The paleolimnology of Haynes Lake, Oak Ridges Moraine, Ontario, Canada: documenting anthropogenic and climatic disturbances     

Melissa A. Watchorn  Paul B. Hamilton  R. Timothy Patterson 《Environmental Earth Sciences》2013,68(7):1823-1834

Haynes Lake is a small kettle lake located on the Oak Ridges Moraine, and is within the Greater metropolitan area of Toronto, Ontario; Canada’s most populous region. Lake sedimentation, flux rates, diatoms and thecamoebians extracted from a benthic core were used as biological proxies to evaluate changes in water quality through time as a function of anthropogenic activity and changing climate. There were two periods of disturbance to the Haynes Lake ecosystem from ca 8,500 years before present (YBP) through to ca A.D. 2003, which were significant enough to cause changes in lake sedimentation, the diatom flora, and thecamoebian fauna. The first disturbance was concomitant with the decline in global temperatures following the Hypsithermal Climate Optimum (ca. 4,700 YBP). The most significant disruption to Haynes Lake over the last 8,500 years, however, was the settlement of Europeans and subsequent urban development (ca. A.D. 1875), including the construction of a road immediately adjacent to the lake. Anthropogenic disturbance of inorganic clays in the recent paleosediment record (<5 cm) is indicative of more recent eutrophication events.  相似文献   

The importance of experiments: Constraints on chondrule formation models   总被引：1，自引：0，他引：1  

Steven J. DESCH  Melissa A. MORRIS  Harold C. CONNOLLY Jr.  Alan P. BOSS 《Meteoritics & planetary science》2012,47(7):1139-1156

Abstract— We review a number of constraints that have been placed on the formation of chondrules and show how these can be used to test chondrule formation models. Four models in particular are examined: the “X‐wind” model (sudden exposure to sunlight <0.1 AU from the proto‐Sun, with subsequent launching in a magnetocentrifugal outflow); solar nebula lightning; nebular shocks driven by eccentric planetesimals; and nebular shocks driven by diskwide gravitational instabilities. We show that constraints on the thermal histories of chondrules during their melting and crystallization are the most powerful constraints and provide the least ambiguous tests of the chondrule formation models. Such constraints strongly favor melting of chondrules in nebular shocks. Shocks driven by gravitational instabilities are somewhat favored over planetesimal bow shocks.  相似文献   

A water cycle for the Anthropocene     

Benjamin W. Abbott  Kevin Bishop  Jay P. Zarnetske  David M. Hannah  Rebecca J. Frei  Camille Minaudo  F.Stuart Chapin  Stefan Krause  Lafe Conner  David Ellison  Sarah E. Godsey  Stephen Plont  Jean Marais  Tamara Kolbe  Amanda Huebner  Tyler Hampton  Sen Gu  Madeline Buhman  Sayedeh Sara Sayedi  Ovidiu Ursache  Melissa Chapin  Kathryn D. Henderson  Gilles Pinay 《水文研究》2019,33(23):3046-3052

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Contrasting pyroclast density spectra from subaerial and submarine silicic eruptions in the Kermadec arc: implications for eruption processes and dredge sampling     

Simon J. Barker  Melissa D. Rotella  Colin J. N. Wilson  Ian C. Wright  Richard J. Wysoczanski 《Bulletin of Volcanology》2012,74(6):1425-1443

Pyroclastic deposits from four caldera volcanoes in the Kermadec arc have been sampled from subaerial sections (Raoul and Macauley) and by dredging from the submerged volcano flanks (Macauley, Healy, and the newly discovered Raoul SW). Suites of 16–32?mm sized clasts have been analyzed for density and shape, and larger clasts have been analyzed for major element compositions. Density spectra for subaerial dry-type eruptions on Raoul Island have narrow unimodal distributions peaking at vesicularities of 80–85%, whereas ingress of external water (wet-type eruption) or extended timescales for degassing generate broader distributions, including denser clasts. Submarine-erupted pyroclasts show two different patterns. Healy and Raoul SW dredge samples and Macauley Island subaerial-emplaced samples are dominated by modes at ~80–85%, implying that submarine explosive volcanism at high eruption rates can generate clasts with similar vesicularities to their subaerial counterparts. A minor proportion of Healy and Raoul SW clasts also show a pink oxidation color, suggesting that hot clasts met air despite 0.5 to >1?km of intervening water. In contrast, Macauley dredged samples have a bimodal density spectrum dominated by clasts formed in a submarine-eruptive style that is not highly explosive. Macauley dredged pyroclasts are also the mixed products of multiple eruptions, as shown by pumice major-element chemistry, and the sea-floor deposits reflect complex volcanic and sedimentation histories. The Kermadec calderas are composite features, and wide dispersal of pumice does not require large single eruptions. When coupled with chemical constraints and textural observations, density spectra are useful for interpreting both eruptive style and the diversity of samples collected from the submarine environment.  相似文献   

Communicating climate change: Climate change risk perceptions and rock lobster fishers, Tasmania   总被引：2，自引：0，他引：2  

Melissa Nursey-Bray  G.T. PeclS. Frusher  C. GardnerM. Haward  A.J. HobdayS. Jennings  A.E. PuntH. Revill  I. van Putten 《Marine Policy》2012,36(3):753-759

World fisheries, already vulnerable, are under increasing pressure from the impacts of climate change. Using the Tasmanian rock lobster industry as a case study, we considered the efficacy of risk perception as a tool to inform how to communicate the science of climate change and suggestions for management in relation to development of adaptation strategies for fisheries. Fishers surveyed in this study operate in a fishery that is expected to undergo large changes as a consequence of climate change. Fishers also reported observations of similar large changes in the marine environment and lobster fishery consistent with climate change; yet most fishers surveyed expressed doubts about whether climate change was a real process. The important point for adaption of the industry to climate change is that fisher perceptions of risk tended to create barriers to acceptance of climate change as an issue. This means that there is a barrier to communication and awareness about climate change and thus a barrier to future action on the issue. Improving acceptance of climate change and thus ability to adapt will require the development of communications that are culturally appropriate and palatable to fishers. We argue that the application of social learning principles in communications about climate change may be one constructive way forward.  相似文献   

Diatoms and pollen as indicators of water quality and land-use change: a case study from the Oak Ridges Moraine,Southern Ontario,Canada     

Melissa?A.?WatchornEmail author  Paul?B.?Hamilton  Thane?W.?Anderson  Helen?M.?Roe  R.?Timothy?Patterson 《Journal of Paleolimnology》2008,39(4):491-509

Swan Lake is a small kettle lake located on the Oak Ridges Moraine; a moraine that is recognized as an important source of ground water for the nearby and rapidly expanding Greater Toronto Area. A paleolimnological reconstruction using pollen and diatoms from the lake sediments showed significant changes in biological community composition through the last ∼400 years. Alterations in the diatom and pollen assemblages were most dramatic ca. A.D. 1850, correlating with the highest sediment flux in the lake between the period ca. A.D. 1850 and A.D. 1870. These changes were directly linked to regional deforestation and agricultural activities associated with European settlement. The pollen record from ca. A.D. 1850 to present day indicated that tree species (e.g. Pinus spp., Tsuga canadensis) were declining, while grass (Poaceae) and invasive species (e.g. Ambrosia) were increasing. Around A.D. 1850, the diatom flora changed from an assemblage dominated by large, benthic species (e.g. Sellaphora pupula, Pinnularia cf. maior, and Stauroneis phoenicenteron) to an assemblage characterized by smaller, tychoplanktonic (e.g. Fragilaria tenera, Staurosirella pinnata) and epiphytic (e.g. Achnanthidium minutissimum, Rossithidium linearis) taxa. This diatom community change supports the intermediate disturbance hypothesis which predicts a high level of diversity and richness following an intermediate to intense disturbance of short duration. Phosphorus concentrations in Swan Lake were inferred using a diatom-based regional calibration model, and the results indicated marked changes in lake water chemistry through time (from below detection limits before land clearance and settlement to 19.3 μg l⁻¹ in the current sediments), which were concurrent with episodes of regional deforestation and land-use change. Although the sediment and biological records indicate that the lake ecology has stabilized over the last 30–50 years, paleolimnological records show that the water quality and biology of Swan Lake has changed dramatically and not returned to pre-settlement conditions. Swan Lake presents a detailed record of the impact created by deforestation and urban development with a population of <50 individuals per km². Detailed paleolimnological studies like Swan Lake, in tandem with global human footprint studies, can create realistic estimates of land-use impacts at the global scale.  相似文献   

Evaluation of forest disturbance legacy effects on dissolved organic matter characteristics in streams at the Hubbard Brook Experimental Forest,New Hampshire     

Kaelin M. Cawley  John Campbell  Melissa Zwilling  Rudolf Jaffé 《Aquatic Sciences - Research Across Boundaries》2014,76(4):611-622

Dissolved organic matter (DOM) source and composition are critical drivers of its reactivity, impact microbial food webs and influence ecosystem functions. It is believed that DOM composition and abundance represent an integrated signal derived from the surrounding watershed. Recent studies have shown that land-use may have a long-term effect on DOM composition. Methods for characterizing DOM, such as those that measure the optical properties and size of the molecules, are increasingly recognized as valuable tools for assessing DOM sources, cycling, and reactivity. In this study we measured DOM optical properties and molecular weight determinations to evaluate whether the legacy of forest disturbance alters the amount and composition of stream DOM. Differences in DOM quantity and composition due to vegetation type and to a greater extent, wetland influence, were more pronounced than effects due to disturbance. Our results suggest that excitation-emission matrix fluorescence with parallel factor analysis is a more sensitive metric of disturbance than the other methods evaluated. Analyses showed that streams draining watersheds that have been clearcut had lower dissolved organic carbon (DOC) concentrations and higher microbially-derived and protein-like fluorescence features compared to reference streams. DOM optical properties in a watershed amended with calcium, were not significantly different than reference watersheds, but had higher concentrations of DOC. Collectively these results improve our understanding of how the legacy of forest disturbances and natural landscape characteristics affect the quantity and chemical composition of DOM in headwater streams, having implications for stream water quality and carbon cycling.  相似文献   

Improving the time resolution of surfzone bathymetry using in situ altimeters     

Melissa Moulton  Steve Elgar  Britt Raubenheimer 《Ocean Dynamics》2014,64(5):755-770

Surfzone bathymetry often is resolved poorly in time because watercraft surveys cannot be performed when waves are large, and remote sensing techniques have limited vertical accuracy. However, accurate high-frequency bathymetric information at fixed locations can be obtained from altimeters that sample nearly continuously, even during storms. A method is developed to generate temporally and spatially dense maps of evolving surfzone bathymetry by updating infrequent spatially dense watercraft surveys with the bathymetric change measured by a spatially sparse array of nearly continuously sampling altimeters. The update method is applied to observations of the evolution of shore-perpendicular rip current channels (dredged in Duck, NC, 2012) and shore-parallel sandbars (observed in Duck, NC, 1994). The updated maps are compared with maps made by temporally interpolating the watercraft surveys, and with maps made by spatially interpolating the altimeter measurements at any given time. Updated maps of the surfzone rip channels and sandbars are more accurate than maps obtained by using either only watercraft surveys or only the altimeter measurements. Hourly altimeter-updated bathymetric estimates of five rip channels show rapid migration and infill events not resolved by watercraft surveys alone. For a 2-month observational record of sandbars, altimeter-updated maps every 6 h between nearly daily surveys improve the time resolution of rapid bar-migration events.  相似文献   

PAH concentrations in Coquina (Donax spp.) on a sandy beach shoreline impacted by a marine oil spill     

Richard A. Snyder  Alexandra VestalChristina Welch  Gracie BarnesRobert Pelot  Melissa Ederington-HagyFredrick Hileman 《Marine pollution bulletin》2014

The BP MC252 well failure in the Gulf of Mexico, April 2010 caused concern for crude oil and polycyclic aromatic hydrocarbon (PAHs) exposure along the sandy beaches of the Florida Panhandle. We began collections of Coquina clams (Donax spp.) from the surf zone of Florida Panhandle beaches to monitor PAH contamination to compliment analysis of surf zone sand samples. These clams had higher levels of PAHs relative to ambient sand, and this allowed us to continue to monitor PAH levels after sand concentrations fell below limits of detection. PAH levels in the Coquina tissues were highly variable, perhaps indicative of the heterogeneous distribution of oil and tar on the beaches and exposure to tar particles. Overall, PAH levels decreased continuously in both sand and Coquina tissues, reaching limits of detection within one and two years respectively after oil landed on Florida Panhandle beaches. Our work suggests these surf zone molluscs may be used to monitor pollutant exposure along high energy sandy beach shorelines.  相似文献   

A Guugu Yimmithir Bam Wii: Ngawiya and Girrbithi: Hunting, planning and management along the Great Barrier Reef, Australia   总被引：1，自引：0，他引：1  

Melissa Nursey-Bray 《Geoforum》2009,40(3):442-453

The integration of Indigenous cultural rights with biodiversity protection can be explored in multiple dimensions and occupy contested grounds. This paper outlines the results of a research project that applied discourse analysis as both a theoretical and methodological tool to examine the power and knowledge relations within a case study of the development of a turtle and dugong hunting management plan by the Hope Vale Aboriginal Community in northern Australia. This paper reports on the results of this analysis and shows how multiple binaries exist within and between the different actors in a resource management problem. Findings show that contested constructions of the environment are hugely influential to the success or failure of natural resource management endeavours. The ontological frames that are adopted in supporting Indigenous peoples to manage their land and seas must be understood, otherwise there is a risk of reinforcing the very binaries that need to be avoided.  相似文献