A Benthic Terrain Classification Scheme for American Samoa   总被引：2，自引：0，他引：2  

Emily R. Lundblad  Dawn J. Wright  Joyce Miller  Emily M. Larkin  Ronald Rinehart  David F. Naar  Brian T. Donahue  S. Miles Anderson  Tim Battista 《Marine Geodesy》2006,29(2):89-111

Coral reef ecosystems, the most varied on earth, continually face destruction from anthropogenic and natural threats. The U.S. Coral Reef Task Force seeks to characterize and map priority coral reef ecosystems in the U.S./Trust Territories by 2009. Building upon NOAA Biogeography shallow-water classifications based on Ikonos imagery, presented here are new methods, based on acoustic data, for classifying benthic terrain below 30 m, around Tutuila, American Samoa. The result is a new classification scheme for American Samoa that extends and improves the NOAA Biogeography scheme, which, although developed for Pacific island nations and territories, is only applicable to a maximum depth of 30 m, due to the limitations of satellite imagery. The scheme may be suitable for developing habitat maps pinpointing high biodiversity around coral reefs throughout the western Pacific.  相似文献   

Sedimentary framework of the modern Huanghe (Yellow River) delta   总被引：12，自引：0，他引：12  

B. D. Bornhold  Z. -S. Yang  G. H. Keller  D. B. Prior  W. J. Wiseman Jr.  Q. Wang  L. D. Wright  W. D. Xu  Z. Y. Zhuang 《Geo-Marine Letters》1986,6(2):77-83

The geometry, stratigraphy, and structure of recently deposited Huanghe (Yellow River) Delta sediments were examined by high resolution subbottom profiles and medium-penetration boomer profiles. The results indicate that the active (post-1976) subaqueous delta advances as a single thin localized lobe with a maximum thickness of only 15 m. Calculations of sediment volumes indicate that 90% or more of the sediment supplied by the Huanghe remains within 30 km of the mouth. Sediment on the delta platform near the mouth is fine sand; elsewhere silts and clays prevail.[/p]  相似文献   

Investigation of a eutrophic tidal basin: part 2nutrients and environmental aspects     

H. A. C. Montgomery  P. G. Soulsby  I. C. Hart  S. L. Wright 《Marine environmental research》1985,15(4):285-302

The eutrophication of Langstone Harbour, a large tidal basin, has been studied by statistically designed nutrient surveys. Rates of input of nutrients from the sea, from effluent discharges and from other sources, have been estimated. Sediment/water interactions have been shown to be important in the phosphate budget of the basin, but they are less important in the nitrogen budget. Deductions were made about the relative importance of the various inputs and processes affecting concentrations of nutrients in the water column.It is concluded that ecologically or aesthetically detrimental growths of macroalgae are unlikely to occur in Langstone Harbour in the foreseeable future and that the removal of nutrient inputs, formerly thought to be necessary, will not, in fact, be required.The principles of the experimental design and of interpreting the data are of general applicability to tidal waters where the ratio of natural to man-made inputs needs to be known, where eutrophication is, or is expected to become, a problem, or where the progressive accumulation of nutrients by recycling is suspected.  相似文献   

Numerical study of the relaxation of one-dimensional gravitational systems: A reply     

B. N. Miller  H. L. Wright  W. E. Stein 《Astrophysics and Space Science》1984,104(1):145-149

This paper is a response to Numerical Study of the Relaxation of One-Dimensional Gravitational Systems, by Luwelet al. (1984) hereafter referred to as (LSR). The subject of their work is a topic studied earlier by us (Wrightet al., 1982) hereafter referred to as (WMS). Each group has studied the dynamical evolution of this system by applying the Kolmogorov-Smirnov goodness of fit test to distributions of the density and velocity. The methods employed and conclusions reached by LSR concerning relaxation in this system are questioned. The earlier work of WMS is clarified.This article was scheduled to appear in the March issue ofAstrophysics and Space Science, along with the article Numerical Study of the Relaxation of One-Dimensional Gravitational Systems by Luwel, Severn, and Rousseeuw. Its Appearance in the September issue is due to an oversight at the time of making up the March issue.  相似文献   

Changes in growing season in the Northeastern United States     

Anthony J. Vega  Robert V. Rohli  Elina Wright 《自然地理学》2020,41(4):343-364

ABSTRACT

Changes in growing season length (GSL) are of concern for agricultural, phenological, economic, epidemiological, and bioclimatological reasons. This research identifies spatial and temporal changes over the last several decades in GSL, along with the day-of-year of the last spring freeze and first autumn freeze, for the northeastern United States – a region particularly susceptible to such changes due to the large population and intense economic activities. Results suggest that growing season has significantly increased in length since 1980 as compared to prior to 1980, and both spatial and temporal variation in GSL has decreased for the region over time. Changes to GSL for this region are driven more by a shift in the first autumn freeze date than the last spring freeze date. The areas of greatest increase in GSL in the pre- vs. post-1980 period tend to be in the high elevations, near large water bodies, and near the largest cities. Results will assist environmental planners as they prepare mitigation and adaptation strategies amid a changing environment.  相似文献   

CPOD successful in trial for detecting Māui dolphin outside harbours     

Andrew J. Wright  Nick Tregenza 《新西兰海洋与淡水研究杂志》2019,53(3):451-459

Critically endangered Māui dolphin (Cephalorhynchus hectori maui) are found exclusively off the west coast of New Zealand’s North Island. One important data gap troubling efforts to reduce the current unsustainable level of bycatch is the limited information on the offshore and alongshore limits of their range. Passive acoustic monitoring studies could address this data gap, but Māui dolphin habitat is dominated by a sandy substrate that can shift greatly in the strong local currents. In February 2016, a short pilot CPOD deployment was thus attempted as a first step to see if the equipment could be deployed and recovered in the area and if the data collected would be viable, with a second unit deployed inside a harbour for comparison with earlier TPOD data. The pilot was largely successful, and roughly 11% of all minutes in the core habitat location contained detections of clicks attributed to Māui dolphin. A visual inspection of the data suggests some trends with diel and tidal patterns. Further work of this type is thus recommended.  相似文献   

≥3700 Ma pre-metamorphic dolomite formed by microbial mediation in the Isua supracrustal belt (W. Greenland): Simple evidence for early life?     

Allen P. Nutman  Clark R.L. Friend  Vickie C. Bennett  David Wright  Marc D. Norman 《Precambrian Research》2010

Chemical (meta)sedimentary rocks in the amphibolite facies ≥3700 Ma Isua supracrustal belt (W. Greenland) are mostly strongly deformed, so there is only a small chance of the survival of features such as stromatolites or microfossils that would be direct proof of a ≥3700 Ma biosphere. Therefore the search for evidence of ≥3700 Ma life in Isua rocks has focused on chemical signatures, particularly C-isotopes. The new approach presented here is based on whole rock chemistry rather than isotopic signatures. Isua chemical sedimentary rocks have Ca–Mg–Fe bulk compositions that coincide with ferroan dolomite – siderite/Fe-oxide mixtures. Most have low Al₂O₃, TiO₂ contents (<0.5 and <0.05 wt% respectively) showing minimal contamination from terriginous materials. Identical seawater-like REE + Y shale-normalised trace element signatures with La, Ce, Eu and Y positive anomalies are found in magnetite-rich banded iron formation (BIF – such as the geochemical standard IF-G), dolomite-rich rocks and quartz–carbonate–calc-silicate rocks. Additionally from a rare, small area of low deformation in Isua, there are ∼3700 Ma pillow lava interstices consisting of quartz + tremolite + calcite derived from pre-metamorphic dolomite + silica. Thus the dolomite in the chemical sediments and the pillow interstice was part of the pre-metamorphic assemblage, and was deposited from seawater and/or low-temperature groundwater (as shown by the REE + Y chemistry). Therefore, at least some Isua carbonate rocks are sedimentary or diagenetic in origin rather than being formed by metasomatism at 600–500 °C as proposed by Rose et al. (1996. American Journal of Science 296, 1004–1044).  相似文献   

The use of local indicators of spatial association to improve LiDAR-derived predictions of potential amphibian breeding ponds     

James T. Julian  John A. Young  John W. Jones  Craig D. Snyder  C. Wayne Wright 《Journal of Geographical Systems》2009,11(1):89-106

We examined whether spatially explicit information improved models that use LiDAR return signal intensity to discriminate in-pond habitat from terrestrial habitat at 24 amphibian breeding ponds. The addition of Local Indicators of Spatial Association (LISA) to LiDAR return intensity data significantly improved predictive models at all ponds, reduced residual error by as much as 74%, and appeared to improve models by reducing classification errors associated with types of in-pond vegetation. We conclude that LISA statistics can help maximize the information content that can be extracted from time resolved LiDAR return data in models that predict the occurrence of small, seasonal ponds.   相似文献   

Numerical forward modelling of peritidal carbonate parasequence development: implications for outcrop interpretation     

P. M. Burgess  V. P. Wright  D. Emery 《Basin Research》2001,13(1):1-16

The mechanisms responsible for formation of peritidal parasequences have been a focus of debate between proponents of contrasting autocyclic and allocyclic models. To contribute to this debate a three‐dimensional numerical forward model of carbonate production, transport and deposition has been developed. Shallowing‐upward parasequences are produced in the model via carbonate island formation and progradation, with an element of self‐organization, and no external forcing. These autocyclic parasequences have characteristics comparable with peritidal parasequences observed in outcrop. Modelled parasequence thickness and duration depend primarily on subsidence rate and sediment transport rate, illustrating the significance of sediment flux in formation of peritidal parasequences. Adding an element of stochastic variation of sediment transport rate and transport path leads to formation of nonuniform‐thickness parasequences that generate Fischer plots showing apparent hierarchies similar to those often interpreted as evidence of eustatic forcing. The model results do not rule out allocylic mechanisms, but suggest that shoreline and island progradation are also plausible mechanisms to create variable‐thickness, shallowing‐upward peritidal parasequences and should be considered in interpretations of such strata.  相似文献   

Effect of salinity and temperature on survival and development of young zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels     

David A. Wright  Eileen M. Setzler-Hamilton  John A. Magee  Victor S. Kennedy  Stephen P. McIninch 《Estuaries and Coasts》1996,19(3):619-628

We reared larval zebra mussels,Dreissena polymorpha, and quagga mussels,D. bugensis, through and beyond metamorphosis (settlement) at salinities of 0–8‰. Juvenile zebra mussels gradually acclimated to 8‰ and 10‰ have been reared at these salinities for over 8 mo. Tolerance to both higher temperatures and higher salinities increases with larval age in both species (though zebra mussel embryos and larvae have a greater degree of salinity tolerance than quagga mussel embryos and larvae). Thus, only 6% of 3-day-old zebra mussel veligers survived after exposure to 4‰ for 8 additional days, whereas there was 22% survival of veligers placed in 4‰ at day 13 and grown to settlement 11 d later. Zebra mussel pediveligers, acclimated to increasing salinity in 2‰ increments beginning at day 23, continued to survive and grow in 8‰ after 5-mo exposure, though the growth rates of these juveniles were significantly less than those of juveniles reared in lower salinities. Quagga mussels did not metamorphose and settle as quickly as zebra mussel pediveligers. No quagga mussel pediveligers had settled before exposure to artificial fresh water (AFW), 2‰ 4‰, 6‰, and 8‰ on day 30. Percent settlement of these quagga mussel juveniles (based on 100% survival at the start of experiments on day 30) was 90% in AFW, 67% at 2‰, 69% at 4‰, 46% at 6‰, and 0.1% at 8‰.  相似文献