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At least 685 records · Page 38Linked to original sources
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↗
USGS2010

Meeting report: knowledge and gaps in developing microbial criteria for inland recreational waters

The U.S. Environmental Protection Agency (EPA) has committed to issuing in 2012 new or revised criteria designed to protect the health of those who use surface waters for recreation. For this purpose, the U.S. EPA has been conducting epidemiologic studies to establish relationships between microbial measures of water quality and adverse health outcomes among swimmers. New methods for testing water quality that would provide same-day results will likely be elements of the new criteria. Although the epidemiologic studies upon which the criteria will be based were conducted at Great Lakes and marine beaches, the new water quality criteria may be extended to inland waters (IWs). Similarities and important differences between coastal waters (CWs) and IWs that should be considered when developing criteria for IWs were the focus of an expert workshop. Here, we summarize the state of knowledge and research needed to base IWs microbial criteria on sound science. Two key differences between CWs and IWs are the sources of indicator bacteria, which may modify the relationship between indicator microbes and health risk, and the relationship between indicators and pathogens, which also may vary within IWs. Monitoring using rapid molecular methods will require the standardization and simplification of analytical methods, as well as greater clarity about their interpretation. Research needs for the short term and longer term are described.

Environmental Health Perspectives↗
USGS2010

Locating inputs of freshwater to Lynch Cove, Hood Canal, Washington, using aerial infrared photography

The input of freshwater and associated nutrients into Lynch Cove and lower Hood Canal (fig. 1) from sources such as groundwater seeps, small streams, and ephemeral creeks may play a major role in the nutrient loading and hydrodynamics of this low dissolved-oxygen (hypoxic) system. These disbursed sources exhibit a high degree of spatial variability. However, few in-situ measurements of groundwater seepage rates and nutrient concentrations are available and thus may not represent adequately the large spatial variability of groundwater discharge in the area. As a result, our understanding of these processes and their effect on hypoxic conditions in Hood Canal is limited. To determine the spatial variability and relative intensity of these sources, the U.S. Geological Survey Washington Water Science Center collaborated with the University of Washington Applied Physics Laboratory to obtain thermal infrared (TIR) images of the nearshore and intertidal regions of Lynch Cove at or near low tide. In the summer, cool freshwater discharges from seeps and streams, flows across the exposed, sun-warmed beach, and out on the warm surface of the marine water. These temperature differences are readily apparent in aerial thermal infrared imagery that we acquired during the summers of 2008 and 2009. When combined with co-incident video camera images, these temperature differences allow identification of the location, the type, and the relative intensity of the sources.

Fact Sheet↗
USGS2026

Pliocene (Piacenzian) planktic foraminiferal biogeography: Insights into how planktic biogeography is linked to climate and socioeconomic impacts on marine ecosystems

The Piacenzian Age (3.60–2.58 Ma) of the Pliocene Epoch was characterized by globally warmer climates, higher sea levels, and atmospheric CO 2 similar to present. Utilizing a robust dataset of 2,101 samples and over 637,000 foraminifer specimens from 77 deep-sea core sites worldwide, we document planktic foraminifer biogeography and biodiversity during the mid-Piacenzian Warm Period (mPWP). Cluster analysis and multidimensional scaling reveal five major bioregions: tropical, warm subtropical, transitional, polar, and a distinct North Atlantic polar bioregion. Each bioregion was dominated by characteristic species with well-established temperature preferences. Analyses demonstrate higher species richness and evenness in low and mid-latitudes, with increased diversity associated with periods of climatic warming and poleward expansion of warm water assemblages. The long-term stability of biogeographic patterns underscores ecological conservatism but also highlights potential vulnerability to rapid anthropogenic climate change. Our findings emphasize the critical role of planktic foraminifers in reconstructing past ocean conditions and offer valuable insights into links between planktic biogeography, climate, and socioeconomic impacts on marine ecosystems. This work advances our understanding of marine ecosystem responses to climate extremes and provides a foundation for future regional and temporal analyses of planktic foraminifer biogeography under global change scenarios.

Frontiers in Earth Science↗
USGS2021

Reduced recruitment of Chinook salmon in a leveed bar-built estuary

Estuaries are commonly touted as nurseries for salmonids, providing numerous advantages for smolts prior to ocean entry. In bar-built estuaries, sandbars form at the mouth of rivers during periods of low stream flow, closing access to the ocean and preventing outmigration. We evaluated how summer residency in a leveed bar-built estuary affects the growth, survival, and recruitment of a Chinook salmon ( Oncorhynchus tshawytscha ) population. We performed a mark–recapture study on outmigrants to determine juvenile estuary abundance, growth, and survival. We used returning adult scales and otoliths to determine the relative proportion of summer estuary residents in spawning adults. Juveniles in the estuary grew less after mouth closure, and ultimately summer estuary residents had lower smolt-to-adult survival and contributed disproportionately less to the spawning population than juveniles that reared in the ocean their first summer. Mouth closure may lower food availability and deteriorate estuary conditions by reducing marine prey influx and estuary circulation. This research demonstrates the complexity of estuary dynamics and function as salmonid nurseries, particularly when considering the extensive modification of estuaries.

California↗
USGS1995

Stratigraphy and paleoenvironments of the Shell 410-1 well, Georges Bank Basin, US North Atlantic outer continental shelf

The Shell 410-1 well is the most downdip (seaward) hydrocarbon exploratory well in the Georges Bank Basin. It was drilled to a total depth of 4745 m RKB, and penetrated a section composed of Middle Jurassic to Quaternary sedimentary rocks. The lithostratigraphy of the section is described. The strata penetrated by the Shell 410-1 well are more marine than rocks at the updip (landward) COST G-1, Exxon 975-1, COST G-2, and Conoco 145-1 well sites. Limestones and calcareous mudstones dominate at the Shell 410-1 site. Dolomite and anhydrite are much more abundant in the Bajocian-Callovian strata of the Shell 410-1 well, which is evidence that the carbonate-bank palaeoenvironments recorded in the Iroquois and Abenaki Formations were more restricted (less marine) here than 47 km to the west-northwest at the Mobil 312-1 well site near the edge of the Jurassic carbonate platform. -from Authors

Northeastern Geology and Environmental Sciences↗
USGS1996

Global distribution of beryllium isotopes in deep ocean water as derived from Fe-Mn crusts

The direct measurement of the ratio of cosmogenic 10 Be ( T 1 2 = 1.5 Ma "> T12= 1.5 Ma ) to stable terrigenously sourced 9 Be in deep seawater or marine deposits can be used to trace water mass movements and to quantify the incorporation of trace metals into the deep sea. In this study a SIMS-based technique has been used to determine the 10 Be 9 Be "> 10Be9Be ratios of the outermost millimetre of hydrogenetic ferromanganese crusts from the worlds oceans. 10 Be 9 Be "> 10Be9Be ratios, time-corrected for radioactive decay of cosmogenic 10 Be using 234 U 238 U "> 234U238U , are in good agreement with AMS measurements of modern deep seawater. Ratios are relatively low in the North and equatorial Atlantic samples (0.4–0.5 × 10 −7 ). In the Southwest Atlantic ratios increase up to 1 × 10 −7 , they vary between 0.7 and 1.0 × 10 −7 in Indian Ocean samples, and have a near constant value of 1.1 ± 0.2 × 10 −7 for all Pacific samples. If the residence time of 10 Be ( τ 10 Be ) in deep water is constant globally, then the observed variations in 10 Be 9 Be "> 10Be9Be ratios could be caused by accumulation of 10 Be in deep water as it flows and ages along the conveyor, following a transient depletion upon its formation in the Northern Atlantic. In this view both 10 Be and 9 Be reach local steady-state concentration in Pacific deep water and the global τ10 Be ≌ 600 a ">≌ τ10Be≌ 600a . An alternative possibility is that the Be isotope abundances are controlled by local scavenging. For this scenario τ 10 Be would vary according to local particle concentration and would ≌ 600 a in the central Pacific, but τ10 Be ≌ 230 a ">≌ τ10Be≌ 230a in the Atlantic. Mass balance considerations indicate that hydrothermal additions of 9 Be to the oceans are negligible and that the dissolved riverine source is also small. Furthermore, aeolian dust input of 9 Be appears insufficient to provide the dissolved 9 Be inventory. The dissolution of only a small proportion (2%) of river-derived particulates could in principle supply the observed seawater 9 Be content. If true, ocean margins would be the sites for 9 Be addition. Due to the particle-reactive nature of Be, these would also be the primary sites of Be removal. A possible net result of horizontal water masses passing through these marginal areas might be a decrease in seawater 10 Be 9 Be "> 10Be9Be , and establishment of a relatively constant 9 Be concentration. As τ 10 Be (∼ 600 a) is less than the apparent age of deep water in the Pacific (∼ 1500 a), the Pacific record of 10 Be 9 Be "> 10Be9Be is not expected to show secular variations due to changes in deep-water flow, despite the large variations in 10 Be 9 Be "> 10Be9Be between different water masses. Because of this insensitivity to deep-water flow, however, it is suggested that the 10 Be 9 Be "> 10Be9Be ratio, determined in the authigenic phase of marine sediments or hydrogenetic precipitates, should be a suitable tool for monitoring changes in continental input or cosmic ray intensity on longer time scales.

Earth and Planetary Science Letters↗