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1.
Manganese and iron distributions off central California influenced by upwelling and shelf width 总被引:4,自引:1,他引:4
Zanna Chase Kenneth S. Johnson Virginia A. Elrod Joshua N. Plant Steve E. Fitzwater Lisa Pickell Carol M. Sakamoto 《Marine Chemistry》2005,95(3-4):235-254
In July 2002, a combination of underway mapping and discrete profiles revealed significant along-shore variability in the concentrations of manganese and iron in the vicinity of Monterey Bay, California. Both metals had lower concentrations in surface waters south of Monterey Bay, where the shelf is about 2.5 km wide, than north of Monterey Bay, where the shelf is about 10 km wide. During non-upwelling conditions over the northern broad shelf, dissolvable iron concentrations measured underway in surface waters reached 3.5 nmol L−1 and dissolved manganese reached 25 nmol L−1. In contrast, during non-upwelling conditions over the southern narrow shelf, dissolvable iron concentrations in surface waters were less than 1 nmol L−1 and dissolved manganese concentrations were less than 5 nmol L−1. A pair of vertical profiles at 1000 m water depth collected during an upwelling event showed dissolved manganese concentrations of 10 decreasing to 2 nmol L−1, and dissolvable iron concentrations of 12–20 nmol L−1 in the upper 100 m in the north, compared to 3.5–2 nmol L−1 Mn and 0.6 nmol L−1 Fe in the upper 100 m in the south, suggesting the effect of shelf width influences the chemistry of waters beyond the shelf.These observations are consistent with current understanding of the mechanism of iron supply to coastal upwelling systems: Iron from shelf sediments, predominantly associated with particles greater than 20 μm, is brought to the surface during upwelling conditions. We hypothesize that manganese oxides are brought to the surface with upwelling and are then reduced to dissolved manganese, perhaps by photoreduction, following a lag after upwelling.Greater phytoplankton biomass, primary productivity, and nutrient drawdown were observed over the broad shelf, consistent with the greater supply of iron. Incubation experiments conducted 20 km offshore in both regions, during a period of wind relaxation, confirm the potential of these sites to become limited by iron. There was no additional growth response when copper, manganese or cobalt was added in addition to iron. The growth response of surface water incubated with bottom sediment (4 nmol L−1 dissolvable Fe) was slightly greater than in control incubations, but less than in the presence of 4 nmol L−1 dissolved iron. This may indicate that dissolvable iron is not as bioavailable as dissolved iron, although the influence of additional inhibitory elements in the sediment cannot be ruled out. 相似文献
2.
Aquatic surface microlayer contamination in chesapeake bay 总被引:1,自引:0,他引:1
John T. Hardy Eric A. Crecelius Liam D. Antrim Steven L. Kiesser Virginia L. Broadhurst 《Marine Chemistry》1990,28(4)
The aquatic surface microlayer (SMIC), 50 μm thick, serves as a concentration point for metal and organic contaminants that have low water solubility or are associated with floatable particles. Also, the eggs and larvae of many fish and shellfish species float on, or come in contact with, the water surface throughout their early development. The objectives of this study were (1) to determine the present degree of aquatic surface microlayer pollution at selected sites in Chesapeake Bay, and (2) to provide a preliminary evaluation of sources contributing to any observed contamination.Twelve stations located in urban bays, major rivers, and the north central bay were sampled three times, each at 5-day intervals during May 1986. Samples of 1.4–4.1 each were collected from the upper 30–60-μm water surface (surface microlayer, SMIC) using a Teflon-coated rotating drum microlayer sampler. One sample of subsurface water was collected in the central bay.At all stations, concentrations of metals, alkanes, and aromatic hydrocarbons in the SMIC were high compared with one bulk-water sample and with typical concentrations in water of Chesapeake Bay and elsewhere. SMIC contamination varied greatly among the three sampling times, but high mean contaminant levels (total polycyclic aromatic hydrocarbons, 1.9–6.2 μg 1−1; Pb, 4.9–24 μg 1−1; Cu, 4–16 μg 1−1; and Zn, 34–59 μg 1−1) were found at the upper Potomac and northern bay sites. Three separate areas were identified on the basis of relative concentrations of different aromatic hydrocarbons in SMIC samples - the northern bay, the Potomac River, and the cleaner southern and eastern portions of the sampling area.Suspected sources of surface contamination include gasoline and diesel fuel combustion, coal combustion, and petroleum product releases. Concentrations of metals and hydrocarbons, at approximately half the stations sampled, are sufficient to pose a threat to the reproductive stages of some fish and shellfish. Sampling and analysis of the surface microlayer provides a sensitive tool for source identification and monitoring of potentially harmful aquatic pollution. 相似文献
3.
Climate change impacts on U.S. Coastal and Marine Ecosystems 总被引:1,自引:0,他引:1
Donald Scavia John C. Field Donald F. Boesch Robert W. Buddemeier Virginia Burkett Daniel R. Cayan Michael Fogarty Mark A. Harwell Robert W. Howarth Curt Mason Denise J. Reed Thomas C. Royer Asbury H. Sallenger James G. Titus 《Estuaries and Coasts》2002,25(2):149-164
Increases in concentrations of greenhouse gases projected for the 21st century are expected to lead to increased mean global air and ocean temperatures. The National Assessment of Potential Consequences of Climate Variability and Change (NAST 2001) was based on a series of regional and sector assessments. This paper is a summary of the coastal and marine resources sector review of potential impacts on shorelines, estuaries, coastal wetlands, coral reefs, and ocean margin ecosystems. The assessment considered the impacts of several key drivers of climate change: sea level change; alterations in precipitation patterns and subsequent delivery of freshwater, nutrients, and sediment; increased ocean temperature; alterations in circulation patterns; changes in frequency and intensity of coastal storms; and increased levels of atmospheric CO2. Increasing rates of sea-level rise and intensity and frequency of coastal storms and hurricanes over the next decades will increase threats to shorelines, wetlands, and coastal development. Estuarine productivity will change in response to alteration in the timing and amount of freshwater, nutrients, and sediment delivery. Higher water temperatures and changes in freshwater delivery will alter estuarine stratification, residence time, and eutrophication. Increased ocean temperatures are expected to increase coral bleaching and higher CO2 levels may reduce coral calcification, making it more difficult for corals to recover from other disturbances, and inhibiting poleward shifts. Ocean warming is expected to cause poleward shifts in the ranges of many other organisms, including commercial species, and these shifts may have secondary effects on their predators and prey. Although these potential impacts of climate change and variability will vary from system to system, it is important to recognize that they will be superimposed upon, and in many cases intensify, other ecosystem stresses (pollution, harvesting, habitat destruction, invasive species, land and resource use, extreme natural events), which may lead to more significant consequences. 相似文献
4.
Edward A. Parson Robert W. Corell Eric J. Barron Virginia Burkett Anthony Janetos Linda Joyce Thomas R. Karl Michael C. MacCracken Jerry Melillo M. Granger Morgan David S. Schimel Thomas Wilbanks 《Climatic change》2003,57(1-2):9-42
Based on the experience of the U.S. National Assessment, we propose a program of research and analysis to advance capability for assessment of climate impacts, vulnerabilities, and adaptation options. We identify specific priorities for scientific research on the responses of ecological and socioeconomic systems to climate and other stresses; for improvement in the climatic inputs to impact assessments; and for further development of assessment methods to improve their practical utility to decision-makers. Finally, we propose a new institutional model for assessment, based principally on regional efforts that integrate observations, research, data, applications, and assessment on climate and linked environmental-change issues. The proposed program will require effective collaboration between scientists, resource managers, and other stakeholders, all of whose expertise is needed to define and prioritize key regional issues, characterize relevant uncertainties, and assess potential responses. While both scientifically and organizationally challenging, such an integrated program holds the best promise of advancing our capacity to manage resources and the economy adaptively under a changing climate. 相似文献
5.
Stanley W. Trimble 《Environmental Geology》1997,32(3):230-234
A significant proportion of stream sediment yield in North America comes from stream channel and bank erosion. One method
used for stream stabilization is the bank installation of timber and stone fish-shelter structures, but there is little evidence
for their potential effectiveness. Nine to nineteen years of precise survey data from Coon Creek, Wisconsin, however, show
that fish structures enhance sediment deposition along the stream and may retard lateral migration of channels. Such structures
have greater utility for sediment control when streams are eroding away a high bank and replacing it with a lower bank.
Received: 18 October 1996 · Accepted: 4 February 1997 相似文献
6.
V. Trimble 《Astronomische Nachrichten》1987,308(6):343-347
The distribution of mass ratios for a sample of common proper motion (CPM) binaries is determined and compared with that of 798 visual binaries (VB's) studied earlier, in hopes of answering the question: Can the member stars of these systems have been drawn at random from the normal initial mass function for single stars? The observed distributions peak strongly toward q = 1·0 for both kinds of systems, but less strongly for the CPM's than for the VB's. Due allowance having been made for assorted observational selection effects, it seems quite probable that the CPM's represent the observed part of a population drawn at random from the normal IMF, while the VB's are much more difficult to interpret that way and could, perhaps, result from a formation mechanism that somewhat favors systems with roughly equal components. 相似文献
7.
An assessment of developing eutrophic conditions in small temperate lagoons along the coast of Rhode Island suggests that in such shallow, macrophyte based systems the response to nutrient enrichment differs from that described for plankton based systems. The nitrogen loadings per unit area of the salt ponds are 240–770 mmol N per m2 per year. Instead of the high nutrient concentrations, increased phytoplankton biomass and turbidity, leading to eventual loss of benthic macrophytes described for such systems as the Chesapeake, Patuxent and Appalachicola Bay, nutrient enrichment of the Rhode Island lagoons has led to increased growth of marine macroalgae. The increased macroalgal growth appears to alter the benthic habitat and a shift from a grazing to detrital food chain appears to be impacting important shellfisheries. As more extensive areas of organic sediments develop, geochemical cycling changes, resulting in higher rates of nitrogen remineralization and accelerated eutrophication. The major sources of nitrogen inputs to the salt ponds have been identified and a series of management initiatives have been designed to limit inputs from present and potential development within the watersheds of the lagoons. 相似文献
8.
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10.
Jennifer L. Ruesink Alan C. Trimble Helen Berry Amy G. Sprenger Megan N. Dethier 《Estuaries and Coasts》2014,37(1):149-159
Production and resource use by intertidal taxa were studied in the estuarine fjord of Puget Sound, Washington, USA. Along nearly 100 km, salinity is similar, and intertidal habitat and immersion time were kept consistent, thus allowing a focus on other environmental variables such as temperature and resource availability that could influence growth. Primary producers (ulvoid and fucoid macroalgae) and suspension feeders (oysters and barnacles) were transplanted on three beaches in each of three regions and assessed for individual-level growth, carbon and nitrogen ratios, and stable isotopes. In most transplants, δ13C and C/N showed no regional variation but δ15N was enriched up-estuary. Among environmental variables, chlorophyll a, total suspended solids, and particulate organic matter had small and/or inconsistent regional variation, but temperature was higher up-estuary. For the most intensively studied species (Pacific oyster, Crassostrea gigas) transplanted four times over 2 years, seasonal and regional variation in growth were best predicted by temperature rather than resource availability. Growth rates continued to increase into Totten Inlet, a shallow finger inlet at the head of Puget Sound. As indicators of environmental conditions, the growth and tissue chemistry of intertidal study taxa affirm that sources and amounts of resources show no strong gradients along this estuarine fjord, and they also support temperature as a key factor for performance, with species-specific responses. Higher temperatures may also have community-level impacts, given prior evidence linking beach temperatures to reduced intertidal diversity and biomass into Puget Sound. 相似文献