The effects of prolonged aquatic macrophyte senescence on the biology of the dominant fish species in a southern African coastal lake     

A.K. Whitfield 《Estuarine, Coastal and Shelf Science》1984,18(3):315-329

The littoral zone of Swartvlei, an estuarine lake on the southern Cape coast, was characterized by extensive beds of submerged aquatic macrophytes. May 1979 marked the beginning of a regression phase which lasted more than three years. The senescence of the Potamogeton pectinatus and charophyte beds resulted in a 60% decline in primary production, a 74% slump in littoral invertebrate biomass and a 54% decline in the abundance of the fishes Monodactylus falciformis (Lacepede) and Rhabdosargus holubi (Steindachner) associated with the macrophytes. Gravimetric and calorific analyses of their food revealed that invertebrates and filamentous algae from the littoral zone were of major importance. The two fish species consumed approximately 2% of the primary production during the Potamogeton canopy phase and 3% during the Potamogeton senescent phase. Invertebrate consumption declined from 33 mg m^?2 day^?1 during the canopy phase to 8 mg m^?2 day^?1 during the senescent phase. The disappearance of the Potamogeton and charophyte beds also resulted in a decrease in the condition of both species but the effect was indirect and related mainly to the collapse of invertebrate stocks associated with the plants.  相似文献   

Fish assemblage structure of Koycegiz Lagoon–Estuary, Turkey: Spatial and temporal distribution patterns in relation to environmental variation     

S. Akin  E. Buhan  K.O. Winemiller  H. Yilmaz 《Estuarine, Coastal and Shelf Science》2005,64(4):671-684

Spatial and temporal variation in fish assemblage structure of Koycegiz Lagoon–Estuarine System (KLES), located on the northwestern Turkish coast of Mediterranean, was investigated along an estuarine gradient where salinity ranged from 5 in upper reaches to 40 in lower reaches during October 1993–September 1994. Throughout the study, 42 species, consisting of marine (25), marine–estuarine-dependent (12), freshwater (3), catadromous (1), and estuarine resident (1) forms, were collected in trammel nets. Although species richness of marine species was greater than that of other groups, numerical contribution by marine species to the total catch was only 16%. Tilapia spp., the most abundant species mostly during summer and early spring at upper reaches, contributed 17% of the total samples. Among the seven species of Mugilidae, which contributed 42% of the total catch, Mugil cephalus, Liza aurata, and Liza salines contributed 10, 13, and 10% of the total catch, respectively. Consistent with findings from other studies, species richness and abundance were highest during late spring and summer and the lowest during winter and early spring. Samples from sites at or near the sea had more marine species. Samples from upper reaches had more freshwater and marine–estuarine-dependent species. Canonical correspondence analysis (CCA) indicated that salinity and turbidity were the most important environmental parameters affecting fishes. Sites near the sea were associated with high salinity and low turbidity, and sites in upper reaches had low salinity and high turbidity. Thus, the pattern observed in fish assemblage structure appears to be strongly influenced by species' responses to dominant salinity and turbidity gradients.  相似文献   

Fish assemblages across the marine to low salinity transition zone of a temperate estuary   总被引：2，自引：0，他引：2  

Edward J. Martino  Kenneth W. Able 《Estuarine, Coastal and Shelf Science》2003,56(5-6):969-987

This 3-year study provides a large-scale perspective of fish assemblage structure across an ocean–estuarine ecotone, given range of salinity encountered (0.1–32) based on sampling at 12 stations along 40 km from the Mullica River (river), Great Bay (bay), and the adjacent inner continental shelf (ocean) in southern New Jersey. Otter trawl (4.9 m, 6 mm mesh) collections were dominated by young-of-the-year of most of the 49 species encountered. Species richness and abundance appeared greatest in the ocean, decreased (with an increase in inter-station variability) in the bay, and appeared to increase again towards the uppermost river stations. The same areas contained three non-discrete, but identifiable, fish assemblages based on Detrended Correspondence Analysis. Members of the Triglidae and Stromateidae characterized the ocean and bay, whereas representatives of the Percichthyidae and Ictaluridae characterized the river. Several species, including Anchoa mitchilli and Cynoscion regalis, exhibited a ubiquitous distribution across the sampling area. Further analyses with Canonical Correspondence Analysis identified salinity and geographic distance, among the variables examined, as the most important determinants in shaping the assemblages. Other contributors included habitat heterogeneity and water depth. In summary, these observations indicate that large-scale patterns in the structure of this estuarine fish assemblage are primarily a result of individual species' responses to dominate environmental gradients, as well as ontogenetic migrations, whereas smaller-scale patterns appear to be the result of habitat associations that are most likely driven by foraging, competition, and/or predator avoidance.  相似文献   

海南岛港湾演变与工程建设     

朱大奎 《海洋地质前沿》2002,18(3):14-17

海南岛沿岸多港湾，主要有3种类型的潮汐汊道型港湾：（1）沙坝-泻湖型潮汐汊道港湾主要分布在东南部海岸，以三亚港最为典型。三亚港原始岸线为基岩港湾海岸，由中生代花岗岩构成。花岗岩风化泥沙充填谷地港湾连成陆地，以沙坝-泻湖体系形式逐渐堆积成海积平原。（2）港湾型潮汐汊道主要分布在海南岛西部，起源于构造断裂带的港湾。其演化的主要因素是河流及海岸侵蚀向湾内供应的沉积物以及巨大的纳潮量形成的潮流动力。消费品流及海岸供沙使纳潮水域淤积，纳潮量相应减少，同时在口门内外形成潮流三角洲（拦门沙浅滩）。（3）溺谷型潮汐汊道主要分布在海南岛北岸、东北岸。其演化过程是：古河口溺谷，沿岸输沙发育海岸沙坝，古河口溺谷逐渐淤积衰退，潮流作用形成 口门外落潮流堆积体及涨潮带入海相细粒物质，使纳潮水域进一步淤浅缩小，目前这类汊道处于发育演化的晚期，接近汊道整体的消亡。  相似文献   

Food and habitat resource partitioning between three estuarine fish species on the Swedish west coast     

Staffan Thorman 《Estuarine, Coastal and Shelf Science》1983,17(6)

In 1978 the food and habitat resource partitioning of three small and common fish species, viz. Pomatoschistus microps (Krøyer), Gasterosteus aculeatus (L.) and Pungitius pungitius (L.) were studied in river Broälven estuary on the Swedish west coast (58°22′N, 11°29′E). The area was divided into three habitats, based on environmental features. In July, September, and October stomach contents and size distribution of each species present were analysed.In July there was high food and habitat overlap between the species. Interference interactions probably occurred between some size classes of P. microps and the other two species. P. pungitius was exposed to both intra- and interspecific interactions. In September the food and habitat overlaps between G. aculeatus and P. pungitius were high, while both had low food and habitat overlaps in relation to P. microps. Interactions between G. aculeatus and P. pungitius were probably influenced by more severe abiotic conditions in one habitat, which caused lower abundances there, and higher abundances in the other two habitats. In October no interactions were observed. These results indicate that competition for food at least temporarily determines the species distribution in a temperate estuary, and that estuarine fish populations are sometimes food limited.  相似文献   

Analysis on the Circulation of the Yangtze River Estuary Based on ADCP Measurements     

严以新陶爱峰  于东生杨金艳 《中国海洋工程》2007,21(3):485-494

According to analysis on field data obtained by ADCP(Acoustic Doppler Current Profiler),the flow regime of the Yangtze River Estuary is studied by use of a 3-D numerical model.The flow field characteristics,under the influence of Coriolis force,saltwater intrusion and freshwater inflow and tidal current interaction,are depicted in details.The main driving forces and some important effective factors of lateral,longitudinal and horizontal circulation are also analyzed.  相似文献   

Fortnightly shifts of intrusion depth of oceanic water into Ise Bay     

Akihide?KasaiEmail author  Tateki?Fujiwara  Takuma?Kimura  Hirokatsu?Yamada 《Journal of Oceanography》2004,60(5):817-824

To clarify the time change in water exchanges between Ise Bay and the adjacent ocean, repeated hydrographic observations were conducted along the longitudinal section in Ise Bay. The results show that the mixing condition at the bay mouth (Irago Strait) changed fortnightly in summer. During the spring tides, the strait water below the pycnocline was well-mixed and nearly homogeneous. By contrast, it was weakly stratified during the neap tide. There is a strong negative correlation between the tidal range and the density difference between the upper and lower layers at the strait. In summer, the intrusion depth of oceanic water into the bay and consequent hydrographic conditions inside the bay changed frequently according to the tidal strength. During the spring tides a prominent bottom front was created at the bay mouth, indicating that the strait water, which is a mixture of oceanic and bay waters, intruded through the middle layer. On the other hand, during the neaps, cold and saline oceanic water intruded through the bottom layer into the bay. The intrusion depth is significantly correlated with the tidal range. It is considered that the wellmixed strait water, which has a density equivalent to the middle layer inside the bay, is lighter than the bottom bay water and thus intrudes through the middle layer during the spring tides, while insufficient mixing makes the bottom water at the strait heavier than the bay water, leading to the bottom intrusion during the neap tides.  相似文献   

河口水与污水混合有机物和磷的转移动力学     

陈松  廖文卓 《台湾海峡》1997,16(4):409-414

污水与九龙江河口水混合研究表明，ＣＯＤ的降解符合一级动力学模式，降解速率常数ｋ在０．０４－０．１１ｄ＾－１之间，水体有机物的转移以降解作用为主；两种水体混合时，先产生磷的吸附，后释放，整个过程表现为颗业磷向溶解无机磷的转移。  相似文献   

Spatial dynamics of estuarine water surface temperature from airborne remote sensing     

Richard D. Hedger  Tim J. Malthus  Andrew M. Folkard  Peter M. Atkinson 《Estuarine, Coastal and Shelf Science》2007,71(3-4):608-615

This paper examines the applicability of airborne remote sensing to the characterization and quantification of the spatial dynamics of water surface temperature (WST) within estuaries. For this, a series of successive airborne Thematic Mapper thermal images was acquired of Kirkcudbright Bay, an estuary in the United Kingdom, on two dates. Spatial dynamics were determined by two techniques: (1) qualitatively, which involved interpreting features ‘by eye’; and (2) by the velocimetric technique of maximum cross correlation (MCC). Qualitatively, complex spatial dynamics were identified over a wide range of spatial and temporal scales, associated with the creation and dissipation of eddies, and the convergence and divergence of fronts, all of which were superimposed on the synoptic tidal flow. MCC was effective for producing synoptic velocity fields, but the minimum cell size was constrained by image noise, limiting the ability to analyze small-scale spatial dynamics. The effectiveness of MCC was related to the ratio of spatially correlated variance to spatially independent variance, as estimated from the variogram. Suggestions for optimizing the application of airborne remote sensing to estuarine spatial dynamics are presented.  相似文献   

河口水Cu²⁺, Zn²⁺的分析、形式、分布、毒性与生态环境   总被引：4，自引：1，他引：4  

顾宏堪 《海洋与湖沼》1996,27(3):336-339

生物毒性实验Ｃｕ＾２＋，Ｚｎ＾２＋等浓度与生物死亡率相关模式表明，海水中加入的Ｃｕ＾２＋，Ｚｎ＾２＋等浓度逐渐增高，生物死主恨率相应增高，同一浓度下，死亡率随时间（２４，４８，７２，９６ｈ）的增加逐步增高，实验加入Ｃｕ＾２＋仅１μｇ／Ｌ和Ｚｎ＾２＋仅５μｇ／Ｌ本底浓度时，其毒性即已开始遵循相关模式。因此，比天然水含量仅高１，２倍的Ｃｕ＾２＋，Ｚｎ＾２＋离子的污染及毒性，就足以破坏鱼虾在河口的产卵，  相似文献