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Results for “Marine Science”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 955 records · Page 53Linked to original sources

USGS1998

Vertical distribution of the chloromonad flagellate Heterosigma carterae in columns: Implications for bloom development

Blooms of the marine flagellate Heterosigma carterae have been associated with catastrophic fish kills at mariculture facilities around the world. The precise cause(s) of the sudden appearance and disappearance of Heterosigma surface blooms has not been completely described or understood. Environmental data from prior studies of blooms indicate the presence of vertical stratification of the water column that is often induced by freshwater runoff. We report the relatively rapid concentration of Heterosigma cells at the surface of tubes shortly after the addition of distilled water to the surface. This phenomenon of cell concentration in surface waters may partially explain the sudden appearance of Heterosigma cells near the surface and subsequent disappearance when vertical stratification is lost due to turbulence or mixing. The results may lead to bloom mitigation techniques for net pen aquaculture.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2004

Migration and rearing histories of chinook salmon (Oncorhynchus tshawytscha) determined by ion microprobe Sr isotope and Sr/Ca transects of otoliths

Strontium isotope and Sr/Ca ratios measured in situ by ion microprobe along radial transects of otoliths of juvenile chinook salmon ( Oncorhynchus tshawytscha ) vary between watersheds with contrasting geology. Otoliths from ocean-type chinook from Skagit River estuary, Washington, had prehatch regions with 87 Sr/ 86 Sr ratios of ~0.709, suggesting a maternally inherited marine signature, extensive fresh water growth zones with 87 Sr/ 86 Sr ratios similar to those of the Skagit River at ~0.705, and marine-like 87 Sr/ 86 Sr ratios near their edges. Otoliths from stream-type chinook from central Idaho had prehatch 87 Sr/ 86 Sr ratios ≥0.711, indicating that a maternal marine Sr isotopic signature is not preserved after the ~1000- to 1400-km migration from the Pacific Ocean. 87 Sr/ 86 Sr ratios in the outer portions of otoliths from these Idaho juveniles were similar to those of their respective streams (~0.7080.722). For Skagit juveniles, fresh water growth was marked by small decreases in otolith Sr/Ca, with increases in Sr/Ca corresponding to increases in 87 Sr/ 86 Sr with migration into salt water. Otoliths of Idaho fish had Sr/Ca radial variation patterns that record seasonal fluctuation in ambient water Sr/Ca ratios. The ion microprobe's ability to measure both 87 Sr/ 86 Sr and Sr/Ca ratios of otoliths at high spatial resolution in situ provides a new tool for studies of fish rearing and migration.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2013

A 600-ka Arctic sea-ice record from Mendeleev Ridge based on ostracodes

Arctic paleoceanography and sea-ice history were reconstructed from epipelagic and benthic ostracodes from a sediment core (HLY0503-06JPC, 800 m water depth) located on the Mendeleev Ridge, Western Arctic Ocean. The calcareous microfaunal record (ostracodes and foraminifers) covers several glacial/interglacial cycles back to estimated Marine Isotope Stage 13 (MIS 13, &sim;500 ka) with an average sedimentation rate of &sim;0.5 cm/ka for most of the stratigraphy (MIS 5–13). Results based on ostracode assemblages and an unusual planktic foraminiferal assemblage in MIS 11 dominated by a temperate-water species Turborotalita egelida show that extreme interglacial warmth, high surface ocean productivity, and possibly open ocean convection characterized MIS 11 and MIS 13 (&sim;400 and 500 ka, respectively). A major shift in western Arctic Ocean environments toward perennial sea ice occurred after MIS 11 based on the distribution of an ice-dwelling ostracode Acetabulastoma arcticum . Spectral analyses of the ostracode assemblages indicate sea ice and mid-depth ocean circulation in western Arctic Ocean varied primarily at precessional (&sim;22 ka) and obliquity (&sim;40 ka) frequencies.

Quaternary Science Reviews↗

USGS2015

Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile

The &sim;500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of &sim;M 8.0–8.5 earthquakes followed by low tsunamis (<4 m) occurring on the megathrust about every 80 years. One exception is the AD 1730 great earthquake (M 9.0–9.5) and high tsunami (>10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is &sim;500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has produced.

Quaternary Science Reviews↗

USGS2005

Biogeochemical controls on diel cycling of stable isotopes of dissolved 02 and dissolved inorganic carbon in the Big Hole River, Montana

Rivers with high biological productivity typically show substantial increases in pH and dissolved oxygen (DO) concentration during the day and decreases at night, in response to changes in the relative rates of aquatic photosynthesis and respiration. These changes, coupled with temperature variations, may impart diel (24-h) fluctuations in the concentration of trace metals, nutrients, and other chemical species. A better understanding of diel processes in rivers is needed and will lead to improved methods of data collection for both monitoring and research purposes. Previous studies have used stable isotopes of dissolved oxygen (DO) and dissolved inorganic carbon (DIC) as tracers of geochemical and biological processes in streams, lakes, and marine systems. Although seasonal variation in δ 18 O of DO in rivers and lakes has been documented, no study has investigated diel changes in this parameter. Here, we demonstrate large (up to 13‰) cycles in δ 18 O-DO for two late summer sampling periods in the Big Hole River of southwest Montana and illustrate that these changes are correlated to variations in the DO concentration, the C-isotopic composition of DIC, and the primary productivity of the system. The magnitude of the diel cycle in δ 18 O-DO was greater in August versus September because of the longer photoperiod and warmer water temperatures. This study provides another biogeochemical tool for investigating the O 2 and C budgets in rivers and may also be applicable to lake and groundwater systems.

Montana↗

USGS2001

Establishment of two invasive crustaceans (Copepoda: Harpacticoida) on the nearshore sands of Lake Michigan

Benthic copepods (Copepoda: Harpacticoida) in the nearshore sediments of southern Lake Michigan appear to be dominated by two new invasive species. We report the first occurrence in North America of Schizopera borutzkyi Montschenko, a native to the Danube River delta, and Heteropsyllus nr. nunni, likely a new species that is morphologically similar to the marine species Heteropsyllus nunni and represents the first occurrence of this genus in freshwater. Schizopera borutzkyi is a euryhaline species occurring in shallow sands in its native habitat and in deeper sands (6-15 m) in southern Lake Michigan. Based on the absence of these species from previous studies, we suggest that they are recent introductions. Heteropsyllus nr. nunni dominated (55-100%) the harpacticoid abundance to depths of 9 m, but S. borutzkyi comprised 75% of the harpacticoid abundance at 15 m. Native harpacticoids were always greatly outnumbered by invasive harpacticoids in our samples, which suggests that the natives are being replaced rapidly or that the invasive species are finding unused resources. The ecological implications of these introductions are not known, but these invasions may represent continued 'invasional meltdown' in Lake Michigan.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2011

Spatial and temporal characteristics of grouper spawning aggregations in marine protected areas in Palau, western Micronesia

In Palau, Ngerumekaol and Ebiil Channels are spawning aggregation sites that have been protected from fishing since 1976 and 2000, respectively. Groupers and other targeted fisheries species were monitored monthly over a 1.5 year period at these two spawning aggregations and two nearby exploited reference sites where grouper formerly aggregated to spawn. At the protected aggregation sites, three grouper species ( Plectropomus areolatus , Epinephelus polyphekadion , and Epinephelus fuscoguttatus ) accounted for 78% of the abundance and 85% of the biomass of all resource species surveyed but comprised <1% of the total abundance and biomass at reference sites not protected from fishing that formally harbored spawning aggregations. Abundance and biomass of grouper species pooled were 54% and 72% higher, respectively, at Ngerumekaol compared to Ebiil. Comparisons with data from the same locations in 1995–1996 showed order of magnitude declines in abundance of E. polyphekadion at both locations. The lower numbers of E. fuscoguttatus and the near absence of E. polyphekadion at Ebiil may reflect the effects of previous and current overexploitation.

Palau↗

USGS1985

Demonstration of two pulses of Paleogene deformation in the Andes of Peru

New radiometric ages of about 25 m.y. on volcanic materials in a marine intercalation within clastic continental strata of the Upper Moquegua Formation near Caraveli, southern Peru, together with an age of 25.3 ± 0.4 m.y obtained by Tosdal et al. from a locality about 300 km to the ESE, show that the formation contains strata of late Oligocene as well as Miocene age, and demonstrate that the coastal region was at a low elevation during latest Oligocene time. Because the unconformities between the Upper Moquegua Formation and the underlying Lower Moquegua Formation, and between the Lower Moquegua Formation and underlying Paleocene rocks cannot both represent the same tectonic event, two discrete Paleogene events must be present in the Andes of Peru. Although the exact timing of these events is uncertain, the unconformities are likely to be of Paleocene and middle Eocene age or possibly of middle Eocene and Oligocene age.

Earth and Planetary Science Letters↗

USGS1996

Anaerobic hydrocarbon degradation in petroleum-contaminated harbor sediments under sulfate-reducing and artificially imposed iron-reducing conditions

The potential use of iron(III) oxide to stimulate in-situ hydrocarbon degradation in anaerobic petroleum-contaminated harbor sediments was investigated. Previous studies have indicated that Fe(III)-reducing bacteria (FeRB) can oxidize some electron donors more effectively than sulfate- reducing bacteria (SRB). In contrast to previous results in freshwater sediments, the addition of Fe(III) to marine sediments from San Diego Bay, CA did not switch the terminal electron-accepting process (TEAP) from sulfate reduction to Fe-(III) reduction. Addition of Fe(III) also did not stimulate anaerobic hydrocarbon oxidation. Exposure of the sediment to air [to reoxidize Fe(II) to Fe(III)] followed by anaerobic incubation of the sediments, resulted in Fe-(III) reduction as the TEAP, but contaminant degradation was not stimulated and in some instances was inhibited. The difference in the ability of FeRB to compete with the SRB in the different sediment treatments was related to relative population sizes. Although the addition of Fe(III) did not stimulate hydrocarbon degradation, the results presented here as well as other recent studies demonstrate that there may be significant anaerobic hydrocarbon degradation under sulfate-reducing conditions in harbor sediments.

Environmental Science & Technology↗

USGS2024

Significant challenges to the sustainability of the California coast considering climate change

Climate change is an existential threat to the environmental and socioeconomic sustainability of the coastal zone and impacts will be complex and widespread. Evidence from California and across the United States shows that climate change is impacting coastal communities and challenging managers with a plethora of stressors already present. Widespread action could be taken that would sustain California’s coastal ecosystems and communities. In this perspective, we highlight the main threat to coastal sustainability: the compound effects of episodic events amplified with ongoing climate change, which will present unprecedented challenges to the state. We present two key challenges for California’s sustainability in the coastal zone: 1) accelerating sea-level rise combined with storm impacts, and 2) continued warming of the oceans and marine heatwaves. Cascading effects from these types of compounding events will occur within the context of an already stressed system that has experienced extensive alterations due to intensive development, resource extraction and harvesting, spatial containment, and other human use pressures. There are critical components that could be used to address these immediate concerns, including comanagement strategies that include diverse groups and organizations, strategic planning integrated across large areas, rapid implementation of solutions, and a cohesive and policy relevant research agenda for the California coast. Much of this has been started in the state, but the scale could be increased, and timelines accelerated. The ideas and information presented here are intended to help expand discussions to sharpen the focus on how to encourage sustainability of California’s iconic coastal region.

California↗

USGS1976

The Viking landing sites: Selection and certification

During the past several years the Viking project developed plans to use Viking orbiter instruments and Earth-based radar to certify the suitability of the landing sites selected as the safest and most scientifically rewarding using Mariner 9 data. During June and July 1976, the Earth-based radar and orbital spacecraft observations of some of the prime and backup sites were completed. The results of these combined observations indicated that the Viking 1 prime landing area in the Chryse region of Mars is geologically varied and possibly more hazardous than expected, and was not certifiable as a site for the Viking 1 landing. Consequently, the site certification effort had to be drastically modified and lengthened to search for a site that might be safe enough to attempt to land. The selected site considered at 47.5°W, 22.4°N represented a compromise between desirable characteristics observed with visual images and those inferred from Earth-based radar. It lies in the Chryse region about 900 kilometers northwest of the original site. Viking 1 landed successfully at this site on 20 July 1976.

Science↗

USGS1992

Continuous 500,000-year climate record from vein calcite in Devils Hole, Nevada

Oxygen-18 (δ 18 O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine δ 18 O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

Nevada↗

USGS2023

Introduction to the special section on seismoacoustics and seismoacoustic data fusion

A variety of geophysical hazards (e.g., volcanic activity, earthquakes, mass movements, marine storms, bolides) and anthropogenic sources (e.g., chemical and nuclear explosions, mining blasts, rocket launches) can release energy as mechanical waves in the ground, ocean, and atmosphere (Arrowsmith et al., 2010; Campus and Christie, 2009). Due to the mechanical coupling between a planetary body, its ocean, and its atmosphere, waves can propagate across these interfaces (Ben-Menahem and Singh, 1981) and carry information about the source and the media they propagated through. The field of seismoacoustics, driven by geophysical observations of both seismic and low-frequency acoustic (infrasound) waves, has several interdisciplinary applications. Observations of both seismic and infrasonic waves can be used to discriminate between atmospheric and subsurface events, such as sonic booms and earthquakes. Moreover, seismoacoustic analyses can provide useful information for the source characterization of shallow anthropogenic events, such as underground or surface explosions, volcanic, and tectonic events (e.g., Arrowsmith et al., 2020; Assink et al., 2016; de Groot-Hedlin and Hedlin, 2019; Matoza et al., 2009). Similarly, remote observations (e.g., on regional seismic and infrasonic arrays) can help monitor natural events such as volcanic eruptions and provide additional details about eruption dynamics. Recent works additionally suggest that infrasound can be used to discriminate between different volcanic processes (Watson et al., 2022). Finally, looking outwards, the study of seismo-acoustics has been a particularly valuable tool for planetary science (e.g., Krishnamoorthy et al., 2018; Martire et al., 2018; Krishnamoorthy et al., 2019; Martire et al., 2020; Garcia et al., 2020; Brissaud et al., 2021).

Bulletin of the Seismological Society of America↗

USGS2010

Response of a macrotidal estuary to changes in anthropogenic mercury loading between 1850 and 2000

Methylmercury (MeHg) bioaccumulation in marine food webs poses risks to fish-consuming populations and wildlife. Here we develop and test an estuarine mercury cycling model for a coastal embayment of the Bay of Fundy, Canada. Mass budget calculations reveal that MeHg fluxes into sediments from settling solids exceed losses from sediment-to-water diffusion and resuspension. Although measured methylation rates in benthic sediments are high, rapid demethylation results in negligible net in situ production of MeHg. These results suggest that inflowing fluvial and tidal waters, rather than coastal sediments, are the dominant MeHg sources for pelagic marine food webs in this region. Model simulations show water column MeHg concentrations peaked in the 1960s and declined by almost 40% by the year 2000. Water column MeHg concentrations respond rapidly to changes in mercury inputs, reaching 95% of steady state in approximately 2 months. Thus, MeHg concentrations in pelagic organisms can be expected to respond rapidly to mercury loading reductions achieved through regulatory controls. In contrast MeHg concentrations in sediments have steadily increased since the onset of industrialization despite recent decreases in total mercury loading. Benthic food web MeHg concentrations are likely to continue to increase over the next several decades at present-day mercury emissions levels because the deep active sediment layer in this system contains a large amount of legacy mercury and requires hundreds of years to reach steady state with inputs.

Environmental Science & Technology↗

USGS1999

Geologic map of the Galaxias quadrangle (MTM 35217) of Mars

The Galaxias region (MTM 35217) is one of a series of 1:500,000-scale science study areas on Mars sponsored by NASA's Planetary Geology and Geophysics Program. Situated near the northern limit of lava flows associated with Elysium Mons, this region includes a mixture of volcanic and nonvolcanic terrains. The region is also of interest for the fluvial systems that originate along the distal margins of the Elysium lava flows. Resolution of Viking Orbiter images used to prepare the base map ranges from 40 to 160 m/pixel. High-resolution frames (40 to 80 m/pixel) are found in the southeastern part of the map area and along the north edge of the quadrangle, but over half the quadrangle is included in medium-resolution frames (150 m/pixel). Two 8 m/pixel, very high resolution scenes are available (see fig. 1). Interpretation is complicated by variable resolution and sun angles that vary from east to west illumination on different images. Mapping methods and principles are adapted from those developed for lunar photogeologic mapping by Shoemaker and Hackman (1962), refined by Wilhelms (1972), and successfully applied by many workers to a variety of planetary surfaces. Mapping units are distinguished by topography and texture and are ranked by relative age on the basis of superposition and transection relations. Material units are assigned to time-stratigraphic systems defined by Scott and Carr (1978) and Tanaka (1986). This area is included within earlier maps that used Mariner 9 images at 1:5,000,000 scale (Elston, 1979) and globally at 1:25,000,000 scale (Scott and Carr, 1978). Regional maps based on the much higher resolutions of Viking Orbiter allowed more detailed discrimination of materials by Greeley and Guest (1987) at 1:15,000,000 scale and Tanaka and others (1992) at 1:5,000,000 scale. Some map units on this 1:500,000-scale map correspond to, or are partially equivalent to, units on the larger scale maps of Greeley and Guest (1987) and Tanaka and others (1992). Established terminology is used where feasible, but the scale of this map requires that some new units be introduced and that some previous terminology be redefined. Photogeologic methods are limited; therefore, more than one geologic explanation is given for some material units that do not readily lend themselves to an unequivocal interpretation.

IMAP↗

USGS2005

The South China sea margins: Implications for rifting contrasts

Implications regarding spatially complex continental rifting, crustal extension, and the subsequent evolution to seafloor spreading are re-examined for the northern and southern-rifted margins of the South China Sea. Previous seismic studies have shown dramatic differences in the present-day crustal thicknesses as the manifestations of the strain experienced during the rifting of the margin of south China. Although the total crustal extension is presumed to be the same along the margin and adjacent ocean basin, the amount of continental crustal extension that occurred is much less along the east and central segments of the margin than along the western segment. This difference was accommodated by the early formation of oceanic crust (creating the present-day South China Sea basin) adjacent to the eastern margin segment while continued extension of continental crust was sustained to the west. Using the observed cross-sectional areas of extended continental crust derived from deep penetration seismics, two end-member models of varying rift zone widths and varying initial crustal thicknesses are qualitatively examined for three transects. Each model implies a time difference in the initiation of seafloor spreading inferred for different segments along the margin. The two models examined predict that the oceanic crust of the South China Sea basin toward the west did not begin forming until sometime between 6-12 my after its initial formation (???32 Ma) toward the east. These results are compatible with crustal age interpretations of marine magnetic anomalies. Assuming rifting symmetry with conjugate margin segments now residing along the southern portions of the South China Sea basin implies that the total width of the zone of rifting in the west was greater than in the east by about a factor of two. We suggest the most likely causes of the rifting differences were east-west variations in the rheology of the pre-rift crust and associated east-west variations in the thermal structure of the pre-rift lithosphere. The calculated widths of rifted continental crust for the northern and southern margins, when combined with the differential widths of seafloor generated during the seafloor spreading phase, indicate the total crustal extension that occurred is about 1100 km and is remarkably consistent to within ???10% for all three (eastern, central, western) segments examined. ?? 2005 Elsevier B.V. All rights reserved.

Earth and Planetary Science Letters↗

USGS2013

The PRISM (Pliocene Palaeoclimate) reconstruction: Time for a paradigm shift

Global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change, but single-temperature representations of the oceanic mixed layer for data–model comparisons are outdated, and the time for a paradigm shift in marine palaeoclimate reconstruction is overdue. The new paradigm in marine palaeoclimate reconstruction stems the loss of valuable climate information and instead presents a holistic and nuanced interpretation of multi-dimensional oceanographic processes and responses. A wealth of environmental information is hidden within the US Geological Survey's P liocene R esearch, I nterpretation and S ynoptic M apping (PRISM) marine palaeoclimate reconstruction, and we introduce here a plan to incorporate all valuable climate data into the next generation of PRISM products. Beyond the global approach and focus, we plan to incorporate regional climate dynamics with emphasis on processes, integrating multiple environmental proxies wherever available in order to better characterize the mixed layer, and developing a finer time slice within the Mid-Piacenzian Age of the Pliocene, complemented by underused proxies that offer snapshots into environmental conditions. The result will be a proxy-rich, temporally nested, process-oriented approach in a digital format - a relational database with geographic information system capabilities comprising a three-dimensional grid representing the surface layer, with a plethora of data in each cell.

Philosophical Transactions of the Royal Society A:↗

USGS1974

Venus: Atmospheric motion and structure from Mariner 10 pictures

The Mariner 10 television cameras imaged the planet Venus in the visible and near ultraviolet for a period of 8 days at resolutions ranging from 100 meters to 130 kilometers. The general pattern of the atmospheric circulation in the upper tropospheric/lower stratospheric region is displayed in the pictures. Atmospheric flow is symmetrical between north and south hemispheres. The equatorial motions are zonal (east-west) at approximately 100 meters per second, consistent with the previously inferred 4-day retrograde rotation. Angular velocity increases with latitude. The subsolar region, and the region downwind from it, show evidence of large-scale convection that persists in spite of the main zonal motion. Dynamical interaction between the zonal motion and the relatively stationary region of convection is evidenced by bowlike waves.

Science↗