Seagrass landscapes and their effects on associated fauna: A review   总被引：1，自引：2，他引：1  

Christoffer Bostrm  Emma L. Jackson  Charles A. Simenstad 《Estuarine, Coastal and Shelf Science》2006,68(3-4):383

Seagrasses comprise some of the most heterogeneous landscape structures of shallow-water estuarine/marine ecosystems in the world. However, while knowledge at the molecular, organism, patch and community scale is pervasive, understanding of seagrass landscape ecology is more fragmentary and has not been synthesized. The growth and recruitment dynamics of seagrasses as well as man-made and/or natural disturbances create complex spatial configurations of seagrass over broad (metres to kilometres) spatial scales. Hence, it is important to identify mechanisms maintaining and/or threatening the diversity-promoting function of seagrass meadows and to understand their effects on benthic populations and communities. Although landscape ecology has recently become more integrated into seagrass research, our understanding of animal responses to variability in seagrass landscape structure is still fragmentary. By reviewing the literature to date, this paper evaluates studies on seagrass landscape ecology, testing the general null hypothesis that concepts developed in terrestrial settings can be generalized across landscapes, and (a) presenting definitions and terms used in seagrass landscape ecology, (b) reviewing geographical patterns of seagrass landscape studies to identify possible key regions and target species, (c) evaluating different methodological approaches, (d) describing the spatial and temporal scales used to describe organism responses to seagrass landscape structure, and (e) placing seagrass landscapes into an applied context.  相似文献   

Expendable ampoules for oxygen determination     

Bertil strm 《Marine Chemistry》1973,1(4):323-327

A new technique for adding Winkler reagents to water samples at sea has been developed. Expendable ampoules containing the reagents replace syringes or pipettes. The main features of the ampoules are simpler handling and safer sampling with preserved accuracy.  相似文献   

Buchbesprechungen     

F. Steinhauser  J. Drimmel  P. Steinhauser  W. Mörikofer 《Meteorology and Atmospheric Physics》1967,16(2-3):273-280

Ohne Zusammenfassung  相似文献   

On lipid surface films on the sea. I. A simple method for sampling and studies of composition     

Kåre Larsson  Göran Odham  Anders Södergren 《Marine Chemistry》1974,2(1):49-57

A method for collection of surface films on the sea has been developed and tested at various places along the Swedish West Coast. Considerable amounts of lipids on the sea surface were found even when no seaslicks were observed. Triglycerides, free fatty acids, and wax esters are the dominating constituents, and there are characteristic deviations in the fatty-acid patterns compared to the corresponding lipids dissolved in the sub-surface water. Organochlorine residues, phthalic acid esters and heavy metals also occur in considerable amounts.  相似文献   

Disorder and recovery of environmental health monitored by means of lysosomal stability in liver of European flounder (Platichthys flesus L.)     

Broeg K  Köhler A  Westernhagen Hv 《Marine environmental research》2002,54(3-5):569-573

From 1995 to 2000 biological effects were studied in liver of flounder (Platichtysflesus L.) from the German Bight. During the study period deleterious consequences of acute discharges of DDT and PCBs in early spring 1996 and after 1998 due to remobilization of contaminants from riverbed deepening of the River Elbe became evident. As core biomarker which reflects toxically induced liver pathologies and integrates effects of various classes of pollutants we measured the integrity of lysosomal membranes in individual flounder liver. During the study period, twice statistically significant disturbances of lysosomal function was detected in fish from the River Elbe: in summer 1996 and in spring 1999. Yet, the detrimental contaminant effects were not only restricted to individuals from the Elbe but expanded to those flounder inhabiting formerly less polluted reference areas. In contrast to flounder of the Elbe, their ability to recover from the lysosomal disorders were limited. While in autumn 2000 Elbe individuals showed clear signs of recovery, those fish caught in areas more distant to the source of toxicant input still maintained significantly decreased lysosomal membrane integrity. It can be speculated that fish populations which are not continuously exposed to chronic anthropogenic stress may have a lower potential or need a longer period to recover from the effects of pollution.  相似文献   

Sedimentological parameters and erosion behaviour of submarine coastal sediments in the south-western Baltic Sea   总被引：9，自引：0，他引：9  

Kai Ziervogel  Björn Bohling 《Geo-Marine Letters》2003,23(1):43-52

The aim of this study was to evaluate the erodibility of submarine coastal sediments for the purpose of modelling sediment dynamics in Mecklenburg Bay, south-western Baltic Sea. Erosion thresholds derived from experiments with a device microcosm on cores of fine sand (n=5, mean grain size=132 µm) and mud (n=5, medium silt size, mean=21 µm), collected at different times of the year, were compared to theoretical critical shear stress velocities based on grain-size measurements. For this purpose, a sedimentological map of natural surface sediments was constructed for the study area. Calculated values for critical shear stress velocities (u* _{cr-Hjulström} ) are 1.2 cm s^?1 for fine sand, and 3.75 cm s^?1 for cohesive mud. At the mud station, erosion experiments showed an initial transport of the fluffy surface layer (u* _cr-initial ) at a mean critical shear stress velocity of 0.39 cm s^?1. Initial rolling transport at the fine sand station for single sand grains was recorded at values of 0.5 cm s^?1. At higher shear stress velocities, the two sediment types showed diverging erosion behaviour. Measurable erosion (ε>5.0×10^?6 kg m^?2 s^?1) of fine sand starts at a mean critical shear stress velocity (u* _cr-erosion ) of 1.15 cm s^?1 whereas fluffy surface material on mud cores was eroded at mean u* _cr-erosion of 0.62 cm s^?1. This indicates that measured erosion thresholds at the fine sand site fit well to calculated critical shear stress velocities whereas calculated erosion thresholds for cohesive mud are roughly 6 times higher than measured values. As erosion behaviour at the mud station was dominated by fluffy surface material, the comparability of measured and calculated threshold values may be reduced. The underlying silt-sized sediment itself was stable due to cohesive effects. This behaviour has to be taken into consideration by using sediment types instead of mean grain sizes for mapping and modelling sediment dynamics. A comparison of the near-bottom hydrodynamic conditions in the study area and experimentally derived critical shear stress velocities suggests that particle transport is controlled by storm events whereas under calm conditions shear stress velocities do not exceed the critical values.  相似文献   

Magmatic evolution of the Easter microplate-Crough Seamount region (South East Pacific)     

Roger Hekinian  Peter Stoffers  Dietrich Akermand  Nicolas Binard  Jean Francheteau  Colin Devey  Dieter Garbe-Schönberg 《Marine Geophysical Researches》1995,17(4):375-397

The Easter microplate-Crough Seamount region located between 25° S–116° W and 25° S–122° W consists of a chain of seamounts forming isolated volcanoes and elongated (100–200 km in length) en echelon volcanic ridges oriented obliquely NE (N 065°), to the present day general spreading direction (N 100°) of the Pacific-Nazca plates. The extension of this seamount chain into the southwestern edge of the Easter microplate near 26°30 S–115° W was surveyed and sampled. The southern boundary including the Orongo fracture zone and other shallow ridges (< 2000 m high) bounding the Southwest Rift of the microplate consists of fault scarps where pillow lava, dolerite, and metabasalts are exposed. The degree of rock alternation inferred from palagonitization of glassy margins suggests that the volcanic ridges are as old as the shallow ridges bounding the Southwest Rift of the microplate. The volcanics found on the various structures west of the microplate consist of depleted (K/Ti < 0.1), transitional (K/Ti = 0.11–0.25) and enriched (K/Ti > 0.25) MORBs which are similar in composition to other more recent basalts from the Southwest and East Rifts spreading axes of the Easter microplate. Incompatible element ratios normalized to chondrite values [(Ce/Yb)_N = 1–2.5}, {(La/Sm)_N = 0.4–1.2} and {(Zr/Y)_N = 0.7–2.5} of the basalts are also similar to present day volcanism found in the Easter microplate. The volcanics from the Easter microplate-Crough region are unrelated to other known South Pacific intraplate magmatism (i.e. Society, Pitcairn, and Salas y Gomez Islands). Instead their range in incompatible element ratios is comparable to the submarine basalts from the recently investigated Ahu and Umu volcanic field (Easter hotspot) (Scientific Party SO80, 1993) and centered at about 80 km west of Easter Island. The oblique ridges and their associated seamounts are likely to represent ancient leaky transform faults created during the initial stage of the Easter microplate formation ( 5 Ma). It appears that volcanic activity on seamounts overlying the oblique volcanic ridges has continued during their westward drift from the microplate as shown by the presence of relatively fresh lava observed on one of these structures, namely the first Oblique Volcanic Ridge near 25° S–118° W at about 160 km west of the Easter microplate West Rift. Based on a reconstruction of the Easter microplate, it is suggested that the Crough seamount (< 800 m depth) was formed by earlier (7–10 Ma) hotspot magmatic activity which also created Easter Island.  相似文献   

Influence of magnesium on the ion-activity product of calcium and carbonate dissolved in seawater: A new approach     

P Möller  P.P Parekh 《Marine Chemistry》1975,3(1):63-77

The influence of Mg²⁺ ions on the ion-activity product of calcium and carbonate dissolved in seawater has been investigated. The present approach is based mainly on: (1) the preponderance of this element in the marine system; (2) the observations by Weyl (1965), Jansen and Kitano (1963), and more recently by Plummer and Mackenzie (1974) on the higher solubility of magnesian calcite relative to pure calcite; and (3) the inferences drawn from our laboratory studies on the Ca²⁺—Mg²⁺ ion-exchange behaviour on surfaces of pure calcite. From these considerations, the pK value corresponding to a calcite containing 12 mole% of MgCO, has been estimated to be 7.7± 0.1 at 20°C. This value has serious reflections on the extent of saturation of seawater with respect to calcium-carbonate polymorphs. The reassessed degree of carbonate saturation for an average warm-surface ocean turns out to be only between 1.0 and 2.2.  相似文献   

All washed up: spatial and temporal variation in the wash-up and fate of chondrichthyan egg cases along a section of the Garden Route,South Africa     

S Schmöle  M Brown 《African Journal of Marine Science》2020,42(2):141-149

Washed-up chondrichthyan egg cases were collected along three different sandy beaches around Plettenberg Bay, South Africa, between April 2016 and March 2017. GPS location was recorded upon collection, and, after being soaked in fresh water for 12 hours, egg cases were identified to species level. Additionally, boreholes, damage, biofouling and state of the hatchling slit were recorded. The hatching success of each egg case was inferred from these factors. Over the year, 6 996 egg cases of nine species were collected. Egg cases of the tiger catshark Halaelurus natalensis had the highest hatching rate at 70%. Egg cases of the leopard catshark Poroderma pantherinum had the highest predation rate at 57%. Season had no significant effect either on overall egg-case counts or on per-species counts. Location, however, significantly affected the overall egg-case counts, as well as per-species counts, with the exceptions of H. natalensis and the St Joseph Callorhinchus capensis. The results of this study provide insight into chondrichthyan species occurrence and spatial variation along a section of the Garden Route in the Western Cape Province and can act as a baseline for future research.  相似文献   

Geographical archives of the Institute for Regional Geography (Länderkunde) at Leipzig,Germany     

M. Linke  I. Hönsch 《GeoJournal》1992,26(2):223-228

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