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USGS2023

Assessing individual movement, habitat use, and behavior of non-breeding marine birds in relation to prey availability in the US Atlantic

Resource availability is a key factor driving marine bird movements and distributions, but direct information on prey availability is difficult to obtain at relevant scales. We present novel methods for describing multi-scale trophic associations, combining movement analyses of marine birds with estimates of forage fish surface aggregations from digital aerial survey data and species occupancy from bottom trawl survey data. We analyzed satellite telemetry data from northern gannets Morus bassanus , red-throated loons Gavia stellata , and long-tailed ducks Clangula hyemalis in the US Atlantic during the non-breeding period. Using discrete-time hidden Markov models to distinguish area-restricted (i.e. putative foraging) from transit movements, we examined how environmental factors influence movement, and how forage fish species distributions and surface aggregations influence habitat use by gannets and loons that have greater dietary reliance. Our results suggest that chlorophyll a concentration significantly affected movement behavior across species, highlighting the importance of higher-productivity areas around estuaries during colder months when regional productivity is low. Though variable across species and seasons, spatial cross-correlation analysis revealed that herring species (Family Clupeidae), including Atlantic menhaden Brevoortia tyrannus , may be important resources; it also showed positive spatial correlations with forage fish aggregations. This suggests that prey patch dynamics and factors driving aggregation formation may be as important as species composition. However, spatial patterns were generally low (<0.3), suggesting a mismatch in spatiotemporal resolution, exemplifying the challenges in quantifying trophic relationships in marine systems. Disentangling predator-prey relationships is critical to understanding the mechanisms driving marine bird behavior in rapidly changing marine systems.

Atlantic Ocean↗

USGS2007

Estimation of gonad volume, fecundity, and reproductive stage of shovelnose sturgeon using sonography and endoscopy with application to the endangered pallid sturgeon

Most species of sturgeon are declining in the Mississippi River Basin of North America including pallid ( Scaphirhynchus albus F. and R.) and shovelnose sturgeons ( S. platorynchus R.). Understanding the reproductive cycle of sturgeon in the Mississippi River Basin is important in evaluating the status and viability of sturgeon populations. We used non-invasive, non-lethal methods for examining internal reproductive organs of shovelnose and pallid sturgeon. We used an ultrasound to measure egg diameter, fecundity, and gonad volume; endoscope was used to visually examine the gonad. We found the ultrasound to accurately measure the gonad volume, but it underestimated egg diameter by 52%. After correcting for the measurement error, the ultrasound accurately measured the gonad volume but it was higher than the true gonad volume for stages I and II. The ultrasound underestimated the fecundity of shovelnose sturgeon by 5%. The ultrasound fecundity was lower than the true fecundity for stage III and during August. Using the endoscope, we viewed seven different egg color categories. Using a model selection procedure, the presence of four egg categories correctly predicted the reproductive stage ± one reproductive stage of shovelnose sturgeon 95% of the time. For pallid sturgeon, the ultrasound overestimated the density of eggs by 49% and the endoscope was able to view eggs in 50% of the pallid sturgeon. Individually, the ultrasound and endoscope can be used to assess certain reproductive characteristics in sturgeon. The use of both methods at the same time can be complementary depending on the parameter measured. These methods can be used to track gonad characteristics, including measuring Gonadosomatic Index in individuals and/or populations through time, which can be very useful when associating gonad characteristics with environmental spawning triggers or with repeated examinations of individual fish throughout the reproductive cycle.

Journal of Applied Ichthyology↗

USGS2011

Spatial interpolation schemes of daily precipitation for hydrologic modeling

Distributed hydrologic models typically require spatial estimates of precipitation interpolated from sparsely located observational points to the specific grid points. We compare and contrast the performance of regression-based statistical methods for the spatial estimation of precipitation in two hydrologically different basins and confirmed that widely used regression-based estimation schemes fail to describe the realistic spatial variability of daily precipitation field. The methods assessed are: (1) inverse distance weighted average; (2) multiple linear regression (MLR); (3) climatological MLR; and (4) locally weighted polynomial regression (LWP). In order to improve the performance of the interpolations, the authors propose a two-step regression technique for effective daily precipitation estimation. In this simple two-step estimation process, precipitation occurrence is first generated via a logistic regression model before estimate the amount of precipitation separately on wet days. This process generated the precipitation occurrence, amount, and spatial correlation effectively. A distributed hydrologic model (PRMS) was used for the impact analysis in daily time step simulation. Multiple simulations suggested noticeable differences between the input alternatives generated by three different interpolation schemes. Differences are shown in overall simulation error against the observations, degree of explained variability, and seasonal volumes. Simulated streamflows also showed different characteristics in mean, maximum, minimum, and peak flows. Given the same parameter optimization technique, LWP input showed least streamflow error in Alapaha basin and CMLR input showed least error (still very close to LWP) in Animas basin. All of the two-step interpolation inputs resulted in lower streamflow error compared to the directly interpolated inputs.

Colorado, Georgia↗

USGS2015

Distribution of near-surface permafrost in Alaska: estimates of present and future conditions

High-latitude regions are experiencing rapid and extensive changes in ecosystem composition and function as the result of increases in average air temperature. Increasing air temperatures have led to widespread thawing and degradation of permafrost, which in turn has affected ecosystems, socioeconomics, and the carbon cycle of high latitudes. Here we overcome complex interactions among surface and subsurface conditions to map nearsurface permafrost through decision and regression tree approaches that statistically and spatially extend field observations using remotely sensed imagery, climatic data, and thematic maps of a wide range of surface and subsurface biophysical characteristics. The data fusion approach generated medium-resolution (30-m pixels) maps of near-surface (within 1 m) permafrost, active-layer thickness, and associated uncertainty estimates throughout mainland Alaska. Our calibrated models (overall test accuracy of ~85%) were used to quantify changes in permafrost distribution under varying future climate scenarios assuming no other changes in biophysical factors. Models indicate that near-surface permafrost underlies 38% of mainland Alaska and that near-surface permafrost will disappear on 16 to 24% of the landscape by the end of the 21st Century. Simulations suggest that near-surface permafrost degradation is more probable in central regions of Alaska than more northerly regions. Taken together, these results have obvious implications for potential remobilization of frozen soil carbon pools under warmer temperatures. Additionally, warmer and drier conditions may increase fire activity and severity, which may exacerbate rates of permafrost thaw and carbon remobilization relative to climate alone. The mapping of permafrost distribution across Alaska is important for land-use planning, environmental assessments, and a wide-array of geophysical studies.

Alaska↗

USGS2022

Intrapopulation differences in polar bear movement and step selection patterns

Background The spatial ecology of individuals often varies within a population or species. Identifying how individuals in different classes interact with their environment can lead to a better understanding of population responses to human activities and environmental change and improve population estimates. Most inferences about polar bear ( Ursus maritimus ) spatial ecology are based on data from adult females due to morphological constraints on applying satellite radio collars to other classes of bears. Recent studies, however, have provided limited movement data for adult males and sub-adults of both sexes using ear-mounted and glue-on tags. We evaluated class-specific movements and step selection patterns for polar bears in the Chukchi Sea subpopulation during spring. Methods We developed hierarchical Bayesian models to evaluate polar bear movement (i.e., step length and directional persistence) and step selection at the scale of 4-day step lengths. We assessed differences in movement and step selection parameters among the three classes of polar bears (i.e., adult males, sub-adults, and adult females without cubs-of-the-year). Results Adult males had larger step lengths and less directed movements than adult females. Sub-adult movement parameters did not differ from the other classes but point estimates were most similar to adult females. We did not detect differences among polar bear classes in step selection parameters and parameter estimates were consistent with previous studies. Conclusions Our findings support the use of estimated step selection patterns from adult females as a proxy for other classes of polar bears during spring. Conversely, movement analyses indicated that using data from adult females as a proxy for the movements of adult males is likely inappropriate. We recommend that researchers consider whether it is valid to extend inference derived from adult female movements to other classes, based on the questions being asked and the spatial and temporal scope of the data. Because our data were specific to spring, these findings highlight the need to evaluate differences in movement and step selection during other periods of the year, for which data from ear-mounted and glue-on tags are currently lacking.

Movement Ecology↗

USGS1998

A strategy for assessing potential future changes in climate, hydrology, and vegetation in the Western United States

Historical and geological data indicate that significant changes can occur in the Earth's climate on time scales ranging from years to millennia. In addition to natural climatic change, climatic changes may occur in the near future due to increased concentrations of carbon dioxide and other trace gases in the atmosphere that are the result of human activities. International research efforts using atmospheric general circulation models (AGCM's) to assess potential climatic conditions under atmospheric carbon dioxide concentrations of twice the pre-industrial level (a '2 X CO2' atmosphere) conclude that climate would warm on a global basis. However, it is difficult to assess how the projected warmer climatic conditions would be distributed on a regional scale and what the effects of such warming would be on the landscape, especially for temperate mountainous regions such as the Western United States. In this report, we present a strategy to assess the regional sensitivity to global climatic change. The strategy makes use of a hierarchy of models ranging from an AGCM, to a regional climate model, to landscape-scale process models of hydrology and vegetation. A 2 X CO2 global climate simulation conducted with the National Center for Atmospheric Research (NCAR) GENESIS AGCM on a grid of approximately 4.5o of latitude by 7.5o of longitude was used to drive the NCAR regional climate model (RegCM) over the Western United States on a grid of 60 km by 60 km. The output from the RegCM is used directly (for hydrologic models) or interpolated onto a 15-km grid (for vegetation models) to quantify possible future environmental conditions on a spatial scale relevant to policy makers and land managers.

Circular↗

USGS2000

Design, revision, and application of ground-water flow models for simulation of selected water-management scenarios in the coastal area of Georgia and adjacent parts of South Carolina and Florida

Ground-water flow models of the Floridan aquifer system in the coastal area of Georgia and adjacent parts of South Carolina and Florida, were revised and updated to ensure consistency among the various models used, and to facilitate evaluation of the effects of pumping on the ground-water level near areas of saltwater contamination. The revised models, developed as part of regional and areal assessments of ground-water resources in coastal Georgia, are--the Regional Aquifer-System Analysis (RASA) model, the Glynn County area (Glynn) model, and the Savannah area (Savannah) model. Changes were made to hydraulic-property arrays of the RASA and Glynn models to ensure consistency among all of the models; results of theses changes are evidenced in revised water budgets and calibration statistics. Following revision, the three models were used to simulate 32 scenarios of hypothetical changes in pumpage that ranged from about 82 million gallons per day (Mgal/d) lower to about 438 Mgal/d higher, than the May 1985 pumping rate of 308 Mgal/d. The scenarios were developed by the Georgia Department of Natural Resources, Environmental Protection Division and the Chatham County-Savannah Metropolitan Planning Commission to evaluate water-management alternatives in coastal Georgia. Maps showing simulated ground-water-level decline and diagrams presenting changes in simulated flow rates are presented for each scenario. Scenarios were grouped on the basis of pumping location--entire 24-county area, central subarea, Glynn-Wayne-Camden County subarea, and Savannah-Hilton Head Island subarea. For those scenarios that simulated decreased pumpage, the water level at both Brunswick and Hilton Head Island rose, decreasing the hydraulic gradient and reducing the potential for saltwater contamination. Conversely, in response to scenarios of increased pumpage, the water level at both locations declined, increasing the hydraulic gradient and increasing the potential for saltwater contamination. Pumpage effects on ground-water levels and related saltwater contamination at Brunswick and Hilton Head Island generally diminish with increased distance from these areas. Additional development of the Upper Floridan aquifer may be possible in parts of the coastal area without affecting saltwater contamination at Brunswick or Hilton Head Island, due to the presence of two hydrologic boundaries--the Gulf Trough, separating the northern and central subareas; and the hypothesized Satilla Line, separating the central and southern subareas. These boundaries diminish pumpage effects across them; and may enable greater ground-water withdrawal in areas north of the Gulf Trough and south of the Satilla Line without producing appreciable drawdown at Brunswick or Hilton Head Island.

Florida, Georgia, South Carolina↗

USGS2012

Associations of benthic macroinvertebrate assemblages with environmental variables in the upper Clear Creek watershed, California

Benthic macroinvertebrates are integral components of stream ecosystems and are often used to assess the ecological integrity of streams. We sampled streams in the upper Clear Creek drainage in the Klamath—Siskiyou Ecoregion of northwestern California in fall 2004 (17 sites) and 2005 (original 17 plus 4 new sites) with the objectives of documenting the benthic macroinvertebrate assemblages supported by the streams in the area, determining how those assemblages respond to environmental variables, assessing the biological condition of the streams using a benthic index of biotic integrity (IBI), and understanding the assemblages in the context of biodiversity of the ecoregion. We collected both reach-wide (RW) and targeted-riffle (TR) macroinvertebrate samples at each site. The macroinvertebrate assemblages were diverse, with over 150 genera collected for each sampling protocol. The macroinvertebrate assemblages appeared to be most responsive to a general habitat gradient based on stream size, gradient, flow, and dominance of riffles. A second important habitat gradient was based on elevation and dominance of riffles. A gradient in water quality based on concentrations of dissolved ions and metals was also important. Models based on these 3 gradients had Spearman's rank correlations with macroinvertebrate taxonomic composition of 0.60 and 0.50 for the TR and RW samples, respectively. The majority (>50%) of the sites were in good or very good biological condition based on IBI scores. The diversity of macroinvertebrate assemblages is associated with the diversity of habitats available in the Klamath—Siskiyou Ecoregion. Maintaining the aquatic habitats in good condition is important in itself but is also vital to maintaining biodiversity in this diverse and unique ecoregion.

California↗

USGS2014

Assessment of suitable habitat for Phragmites australis (common reed) in the Great Lakes coastal zone

In the Laurentian Great Lakes, the invasive form of Phragmites australis (common reed) poses a threat to highly productive coastal wetlands and shorelines by forming impenetrable stands that outcompete native plants. Large, dominant stands can derail efforts to restore wetland ecosystems degraded by other stressors. To be proactive, landscape-level management of Phragmites requires information on the current spatial distribution of the species and a characterization of areas suitable for future colonization. Using a recent basin-scale map of this invasive plant’s distribution in the U.S. coastal zone of the Great Lakes, environmental data (e.g., soils, nutrients, disturbance, climate, topography), and climate predictions, we performed analyses of current and predicted suitable coastal habitat using boosted regression trees, a type of species distribution modeling. We also investigated differential influences of environmental variables in the upper lakes (Lakes Superior, Michigan, and Huron) and lower lakes (Lakes St. Clair, Erie, and Ontario). Basin-wide results showed that the coastal areas most vulnerable to Phragmites expansion were in close proximity to developed lands and had minimal topographic relief, poorly drained soils, and dense road networks. Elevated nutrients and proximity to agriculture also influenced the distribution of Phragmites . Climate predictions indicated an increase in suitable habitat in coastal Lakes Huron and Michigan in particular. The results of this study, combined with a publicly available online decision support tool, will enable resource managers and restoration practitioners to target and prioritize Phragmites control efforts in the Great Lakes coastal zone.

Great Lakes↗

USGS2005

Watershed-based survey designs

Watershed-based sampling design and assessment tools help serve the multiple goals for water quality monitoring required under the Clean Water Act, including assessment of regional conditions to meet Section 305(b), identification of impaired water bodies or watersheds to meet Section 303(d), and development of empirical relationships between causes or sources of impairment and biological responses. Creation of GIS databases for hydrography, hydrologically corrected digital elevation models, and hydrologic derivatives such as watershed boundaries and upstream–downstream topology of subcatchments would provide a consistent seamless nationwide framework for these designs. The elements of a watershed-based sample framework can be represented either as a continuous infinite set defined by points along a linear stream network, or as a discrete set of watershed polygons. Watershed-based designs can be developed with existing probabilistic survey methods, including the use of unequal probability weighting, stratification, and two-stage frames for sampling. Case studies for monitoring of Atlantic Coastal Plain streams, West Virginia wadeable streams, and coastal Oregon streams illustrate three different approaches for selecting sites for watershed-based survey designs.

Environmental Monitoring and Assessment↗

USGS2011

A geographic information system tool for aquatic resource conservation in the Red and Sabine River Watersheds of the southeast United States

Our goal was to build a geographic information system (GIS) tool to enhance modeling and hypothesis testing relevant to watersheds and fish fauna of the Red and Sabine Rivers in the southeastern United States. Species of concern were identified from wildlife action plans and Web sites. Spatial distributions of fish species and mercury in fillets were delineated using data from states. Public georeferenced data were obtained on land cover, soil type, forest canopy, impervious surfaces, wastewater facilities and 303(d) impaired waters. Overlay maps highlighted patterns across 8-digit hydrologic unit codes (HUCs). Bossier City, Louisiana and Beaumont, Texas areas displayed impervious surfaces over 10% and 303(d) waters per HUC were 20% and 8%, respectively. Because bowfin (Amia calva) (n=299) and bass (Micropterus spp.) (n=1493) occurred in up to 44% of HUCs and fillets contained elemental mercury concentrations across ranges monitored, they were appropriate indicators of bioavailable mercury. Of the total fish number showing >0.5ppm, 81% of records were derived from bowfin and bass, and stepwise multiple linear regressions indicated fish with mercury at these concentrations correlated with environmental variables. Detrended correspondence analysis showed total species occurrence and environmental relationships significant, where 81.6% of the variability in fish occurrence was explained by impervious surface, land cover other than canopy or impervious surface (such as wetlands and agricultural area) and canopy (forest type). Two-way indicator species analysis delineated species co-occurrence in HUCs (14 groups) and similarity of species composition (nine groups). Results identified three HUC groupings as potential targets for managerial interest. Quality control concerns for GIS development included site name data and priority rankings of critical fish species. This tool can be used to support modeling and trend analyses for several purposes, such as those relevant for developing and reporting on water quality standards and critical habitat assessments.

Arkansas, Louisiana, Oklahoma, Texas↗

USGS2011

Valuing ecosystem and economic services across land-use scenarios in the Prairie Pothole Regions of the Dakotas, USA

This study uses biophysical values derived for the Prairie Pothole Region (PPR) of North and South Dakota, in conjunction with value transfer methods, to assess environmental and economic tradeoffs under different policy-relevant land-use scenarios over a 20-year period. The ecosystem service valuation is carried out by comparing the biophysical and economic values of three focal services (i.e. carbon sequestration, reduction in sedimentation, and waterfowl production) across three focal land uses in the region [i.e. native prairie grasslands, lands enrolled in the Conservation Reserve and Wetlands Reserve Programs (CRP/WRP), and cropland]. This study finds that CRP/WRP lands cannot mitigate (hectare for hectare) the loss of native prairie from a social welfare standpoint. Land use scenarios where native prairie loss was minimized, and CRP/WRP lands were increased, provided the most societal benefit. The scenario modeling projected native prairie conversion to cropland over the next 20 years would result in a social welfare loss valued at over $4 billion when considering the study's three ecosystem services, and a net loss of about $3.4 billion when reductions in commodity production are accounted for.

North Dakota;South Dakota↗

USGS1999

International river basins of the world

It is becoming acknowledged that water is likely to be the most pressing environmental concern of the next century. Difficulties in river basin management are only exacerbated when the resource crosses international boundaries. One critical aid in the assessment of international waters has been the Register of International Rivers a compendium which listed 214 international waterways that cover 47% of the earth's continental land surface. The Register, though, was last updated in 1978 by the now defunct United Nations Department of Economic and Social Affairs. The purpose of this paper is to update the Register in order to reflect the quantum changes that have taken place over the last 22 years, both in global geopolitics and in map coverage and technology. By accessing digital elevation models at spatial resolutions of 30 arc seconds, corroborating at a unified global map coverage of at least 1:1 000 000, and superimposing the results over complete coverage of current political boundaries, we are able to provide a new register which lists 261 international rivers, covering 45.3% of the land surface of the earth (excluding Antarctica). This paper lists all international rivers with their watershed areas, the nations which share each watershed,their respective territorial percentages, and notes on changes in or disputes over international boundaries since 1978.

International Journal of Water Resources Developme↗

USGS2011

Quantifying seascape structure: Extending terrestrial spatial pattern metrics to the marine realm

Spatial pattern metrics have routinely been applied to characterize and quantify structural features of terrestrial landscapes and have demonstrated great utility in landscape ecology and conservation planning. The important role of spatial structure in ecology and management is now commonly recognized, and recent advances in marine remote sensing technology have facilitated the application of spatial pattern metrics to the marine environment. However, it is not yet clear whether concepts, metrics, and statistical techniques developed for terrestrial ecosystems are relevant for marine species and seascapes. To address this gap in our knowledge, we reviewed, synthesized, and evaluated the utility and application of spatial pattern metrics in the marine science literature over the past 30 yr (1980 to 2010). In total, 23 studies characterized seascape structure, of which 17 quantified spatial patterns using a 2-dimensional patch-mosaic model and 5 used a continuously varying 3-dimensional surface model. Most seascape studies followed terrestrial-based studies in their search for ecological patterns and applied or modified existing metrics. Only 1 truly unique metric was found (hydrodynamic aperture applied to Pacific atolls). While there are still relatively few studies using spatial pattern metrics in the marine environment, they have suffered from similar misuse as reported for terrestrial studies, such as the lack of a priori considerations or the problem of collinearity between metrics. Spatial pattern metrics offer great potential for ecological research and environmental management in marine systems, and future studies should focus on (1) the dynamic boundary between the land and sea; (2) quantifying 3-dimensional spatial patterns; and (3) assessing and monitoring seascape change.

Marine Ecology Progress Series↗

USGS2018

Patch and landscape responses of bird abundance to fragmentation in agroecosystems of east-central Argentina

Forest fragmentation in agroecosystems is linked to declines of avian species worldwide. Agriculture has greatly reduced native forest cover in east-central Argentina. Assessing the influence of fragmentation on forest bird populations is vital to inform reliable conservation and management strategies for the Espinal region of Argentina. We determined the relationships of vegetation structure within native forest patches, size and shape of these patches (patch scale), composition and spatial configuration (at landscape scale) to relative abundance of 17 forest bird species during austral fall-winter and spring-summer seasons. Birds were sampled from 2007 – 2009 in 45 forest patches within three landscape mosaics (30x30 km) representing a gradient of native forest fragmentation in east-central Argentina. We used an information-theoretic approach and approximated model inference to examine the effect of predictor environmental variables at two spatial scales on patterns of forest bird abundance. Density of trees within forest patches was the main predictor of bird abundance at the patch scale. Amount of forest and spatial configuration were also important. The abundance of several bird species was greater in patches with high density of trees and landscapes characterized by more forest cover and larger patches in close proximity. We found two main avian response patterns to forest fragmentation and patch characteristics. This information contributes reliable knowledge for the design of conservation measures of agricultural landscapes in the Espinal region of Argentina.

Avian Conservation and Ecology↗

USGS2009

Mineral Resource Assessment of Marine Sand Resources in Cape- and Ridge-Associated Marine Sand Deposits in Three Tracts, New York and New Jersey, United States Atlantic Continental Shelf

Demand is growing in the United States and worldwide for information about the geology of offshore continental shelf regions, the character of the seafloor, and sediments comprising the seafloor and subbottom. Interest in locating sand bodies or high quality deposits that have potential as sources for beach nourishment and ecosystem restoration is especially great in some regions of the country. The Atlantic coast, particularly New York and New Jersey, has been the focus of these studies for the past 40 years with widely varying results. This study is the first attempt at applying probability statistics to modeling Holocene-age cape-and ridge-associated sand deposits and thus focuses on distinct sand body morphology. This modeling technique may have application for other continental shelf regions that have similar geologic character and late Quaternary sea-level transgression history. An estimated volume of 3.9 billion m3 of marine sand resources is predicted in the cape-and ridge-associated marine sand deposits in three representative regions or tracts on the continental shelf offshore of New York and New Jersey. These estimates are taken from probabilistic distributions of sand resources and are produced using deposit models and Monte Carlo Simulation (MCS) techniques. The estimated sand resources presented here are for only three tracts as described below and for Holocene age sand resources contained in cape-and ridge-associated marine sand deposit types within this area. Other areas may qualify as tracts for this deposit type and other deposit types and geologic ages (for example, paleo-stream channels, blanket and outwash deposits, ebb-tide shoals, and lower sea level-stand deltas), which are present on the New Jersey and New York continental shelf area but are not delineated and modeled in this initial evaluation. Admittedly, only a portion of these probable sand resources will ultimately be available and suitable for production, dependent largely on geographic, economic, preemptive use, environmental, geologic and political factors. In addition, offshore sand resources should only be considered if the area is seaward of the active zone of significant nearshore sediment transport, about 10 to 12 m in depth, and in sufficiently shallow water so that sand can be extracted within U.S. dredging equipment limits, currently about 40 m in depth. If the material is to be used for beach nourishment, material must be of an appropriate sediment texture and character (grain size, sorting, shape, and color) to match the native beach and have mineralogical properties important to its use. Extraction of sand can disturb or alter the benthic habitat and seafloor ecology, so these factors and other site-specific effects will need to be evaluated for any intended use. These and other factors are not considered in this report but can be expected to reduce the total net volume of sand resources available for production. The purpose of this report is to describe and present results from a probabilistic mineral modeling technique previously applied to onshore mineral resources. This modeling and assessment procedure is being used for the first time to assess and estimate offshore aggregate resources; this study is part of the U.S. Geological Survey (USGS) Marine Aggregates Resources and Processes Project (http://woodshole.er.usgs.gov/project-pages/aggregates/).

Bulletin↗

USGS2025

Multi-species telemetry quantifies current and future efficacy of a remote marine protected area

Large-scale marine protected areas (LSMPAs; > 1000 km 2 ) provide important refuge for large mobile species, but most do not encompass species' ranges. To better understand current and future LSMPA value, we concurrently tracked nine species (seabirds, cetaceans, pelagic fishes, manta rays, reef sharks) at Palmyra Atoll and Kingman Reef (PKMPA) in the U.S. Pacific Islands Heritage Marine National Monument. PKMPA and the U.S. Exclusive Economic Zone encompassed 39% and 54% of species movements ( n = 83; tracking duration range: 0.5–350 days), respectively. Species distribution models indicated 73% of PKMPA contained highly suitable habitat. Under two projected future scenarios (SSP 1–2.6, “Sustainability”; SSP 3–7.0, “Rocky Road”), strong sea surface temperature gradients initially could cause abrupt oceanic change resulting in predicted habitat loss in 2040–2050, followed by an equilibrium response and regained habitat by 2090–2100. Current and future suitable habitats were available adjacent to PKMPA, suggesting that increased MPA size could enhance protection. Our three-tiered approach combining animal tracking with publicly available remote sensing data and future projected environmental scenarios could be used to design, study, and monitor protected areas throughout the world. Holistic approaches that encompass diverse species and habitat use can enhance assessments of protected area designs. Animal telemetry and remote sensing may be helpful for ascertaining the extent to which other MPAs protect large mobile species in the future.

Kingman Reef, Palmyra Atoll, U.S. Pacific Islands ↗

USGS2025

Spatial distribution and relative biomass of bigheaded carps in Lake Balaton, Hungary estimated from an environmental DNA survey

Silver carp ( Hypophthalmichthys nobilis ), bighead carp ( H. molitrix ) and their hybrids, collectively known as bigheaded carps, have been introduced to Lake Balaton, Hungary. The current stock sizes are difficult to assess. We investigated environmental DNA (eDNA) techniques targeted for bigheaded carps, assessed the spatial distribution of eDNA in Lake Balaton, compared eDNA concentrations to environmental variables to assess potential habitat selection based on those variables, and provided an estimate of biomass of bigheaded carps relative to eDNA shedding rates per unit biomass observed in controlled experiments. Water samples were collected from 70 sites in an array across the lake. Biomass estimation was calculated using mean eDNA concentration obtained by quantitative PCR of the samples and previously determined eDNA shedding rates of bigheaded carps under controlled conditions in a laboratory. Concentration of eDNA was highly variable between sites, resulting in wide confidence intervals. Basins did not significantly differ in eDNA concentration, and there were no strong relationships between environmental variables and eDNA concentration, indications that bigheaded carps use the entire lake. The model provided an estimate of 4,830 metric tonnes (2,750–8,030 tonnes) of bigheaded carps in Lake Balaton, or 81.0 kg/ha. The eDNA method produced a value close to previous estimates by traditional means of total biomass of bigheaded carps in the lake, and like traditional methods, there was a broad confidence interval on the estimate of the mean. The results of the present study support the utility of aquatic eDNA analysis, and the need for further comparisons with fisheries methods and supporting data from laboratory studies.

Lake Balaton↗