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USGS2021

Yellowstone Volcano Observatory 2020 annual report

The Yellowstone Volcano Observatory (YVO) monitors volcanic and hydrothermal activity associated with the Yellowstone magmatic system, conducts research into magmatic processes occurring beneath Yellowstone Caldera, and issues timely warnings and guidance related to potential future geologic hazards. This report summarizes the activities and findings of YVO during the year 2020, focusing on the Yellowstone volcanic system. Highlights of YVO research and related activities during 2020 include an active-source seismic experiment to image the top of Yellowstone’s magma reservoir; semipermanent Global Positioning System array deployment, including a new site near Mary Mountain; studies of hydrothermal activity in the southwest portion of Yellowstone National Park; numerous geological studies, including characterization of hydrothermal explosion craters, updating existing maps, and refining the ages of Yellowstone volcanic units; investigation of a dormant period at Old Faithful Geyser that may be related to regional drought 800–650 years ago, and development of a publicly available online map interface. Steamboat Geyser, in Norris Geyser Basin, continued the pattern of frequent eruptions that began in 2018 with 48 water eruptions in 2020, matching the record for a calendar year that was set in 2019. Giantess Geyser, in the Upper Geyser Basin, erupted for the first time in 6 years in August 2020 and experienced a second eruption in September. Patterns of both seismicity and deformation in 2020 were similar to those in 2019. Deformation patterns during 2020 showed trends that were similar to previous years. Overall subsidence of the caldera floor, ongoing since late 2015 or early 2016, continued at rates of a few centimeters (1–2 inches) per year, and minor subsidence of Norris Geyser Basin that began in 2018 slowed during 2020 and stopped by the end of the year. Throughout 2020, the aviation color code for Yellowstone Caldera remained at “green” and the volcano alert level remained at “normal.”

Idaho, Montana, Wyoming↗
USGS2024

StreamStats—A quarter century of delivering web-based geospatial and hydrologic information to the public, and lessons learned

StreamStats is a U.S. Geological Survey (USGS) web application that provides streamflow statistics, such as the 1-percent annual exceedance probability peak flow, the mean flow, and the 7-day, 10-year low flow, to the public through a map-based user interface. These statistics are used in many ways, such as in the design of roads, bridges, and other structures; in delineation of floodplains for land-use zoning and setting of insurance rates; for regulatory purposes, such as the permitting of wastewater discharges; and for hydrologic and climate change studies. StreamStats was first developed for Massachusetts and released in 2001. The application provided users with the ability to obtain streamflow statistics computed from data collected at USGS streamgages and to obtain estimates of streamflow statistics for user-selected ungaged sites. Massachusetts StreamStats used geographic information system software and digital mapping to compute drainage-basin characteristics, which were then used in statistical models to estimate streamflow statistics for the user-selected sites. The statistical models were in the form of equations that were developed through a process known as regression analysis. StreamStats was the first known web application with the ability to do interactive geoprocessing. The utility of Massachusetts StreamStats was instantly apparent, leading the USGS to develop a version of StreamStats that could be implemented nationally. USGS State offices normally were required to develop custom regression equations and prepare local digital mapping data needed for implementing StreamStats for their States. Funding needed to complete this work usually was provided through cooperative agreements between the USGS and State agencies. In 2004, Idaho became the first to be released in the national version of StreamStats. By 2023, 44 States were fully implemented and six were undergoing implementation. StreamStats has undergone many modifications over the years to keep up with changes to the underlying software and to add functionality. Customized functionality and separate linked StreamStats applications were developed for several States. Meeting the high demand for additions and improvements to StreamStats while also adhering to budgetary constraints has, at times, been challenging. The StreamStats development team has identified numerous additional improvements that could be made to provide better performance and more functionality. The lessons learned from the experience of building and operating StreamStats for nearly 25 years could be relevant to others interested in pursuing efforts of a similar scale.

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USGS2025

ShakeAlert®—Communication, education, outreach and technical engagement strategic vision

Executive Summary In 2006, the U.S. Geological Survey (USGS) began directly supporting ShakeAlert ® research and in 2012 the ShakeAlert demonstration system began testing ( Given and others, 2018 ). The ShakeAlert earthquake early warning (EEW) system is a partnership between the U.S. Geological Survey (USGS) and the three West Coast States (Washington, Oregon, and California) served by the ShakeAlert System, which is part of the larger Advanced National Seismic System (ANSS). With more than 143 million people exposed to potentially damaging shaking in the United States ( Jaiswal and others, 2015 ), earthquakes are a national hazard. Most of our Nation’s earthquake risk is concentrated in the highly populated areas on the active plate tectonic boundaries on the West Coast of the conterminous United States. ShakeAlert is the first public alert system in the United States to provide rapid mass notification of earthquake detection, potentially offering seconds of warning before strong shaking arrives. A few seconds may not seem like much time, but the information in ShakeAlert Messages can be used to trigger automated actions that can prevent injury or death, reduce immediate damage, and speed recovery from earthquakes. The information product issued by the ShakeAlert system is called a ShakeAlert Message and is one of the information products and tools of the ANSS. The ShakeAlert System includes the USGS component, plus the pathways by which ShakeAlert-powered products and (or) services are delivered to end users. Alerts can be delivered to cell phones or be used to trigger automated systems to protect equipment, facilities, and infrastructure, such as slowing or stopping a train. ShakeAlert-powered automated actions can include fire house doors that can be opened to prevent jamming, heavy equipment (for example, trains, elevators, and cranes) that can be automatically stopped or parked in safe positions, and pipeline valves that can be closed to prevent surges and spills. A few seconds of warning also may be sufficient for people to take protective actions, such as drop, cover, and hold on or modified protective actions for a broad range of populations. Advance training may increase the benefit of a speedy response to an alert. Outreach and education about EEW may raise awareness of the overall earthquake threat and how people can best react when they receive an alert or feel shaking. ShakeAlert communication, education, outreach, and technical engagement (CEO&TE) efforts are highly collaborative and essential for the success of the ShakeAlert System. This strategic vision informs how the vast ShakeAlert CEO&TE Community operates and works together. The CEO&TE Community delineates a strategic framework that is intended to set the path for a long-term, sustainable approach to CEO&TE through three focus areas and five priorities. Focus Areas Technical engagement.— The objective of this focus area is to expand and broaden ShakeAlert technical engagement and implementation. External engagement.— This focus area targets engagement in long-term communication, education, and outreach planning, implementation, and evaluation. Internal engagement.— The purpose of this focus area is to build and sustain a robust infrastructure to optimize collaboration, information sharing, and project planning among the community of stakeholders charged with implementing ShakeAlert CEO&TE. Priorities The enumeration of the five priorities listed below does not suggest priority ranking. Public safety, preparedness, and resilience; Technical implementation and engagement; Consistent messaging and communication; Integration with other Federal and State earthquake hazards products; and Educational resources development and dissemination. This strategic vision is a tangible outcome of collaboration among many stakeholders beginning in July 2016. Since then, the work of the ShakeAlert CEO&TE Community has grown into an international effort. The USGS has developed, tested, and implemented a broad spectrum of communication, education, and outreach tools and resources—all of which recognize that seconds matter when it comes to safety and mitigating harm from earthquake hazards. The CEO&TE social science research effort has provided invaluable insights into the ShakeAlert System’s human interface. USGS-licensed technical partners develop, test, and implement real-world applications using ShakeAlert Messages. The success of ShakeAlert CEO&TE efforts is predicated on robust collaboration across numerous agencies, organizations, and groups. As such, this strategic vision outlines a “partnership model” that delineates roles and responsibilities to ensure alignment with focus areas and priorities. The partnership model includes the CEO&TE lead agency (USGS); its principal partners (State agencies and university partners); its implementation partners (for example, technical partners who build systems to deliver ShakeAlert-powered products and (or) services [focus area one]), earthquake education partners who work to increase public preparedness for seismic events (focus area two); and other organizations that work together to enhance the adoption and effectiveness of the ShakeAlert System. These partners collaborate and convene through a variety of working groups and forums, which are also described in this strategic vision and align with focus area three (internal engagement). The CEO&TE Community collaboratively developed its operating principles and a consensus-based, decision-making strategic framework to guide its collective work. Performance metrics are used to continually measure success. Ultimately, the USGS and ShakeAlert CEO&TE Community are advancing the ShakeAlert System that as of the publication of this strategic vision to “provide earthquake early warning for all” serves more than 50 million people.

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USGS1978

Stratigraphic test well, Nantucket Island, Massachusetts

The U.S. Geological Survey, in cooperation with the Massachusetts Water Resources Commission and the Nantucket Conservation Foundation, continuously cored 514 m of sediment and volcanic rock in a stratigraphic and water-quality test near the geographic center of Nantucket Island. Stratified sediments were divided texturally into three zones: the upper zone (0-128 m) contains mostly coarse sand and gravel; the middle zone (128-349 m) contains mostly silty clay and a few beds of sand and silt; and the lower zone (349-457 m) contains soft, unconsolidated, clayey sand. Below the lower zone, a saprolite, composed mostly of clay, grades abruptly downward at 470 m into partially altered basalt that extends to the bottom of the hole at 514 m. Calculations based on the Ghyben-Herzberg principle predicted a zone of freshwater 120-150 m thick. This principle is the theory of hydrostatic equilibrium between freshwater and more dense seawater in a coastal aquifer; it states that for each meter of ground-water elevation above sea level, the freshwater lens will depress the saltwater interface about 40 m below sea level. Freshwater or low-salinity brackish water was found in sediments far below the depth predicted by the Ghyben-Herzberg principle. These interstitial waters are probably relict ground water emplaced during times of low sea level during the Pleistocene. (Woodard-USGS)

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USGS2026

USGS Geochron—A database of geochronological and thermochronological dates and data—Technical documentation

Geochronological and thermochronological data are essential for constraining the timing and rates of geological processes, supporting geologic mapping, natural hazard assessment, and resource exploration. The U.S. Geological Survey (USGS) Geochron Database is a centralized, relational database that integrates USGS and State geological survey data in accordance with the National Geologic Mapping Act of 1992 and its reauthorizations. This report documents the structure and development of the database, including its standardized schema, controlled vocabularies, and protocols for compiling legacy and newly published data. The database is designed to adhere to FAIR (Findable, Accessible, Interoperable, and Reusable) data principles and currently (2026) includes data from a wide range of geochronological and thermochronological methods. Public access is provided through the USGS Geochron Database Explorer, a browser-based geographic information system (GIS) interface, and through versioned data releases available on ScienceBase, which provide sample-level summary data and detailed analytical information. The USGS Geochron Database is structured to be extensible, supporting the inclusion of additional methods and data types as they are compiled. This format ensures long-term utility and aligns with the Mapping Act’s directive to create a national archive of geochronological information that adds interpretive value to geologic map data. Its design reflects a commitment to data transparency, scientific reproducibility, and national geoscience priorities.

Data Report↗
USGS2014

Magnetic susceptibility data for some exposed bedrock in the western conterminous United States

In-place rock magnetic susceptibility measurements for 746 sites in the western conterminous United States are reported in a database. Of these 746 sites, 408 sites are in the Silverton Caldera area of the San Juan Mountains of southwestern Colorado. Of the 408 sites in the Silverton Caldera area, 106 sites are underground. The remaining 338 sites outside the Silverton Caldera area were on outcropping rock, are distributed from southern Arizona to northwestern Wyoming, and include data from California, Nevada, Utah, Colorado, and New Mexico. Rock-density measurements are included for some sites. These data have been collected by various U.S. Geological Survey studies from 1991 through 2012 and are intended to help improve geophysical modeling of the Earth’s crust in the Western United States. A map-based graphical user interface is included to facilitate use of the data.

Arizona, California, Colorado, Nevada, New Mexico,↗
USGS2014

Land-margin ecosystem hydrologic data for the coastal Everglades, Florida, water years 1996-2012

Mangrove forests and salt marshes dominate the landscape of the coastal Everglades (Odum and McIvor, 1990). However, the ecological effects from potential sea-level rise and increased water flows from planned freshwater Everglades restoration on these coastal systems are poorly understood. The National Park Service (NPS) proposed the South Florida Global Climate Change Project (SOFL-GCC) in 1990 to evaluate climate change and the effect from rising sea levels on the coastal Everglades, particularly at the marsh/mangrove interface or ecotone (Soukup and others, 1990). A primary objective of SOFL-GCC project was to monitor and synthesize the hydrodynamics of the coastal Everglades from the upstream freshwater marsh to the downstream estuary mangrove. Two related hypotheses were set forward (Nuttle and Cosby, 1993): 1. There exists hydrologic conditions (tide, local rainfall, and upstream water deliveries), which characterize the location of the marsh/mangrove ecotone along the marine and terrestrial hydrologic gradient; and 2. The marsh/mangrove ecotone is sensitive to fluctuations in sea level and freshwater inflow from inland areas. Hydrologic monitoring of the SOFL-GCC network began in 1995 after startup delays from Hurricane Andrew (August 1992) and organizational transfers from the NPS to the National Biological Survey (October 1993) and the merger with the U.S. Geological Survey (USGS) Biological Research Division in 1996 (Smith, 2004). As the SOFL-GCC project progressed, concern by environmental scientists and land managers over how the diversion of water from Everglades National Park would affect the restoration of the greater Everglades ecosystem. Everglades restoration scenarios were based on hydrodynamic models, none of which included the coastal zone (Fennema and others, 1994). Modeling efforts were expanded to include the Everglades coastal zone (Schaffranek and others, 2001) with SOFL-GCC hydrologic data assisting the ecological modeling needs. In 2002, as a response for a more interdisciplinary science approach to understanding the coastal Everglades ecological system, the SOFL-GCC hydrology project was integrated into the “Dynamics of Land-Margin Ecosystems: Historical Change, Hydrology, Vegetation, Sediment, and Climate” study (Smith and others, 2002). Data from the ongoing study has been useful in providing an empirical hydrologic baseline for the greater Everglades ecosystem restoration science and management needs. The hydrology network consisted of 13 hydrologic gaging stations installed in the southwestern coastal region of Everglades National Park along three transects: Shark River (Shark or SH) transect, Lostmans River (Lostmans or LO) transect, and Chatham River (Chatham or CH) transect (fig. 1). There were five paired surface-water/groundwater gaging stations on the Shark transect (SH1, SH2, SH3, SH4, and SH5) and one stage gaging station (BSC) in the Big Sable Creek; four paired surface-water/groundwater gaging stations on the Lostmans transect (LO1, LO2, LO3, and LO4); and three paired surface-water/groundwater gaging stations on the Chatham transect (CH1, CH2, and CH3). Both surface-water and groundwater levels, salinities, and temperatures were monitored at the paired gaging stations. Rainfall was recorded at marsh and open canopy gaging stations. This report details the study introduction, method, and description of data collected, which are accessible through the final instantaneous hydrologic dataset stored in the USGS South Florida Information Access (SOFIA) South Florida Hydrology Database website, http://sofia.usgs.gov/exchange/sfl_hydro_data/location.html#brdlandmargin .

Florida↗
USGS2015

Seismic data collection from water gun and industrial background sources in the Chicago Sanitary and Ship Canal area, Illinois, 2011

The water gun is a tool adapted from deep marine geophysical surveys that is being evaluated for use as an acoustic fish deterrent to control the movement of invasive marine species. The water gun creates a seismic signal by using a compressed air discharge to move a piston rapidly within the water, resulting in an implosion. This energy pulse may be able to modify fish behavior or destroy marine life, such as the Asian carp, at some distance. The effects of this energy pulse on structures in the Chicago Sanitary and Ship Canal (CSSC), such as canal walls, shore lines, and lock structures, are not known. The potential effects of the use of a water gun on structures was identified as a concern in the CSSC and was assessed relative to existing background sources during this study. During September 2011, two water guns with piston sizes of 80 and 343 cubic inches, respectively, were tested in the CSSC at varying pressures and distances from a canal wall consisting of dolomite and dolomite setblock. Seismic data were collected during these water gun firings using geophones on land, in boreholes, and at the canal wall interface. Data were collected at varying depths in the canal water using hydrophones. Seismic data were also collected during the occurrences of barge traffic, railroad traffic located near the electric fish barrier in Lemont, and coal-loading operations at a coal power plant near the electric fish barrier. In general, energy produced by barge and railroad sources was less than energy created by the water gun. Energy levels produced by coal-loading operations at least 200 feet from geophones were approximately four times lower than energy levels measured during water gun operations.

Illinois↗
USGS2003

Effects of hydrology on red mangrove recruits

Coastal wetlands along the Gulf of Mexico have been experiencing significant shifts in hydrology and salinity levels over the past century as a result of changes in sea level and freshwater drainage patterns. Local land management in coastal zones has also impacted the hydrologic regimes of salt marshes and mangrove areas. Parks and refuges in south Florida that contain mangrove forests have, in some cases, been ditched or impounded to control mosquito outbreaks and to foster wildlife use. And while mangroves dominate the subtropical coastlines of Florida and thrive in saltwater environments, little is known about how they respond to changes in hydrology under managed or variable tidal conditions. USGS researchers designed a study to evaluate the basic hydrological requirements of mangroves so that their health and survival may be more effectively managed in controlled impoundments and restored wetlands. Mangroves are commonly found in the intertidal zone (between low and high tides) in a rather broad spectrum of hydrologic settings. Because they thrive at the interface of land and sea, mangroves are subject to changes in freshwater flow (flow rate, nutrients, pollutants) and to marine influences (sea-level rise, salinity). Salinity has long been recognized as a controlling factor that determines the health and distribution of mangrove forests. Field and experimental observations indicate that most mangrove species achieve their highest growth potential under brackish conditions (modest salinity) between 10 and 20 parts per thousand (ppt). Yet, if provided with available propagules, successful regeneration, and limited competition from other plants, then mangroves can survive and thrive in freshwater systems as well. Because little is known about the growthand survival patterns of mangrove species relative to changing hydrology, USGS scientists conducted greenhouse and field experiments to determine how flooded or drained patterns of hydrology would influence growth of the red mangrove, Rhizophora mangle (fig. 1). Red mangrove propagules (recruits) of select sizes and genotypes (i.e., genetically similar groups) were planted both in greenhouses and in the field. Seedling growth was monitored in both studies on a quarterly basis for over a year; measurements included shoot growth, seedling height, and a final harvest of plant biomass.

Fact Sheet↗
USGS1997

Revision and product generation software

The U.S. Geological Survey (USGS) developed revision and product generation (RevPG) software for updating digital line graph (DLG) data and producing maps from such data. This software is based on ARC/INFO, a geographic information system from Environmental Systems Resource Institute (ESRI). RevPG consists of ARC/INFO Arc Macro Language (AML) programs, C routines, and interface menus that permit operators to collect vector data using aerial images, to symbolize the data on-screen, and to produce plots and color-separated files for use in printing maps.

Fact Sheet↗
USGS1999

U.S. Geological Survey and Microsoft Cooperative Research and Development Agreement: Geospatial Data Browsing and Retrieval Site on the World Wide Web

In May 1997, the U.S. Geological Survey (USGS) and the Microsoft Corporation of Redmond, Wash., entered into a cooperative research and development agreement (CRADA) to make vast amounts of geospatial data available to the general public through the Internet. The CRADA is a 36-month joint effort to develop a general, public-oriented browsing and retrieval site for geospatial data on the Internet. Specifically, Microsoft plans to (1) modify a large volume of USGS geospatial data so the images can be displayed quickly and easily over the Internet, (2) implement an easy-to-use interface for low-speed connections, and (3) develop an Internet Web site capable of servicing millions of users per day.

Fact Sheet↗
USGS1997

Predicting coastal flooding and wetland loss

The southeastern coastal region encompasses vast areas of wetland habitat important to wildlife and other economically valuable natural resources. Located on the interface between sea and land, these wetland habitats are affected by both sea-level rise and hurricanes, and possibly by hydroperiod associated with regional climatic shifts. Increased sea level is expected to accompany global warming because of higher sea temperatures and ice melt. To help determine the effects of sea-level rise on these wetlands, USGS scientists created computer models of coastal flooding and wetland loss.

Florida↗
USGS2000

Obtaining Streamflow Statistics for Massachusetts Streams on the World Wide Web

A World Wide Web application has been developed to make it easy to obtain streamflow statistics for user-selected locations on Massachusetts streams. The Web application, named STREAMSTATS (available at http://water.usgs.gov/osw/streamstats/massachusetts.html ), can provide peak-flow frequency, low-flow frequency, and flow-duration statistics for most streams in Massachusetts. These statistics describe the magnitude (how much), frequency (how often), and duration (how long) of flow in a stream. The U.S. Geological Survey (USGS) has published streamflow statistics, such as the 100-year peak flow, the 7-day, 10-year low flow, and flow-duration statistics, for its data-collection stations in numerous reports. Federal, State, and local agencies need these statistics to plan and manage use of water resources and to regulate activities in and around streams. Engineering and environmental consulting firms, utilities, industry, and others use the statistics to design and operate water-supply systems, hydropower facilities, industrial facilities, wastewater treatment facilities, and roads, bridges, and other structures. Until now, streamflow statistics for data-collection stations have often been difficult to obtain because they are scattered among many reports, some of which are not readily available to the public. In addition, streamflow statistics are often needed for locations where no data are available. STREAMSTATS helps solve these problems. STREAMSTATS was developed jointly by the USGS and MassGIS, the State Geographic Information Systems (GIS) agency, in cooperation with the Massachusetts Departments of Environmental Management and Environmental Protection. The application consists of three major components: (1) a user interface that displays maps and allows users to select stream locations for which they want streamflow statistics (fig. 1), (2) a data base of previously published streamflow statistics and descriptive information for 725 USGS data-collection stations, and (3) an automated procedure that determines characteristics of the land-surface area (basin) that drains to the stream and inserts those characteristics into equations that estimate the streamflow statistics. Each of these components is described and guidance for using STREAMSTATS is provided below.

Fact Sheet↗
USGS1998

U.S. Geological Survey and Microsoft Cooperative Research and Development Agreement: Geospatial Data Browsing and Retrieval Site on the World Wide Web

In May 1997, the U.S. Geological Survey (USGS) and the Microsoft Corporation of Redmond, Wash., entered into a cooperative research and development agreement (CRADA) to make vast amounts of geospatial data available to the general public through the Internet. The CRADA is a 36-month joint effort to develop a general, public-oriented browsing and retrieval site for geospatial data on the Internet. Specifically, Microsoft plans to (1) modify a large volume of USGS geospatial data so the images can be displayed quickly and easily over the Internet, (2) implement an easy-to-use interface for low-speed connections, and (3) develop an Internet Web site capable of servicing millions of users per day.

Fact Sheet↗
USGS1997

Estimated rate of recharge in outcrops of the Chicot and Evangeline aquifers near Houston, Texas

During 1989-90, the U.S. Geological Survey (USGS), in cooperation with the Harris-Galveston Coastal Subsidence District, conducted a field study to determine the depth to the water table and to estimate the rate of recharge in outcrops of the Chicot and Evangeline aquifers near Houston, Texas. The study area (fig. 1) comprises about 2,000 square miles of outcrops of the Chicot and Evangeline aquifers in northwestern Harris County, Montgomery County, and southern Walker County. The depth to the water table was estimated using seismic refraction, and an estimated rate of recharge in the aquifer outcrops was computed using the tritium-interface method (Andres and Egger, 1985) in which environmental tritium is the ground-water tracer. The water table generally ranges in depth between 10 and 30 feet in the study area, and the average total recharge rate was estimated to be not larger than 6 inches per year. The rate is total recharge to the saturated zone, rather than net recharge to the deep regional flow system. The total recharge can be reduced by evapotranspiration and by local discharge, mainly to streams. These results are published in USGS Water-Resources Investigations Report 96-4018 (Noble and others, 1996). A second study of environmental tritium in the same area as the 1989-90 study, also in cooperation with the Harris-Galveston Coastal Subsidence District, was done in 1996 to confirm the results of the original study. This fact sheet documents the estimation of an upper limit on the average total recharge rate on the basis of the vertical movement of tritium in ground water during 1953-89 and during 1953-95.

Fact Sheet↗
USGS1996

Technology transfer opportunities: new development: computerized field manual provides valuable resource for hydrologic investigations

The U.S. Geological Survey (USGS) is known throughout the world for conducting quality scientific investigation is hydrologic environments. Proper and consistent field techniques have been an integral part of this good research. Over the past few decades, the USGS has developed and published detailed, standard protocols for conducting studies in most aspects of the hydrologic environment. These protocols have been published in a number of diverse documents. The wealth of information contained in these diverse documents can benefit other scientists in industry, government, and academia that are involved in conducting hydrologic studies. Scientists at the USGS have brought together many of the most important of the field protocols in a user-friendly, graphical-interfaced field manual that will be useful in both the field and in the office. This electronic field manual can assist hydrologists and other scientists in conducting and documenting their field activities in a manner that is recognized standard throughout the hydrologic community.

Fact Sheet↗
USGS2004

Novel geophysical and geochemical techniques used to study submarine groundwater discharge in Biscayne Bay, Florida

Introduction Submarine groundwater discharge (SGD) is a problem of major proportions on a world-wide scale. The ubiquitous nature of SGD along varied coastlines and its importance to coastal water and geochemical budgets have recently been thrust into the global spotlight . For example, the discharge of nutrient-enriched groundwater into coastal waters may cause nutrient imbalances that can lead to eutrophication or near-shore micro-organism blooms . Similarly, SGD can also directly affect threatened coastal freshwater resources and impact fragile coastal ecosystems, such as coral reefs. Recently, much effort has been devoted to developing and adapting new tracer techniques and methods for the identification and quantification of SGD. As the discharge of coastal groundwater most often occurs as diffuse seepage rather than through a single vent feature, assessing SGD has remained difficult for both oceanographers and hydrologists alike. Burnett and colleagues have developed a systematic approach to investigate SGD by using a combination of both physical seepage measurements and a suite of naturally occurring isotopic tracers in the U/Th decay chain – 222 Rn and 223,224,226,228 Ra. Manheim et al. further extended SGD investigations by adapting geophysical resistivity techniques to examine fine-scale change in conductivity fields within coastal sediments. Such streaming resistivity profiling has been successfully applied to identify sites of SGD, as well as the dynamic position of the fresh water/saltwater interface.

Florida↗
USGS2004

Nutrient controls on biocomplexity of mangrove ecosystems

Mangrove forests are important coastal ecosystems that provide a variety of ecological and societal services. These intertidal, tree-dominated communities along tropical coastlines are often described as “simple systems,” compared to other tropical forests with larger numbers of plant species and multiple understory strata; however, mangrove ecosystems have complex trophic structures, and organisms exhibit unique physiological, morphological, and behavioral adaptations to environmental conditions characteristic of the land-sea interface. Biogeochemical functioning of mangrove forests is also controlled by interactions among the microbial, plant, and animal communities and feedback linkages mediated by hydrology and other forcing functions. Scientists with the U.S. Geological Survey (USGS) at the National Wetlands Research Center are working to understand more fully the impact of nutrient variability on these delicate and important ecosystems.

Fact Sheet↗