SEARCH · Geology Reports

Results for “Interfaces”

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

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

USGS1999

Upgrade to MODFLOW-GUI; addition of MODPATH, ZONEBDGT, and additional MODFLOW packages to the U.S. Geological Survey MODFLOW-96 Graphical-User Interface

This report describes enhancements to a Graphical-User Interface (GUI) for MODFLOW-96, the U.S. Geological Survey (USGS) modular, three-dimensional, finitedifference ground-water flow model, and MOC3D, the USGS three-dimensional, method-ofcharacteristics solute-transport model. The GUI is a plug-in extension (PIE) for the commercial program Argus ONEe. The GUI has been modified to support MODPATH (a particle tracking post-processing package for MODFLOW), ZONEBDGT (a computer program for calculating subregional water budgets), and the Stream, Horizontal-Flow Barrier, and Flow and Head Boundary packages in MODFLOW. Context-sensitive help has been added to make the GUI easier to use and to understand. In large part, the help consists of quotations from the relevant sections of this report and its predecessors. The revised interface includes automatic creation of geospatial information layers required for the added programs and packages, and menus and dialog boxes for input of parameters for simulation control. The GUI creates formatted ASCII files that can be read by MODFLOW-96, MOC3D, MODPATH, and ZONEBDGT. All four programs can be executed within the Argus ONEe application (Argus Interware, Inc., 1997). Spatial results of MODFLOW-96, MOC3D, and MODPATH can be visualized within Argus ONEe. Results from ZONEBDGT can be visualized in an independent program that can also be used to view budget data from MODFLOW, MOC3D, and SUTRA. Another independent program extracts hydrographs of head or drawdown at individual cells from formatted MODFLOW head and drawdown files. A web-based tutorial on the use of MODFLOW with Argus ONE has also been updated. The internal structure of the GUI has been modified to make it possible for advanced users to easily customize the GUI. Two additional, independent PIEs were developed to allow users to edit the positions of nodes and to facilitate exporting the grid geometry to external programs.

Open-File Report↗

USGS2004

Development of a benthic-flux chamber for measurement of ground-water seepage and water sampling for mercury analysis at the sediment-water interface

A benthic-flux chamber was constructed to collect data to determine the relation between ground- and surface-water interaction and mercury concentrations in water at the sediment- water interface. The benthic-flux chamber was successfully used to measure the rate of ground water seeping to surface water or surface water seeping to ground water, and to collect water samples for mercury analysis from the sedimentwater interface in a lake setting. The benthic-flux chamber was designed to be deployed in relatively calm fresh water lakes, in areas of water less than 2 meters deep. The groundwater seepage rate data were comparable to data from an in-line flow meter in a calibration tank and with data from two 55-gallon drum seepage meters concurrently deployed in two different lakes. The benthic-flux chamber was used to collect possible water samples for analysis of total mercury and methylmercury concentrations.

Minnesota↗

USGS2008

Estimating Water Fluxes Across the Sediment-Water Interface in the Lower Merced River, California

The lower Merced River Basin was chosen by the U.S. Geological Survey?s (USGS) National Water Quality Assessment Program (NAWQA) to be included in a national study on how hydrological processes and agricultural practices interact to affect the transport and fate of agricultural chemicals. As part of this effort, surface-water?ground-water (sw?gw) interactions were studied in an instrumented 100-m reach on the lower Merced River. This study focused on estimating vertical rates of exchange across the sediment?water interface by direct measurement using seepage meters and by using temperature as a tracer coupled with numerical modeling. Temperature loggers and pressure transducers were placed in monitoring wells within the streambed and in the river to continuously monitor temperature and hydraulic head every 15 minutes from March 2004 to October 2005. One-dimensional modeling of heat and water flow was used to interpret the temperature and head observations and deduce the sw?gw fluxes using the USGS numerical model, VS2DH, which simulates variably saturated water flow and solves the energy transport equation. Results of the modeling effort indicate that the Merced River at the study reach is generally a slightly gaining stream with small head differences (cm) between the surface water and ground water, with flow reversals occurring during high streamflow events. The average vertical flux across the sediment?water interface was 0.4?2.2 cm/day, and the range of hydraulic conductivities was 1?10 m/day. Seepage meters generally failed to provide accurate data in this high-energy system because of slow seepage rates and a moving streambed resulting in scour or burial of the seepage meters. Estimates of streambed hydraulic conductivity were also made using grain-size analysis and slug tests. Estimated hydraulic conductivity for the upstream transect determined using slug tests ranged from 40 to 250 m/day, whereas the downstream transect ranged from 10 to 100 m/day. The range in variability was a result of position along each transect. A relative percent difference was used to describe the variability in estimates of hydraulic conductivity by grain-size analysis and slug test. Variability in applied methods at the upstream transect ranged from 0 to 9 percent, whereas the downstream transect showed greater variability, with a range of 80 to 133 percent.

Scientific Investigations Report↗

USGS2022

U.S. Geological Survey Hydrologic Toolbox — A graphical and mapping interface for analysis of hydrologic data

The Hydrologic Toolbox is a Windows-based desktop software program that provides a graphical and mapping interface for analysis of hydrologic time-series data with a set of widely used and standardized computational methods. The software combines the analytical and statistical functionality provided in the U.S. Geological Survey Groundwater and Surface-Water Toolboxes and provides several enhancements to these programs. The main analytical methods are the computation of hydrologic-frequency statistics such as the 7-day minimum flow that occurs on average only once every 10 years (7Q10); the computation of design flows, including biologically based flows; the computation of flow-duration curves and duration hydrographs; eight computer-programming methods for hydrograph separation of a streamflow time series, including the Base-Flow Index (BFI), HYSEP, PART, and SWAT Bflow methods and Eckhardt’s two-parameter digital-filtering method; and the RORA recession-curve displacement method and associated RECESS program to estimate groundwater-recharge values from streamflow data. Several of the statistical methods provided in the Hydrologic Toolbox are used primarily for computation of critical low-flow statistics. The Hydrologic Toolbox also facilitates retrieval of streamflow and groundwater-level time-series data from the U.S. Geological Survey National Water Information System and outputs text reports that describe their analyses. The Hydrologic Toolbox was developed by use of the DotSpatial geographic information system (GIS) programming library, which is part of the MapWindow project. DotSpatial is a nonproprietary, open-source program written for the .NET framework that includes a spatial data viewer and GIS capabilities. Advantages of the DotSpatial system include its pure .NET implementation for both the user interface and the GIS mapping engine, and thus the DotSpatial system simplifies software deployment and installation. In addition to combining the functionality of the separate Groundwater and Surface-Water Toolboxes, the Hydrologic Toolbox also organizes the functionality by theme (Groundwater Tools, Surface-Water Tools, and general Time-Series Tools). This report provides a description of how to build a Hydrologic Toolbox project and to download and manage hydrologic time-series data. It includes an overview of the analytical and statistical capabilities of the Hydrologic Toolbox and highlights the primary differences between the Hydrologic Toolbox and the Groundwater and Surface-Water Toolboxes. The report supplements information available in an extensive online Help manual and is intended to provide a set of instructions that will allow users to quickly develop skills to use the mapping, data-retrieval, and computational tools of the program.

Techniques and Methods↗

USGS2006

JUPITER: Joint Universal Parameter IdenTification and Evaluation of Reliability - An Application Programming Interface (API) for Model Analysis

he Joint Universal Parameter IdenTification and Evaluation of Reliability Application Programming Interface (JUPITER API) improves the computer programming resources available to those developing applications (computer programs) for model analysis. The JUPITER API consists of eleven Fortran-90 modules that provide for encapsulation of data and operations on that data. Each module contains one or more entities: data, data types, subroutines, functions, and generic interfaces. The modules do not constitute computer programs themselves; instead, they are used to construct computer programs. Such computer programs are called applications of the API. The API provides common modeling operations for use by a variety of computer applications. The models being analyzed are referred to here as process models, and may, for example, represent the physics, chemistry, and(or) biology of a field or laboratory system. Process models commonly are constructed using published models such as MODFLOW (Harbaugh et al., 2000; Harbaugh, 2005), MT3DMS (Zheng and Wang, 1996), HSPF (Bicknell et al., 1997), PRMS (Leavesley and Stannard, 1995), and many others. The process model may be accessed by a JUPITER API application as an external program, or it may be implemented as a subroutine within a JUPITER API application . In either case, execution of the model takes place in a framework designed by the application programmer. This framework can be designed to take advantage of any parallel processing capabilities possessed by the process model, as well as the parallel-processing capabilities of the JUPITER API. Model analyses for which the JUPITER API could be useful include, for example: Compare model results to observed values to determine how well the model reproduces system processes and characteristics. Use sensitivity analysis to determine the information provided by observations to parameters and predictions of interest. Determine the additional data needed to improve selected model predictions. Use calibration methods to modify parameter values and other aspects of the model. Compare predictions to regulatory limits. Quantify the uncertainty of predictions based on the results of one or many simulations using inferential or Monte Carlo methods. Determine how to manage the system to achieve stated objectives. The capabilities provided by the JUPITER API include, for example, communication with process models, parallel computations, compressed storage of matrices, and flexible input capabilities. The input capabilities use input blocks suitable for lists or arrays of data. The input blocks needed for one application can be included within one data file or distributed among many files. Data exchange between different JUPITER API applications or between applications and other programs is supported by data-exchange files. The JUPITER API has already been used to construct a number of applications. Three simple example applications are presented in this report. More complicated applications include the universal inverse code UCODE_2005 (Poeter et al., 2005), the multi-model analysis MMA (Eileen P. Poeter, Mary C. Hill, E.R. Banta, S.W. Mehl, and Steen Christensen, written commun., 2006), and a code named OPR_PPR (Matthew J. Tonkin, Claire R. Tiedeman, Mary C. Hill, and D. Matthew Ely, written communication, 2006). This report describes a set of underlying organizational concepts and complete specifics about the JUPITER API. While understanding the organizational concept presented is useful to understanding the modules, other organizational concepts can be used in applications constructed using the JUPITER API.

Techniques and Methods↗

USGS2011

ModelMate - A graphical user interface for model analysis

ModelMate is a graphical user interface designed to facilitate use of model-analysis programs with models. This initial version of ModelMate supports one model-analysis program, UCODE_2005, and one model software program, MODFLOW-2005. ModelMate can be used to prepare input files for UCODE_2005, run UCODE_2005, and display analysis results. A link to the GW_Chart graphing program facilitates visual interpretation of results. ModelMate includes capabilities for organizing directories used with the parallel-processing capabilities of UCODE_2005 and for maintaining files in those directories to be identical to a set of files in a master directory. ModelMate can be used on its own or in conjunction with ModelMuse, a graphical user interface for MODFLOW-2005 and PHAST.

Techniques and Methods↗

USGS1995

Numerical Simulation of Regional Changes in Ground-Water Levels and in the Freshwater-Saltwater Interface Induced by Increased Pumpage at Barbers Point Shaft, Oahu, Hawaii

The effect on the regional ground-water system of southern Oahu from increased pumpage at Barbers Point shaft was estimated by a numerical ground-water model developed for the Oahu Regional Aquifer Systems Analysis (RASA) study. The RASA model was updated by revising pumping and ground-water recharge data. Pumpage data used in the new simulations were based on the allocated pumping rates for 1995 as set by the State Commission on Water Resource Management. On the basis of numerical simulation, Barbers Point shaft can sustain a withdrawal rate of 4.34 million gallons per day without adversely affecting wells in the Waianae aquifer. From results of numerical simulations, it is estimated that, as a result of increasing pumpage in Barbers Point shaft by 2 million gallons per day above the 1995-allocated rate of 2.337 million gallons per day, regional declines in ground-water levels will be about 0.4 to 0.7 feet throughout the Waianae aquifer and about 0.8 ft at the shaft. The corresponding rise of the freshwater-saltwater interface, as a result of declines in ground-water levels, is estimated to be about 20 to 30 feet. Numerical simulation also indicates that changes in ground-water levels greater than about 0.1 feet do not extend across either the Waianae-Koolau unconformity or the south Schofield barrier. The model-estimated position of the freshwater-saltwater interface, as a result of additional pumpage, ranges from 500 to 860 feet below sea level in the southern and northern parts of the aquifer, respectively, and about 540 feet below sea level at the shaft. On the basis of an estimate of the thickness of the transition-zone, the freshwater lens would remain about 240 feet thick below the shaft. In addition, the estimated declines in ground-water levels throughout the aquifer are small compared with the thickness of the freshwater lens and these declines would not be expected to affect the yields of other wells in terms of quantity. Chloride concentrations in the water pumped at Barbers Point shaft were about 240 milligrams per liter in 1992. The estimated background chloride concentration is 200 to 220 milligrams per liter because of low rainfall and the contamination of recharge water from natural salt accumulation in the soil. A reduction in irrigation through 1995 is expected to reduce recharge to the aquifer from irrigation-return water and chloride concentrations associated with the irrigation water throughout the Waianae aquifer. As a result of these combined effects, chloride concentrations of water pumped from the Barbers Point shaft will likely decrease, although the length of time required for this lowering is unknown.

Water-Resources Investigations Report↗

USGS1999

Geochemistry and hydrogeologic framework of the saline-freshwater interface and the calculation of net recharge in the Dorado area, north-central Puerto Rico

The upper aquifer near Dorado, Puerto Rico, is a major source of water for both public and private supply. The aquifer is composed of portions of the Aguada Limestone, Aymam6n Limestone, and adjacent permeable portions of unconsolidated deposits. As water moves through the aquifer it changes from a calcium-bicarbonate type water in the upgradient portions of the aquifer to a sodium-chloride type water in the downgradient portions of the aquifer near the coast. Pumping from the aquifer for industrial use and public supply has lowered the water table to near sea level in some areas, causing saline intrusion to be a concern. The saline-freshwater interface was located by drilling and borehole geophysics. Drilling and borehole geophysics helped locate the lower limit of the aquifer. The saline-freshwater interface is narrow close to the coast and thickens with distance from the coast. Ground-water hydrographs in the study area were simulated with a deterministic model that allows net recharge to be calculated from precipitation data and ground water level data. Calculated net recharge rates ranged from 160 millimeters per year in 1995 at the Santa Rosa well site to 260 millimeters per year in 1996 at the Maguayo well site.

Water-Resources Investigations Report↗

USGS2014

Stratigraphic controls on fluid and solute fluxes across the sediment-water interface of an estuary

Shallow stratigraphic features, such as infilled paleovalleys, modify fresh groundwater discharge to coastal waters and fluxes of saltwater and nutrients across the sediment–water interface. We quantify the spatial distribution of shallow surface water–groundwater exchange and nitrogen fluxes near a paleovalley in Indian River Bay, Delaware, using a hand resistivity probe, conventional seepage meters, and pore-water samples. In the interfluve (region outside the paleovalley) most nitrate-rich fresh groundwater discharges rapidly near the coast with little mixing of saline pore water, and nitrogen transport is largely conservative. In the peat-filled paleovalley, fresh groundwater discharge is negligible, and saltwater exchange is deep (∼1 m). Long pore-water residence times and abundant sulfate and organic matter promote sulfate reduction and ammonium production in shallow sediment. Reducing, iron-rich fresh groundwater beneath paleovalley peat discharges diffusely around paleovalley margins offshore. In this zone of diffuse fresh groundwater discharge, saltwater exchange and dispersion are enhanced, ammonium is produced in shallow sediments, and fluxes of ammonium to surface water are large. By modifying patterns of groundwater discharge and the nature of saltwater exchange in shallow sediments, paleovalleys and other stratigraphic features influence the geochemistry of discharging groundwater. Redox reactions near the sediment–water interface affect rates and patterns of geochemical fluxes to coastal surface waters. For example, at this site, more than 99% of the groundwater-borne nitrate flux to the Delaware Inland Bays occurs within the interfluve portion of the coastline, and more than 50% of the ammonium flux occurs at the paleovalley margin.

Delaware↗

USGS2005

The GIS weasel - An interface for the development of spatial information in modeling

The GIS Weasel is a map and Graphical User Interface (GUI) driven tool that has been developed as an aid to modelers in the delineation, characterization of geographic features, and their parameterization for use in distributed or lumped parameter physical process models. The interface does not require user expertise in geographic information systems (GIS). The user does need knowledge of how the model will use the output from the GIS Weasel. The GIS Weasel uses Workstation ArcInfo and its the Grid extension. The GIS Weasel will run on all platforms that Workstation ArcInfo runs (i.e. numerous flavors of Unix and Microsoft Windows).The GIS Weasel requires an input ArcInfo grid of some topographical description of the Area of Interest (AOI). This is normally a digital elevation model, but can be the surface of a ground water table or any other data that flow direction can be resolved from. The user may define the AOI as a custom drainage area based on an interactively specified watershed outlet point, or use a previously created map. The user is then able to use any combination of the GIS Weasel's tool set to create one or more maps for depicting different kinds of geographic features. Once the spatial feature maps have been prepared, then the GIS Weasel s many parameterization routines can be used to create descriptions of each element in each of the user s created maps. Over 200 parameterization routines currently exist, generating information about shape, area, and topological association with other features of the same or different maps, as well many types of information based on ancillary data layers such as soil and vegetation properties. These tools easily integrate other similarly formatted data sets.

Conference Paper↗

USGS2007

Multi-channel resistivity investigations of the freshwater-saltwater interface: A new tool to study an old problem

It has been well established that fresh or brackish groundwater can exist both near and far from shore in many coastal and marine environments. The often permeable nature of marine sediments and the underlying bedrock provides abundant pathways for submarine groundwater discharge. While submarine groundwater discharge as a coastal hydrogeological phenomenon has been widely recognized, only recent advances in both geochemical tracers and geophysical tools have enabled a realistic, systematic quantification of the scales and rates of this coastal groundwater discharge. Here we present multichannel electrical resistivity results using both a time series, stationary cable that has 56 electrodes spaced 2 m apart, as well as a 120 m streaming resistivity cable that has two current-producing electrodes and eight potential electrodes spaced 10 m apart. As the cable position remains fixed in stationary mode, we can examine in high resolution tidal forcing on the freshwater-saltwater interface. Using a boat to conduct streaming resistivity surveys, relatively large spatial transects can be rapidly (travel speed -2-3 knots) acquired in shallow (-1-20 m) waters. Sediment formation factors, used to convert resistivity values to salinity, were calculated from porewater and sediment samples collected during the installation of an offshore well in Tampa Bay, Florida, USA. Here we examine the seabed resistivity from sites within Tampa Bay using both stationary and streaming configurations and discuss their overall effectiveness as a new tool to examine the dynamic nature of the freshwater-saltwater interface.

Conference Paper↗

USGS2011

The need to consider temporal variability when modelling exchange at the sediment-water interface

Most conceptual or numerical models of flows and processes at the sediment-water interface assume steady-state conditions and do not consider temporal variability. The steady-state assumption is required because temporal variability, if quantified at all, is usually determined on a seasonal or inter-annual scale. In order to design models that can incorporate finer-scale temporal resolution we first need to measure variability at a finer scale. Automated seepage meters that can measure flow across the sediment-water interface with temporal resolution of seconds to minutes were used in a variety of settings to characterize seepage response to rainfall, wind, and evapotranspiration. Results indicate that instantaneous seepage fluxes can be much larger than values commonly reported in the literature, although seepage does not always respond to hydrological processes. Additional study is needed to understand the reasons for the wide range and types of responses to these hydrologic and atmospheric events.

Conference Paper↗

USGS2017

Nutrient processes at the stream-lake interface for a channelized versus unmodified stream mouth

Inorganic forms of nitrogen and phosphorous impact freshwater lakes by stimulating primary production and affecting water quality and ecosystem health. Communities around the world are motivated to sustain and restore freshwater resources and are interested in processes controlling nutrient inputs. We studied the environment where streams flow into lakes, referred to as the stream-lake interface (SLI), for a channelized and unmodified stream outlet. Channelization is done to protect infrastructure or recreational beach areas. We collected hydraulic and nutrient data for surface water and shallow groundwater in two SLIs to develop conceptual models that describe characteristics that are representative of these hydrologic features. Water, heat, and solute transport models were used to evaluate hydrologic conceptualizations and estimate mean residence times of water in the sediment. A nutrient mass balance model is developed to estimate net rates of adsorption and desorption, mineralization, and nitrification along subsurface flow paths. Results indicate that SLIs are dynamic sources of nutrients to lakes and that the common practice of channelizing the stream at the SLI decreases nutrient concentrations in pore water discharging along the lakeshore. This is in contrast to the unmodified SLI that forms a barrier beach that disconnects the stream from the lake and results in higher nutrient concentrations in pore water discharging to the lake. These results are significant because nutrient delivery through pore water seepage at the lakebed from the natural SLI contributes to nearshore algal communities and produces elevated concentrations of inorganic nutrients in the benthic zone where attached algae grow.

Water Resources Research↗

USGS2022

The wildland-urban interface in the United States based on 125 million building locations

The wildland-urban interface (WUI) is the focus of many important land management issues, such as wildfire, habitat fragmentation, invasive species, and human-wildlife conflicts. Wildfire is an especially critical issue, because housing growth in the WUI increases wildfire ignitions and the number of homes at risk. Identifying the WUI is important for assessing and mitigating impacts of development on wildlands and for protecting homes from natural hazards, but data on housing development for large areas are often coarse. We created new WUI maps for the conterminous U.S. based on 125 million individual building locations, offering higher spatial precision compared to existing maps based on U.S. census housing data. Building point locations were based on a building footprint dataset from Microsoft®. We classified WUI across the conterminous U.S. at 30-m resolution using a circular neighborhood mapping algorithm with a variable radius to determine thresholds of housing density and vegetation cover. We used our maps to (1) determine the total area of the WUI and number of buildings included, (2) assess the sensitivity of WUI area included and spatial pattern of WUI maps to choice of neighborhood size, (3) assess regional differences between building-based WUI maps and census-based WUI maps, and (4) determine how building location accuracy affected WUI map accuracy. Our building-based WUI maps identified 5.6% – 18.8% of the conterminous U.S. as being in the WUI, with larger neighborhoods increasing WUI area but excluding isolated building clusters. Building-based maps identified more WUI area relative to census-based maps for all but the smallest neighborhoods, particularly in the north-central states, and large differences were attributable to high numbers of non-housing structures in rural areas. Overall WUI classification accuracy was 98.0%. For wildfire risk mapping and for general purposes, WUI maps based on the 500-m neighborhood represent the original Federal Register definition of the WUI; these maps include clusters of buildings in and adjacent to wildlands and exclude remote, isolated buildings. Our approach for mapping the WUI offers flexibility and high spatial detail, and can be widely applied to take advantage of the growing availability of high-resolution building footprint datasets and classification methods.

Conterminous United States↗

USGS2019

Advances in computational morphodynamics using the International River Interface Cooperative (iRIC) software

Results from computational morphodynamics modeling of coupled flow-bed-sediment systems are described for ten applications as a review of recent advances in the field. Each of these applications is drawn from solvers included in the public-domain International River Interface Cooperative (iRIC) software package. For mesoscale river features such as bars, predictions of alternate and higher mode river bars are shown for flows with equilibrium sediment supply and for a single case of oversupplied sediment. For microscale bed features such as bedforms, computational results are shown for the development and evolution of two-dimensional bedforms using a simple closure-based two-dimensional model, for two- and three-dimensional ripples and dunes using a three-dimensional large-eddy simulation flow model coupled to a physics-based particle transport model, and for the development of bed streaks using a three-dimensional unsteady Reynolds-averaged Navier-Stokes solver with a simple sediment-transport treatment. Finally, macroscale or channel evolution treatments are used to examine the temporal development of meandering channels, a failure model for cantilevered banks, the effect of bank vegetation on channel width, the development of channel networks in tidal systems, and the evolution of bedrock channels. In all examples, computational morphodynamics results from iRIC solvers are shown to compare well to observations of natural bed morphology. For each of the three scales investigated here, brief suggestions for future work and potential research directions are offered.

Earth Surface Processes and Landforms↗

USGS2017

The land-sea interface: A source of high-quality phytoplankton to support secondary production

Coastal-estuarine systems are among the most productive marine ecosystems and their special role in producing harvestable fish and shellfish has been attributed to high primary production fueled by nutrient runoff from land and efficient trophic transfer. Here we ask if phytoplankton species composition and their food quality based on the percentage of long-chain essential fatty acids (LCEFA) is another factor contributing to high secondary production in these ecosystems. We used long-term measurements of major phytoplankton taxonomic groups and estimated their content of LCEFA along the salinity gradient in coastal-estuarine ecosystems, with emphasis on Chesapeake Bay and the Baltic Sea, and an oceanic transect. Our data show that cyanobacteria with low nutritional quality often dominate at low-salinity regions, while intermediate to higher salinity regions produce diatoms and dinoflagellates that have a higher content of LCEFA and are thus a higher-quality food resource for consumers. Higher salinity regions have less pronounced seasonal changes in the percentage of phytoplankton LCEFA compared to low salinity regions, providing a stable supply of nutritious phytoplankton to consumers. The phytoplankton LCEFA content is similarly high in coastal upwelling systems and it decreases further offshore in oligotrophic oceanic regions dominated by picophytoplankton. Our results from a broad range of coastal-ecosystem types show that ecosystems at the land-sea interface provide a valuable service by producing phytoplankton enriched in the biochemicals essential for consumers. High primary production, coupled with high quality of that production, explain why the production of fish and shellfish is high where land and sea meet.

Limnology and Oceanography↗

USGS2020

Introduction: Ecological subsidies as a framework for understanding contaminant fate, exposure, and effects at the land-water interface

Ecologists have long recognized that ecological subsidies (the flow of organic matter, nutrients, and organisms between ecosystems) can strongly affect ecosystem processes and community structure in the recipient ecosystem. Animal movements, organic matter flows, and food web dynamics between linked aquatic and terrestrial systems can also influence contaminant fate, exposure, and effects at the land-water interface. Here and in this book, we develop a broad framework that highlights two important ways that ecological subsidies and contaminants interact. Ecological subsidies from the donor system can drive exposure to recipient systems, and contaminant exposures in the donor system can control subsidies and contaminant fluxes to the recipient systems. In the case of prey movement between ecosystems, subsidies drive exposure when contaminants present in aquatic environments bioaccumulate in the tissues of prey organisms at levels that are relatively non-toxic to the prey themselves. Conversely, exposure in the aquatic system can limit subsidies when pollutants are relatively toxic to prey organisms themselves and the magnitude of the subsidy (i.e., biomass of aquatic insects emerging to the terrestrial environment) is reduced. These effects of contaminants on subsidies are shaped by other global stressors that are ubiquitous in aquatic-riparian ecosystems (e.g., climate and land use change, species extinction and invasion, and eutrophication). As our understanding of these ecological and toxicological processes advances, there are increasing opportunities to make landscape-scale predictions of contaminant and animal fluxes and to integrate this knowledge of aquatic-riparian linkages into managing contaminant risks. Through these efforts to integrate the fields of ecology and ecotoxicology on this subject, we expect to gain greater insight on the ecological effects of contaminants on linked ecosystems as well as the ways in which food web dynamics and ecosystem processes can themselves govern the fate, transport, and exposure to contaminants in the environment.

Book chapter↗

USGS2013

The Hyper-Envelope Modeling Interface (HEMI): A Novel Approach Illustrated Through Predicting Tamarisk ( Tamarix spp.) Habitat in the Western USA

Habitat suitability maps are commonly created by modeling a species’ environmental niche from occurrences and environmental characteristics. Here, we introduce the hyper-envelope modeling interface (HEMI), providing a new method for creating habitat suitability models using Bezier surfaces to model a species niche in environmental space. HEMI allows modeled surfaces to be visualized and edited in environmental space based on expert knowledge and does not require absence points for model development. The modeled surfaces require relatively few parameters compared to similar modeling approaches and may produce models that better match ecological niche theory. As a case study, we modeled the invasive species tamarisk ( Tamarix spp.) in the western USA. We compare results from HEMI with those from existing similar modeling approaches (including BioClim, BioMapper, and Maxent). We used synthetic surfaces to create visualizations of the various models in environmental space and used modified area under the curve (AUC) statistic and akaike information criterion (AIC) as measures of model performance. We show that HEMI produced slightly better AUC values, except for Maxent and better AIC values overall. HEMI created a model with only ten parameters while Maxent produced a model with over 100 and BioClim used only eight. Additionally, HEMI allowed visualization and editing of the model in environmental space to develop alternative potential habitat scenarios. The use of Bezier surfaces can provide simple models that match our expectations of biological niche models and, at least in some cases, out-perform more complex approaches.

Environmental Management↗