleistocene in the southern section of the Bohai Sea, China. It is obvious that a multi-source fluvial delta sedimentary system may be more dominant in a sedimentary environment. Based on previous research and survey or historical data, we carried out studies on the division of sedimentary units, sedimentary facies analysis and strata division and comparison, which aim to establish the sedimentary stratigraph of Laizhou Bay. We focus on the sedimentary procession of the Laizhou Bay since the early Late Pleistocene. It can be divided into two glacial periods and three interglacial periods, corresponding to two regression and three transgression events in Laizhou Bay since Late Pleistocene. In 124.6–72.0 ka BP, 60.0–24.4 ka BP and 10.2–4.0 ka BP, three times warm-wet periods occurred, respectively corresponding to the Cangzhou transgression, Xianxian transgression, and Huanghua transgression. In 72.0–60.0 ka BP and 24.4–10.2 ka BP, two dry and cold periods, it was the continental sedimentary environment, corresponding to Wurm early glacier and Wurm late glacier. The results show: (1) Sediments have the characteristics of phase and stage under the terrestrial input of the Yellow River and middle-small rivers in the southern section of the Bohai Sea. (2) PI moved towards coastal in Cangzhou transgression strata in early Late Pleistocene. PI moved northward from land in Xianxian transgression strata in the late Pleistocene. PI moved further north in the Huanghua transgression strata in Holocene. (3) During the regressive period, the land source input increased and the estuarine or lagoon sedimentation developed, which manifested as progradational superposition. (4) During the transgressive period, it mainly developed shallow coastal sediment and transitionally formed regressive deposition to the south in delta/tidal flat deposition.©2019 China Geology Editorial Office. 相似文献
508.
509.
The whole metazoan community inhabiting Laizhou Bay and adjacent Bohai Sea waters were sampled in late autumn,2006.Secondary production estimates for macrofauna and meiofauna were made separately.Total benthic secondary production was as high as 8.38 ± 4.08 g ash-free dry weight(AFDW) m-2 a-1,which represented the autumn production level.In general,macrofaunal secondary production in Laizhou Bay was much lower than that in adjacent Bohai Sea areas.In contrast,meiofaunal secondary production in Laizhou Bay was higher than that in adjacent Bohai Sea areas.Macrofauna contributed 61% to benthic secondary production(5.09 ± 3.26 g AFDW m-2 a-1),lower than the value in previous studies in Bohai Sea.Sediment granulometric characteristics and bottom-water salinity could explain the substantial variability in the macrofauna biomass and production.Meiofaunal production was an important component of benthic production and exceeded macrofauna production under exceptional conditions,e.g.in Laizhou Bay,where macrofauna was restricted.Chlorophyll pigments(Chl-a) concentrations in sediment explained the general meiofaunal biomass and production distribution here. 相似文献
510.
Fluxes of dissolved inorganic nutrients: NH4+, NO2-, NO3-, PO4(3-) and Si(OH)4 from nearshore sediments of Gazi Bay were measured in situ within mangrove, seagrass and coral reef biotopes using benthic flux bell-jar chambers of cross-sectional area 0.066 m2 and volume 0.0132 m3. The objectives were: (1) to determine the influence of benthic fluxes, fluvial discharge and seasonal variations on the nutrient budget in the Bay waters; (2) to determine the effect of tidal and spatial variations on nutrient loads in the water column and (3) to establish the relative importance of the nutrient sources with regard to total community production of the Bay. The directly measured fluxes ranged from -270 to +148 micromol NH4+-N/m2/h; -60 to +63 micromol NO2(-)-N/m2/h; -79 to +41 micromol NO3(-)-N/m2/h; -79 to +75 micromol PO4(3-)-P/m2/h and +30 to +350 micromol Si(OH)4-Si/m2/h for and respectively. It was established that benthic fluxes are the major sources of dissolved inorganic NH4+, NO2- and Si(OH)4 while fluvial sources are important for NO3- and PO4(3-) into Gazi Bay waters. Seasonal variations had an appreciable effect on the PO4(3-) fluxes, N:Si ratio, river nutrient discharge, plankton productivity and important environmental factors such as salinity and temperature. Tidal and spatial variations had no significant effect on nutrient concentrations and net fluxes within the water column. The results imply that benthic fluxes are largely responsible for the nutrient dynamics of the nearshore coastal ecosystems especially where direct terrestrial inputs do not contribute significantly to the nutrient budget. 相似文献