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1.
Young-of-the-year spot,Leiostomus xanthurus, were sampled in Town Creek of North Inlet Estuary, South Carolina, with towed plankton nets, seines, and stationary block nets from February 14 to May 2, 1981. Age estimates obtained by analysis of daily growth increments in the sagittal otoliths showed that these fish hatched between late November 1980 and mid-February 1981. The youngest spot was estimated to be 60 days old, indicating a prolonged migration period from offshore spawning grounds. Age-length regressions permitted calculations of growth and estimates of age from standard length measurements. An increase in growth rate was observed with an increase in size of fish; however, growth of fish of equal sizes was lower in April and early May than in February and March. Age estimates suggested that the hatching period for young-of-the-year spot was concentrated between late November and mid-January. Recruitment of three separate cohorts into Town Creek occurred at approximately monthly intervals, and immigration of each cohort into the estuary took place approximately 2 months after its estimated date-of-hatch.  相似文献   

2.
Wetland delineation is commonly based on terrain unit, soil form, soil wetness and vegetation indicators which along with the shallow groundwater or proximate surface water are often absent in many ephemeral inland South African areas due to, for instance, prolonged dry periods (seasons to years) which mask these indicators, as well as disruption of surface materials due to construction, agricultural activities and field fires. Furthermore, many “wetlands” in South Africa comply with the four indicators, but the notable absent requirement for wetlands is missing, namely the shallow groundwater table, as many of these systems form in hillslope seeps, catenas or from perched water tables. A 200-m-long excavation through one such a system is being studied in Midrand (Gauteng, South Africa). The site is underlain by Lanseria Gneiss and is waterlogged after long and intense periods of intense rainfall. Frequent downslope soil profiling, horizon-specific laboratory analyses for grading and Atterberg Limits, X-Ray Diffraction and X-Ray Fluorescence Spectroscopy data are interpreted together with soil percolation tests to generate a conceptual model of the system. The results are discussed in terms of the need to consider these temporary systems that do not have a shallow groundwater table and that are not in direct contact with surface drainage features as a possible special type of wetlands, notably in arid regions where they play a very important role in biodiversity and should, therefore, be protected.  相似文献   

3.
The fish assemblages of two South Carolina estuarine tide pools located in the North Edisto River were sampled from June to October 1977, and during June and July 1978, by haul seine, lift net and channel net. The nekton was dominated numerically byFundulus heteroclitus, Leiostomus xanthurus, Menidia menidia andAnchoa mitchilli. Oyster reef areas were dominated numerically byGobiosoma bosci andF. heteroclitus. The relative abundance of tide pool fishes differs from deep water areas of the North Edisto River as described from otter trawls, but is similar to that described by others for South Carolina tidal creeks.  相似文献   

4.
Pasteurella multocida, the causative bacterium of avian cholera, was isolated from cultures of the liver and heart blood of a female, adult American oystercatcher (Haematopus palliatus) found dead on the Cape Romain National Wildlife Refuge, South Carolina, in May 1973. This is apparently the first record of avian cholera in the oystercatcher. Low levels of DDE were identified in tissues of the oystercatcher.  相似文献   

5.
Toxaphene concentrations in rainfall over a South Carolina salt marsh were monitored from 1976–1978. This insecticide is toxic to some organisms in the low μg/kg range and causes sublethal effects in the very low ng/kg range. Rainfall was sampled by both continuously exposed collectors and by collectors which were exposed only during actual precipitation. Toxaphene concentrations in individual rainstorms showed a high day-to-day variation, and in general were 10–100 times higher than PCB and DDT levels. Washout ratios for toxaphene were higher than those reported for other chlorinated hydrocarbons, but lower than those of trace metals. During and immediately following the summer use season, toxaphene levels in rain exceeded by several times those concentrations reported to produce bone damage to young fish in laboratory experiments. The estimated aerial input of toxaphene to the 26 km2 estuary was 1.2 kg over a 4-month period. Most of this input appeared to be due to rainfall rather than dry deposition. *** DIRECT SUPPORT *** A01BY010 00007  相似文献   

6.
The occurrence of corroded megacrysts and cumulates of olivine, clinopyroxene, orthopyroxene, plagioclase, ilmenite and apatite in near-saturated hawaiites from the mid-north coast of New South Wales point to the derivation of these hawaiites at elevated pressures. In an experimental study on one of these hawaiites under conditions ranging from 5–15 kb and 0–5% H2O, orthopyroxene was identified in only one run with 2% H2O at 1040° C and 6.5 kb. In this run it was associated with olivine, clinopyroxene and Fe-Ti oxide. The early appearance of plagioclase in the “dry” experimental runs and amphibole in runs with 5% H2O, indicates that the water content in the natural hawaiite was intermediate to these values. The near-duplication of the natural megacryst-cumulate assemblage suggests that the hawaiite host precipitated these phases at a depth of approximately 20–24 km, prior to rapid eruption to higher crustal levels.  相似文献   

7.
Juvenile spot,Leiostomus xanthurus (Pisces), were collected at 2-h intervals over two 48-h periods in a tidal creek in North Inlet, South Carolina, during July 1986. Gut fullness, dry gut contents weight as a percentage of fish wet weight, was measured to test the hypothesis that feeding intensity is randomly distributed through time. Spot were also collected and serially sacrificed from a holding tank to estimate their gut evacuation rate. Gut fullness was greatest during periods of ebb and high tides and was little affected by the amount of light available. Gut contents were evacuated at a rate of about 15% per hour in the laboratory, in close agreement with field emptying times of about 6 h from peak fullness to empty guts. A conservative estimate of daily ration for juvenile spot (19–42 mm standard length) was 4.5% of their live body weight per day. Studies of spot feeding ecology can be greatly affected by when fish are collected during the tidal cycle.  相似文献   

8.
The magnitude of sheet flow in a small South Carolina salt marsh was evaluated by comparing the storage curve for the basin based on topographic data with that based on current measurements in the main channel. The results indicate that on spring tides more than 50% of the volume of water that enters the basin enters as sheet flow over the grassy flats of the marsh. The current data also suggest that the actual storage curve may be a hysteresis loop with separate flood and ebb segments.  相似文献   

9.
Water samples have been taken daily at 1030 EST from three locations within North Inlet (South Carolina) since June of 1980 in order to evaluate the tidal, seasonal, and eventually annual variability in carbon concentrations within this system and generate hypotheses explaining the observed trends. Dissolved organic carbon (DOC) concentrations within North Inlet (South Carolina) vary inversely with salinity (r2=0.65), suggesting the main source of DOC in North Inlet is freshwater entering from the adjacent forested watershed. This assertion is supported by an observed decrease of tidal water salinity with the onset of streamflow. DOC variability is also associated with (1) groundwater advection and/or runoff and seepage from the marsh surface; (2) removal from tidal water via either physical sorption or biological uptake; (3) sampling location; and (4) origin of water mass. Particulate organic carbon (POC) concentrations vary seasonally, higher values found during the summer. POC variability is controlled by a series of physical and biological factors. Evidence suggests that in the smaller tidal creeks, POC concentrations are associated with (1) rain events scouring the marsh surface, (2) phytoplankton concentrations varying as a function of tidal stage, and (3) removal of particulate material from the marsh surface on the ebb tide. In the larger tidal creeks tidal water velocity appears to be the main factor influencing POC values.  相似文献   

10.
The uptake and release of materials by intertidal mussel beds were directly measured in two cultivated Dutch estuaries. Generally, chlorophylla, seston, and particulate organic carbon were taken up, while ammonium, orthophosphate, and silicate were released. The observed rates were higher than values computed from organismic observations and similar to those observed for intertidal oyster reefs in South Carolina. Specific estuarine material turnover rates varied from 1 week to 38 weeks when calculated with mussel bed fluxes. The fastest turnover rates were for chlorophylla and ammonium. These results support the idea that dense assemblages of bivalves are major components in the recycling of nutrients in estuaries.  相似文献   

11.
Sm-Nd geochronology may be used to bracket the age of metamorphism in rocks which are difficult to date by other methods. By coupling whole rock Sm-Nd analyses of the principal members of the South Harris Igneous Complex, with Sm-Nd mineral isochrons on two anothositic gabbros, the age of granulite facios metamorphism has been defined. Whole rock analyses of three pairs of closely spaced samples of the anorthosite give consistent ages averaging 2.18±0.06 Gyr, but in general the data from the anorthosite do not define an isochron as a result of variable contamination of the evolving magma chamber. Whole rock data on the tonalite indicate that it is younger than 2.06 Gyr; its mean TCHUR age is 1.86±0.05 Gyr. Garnet-pyroxene-amphibole-plagioclase mineral isochrons on two anorthosite samples give identical 1.87±0.04 Gyr ages which date cooling after the high pressure granulite facies metamorphism. Together with the tonalite whole rock data this defines the age of that metamorphism and confirms Dearnley's original assignment of an early Laxfordian age.  相似文献   

12.
During 1973 and 1974 seasonal abundance and mean total length of Atlantic croaker,Micropogonias undulatus, were investigated by otter trawl at 33 stations in South Carolina estuaries in relation to bottom salinity and temperature. Relative abundance of Atlantic croaker was measured by catch per unit effort at 3°C temperature intervals and 3‰ salinity intervals. Croaker occurred over a bottom temperature range of 9.0–31.4°C while occurring most abundantly in waters above 24.0°C. No significant correlation between size and temperature was found. Croaker were collected in salinities from 0.4 to 34.4‰. High correlations of size and salinity were evident in 1973 during winter (r=0.79), summer (r=0.82), and fall (r=0.94). In 1974, correlations were significant only during fall (r=0.76).  相似文献   

13.
Two-hundred eighty-one diamondback terrapins (195♂, 86♀) were captured in baited and unbaited crab pots during premolt crab capture studies in South Carolina. Sampling was conducted four consecutive days each week from mid April to mid November, 1979, in the Ashley River estuary, and daily from April to July, 1980 and 1981, in the Wando River estuary. Fifty-five percent of the total were captured in April, and 32% in May. Males outnumbered females 2.3∶1, but this ratio may reflect crab pot entrance bias which restricted entry of large females. Median plastron length of females was 121 mm (range 76–175) and that for males 100 mm. (range 79–128); only two male terrapins equalled or exceeded the minimum legal size limit of 127 mm. Few captured terrapins were drowned when crab pots were checked daily, and it is estimated that capture mortality amounted to 10%. Terrapin catch per baited crab pot averaged 0.16 daily in April and May. Incidental terrapin capture by 743 commercial crabbers (fiscal year 1982 numbers) in South Carolina during April and May was estimated at 2,853 daily, and mortality was estimated at 285. These estimates are exclusive of mortalities resulting from lost pots. The impact of crabbing activities is believed to pose no threat to the terrapin population at current levels of commercial terrapin harvest. Because female terrapins mature at the minimum legal size, no segment of the egg laying population is protected except seasonally. If direct harvest of terrapins ever approaches that of the early twentieth century, then it is recommended that legal size limits be changed to protect a segment of the mature female population.  相似文献   

14.
Mapping of the Southwestern Hesperian Massif (South Western Spain) has permitted the definition of two principal systems of wrench faults in conjugate directions, SW-NE and NNW-SSE. By their dimensions and their association with deep basic rocks, they may be considered as accidents which interest the entirety of the crust. The directions of these systems are enclosed in a scheme of late-Hercynian wrench faults produced in the dismantling of the Iberian Peninsula at the end of the orogenic Hercynian phases. According to these large lines of fracture it is possible to relate a) the areas of Mesozoic sedimentation, pre-Alpine distension, b) the reliefs of the Mesozoic covering of the interior of the Hesperic Massif, c) the reliefs and the tectonic basins of the interior of the Meseta and d) the possible evolution of the Iberian Plate with relation to the Bay of Biscay and the areas of Alpine compression of the meridional edge, Betic Chains.  相似文献   

15.
A suite of cordierite-bearing biotite-muscovite intrusive granites in the New England Batholith, New South Wales, outcrops over 3400 sq km and is the largest reported occurrence of granites of this type. Compositionally the granites are close to the low temperature minimum and display only limited chemical variation. The corundum-normative nature of the granites suggests a pelitic sedimentary parentage. Cordierite with an average 100 Mg/ Mg + Fe of 55 occurs as large tabular crystals and is considered to be a refractory phase brought up from the zone of partial melting. The presence of cordierite and the absence of garnet in these granites suggests a partial melting at a pressure maximum of 6 kb, equivalent to 22 km depth.  相似文献   

16.
Through the investigation of tropical cyclone (TC) characteristics related to climate change, this study found that the frequency of TCs occurring over the Western North Pacific has recently decreased slightly, while their average intensity has increased. The number of overall TCs that passed within the vicinity of South Korea has also been reduced, but the number of strong typhoons in the area, those with maximum wind speeds of more than 44 m/s, has significantly increased. These changes are closely related to the following phenomena. (1) The average genesis region of TCs that influence South Korea has moved eastward. Accordingly, the TCs tend to strengthen as they move westward for long distances along the Intertropical Convergence Zone (ITCZ) trade easterlies and the southern boundary of the North Pacific Subtropical High (NPSH). (2) The NPSH and Asia Monsoon trough, which are known to affect TC tracks, have extended to the northwest and southeast. This has caused TCs that travel to higher latitudes and curve back toward the Korean Peninsula to become more frequent. (3) TCs have approached the Korean Peninsula without hitting land. In addition, the sea surface temperature became higher than it was before. These factors have caused TCs to maintain their strength or become stronger than before.  相似文献   

17.
Three gear types were used to collect finfish species from several tributaries of the South Creek estuary near Aurora, North Carolina, to ascertain whether a man-initiated marsh and creek system resembled adjacent natural areas in finfish species composition and abundance. Project Area II was the man-initiated area constructed in 1983 as up-front mitigation by North Carolina Phosphate Corporation prior to its anticipated mining in the headwaters of nearby natural wetlands. Two creeks served as controls throughout the study: Drinkwater Creek and Jacks Creek. Otter trawls were used monthly from July 1984 through December 1988. Wegener rings were used in April, July, and October from 1984 through 1987. An experimental gill net was used monthly from June 1984 through 1985. A total of 48 finfish species was captured during the study; only 14 species (29.2%) were common among gear types. The species collected were mud sunfish, blueback herring, alewife American shad, striped anchovy, bay anchovy, inland silverside, American eel, silver perch, Atlantic menhaden, crevalle jack, common carp, spotted seatrout, weakfish, sheepshead minnow, gizzard shad, ladyfish, chain pickerel, banded killifish, mummichog, striped killifish, rainwater killifish, mosquitofish, naked goby, green goby, white catfish, brown bull-head, pinfish, longnose gar, green sunfish, pumpkinseed, bluegill, redear sunfish, spot, Atlantic croaker, largemouth bass, white perch, striped bass, striped mullet, white mullet, golden shiner, summer flounder, southern flounder, yellow perch, bluefish, Atlantic needlefish, hogchoker, andTilapia species. Abundance of finfish species was a function of gear type. Bay anchovy and spot represented about 85% of all fish in trawl samples. The remainder was comprised of 27 other species. In Wegener rings, five species—bay anchovy, menhaden, rainwater killifish, spot, and inland silverside—each represented over 10% of all fish collected. Croaker and striped mullet each comprised more than 5% of all fish collected in Wegener rings, but were present in substantial numbers only in 1985. Based on trawl samples, the total number of finfish collected from Project Area II during the period 1984–1988 was statistically similar to those collected from the control creeks; Wegener ring data analysis indicated significantly greater catches in Project Area II compared to the control creeks. Bay anchovy catches were not significantly different among the three creeks by either trawl or Wegener ring. The same result was true for Atlantic menhaden and southern flounder. The abundance of spot in trawl samples from Project Area II was significantly greater than for the control creeks; abundance in ring samples from Project Area II was statistically similar to Jacks Creek, but significantly higher than Drinkwater Creek. The number of Atlantic croaker in Project Area II trawl samples was significantly lower than for the cotnrol creeks. Wegener rings did not sample croaker effectively.  相似文献   

18.
Water volume discharge estimates were made at a sample cross-section of the Canary Creek salt marsh (Lewes, Delaware). To account for cross-sectional velocity variations, a dense spatial array of current meters was used. Simultaneous measurements were taken at hourly intervals over three complete tidal cycles. A practical method is presented whereby instantaneous average cross-sectional velocity, instantaneous cross-sectional discharge and tidal cycle discharge can be estimated from a dense current meter array, orideal data set. Based on theseideal estimates, it is shown that a simplified spatial array can be used to estimate water discharges within acceptable error limits. Instantaneous cross-sectional discharges and total tidal cycle discharges were estimated with uncertainties of ±11% and ±7%, respectively. To minimize errors when estimating material exchange between salt marshes and adjacent waters, it is suggested that a comprehensive assessment of cross-sectional lateral current velocity variations be conducted.  相似文献   

19.
The Condition Index [(dry meat weight)(100)/(internal cavity volume)] has been analyzed and compared in the American oyster,Crassostrea virginica, from two South Carolina estuaries, one of which was considered polluted by coliform bacteria standards. During the warmer months, oysters from the unpolluted habitat showed a consistently and significantly higher Condition Index. Best fit and power function regressions of Condition Index on total coliform bacteria levels conform with previously cited effects of pollutants on oysters. Condition Index droped markedly as the incidence of total coliforms increased toward levels of 100 per 100 ml of water. Our results and the known sensitivity of oysters to a spectrum of pollutants suggest that their condition could be used to monitor waterborne pollution in coastal zone areas.  相似文献   

20.
The Earth's stress field is composed of 4 sub-fields that are induced by
  1. the gravitational force (impacts, etc; geodynamic theories on the expansion or contraction of the globe);
  2. the centrifugal force of the spinning Earth (models on continental drift explaining the equatorial Alpine-Himalayan collisional mountain belt and longitudinally orientated rifts or oceans);
  3. thermal convection (plate tectonic model);
  4. tidal forces (extended plate tectonic model).
A standard global stress field results from a combination of these four sub-stress-fields. From the existence of six otherwise inexplicable geodynamic phenomena, it has to be concluded that the standard global stress field of the present can only be an instantaneous (still) photograph of a field that constantly migrates eastwards relative to the Earth's continents. This disclosure can be explained with an extended plate tectonic model, in which the Earth's surface is subdivided by the circum-Pacific ring of subduction zones, into a Pacific area and a continental or Pangaea area with intra-Pangaea oceans (Atlantic, Indian Ocean, etc.). The Pangaea area in turn is subdivided into a North Pangaea area and a South Pangaea area. Due to the off-centre rotation of the spinning Earth around the gravitational centre of the Earth-Moon (-Sun) system (tidal forces), the lower mantle, the Pacific basin, area or state (Pacific crust = lower mantle?), the remaining states that together with the Pacific state compose the Wilson Cycle of ocean opening and closing (Rift/Red Sea state, Atlantic state, Pacific state, Collision/Himalayas state), the ocean sequence of which is permanently arranged from E to W through 360° around the globe, and the standard global stress field as an expression of the Wilson Cycle, are constantly displaced eastwards relative to the upper mantle, the continents or the North and South Pangaea areas with Intra-Pangaea oceans, completing one full turn around the globe in 200 to 250 my (principle of hypocycloid gearing). The continents migrate westwards around the globe and around the Pacific basin in the N and S hemispheres, through sequences of plate tectonic settings of the Oceanic or Wilson Cycle that possess distinct regional stress fields as parts of the standars global stress field, or else the continents are subjected to eastward migrating sequences of settings with distinct regional stress fields as parts of the Wilson Cycle/standard global stress field. By rotations and N-S migrations of the individual continents dissected in all directions by groups of parallel structural planes (fracture systems) through the standard global stress field, the orientation of which is aligned with the spinning Earth's axis and equator and that constantly migrates eastwards relative to the continents, the amount and nature of stress (compression, tension, shearing) a given fracture system is subjected to is constantly altered and the tectonic activity may gradually be transferred from the system under consideration to another fracture system, with slightly different strike directions. Every 400 to 500 my or each Pangaea Cycle (two complete W-E/E-W displacements around the globe between the continents/Pangaea areas with Intra-Pangaea Oceans/upper mantle on the one side and the lower mantle/Pacific basin/ sequence of ocean states and local stress fields of the Wilson Cycle and the standard global stress field on the other) the inhomogeneous standard global stress field is reversed in the N-S direction. Any model proposing the long-time existence of extended lineaments or fracture systems that do not end at the margin of the respective continent or at an orogen/suture zone/former continental margin, in the event of being older than the respective orogenesis, but which cross the surrounding ocean or the younger orogen and continue in the neighbouring continents or former independent continents or even encompass the whole globe, and which puts foreward simultaneous tectonic activity along the whole length of such lineament or fracture system and proposes their longevity or permanent existence, contradicts the physical laws that are the foundation of plate tectonics and mobilism.  相似文献   

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