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1.
AWAPer: An R package for area weighted catchment daily meteorological data anywhere within Australia
Meteorological time-series data are a fundamental input to hydrological investigations. But sourcing data is often laborious and plagued with difficulties. In an effort to improve efficiency and rigor we present an R-package, named AWAPer ( https://github.com/peterson-tim-j/AWAPer ), for the efficient estimation of daily area weighted catchment average and spatial variance of meteorological variables, including evapotranspiration. The package allows creation and updating of a data-cube of gridded daily data from 1900 onwards. Once created, point and area weighted estimates can be extracted at user-defined locations and time periods for anywhere within Australia. Examples of point and catchment average extraction are presented. 相似文献
2.
Analyses (n = 525) of chloride (Cl−), bromide (Br−), nitrate as nitrogen (NO3-N), sodium (Na+), calcium (Ca2+) and potassium (K+) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl− originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl− concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl− concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl− to Br− (p = .045), to NO3-N (p < .0001), to Ca2+ (p < .0001), and to Na+ (p < .0001) to be significantly different between urban and agricultural waters. While Cl− ratios indicate that road salt was the dominant source of Cl− in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl− dynamics; however, agricultural practices contributed Cl− year-round, elevating stream base flow Cl− concentrations above the background level. 相似文献
3.
Charles C. Wall Bradley J. Peterson Christopher J. Gobler 《Estuaries and Coasts》2011,34(6):1262-1277
While many coastal ecosystems previously supported high densities of seagrass and abundant bivalves, the impacts of overfishing,
eutrophication, harmful algal blooms, and habitat loss have collectively contributed to the decline of these important resources.
Despite improvements in wastewater treatment in some watersheds and subsequent reduced nutrient loading to neighboring estuaries,
seagrass and bivalve populations in these locations have generally not recovered. We performed three mesocosm experiments
to simultaneously examine the contrasting effects of nutrient loading and historic suspension-feeding bivalve densities on
the growth of eelgrass (Zostera marina), juvenile bivalves (northern quahogs, Mercenaria mercenaria; eastern oysters, Crassostrea virginica; and bay scallops, Argopecten irradians), and juvenile planktivorous fish (sheepshead minnow, Cyprinodon variegatus). High nutrient loading rates led to significantly higher phytoplankton (chlorophyll a) levels in all experiments, significantly increased growth of juvenile bivalves relative to controls with lower nutrient
loading rates in two experiments, and significantly reduced the growth of eelgrass in one experiment. The filtration provided
by adult suspension feeders (M. mercenaria and C. virginica) significantly decreased phytoplankton levels in all experiments, significantly increased light penetration and the growth
of eelgrass in one experiment, and significantly decreased the growth of juvenile bivalves and fish in two experiments, all
relative to controls with no filtration from adult suspension feeders. These results demonstrate that an appropriate level
of nutrient loading can have a positive effect on some estuarine resources and that bivalve filtration can mediate the effects
of nutrient loading to the benefit or detriment of different estuarine resources. Future ecosystem-based approaches will need
to simultaneously account for anthropogenic nutrient loading and bivalve restoration to successfully manage estuarine resources. 相似文献
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Clint C. Muhlfeld J. Joseph Giersch F. Richard Hauer Gregory T. Pederson Gordon Luikart Douglas P. Peterson Christopher C. Downs Daniel B. Fagre 《Climatic change》2011,106(2):337-345
Climate warming in the mid- to high-latitudes and high-elevation mountainous regions is occurring more rapidly than anywhere
else on Earth, causing extensive loss of glaciers and snowpack. However, little is known about the effects of climate change
on alpine stream biota, especially invertebrates. Here, we show a strong linkage between regional climate change and the fundamental
niche of a rare aquatic invertebrate—the meltwater stonefly Lednia tumana—endemic to Waterton-Glacier International Peace Park, Canada and USA. L. tumana has been petitioned for listing under the U.S. Endangered Species Act due to climate-change-induced glacier loss, yet little
is known on specifically how climate impacts may threaten this rare species and many other enigmatic alpine aquatic species
worldwide. During 14 years of research, we documented that L. tumana inhabits a narrow distribution, restricted to short sections (~500 m) of cold, alpine streams directly below glaciers, permanent
snowfields, and springs. Our simulation models suggest that climate change threatens the potential future distribution of
these sensitive habitats and the persistence of L. tumana through the loss of glaciers and snowfields. Mountaintop aquatic invertebrates are ideal early warning indicators of climate
warming in mountain ecosystems. Research on alpine invertebrates is urgently needed to avoid extinctions and ecosystem change. 相似文献
7.
Melissa M. Foley Benjamin S. Halpern Fiorenza Micheli Matthew H. Armsby Margaret R. Caldwell Caitlin M. Crain Erin Prahler Nicole Rohr Deborah Sivas Michael W. Beck Mark H. Carr Larry B. Crowder J. Emmett Duffy Sally D. Hacker Karen L. McLeod Stephen R. Palumbi Charles H. Peterson Helen M. Regan Mary H. Ruckelshaus Paul A. Sandifer Robert S. Steneck 《Marine Policy》2010
The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP—maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity—and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits. 相似文献
8.
Abstract Forecast ice drift rates and thicknesses displayed on daily ice charts and forecast winds for the Canadian east coast are compared to on‐ice observations made during the second Canadian Atlantic Storm Program (CASP II) of March 1992. Observed and 24‐hour forecasts of daily ice drift rates were weakly correlated even though long‐term means closely matched observations. Daily drift rates have an RMS error of 13 cm s‐1 relative to a 15 cm s‐1 mean in addition to an RMS direction error of 50 degrees. Contributions towards daily drift uncertainties were: the estimation of winds, unmodelled physics of ocean and ice cover processes; and the inconsistency in the methods used by the ice forecaster. Correlation coefficients between forecast winds and on‐ice observed winds decreased from 0.8 at 0‐hour to 0.7 for the 30‐hour forecast. Similar results were found between ice drift rates from forecast winds. Histograms of ice thicknesses observed along narrow swaths using a helicopter‐towed electromagnetic sensor compared well with undeformed ice thicknesses representing large areas on ice charts, with differences mainly caused by difference in ice type representation and by co‐registering the two data sets. 相似文献
9.
Ingrid Peterson 《大气与海洋》2013,51(4):402-415
Abstract Ice floes along the Labrador Coast were tracked using visible NOAA satellite images on two consecutive days (26 and 27 April, 1984) when the ice‐pack extended beyond the Labrador Current, and winds were weak. The resulting “snapshot” of the velocity field reveals strong topographic steering of the Labrador Current, such that the current speed and width in different areas are dependent on the steepness of the continental slope, and the current deflects into and out of Hopedale Saddle. Between 55 and 58°N, the main core of the current is 60–90 km wide, with speeds of 30–55 cm s?1. The overall circulation pattern is in good agreement with historical water mass analyses over the shelf and slope, and with estimates of the speed of the Labrador Current obtained by other methods. 相似文献
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