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At least 721 records · Page 40Linked to original sources
USGS1973

Effect of sea water interaction on strontium isotope composition of deep-sea basalts

Analyses of rim-to-interior samples of fresh tholeiitic pillow basalts, deuterically altered holocrystalline basalts, and older, weathered tholeiitic basalts from the deep sea indicate that 87 Sr/ 86 Sr ratios of the older basalts are raised by low temperature interaction with strontium dissolved in sea water. 87 Sr/ 86 Sr correlates positively with H 2 O in these basalts; however, there is little detectable modification of the strontium isotope composition in rocks with H 2 O contents less than 1%. The isotope changes appear to be a function of relatively long-term, low-temperature weathering, rather than high-temperature or deuteric alteration. Strontium abundance and isotopic data for these rocks suggest that strontium content is only slightly modified by interaction with sea water, and it is a relatively insensitive indicator of marine alteration. Average Rb-Sr parameters for samples of apparently unaltered basalt are: Rb= 1.11ppm; Sr= 132ppm; 87 Sr/ 86 Sr= 0.70247.

Earth and Planetary Science Letters↗
USGS2018

Volcanic ash deposition, eelgrass beds, and inshore habitat loss from the 1920s to the 1990s at Chignik, Alaska

We quantified the shallowing of the seafloor in five of six bays examined in the Chignik region of the Alaska Peninsula, confirming National Ocean Service observations that 1990s hydrographic surveys were shallower than previous surveys from the 1920s. Castle Bay, Chignik Lagoon, Hook Bay, Kujulik Bay and Mud Bay lost volume as calculated from Mean Lower Low Water (Chart Datum) to the deepest depths and four of these sites lost volume from Mean High Water to the deepest depths. Calculations relative to each datum were made because tidal datum records exhibited an increase in tidal range in this region from the 1920s to the 1990s. Our analysis showed that Mud Bay is quickly disappearing while Chignik Lagoon is being reduced to narrow channels. Anchorage Bay was the only site that increased in depth over time, perhaps due to erosion. Volcanoes dominate the landscape of the Chignik area. They have blanketed the region in deep ash deposits before the time frame of this study, and some have had smaller ash-producing eruptions during the time frame of this study. Remobilization of land-deposited ash and redeposition in marine areas - in some locations facilitated by extensive eelgrass ( Zostera marina ) beds (covering 54% of Chignik Lagoon and 68% of Mud Bay in 2010) - is the most likely cause of shallowing in the marine environment. Loss of shallow water marine habitat may alter future abundance and distribution of several fish, invertebrate and avian species.

Alaska↗
USGS2017

Late Quaternary uplift along the North America-Caribbean plate boundary: Evidence from the sea level record of Guantanamo Bay, Cuba

The tectonic setting of the North America-Caribbean plate boundary has been studied intensively, but some aspects are still poorly understood, particularly along the Oriente fault zone. Guantanamo Bay, southern Cuba, is considered to be on a coastline that is under a transpressive tectonic regime along this zone, and is hypothesized to have a low uplift rate. We tested this by studying emergent reef terrace deposits around the bay. Reef elevations in the protected, inner part of the bay are ∼11–12 m and outer-coast, wave-cut benches are as high as ∼14 m. Uranium-series analyses of corals yield ages ranging from ∼133 ka to ∼119 ka, correlating this reef to the peak of the last interglacial period, marine isotope stage (MIS) 5.5. Assuming a span of possible paleo-sea levels at the time of the last interglacial period yields long-term tectonic uplift rates of 0.02–0.11 m/ka, supporting the hypothesis that the tectonic uplift rate is low. Nevertheless, on the eastern and southern coasts of Cuba, east and west of Guantanamo Bay, there are flights of multiple marine terraces, at higher elevations, that could record a higher rate of uplift, implying that Guantanamo Bay may be anomalous. Southern Cuba is considered to have experienced a measurable but modest effect from glacial isostatic adjustment (GIA) processes. Thus, with a low uplift rate, Guantanamo Bay should show no evidence of emergent marine terraces dating to the ∼100 ka (MIS 5.3) or ∼80 ka (MIS 5.1) sea stands and results of the present study support this.

Guantanamo Bay↗
USGS2003

Response of North American Great Basin Lakes to Dansgaard-Oeschger oscillations

We correlate oscillations in the hydrologic and/or cryologic balances of four Great Basin surface-water systems with Dansgaard-Oeschger (D-O) events 2-12. This correlation is relatively strong at the location of the magnetic signature used to link the lake records, but becomes less well constrained with distance/time from the signature. Comparison of proxy glacial and hydrologic records from Owens and Pyramid lakes indicates that Sierran glacial advances occurred during times of relative dryness. If our hypothesized correlation between the lake-based records and the GISP2 ??18O record is correct, it suggests that North Atlantic D-O stades were associated with relatively cold and dry conditions and that interstades were associated with relatively warm and wet conditions throughout the Great Basin between 50,500 and 27,000 GISP2yr B.P. The Great Basin lacustrine climate records reinforce the hypothesis that D-O events affected the climate throughout much of the Northern Hemisphere during marine isotope stages 2 and 3. However, the absolute phasing between lake-size and ice-core ??18O records remains difficult to determine.

Quaternary Science Reviews↗
USGS2021

Carbonate-hosted microbial communities are prolific and pervasive methane oxidizers at geologically diverse marine methane seep sites

At marine methane seeps, vast quantities of methane move through the shallow subseafloor, where it is largely consumed by microbial communities. This process plays an important role in global methane dynamics, but we have yet to identify all of the methane sinks in the deep sea. Here, we conducted a continental-scale survey of seven geologically diverse seafloor seeps and found that carbonate rocks from all sites host methane-oxidizing microbial communities with substantial methanotrophic potential. In laboratory-based mesocosm incubations, chimney-like carbonates from the newly described Point Dume seep off the coast of Southern California exhibited the highest rates of anaerobic methane oxidation measured to date. After a thorough analysis of physicochemical, electrical, and biological factors, we attribute this substantial metabolic activity largely to higher cell density, mineral composition, kinetic parameters including an elevated V max , and the presence of specific microbial lineages. Our data also suggest that other features, such as electrical conductance, rock particle size, and microbial community alpha diversity, may influence a sample’s methanotrophic potential, but these factors did not demonstrate clear patterns with respect to methane oxidation rates. Based on the apparent pervasiveness within seep carbonates of microbial communities capable of performing anaerobic oxidation of methane, as well as the frequent occurrence of carbonates at seeps, we suggest that rock-hosted methanotrophy may be an important contributor to marine methane consumption.

Proceedings of the National Academy of Sciences (P↗
USGS1988

A 250,000-year climatic record from Great Basin vein calcite: Implications for Milankovitch theory

A continuous record of oxygen-18 (δ 18 O) variations in the continental hydrosphere during the middle-to-late Pleistocene has been obtained from a uranium-series dated calcitic vein in the southern Great Basin. The vein was deposited from ground water that moved through Devils Hole—an open fault zone at Ash Meadows, Nevada—between 50 and 310 ka (thousand years ago). The configuration of the δ 18 O versus time curve closely resembles the marine and Antarctic ice core (Vostok) δ 18 O curves; however, the U-Th dates indicate that the last interglacial stage (marine oxygen isotope stage 5) began before 147 ± 3 ka, at least 17,000 years earlier than indicated by the marine δ 18 O record and 7,000 years earlier than indicated by the less well dated Antarctic δ 18 O record. This discrepancy and other differences in the timing of key climatic events suggest that the indirectly dated marine δ 18 O chronology may need revision and that orbital forcing may not be the principal cause of the Pleistocene ice ages.

Nevada↗
USGS2003

Influence of salinity and temperature on the physiology of Limia melanonotata (Cyprinodontiformes: Poeciliidae): A search for abiotic factors limiting insular distribution in Hispaniola

We investigated salinity and temperature effects on routine metabolic rate (RMR), temperature tolerance (CTMax, critical thermal maximum), and salinity tolerance of Limia melanonotata, a poecliid fish that occurs in west-central inland waters of Hispaniola. Routine metabolic rate and CTMax were measured in fish acclimated to three salinities (0, 30, and 60 ppt) and temperatures (25??, 30??, and 35??C) for nine temperature-salinity combinations. Salinity and temperature did not significantly interact in their effect on RMR. For combined salinity acclimations, adjusted RMR (ANCOVA) was significantly lower at 25??C than either 30?? or 35??C. For combined temperature acclimations, mean RMR was significantly lower at 60 ppt than either 0 or 30 ppt. Salinity and temperature had a significant interactive effect on temperature tolerance. Mean CTMax was significantly higher at 30?? than 25??C at all salinities, but at 35??C was significantly higher than at 25?? or 30??C only among fish acclimated in fresh water. Fish exposed to a chronic increase in salinity experienced most mortality in a salinity range of 70-107 ppt, with females exhibiting greater salinity tolerance than males. Limia melanonotata approaches the upper extreme in salinity and temperature tolerances known for poeciliids. Our results also suggest that L. melanonotata may reduce energy expenditures at environmental extremes to tolerate harsh conditions for extended periods. Despite its curythermal and euryhaline adaptations, L. melanonotata has a relatively restricted inland range in Hispaniola and is unknown from inshore brackish or marine habitats. The present distribution of this species and congeners may be the result of a combination of factors that include historical zoogeography and ecological requirements.

Caribbean Journal of Science↗
USGS2023

Ice and ocean constraints on early human migrations into North America along the Pacific Coast

Founding populations of the first Americans likely occupied parts of Beringia during the Last Glacial Maximum (LGM). The timing, pathways, and modes of their southward transit remain unknown, but blockage of the interior route by North American ice sheets between ~26 and 14 cal kyr BP (ka) favors a coastal route during this period. Using models and paleoceanographic data from the North Pacific, we identify climatically favorable intervals when humans could have plausibly traversed the Cordilleran coastal corridor during the terminal Pleistocene. Model simulations suggest that northward coastal currents strengthened during the LGM and at times of enhanced freshwater input, making southward transit by boat more difficult. Repeated Cordilleran glacial-calving events would have further challenged coastal transit on land and at sea. Following these events, ice-free coastal areas opened and seasonal sea ice was present along the Alaskan margin until at least 15 ka. Given evidence for humans south of the ice sheets by 16 ka and possibly earlier, we posit that early people may have taken advantage of winter sea ice that connected islands and coastal refugia. Marine ice-edge habitats offer a rich food supply and traversing coastal sea ice could have mitigated the difficulty of traveling southward in watercraft or on land over glaciers. We identify 24.5 to 22 ka and 16.4 to 14.8 ka as environmentally favorable time periods for coastal migration, when climate conditions provided both winter sea ice and ice-free summer conditions that facilitated year-round marine resource diversity and multiple modes of mobility along the North Pacific coast.

Pacific Coast↗
USGS2021

Geochemistry of coastal permafrost and erosion-driven organic matter fluxes to the Beaufort Sea near Drew Point, Alaska

Accelerating erosion of the Alaska Beaufort Sea coast is increasing inputs of organic matter from land to the Arctic Ocean, and improved estimates of organic matter stocks in eroding coastal permafrost are needed to assess their mobilization rates under contemporary conditions. We collected three permafrost cores (4.5–7.5 m long) along a geomorphic gradient near Drew Point, Alaska, where recent erosion rates average 17.2 m year −1 . Down-core patterns indicate that organic-rich soils and lacustrine sediments (12–45% total organic carbon; TOC) in the active layer and upper permafrost accumulated during the Holocene. Deeper permafrost (below 3 m elevation) mainly consists of Late Pleistocene marine sediments with lower organic matter content (∼1% TOC), lower C:N ratios, and higher δ 13 C values. Radiocarbon-based estimates of organic carbon accumulation rates were 11.3 ± 3.6 g TOC m −2 year −1 during the Holocene and 0.5 ± 0.1 g TOC m −2 year −1 during the Late Pleistocene (12–38 kyr BP). Within relict marine sediments, porewater salinities increased with depth. Elevated salinity near sea level (∼20–37 in thawed samples) inhibited freezing despite year-round temperatures below 0°C. We used organic matter stock estimates from the cores in combination with remote sensing time-series data to estimate carbon fluxes for a 9 km stretch of coastline near Drew Point. Erosional fluxes of TOC averaged 1,369 kg C m −1 year −1 during the 21st century (2002–2018), nearly doubling the average flux of the previous half-century (1955–2002). Our estimate of the 21st century erosional TOC flux year −1 from this 9 km coastline (12,318 metric tons C year −1 ) is similar to the annual TOC flux from the Kuparuk River, which drains a 8,107 km 2 area east of Drew Point and ranks as the third largest river on the North Slope of Alaska. Total nitrogen fluxes via coastal erosion at Drew Point were also quantified, and were similar to those from the Kuparuk River. This study emphasizes that coastal erosion represents a significant pathway for carbon and nitrogen trapped in permafrost to enter modern biogeochemical cycles, where it may fuel food webs and greenhouse gas emissions in the marine environment.

Alaska↗
USGS1972

Acoustic-reflection profiles, Bay of Campeche: International Decade of Ocean Exploration, U.S. Geological Survey, Leg 1, 1971 cruise, UNITEDGEO I

Introduction As part of a cooperative marine research program designated the International Decade of Ocean Exploration (IDOE), the United States Geological Survey is participating in an investigation of the geologic framework and resource potential of continental margins and small ocean basins in the Gulf of Mexico, Caribbean Sea, and west African continental shelf areas. These studies are funded through the National Science Foundation. Acoustic-reflec­tion profiles of Leg 1, described in this report concern mainly a 200 X 250 kilometer project area in the Bay of Campeche in the southwestern part of the Gulf of Mexico. The cruise leg began at Corpus Christi, Texas, and ended at Veracruz, Mexico. Other geophysical records collected during the cruise include magnetometry, gravimetry, and bathymetry. Visiting scientists from the Institute of Geophysics of the National University of Mexico, the Oceanographic Commission of the Mexican Navy, and the Mexican Institute of Petroleum joined the research vessel UNITEDGEO I throughout the cruise in the Bay of Campeche. The cruise offered an excellent opportunity for scientific interchange between investigators from Mexico and the United States and permitted collaboration in the instru­mentation, operational techniques, and interpretation of acoustic-­reflection records aboard the research vessel.

Bay Of Campeche;Gulf Of Mexico↗
USGS1972

Acoustic-reflection profiles, eastern Greater Antilles: Leg 3, 1971 cruise, UNITEDGEO I

Introduction As part of a cooperative marine research program designated the Internataional Decade of Ocean Exploration (IDOE), the United states Geological Survey is participating in an investigation of the geologic framework and resource potential of continental margins and small ocean basins in the Gulf of Mexico, Caribbean Sea, and west African continental shelf areas. These studies are funded through the National Science Foundation. Legs 1 and 2, completed June 22 and July 8, respectively, were concerned with subbottom features of the Bay of Campeche and with the tectonic framework of the continental margin east of the Yucatan Peninsula. Leg 3, described in this report was conducted in the Antilles region of the northeastern Caribbean between July 17 and August 4, 1971. This report presents the unedited records of the approximately 5840 km of acoustic reflection profiling made during Leg 3. Magnetic and gravity data were collected also but are being reported elsewhere in conjunction with the results of the study.

Report↗
USGS2016

Saharan dust nutrients promote Vibrio bloom formation in marine surface waters

Vibrio is a ubiquitous genus of marine bacteria, typically comprising a small fraction of the total microbial community in surface waters, but capable of becoming a dominant taxon in response to poorly characterized factors. Iron (Fe), often restricted by limited bioavailability and low external supply, is an essential micronutrient that can limit Vibrio growth. Vibrio species have robust metabolic capabilities and an array of Fe-acquisition mechanisms, and are able to respond rapidly to nutrient influx, yet Vibrio response to environmental pulses of Fe remains uncharacterized. Here we examined the population growth of Vibrio after natural and simulated pulses of atmospherically transported Saharan dust, an important and episodic source of Fe to tropical marine waters. As a model for opportunistic bacterial heterotrophs, we demonstrated that Vibrio proliferate in response to a broad range of dust-Fe additions at rapid timescales. Within 24 h of exposure, strains of Vibrio cholerae and Vibrio alginolyticus were able to directly use Saharan dust–Fe to support rapid growth. These findings were also confirmed with in situ field studies; arrival of Saharan dust in the Caribbean and subtropical Atlantic coincided with high levels of dissolved Fe, followed by up to a 30-fold increase of culturable Vibrio over background levels within 24 h. The relative abundance of Vibrio increased from ∼1 to ∼20% of the total microbial community. This study, to our knowledge, is the first to describe Vibrio response to Saharan dust nutrients, having implications at the intersection of marine ecology, Fe biogeochemistry, and both human and environmental health.

Proceedings of the National Academy of Sciences of↗
USGS2010

Decadal trends in marine reserves reveal differential rates of change in direct and indirect effects

Decadal-scale observations of marine reserves suggest that indirect effects on taxa that occur through cascading trophic interactions take longer to develop than direct effects on target species. Combining and analyzing a unique set of long-term time series of ecologic data in and out of fisheries closures from disparate regions, we found that the time to initial detection of direct effects on target species (+ or -SE) was 5.13 + or - 1.9 years, whereas initial detection of indirect effects on other taxa, which were often trait mediated, took significantly longer (13.1 + or - 2.0 years). Most target species showed initial direct effects, but their trajectories over time were highly variable. Many target species continued to increase, some leveled off, and others decreased. Decreases were due to natural fluctuations, fishing impacts from outside reserves, or indirect effects from target species at higher trophic levels. The average duration of stable periods for direct effects was 6.2 + or - 1.2 years, even in studies of more than 15 years. For indirect effects, stable periods averaged 9.1 + or - 1.6 years, although this was not significantly different from direct effects. Populations of directly targeted species were more stable in reserves than in fished areas, suggesting increased ecologic resilience. This is an important benefit of marine reserves with respect to their function as a tool for conservation and restoration.

Proceedings of the National Academy of Sciences↗
USGS2024

Critical considerations for communicating environmental DNA science

The economic and methodological efficiencies of environmental DNA (eDNA) based survey approaches provide an unprecedented opportunity to assess and monitor aquatic environments. However, instances of inadequate communication from the scientific community about confidence levels, knowledge gaps, reliability, and appropriate parameters of eDNA-based methods have hindered their uptake in environmental monitoring programs and, in some cases, has created misperceptions or doubts in the management community. To help remedy this situation, scientists convened a session at the Second National Marine eDNA Workshop to discuss strategies for improving communications with managers. These include articulating the readiness of different eDNA applications, highlighting the strengths and limitations of eDNA tools for various applications or use cases, communicating uncertainties associated with specified uses transparently, and avoiding the exaggeration of exploratory and preliminary findings. Several key messages regarding implementation, limitations, and relationship to existing methods were prioritized. To be inclusive of the diverse managers, practitioners, and researchers, we and the other workshop participants propose the development of communication workflow plans, using RACI (Responsible, Accountable, Consulted, Informed) charts to clarify the roles of all pertinent individuals and parties and to minimize the chance for miscommunications. We also propose developing decision support tools such as Structured Decision-Making (SDM) to help balance the benefits of eDNA sampling with the inherent uncertainty, and developing an eDNA readiness scale to articulate the technological readiness of eDNA approaches for specific applications. These strategies will increase clarity and consistency regarding our understanding of the utility of eDNA-based methods, improve transparency, foster a common vision for confidently applying eDNA approaches, and enhance their benefit to the monitoring and assessment community.

Environmental DNA↗
USGS2007

USGS: Science to understand and forecast change in coastal ecosystems

The multidisciplinary approach of the US Geological Survey (USGS), a principal science agency of the US Department of the Interior (DOI), to address the complex and cumulative impacts of human activities and natural events on the US coastal ecosystems has been considered remarkable for understanding and forecasting the changes. The USGS helps explain geologic, hydrologic, and biologic systems and their connectivity across landscapes and seascapes along the coastline. The USGS coastal science programs effectively address science and information to other scientists, managers, policy makers, and the public. The USGS provides scientific expertise, capabilities, and services to collaborative federal, regional, and state-led efforts, which are in line with the goals of Ocean Action Plan (OAP) and Ocean Research Priorities Plan (ORPP). The organization is a leader in understanding terrestrial and marine environmental hazards such as earthquakes, tsunamis, floods, and landslides and assessing and forecasting coastal impacts using various specialized visualization techniques.

Sea Technology↗
USGS1966

Sediment transport in a Precambrian ice age: The Huronian Gowganda Formation

The Gowganda Formation of Ontario consists of conglomerates, quartzites, and argillites deposited in a glacial environment. The distribution of varved argillites and silty limestones suggests continental and marine facies, respectively. Pebble and ripple-drift orientations, distribution of limestones, striated pavements, distribution of the underlying Bruce Group, and Huronian quartzite paleocurrents support the conclusion that sediment transport was from north to south.

Ontario↗
USGS2019

A Bayesian life-cycle model to estimate escapement at maximum sustained yield in salmon based on limited information

Life-cycle models combine several strengths for estimating population parameters and biological reference points of harvested species and are particularly useful for those exhibiting distinct habitat shifts and experiencing contrasting environments. Unfortunately, time series data are often limited to counts of adult abundance and harvest. By incorporating data from other populations and by dynamically linking the life-history stages, Bayesian life-cycle models can be used to estimate stage-specific productivities and capacities as well as abundance of breeders that produce maximum sustained yield (MSY). Using coho salmon ( Oncorhynchus kisutch ) as our case study, we show that incorporating information on marine survival variability from nearby populations can improve model estimates and affect management parameters such as escapement at MSY. We further show that the expected long-term average yield of a fishery managed for a spawner escapement target that produces MSY strongly depends on the average marine survival. Our results illustrate the usefulness of incorporating information from other sources and highlight the importance of accounting for variation in marine survival when making inferences about the management of Pacific salmon.

Washington↗