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At least 901 records · Page 50Linked to original sources
USGS2005

Salt tolerance underlies the cryptic invasion of North American salt marshes by an introduced haplotype of the common reed Phragmites australis (Poaceae)

A distinct, non-native haplotype of the common reed Phragmites australis has become invasive in Atlantic coastal Spartina marshes. We compared the salt tolerance and other growth characteristics of the invasive M haplotype with 2 native haplotypes (F and AC) in greenhouse experiments. The M haplotype retained 50% of its growth potential up to 0.4 M NaCl, whereas the F and AC haplotypes did not grow above 0.1 M NaCl. The M haplotype produced more shoots per gram of rhizome tissue and had higher relative growth rates than the native haplotypes on both freshwater and saline water treatments. The M haplotype also differed from the native haplotypes in shoot water content and the biometrics of shoots and rhizomes. The results offer an explanation for how the M haplotype is able to spread in coastal salt marshes and support the conclusion of DNA analyses that the M haplotype is a distinct ecotype of P. australis .

Marine Ecology Progress Series↗
USGS2017

Use of fish telemetry in rehabilitation planning, management, and monitoring in Areas of Concern in the Laurentian Great Lakes

Freshwater ecosystems provide many ecosystem services; however, they are often degraded as a result of human activity. To address ecosystem degradation in the Laurentian Great Lakes, Canada and the United States of America established the Great Lakes Water Quality Agreement (GLWQA). In 1987, 43 highly polluted and impacted areas were identified under the GLWQA as having one or more of 14 Beneficial Use Impairments (BUIs) to the physical and chemical habitat for fish, wildlife and humans, and were designated as Areas of Concern (AOC). Subnational jurisdictions combined with local stakeholders, with support from federal governments, developed plans to remediate and restore these sites. Biotelemetry (the tracking of animals using electronic tags) provides information on the spatial ecology of fish in the wild relevant to habitat management and stock assessment. Here, seven case studies are presented where biotelemetry data were directly incorporated within the AOC Remedial Action Plan (RAP) process. Specific applications include determining seasonal fish–habitat associations to inform habitat restoration plans, identifying the distribution of pollutant-indicator species to identify exposure risk to contamination sources, informing the development of fish passage facilities to enable fish to access fragmented upstream habitats, and assessing fish use of created or restored habitats. With growing capacity for fish biotelemetry research in the Great Lakes, we discuss the strengths and weaknesses of incorporating biotelemetry into AOC RAP processes to improve the science and practice of restoration and to facilitate the delisting of AOCs.

Great Lakes↗
USGS2019

Infection at an ecotone: Cross‐system foraging increases satellite parasites but decreases core parasites in raccoons

Ecotones can increase free-living species richness, but little is known about how parasites respond to ecotones. Here we use parasite communities in raccoons (Procyon lotor) to test the hypothesis that parasite communities can be divided into core and satellite species, each with fundamentally different responses to ecotones. We used published parasite surveys to classify parasites as common core or rare satellite species and then surveyed raccoons in coastal California to examine how proximity to two aquatic ecotones altered parasite communities. Raccoons near ecotones had more satellite and fewer core parasite species. Specifically, the marine ecotone increased parasite diversity by adding satellite species to a persistent core community, whereas the freshwater ecotone shifted the community from core to satellite species without a net change in parasite richness. We hypothesize that increased parasite richness at the marine ecotone resulted from increased diet diversity, but that raccoons were sinks for some parasites. Increased exposure to rare parasites at ecotones has implications for wildlife health and provides insight into observed associations between ecotones and emerging disease.

California↗
USGS2022

Ocean connectivity drives trophic support for consumers in an intermittently closed coastal lagoon

Estuarine food webs are complex, as marine, freshwater, and terrestrial inputs combine and contribute variable amounts of organic material. Seasonal fluctuations in precipitation amplify the dynamism inherent to estuarine food webs, particularly in lagoonal estuaries, which can be seasonally closed and disconnected from the ocean in low-runoff periods (bar-built lagoons). Despite their abundance along coastlines in Mediterranean climates, the organic matter sources fueling bar-built lagoon food webs are poorly understood, particularly with respect to seasonal hydrologic variability, episodic marine connections, and internal nutrient cycling. In this study, we evaluate the food web of a bar-built lagoon with respect to seasonal differences in lagoon water quality, the sources of organic matter which support consumers, and the trophic ecology of resident fishes. Observed water quality conditions reflected biogeochemical processes associated with salinity-driven stratification and high lagoon residence times and were associated with strong seasonal differences in the contribution of different organic matter sources to lagoon consumers. A variety of organic matter sources supported consumers; marine inputs were important to lagoon food webs in spring when the lagoon was open, while summer food webs were largely driven by phytoplankton which was likely fueled by internal nutrient cycling. Fish diets were largely comprised of crustaceans and fish eggs, with clearly defined trophic niches in spring but high overlap in summer. This study demonstrates that the seasonal changes in bar-built lagoon food webs are largely dependent on ocean connectivity and internal cycling within the lagoon, rather than watershed processes as is typical for many estuaries.

California↗
USGS2026

Detection of Naegleria fowleri in thermally impacted recreational waters of western United States national parks

Naegleria fowleri is a thermophilic free-living amoeba (FLA) and the causative agent of primary amoebic meningoencephalitis, posing public health risks in warm freshwater environments. This multiyear, multiagency study surveyed 40 thermally impacted recreational waters across five western United States national parks and recreation areas–Yellowstone National Park, Grand Teton National Park, Olympic National Park, Newberry National Volcanic Monument, and Lake Mead National Recreation Area–to assess N. fowleri presence, concentration, and associated environmental conditions. A total of 185 water samples were analyzed by qPCR and Sanger sequencing, revealing widespread detection of N. fowleri in 34% of samples with positive detections from Lake Mead, Yellowstone, and Grand Teton hot springs and thermally impacted waters, with concentrations ranging from 4.9 to 115.7 cells/L. Multiple codetections of N. fowleri with nonpathogenic species including Naegleria australiensis were identified, suggesting they may inhabit similar ecological niches in the natural systems in contrast to engineered systems. These findings indicate that N. fowleri is present in thermally impacted areas across the western United States and underscore the use of enhanced monitoring, public awareness, and risk management strategies in thermally influenced recreational waters.

Arizona, Nevada, Oregon, Washington, Wyoming↗
USGS2018

The influence of drought on flow‐ecology relationships in Ozark Highland streams

Drought and summer drying can have strong effects on abiotic and biotic components of stream ecosystems. Environmental flow‐ecology relationships may be affected by drought and drying, adding further uncertainty to the already complex interaction of flow with other environmental variables, including geomorphology and water quality. Environment–ecology relationships in stream communities in Ozark Highland streams, USA, were examined over two years with contrasting environmental conditions, a drought year (2012) and a flood year (2013). We analysed fish, crayfish and benthic macroinvertebrate assemblages using two different approaches: (1) a multiple regression analysis incorporating predictor variables related to habitat, water quality, geomorphology and hydrology and (2) a canonical ordination procedure using only hydrologic variables in which forward selection was used to select predictors that were most related to our response variables. Reach‐scale habitat quality and geomorphology were found to be the most important influences on community structure, but hydrology was also important, particularly during the flood year. We also found substantial between‐year variation in environment–ecology relationships. Some ecological responses differed significantly between drought and flood years, while others remained consistent. We found that magnitude was the most important flow component overall, but that there was a shift in relative importance from low flow metrics during the drought year to average flow metrics during the flood year, and the specific metrics of importance varied markedly between assemblages and years. Findings suggest that understanding temporal variation in flow‐ecology relationships may be crucial for resource planning. While some relationships show temporal variation, others are consistent between years. Additionally, different kinds of hydrologic variables can differ greatly in terms of which assemblages they affect and how they affect them. Managers can address this complexity by focusing on relationships that are temporally stable and flow metrics that are consistently important across groups, such as flood frequency and flow variability.

Arkansas, Missouri, Oklahoma↗
USGS2011

Fort Collins Science Center fiscal year 2010 science accomplishments

The scientists and technical professionals at the U.S. Geological Survey (USGS), Fort Collins Science Center (FORT), apply their diverse ecological, socioeconomic, and technological expertise to investigate complicated ecological problems confronting managers of the Nation's biological resources. FORT works closely with U.S. Department of the Interior (DOI) agency scientists, the academic community, other USGS science centers, and many other partners to provide critical information needed to help answer complex natural-resource management questions. In Fiscal Year 2010 (FY10), FORT's scientific and technical professionals conducted ongoing, expanded, and new research vital to the science needs and management goals of DOI, other Federal and State agencies, and nongovernmental organizations in the areas of aquatic systems and fisheries, climate change, data and information integration and management, invasive species, science support, security and technology, status and trends of biological resources (including the socioeconomic aspects), terrestrial and freshwater ecosystems, and wildlife resources, including threatened and endangered species. This report presents selected FORT science accomplishments for FY10 by the specific USGS mission area or science program with which each task is most closely associated, though there is considerable overlap. The report also includes all FORT publications and other products published in FY10, as well as staff accomplishments, appointments, committee assignments, and invited presentations.

Open-File Report↗
USGS2008

Estimates of Nutrient Loading by Ground-Water Discharge into the Lynch Cove Area of Hood Canal, Washington

Low dissolved oxygen concentrations in the waters of Hood Canal threaten marine life in late summer and early autumn. Oxygen depletion in the deep layers and landward reaches of the canal is caused by decomposition of excess phytoplankton biomass, which feeds on nutrients (primarily nitrogen compounds) that enter the canal from various sources, along with stratification of the water column that prevents mixing and replenishment of oxygen. Although seawater entering the canal is the largest source of nitrogen, ground-water discharge to the canal also contributes significant quantities, particularly during summer months when phytoplankton growth is most sensitive to nutrient availability. Quantifying ground-water derived nutrient loads entering an ecologically sensitive system such as Hood Canal is a critical component of constraining the total nutrient budget and ultimately implementing effective management strategies to reduce impacts of eutrophication. The amount of nutrients entering Hood Canal from ground water was estimated using traditional and indirect measurements of ground-water discharge, and analysis of nutrient concentrations. Ground-water discharge to Hood Canal is variable in space and time because of local geology, variable hydraulic gradients in the ground-water system adjacent to the shoreline, and a large tidal range of 3 to 5 meters. Intensive studies of ground-water seepage and hydraulic-head gradients in the shallow, nearshore areas were used to quantify the freshwater component of submarine ground-water discharge (SGD), whereas indirect methods using radon and radium geochemical tracers helped quantify total SGD and recirculated seawater. In areas with confirmed ground-water discharge, shore-perpendicular electrical resistivity profiles, continuous electromagnetic seepage-meter measurements, and continuous radon measurements were used to visualize temporal variations in ground-water discharge over several tidal cycles. The results of these field investigations show that ground-water discharge into the Lynch Cove area of Hood Canal is highly dynamic and strongly affected by the large tidal range. In areas with a steep shoreline and steep hydraulic gradient, ground-water discharge is spatially concentrated in or near the intertidal zone, with increased discharge during low tide. Topographically flat areas with weak hydraulic gradients had more spatial variability, including larger areas of seawater recirculation and more widely dispersed discharge. Measured total-dissolved-nitrogen concentrations in ground water ranged from below detection limits to 2.29 milligrams per liter and the total load entering Lynch Cove was estimated to be approximately 98 ? 10.3 metric tons per year (MT/yr). This estimate is based on net freshwater seepage rates from Lee-type seepage meter measurements and can be compared to estimates derived from geochemical tracer mass balance estimates (radon and radium) of 231 to 749 MT/yr, and previous water-mass-balance estimates (14 to 47 MT/ yr). Uncertainty in these loading estimates is introduced by complex biogeochemical cycles of relevant nutrient species, the representativeness of measurement sites, and by energetic dynamics at the coastal aquifer-seawater interface caused by tidal forcing.

Scientific Investigations Report↗
USGS1996

South Florida wetlands ecosystem; biogeochemical processes in peat

The South Florida wetlands ecosystem is an environment of great size and ecological diversity (figs. 1 and 2). The landscape diversity and subtropical setting of this ecosystem provide a habitat for an abundance of plants and wildlife, some of which are unique to South Florida. South Florida wetlands are currently in crisis, however, due to the combined effects of agriculture, urbanization, and nearly 100 years of water management. Serious problems facing this ecosystem include (1) phosphorus contamination producing nutrient enrichment, which is causing changes in the native vegetation, (2) methylmercury contamination of fish and other wildlife, which poses a potential threat to human health, (3) changes in the natural flow of water in the region, resulting in more frequent drying of wetlands, loss of organic soils, and a reduction in freshwater flow to Florida Bay, (4) hypersalinity, massive algal blooms, and seagrass loss in parts of Florida Bay, and (5) a decrease in wildlife populations, especially those of wading birds. This U.S. Geological Survey (USGS) project focuses on the role of organic-rich sediments (peat) of South Florida wetlands in regulating the concentrations and impact of important chemical species in the environment. The cycling of carbon, nitrogen, phosphorus, and sulfur in peat is an important factor in the regulation of water quality in the South Florida wetlands ecosystem. These elements are central to many of the contamination issues facing South Florida wetlands, such as nutrient enrichment, mercury toxicity, and loss of peat. Many important chemical and biological reactions occur in peat and control the fate of chemical species in wetlands. Wetland scientists often refer to these reactions as biogeochemical processes, because they are chemical reactions usually mediated by microorganisms in a geological environment. An understanding of the biogeochemical processes in peat of South Florida wetlands will provide a basis for evaluating the effects on water quality of (1) constructing buffer wetlands to alleviate nutrient contamination and (2) replumbing the ecosystem to restore natural water flow. The results may also suggest new approaches for solving problems of contamination and water quality in these wetlands. A second focus of this project will be on the geochemical history of the South Florida ecosystem. Peat is a repository of the history of past environmental conditions in the wetland. Before effective action can be taken to correct many of the problems facing these wetlands, we must first study the biogeochemistry of the peat at depth in order to understand whether current problems are the result of recent human activity or are part of a long-term natural cycle. Coordination with other (USGS) projects for South Florida is ongoing. These projects are studying the biological history of the ecosystem by using pollen and shells buried in the peat, together with procedures for dating the peat at various depths, to develop an overall ecosystem history model, with emphasis on the last 100 years.

Fact Sheet↗
USGS2014

Standardized phenology monitoring methods to track plant and animal activity for science and resource management applications

Phenology offers critical insights into the responses of species to climate change; shifts in species’ phenologies can result in disruptions to the ecosystem processes and services upon which human livelihood depends. To better detect such shifts, scientists need long-term phenological records covering many taxa and across a broad geographic distribution. To date, phenological observation efforts across the USA have been geographically limited and have used different methods, making comparisons across sites and species difficult. To facilitate coordinated cross-site, cross-species, and geographically extensive phenological monitoring across the nation, the USA National Phenology Network has developed in situ monitoring protocols standardized across taxonomic groups and ecosystem types for terrestrial, freshwater, and marine plant and animal taxa. The protocols include elements that allow enhanced detection and description of phenological responses, including assessment of phenological “status”, or the ability to track presence–absence of a particular phenophase, as well as standards for documenting the degree to which phenological activity is expressed in terms of intensity or abundance. Data collected by this method can be integrated with historical phenology data sets, enabling the development of databases for spatial and temporal assessment of changes in status and trends of disparate organisms. To build a common, spatially, and temporally extensive multi-taxa phenological data set available for a variety of research and science applications, we encourage scientists, resources managers, and others conducting ecological monitoring or research to consider utilization of these standardized protocols for tracking the seasonal activity of plants and animals.

International Journal of Biometeorology↗
USGS2019

Age and growth of Freshwater Drum and Gizzard Shad occupying two reservoir-river complexes with different groundwater contributions

Restoring groundwater flow is a management option that improves water temperature regimes and benefits fishes. Although this strategy applies more readily to river systems, the thermal character of reservoirs is heavily influenced by inflowing rivers. We examined differences in age, structure, and growth of both Freshwater Drum Aplodinotus grunniens and Gizzard Shad Dorosoma cepedianum that occupy catchments with varying groundwater contributions in the south‐central United States. Seepage run data indicated that the Kiamichi River was losing surface water to groundwater in summer 2016, whereas groundwater inflows were apparent in the Elk River basin. Summer 2016 data showed that the Elk River had cooler water temperatures than the Kiamichi River and Grand Lake O’ the Cherokees water temperatures were similar to those in the incoming Elk River. We found higher densities of older Freshwater Drum and Gizzard Shad (maximums of 32 and 8 years old, respectively) in samples from the Grand basin than among fish that were sampled from the Kiamichi River basin (21 and 6 years old, respectively). Freshwater Drum grew at similar rates in both basins even though they reached larger maximum lengths in the Grand basin (649 mm TL) than in the Kiamichi River basin (600 mm). The average asymptotic length was greater for the Kiamichi population ( L ∞ = 613 mm) than for the Grand population ( L ∞ = 557 mm). Gizzard Shad from the Grand basin were larger than those from the Kiamichi River basin, though the latter population grew faster initially (Brody growth coefficient: K = 0.787 versus K = 0.179, respectively), but they had smaller asymptotic length ( L ∞ = 206 mm versus L ∞ = 343 mm). The role that groundwater plays in temperature regulation in these basins partially explains the observed differences. Our results suggest that the metabolic theory of ecology can be applied to fisheries management at a finer spatial scale.

Oklahoma↗
USGS2018

Biota connect aquatic habitats throughout freshwater ecosystem mosaics

Freshwater ecosystems are linked at various spatial and temporal scales by movements of biota adapted to life in water. We review the literature on movements of aquatic organisms that connect different types of freshwater habitats, focusing on linkages from streams and wetlands to downstream waters. Here, streams, wetlands, rivers, lakes, ponds, and other freshwater habitats are viewed as dynamic freshwater ecosystem mosaics (FEMs) that collectively provide the resources needed to sustain aquatic life. Based on existing evidence, it is clear that biotic linkages throughout FEMs have important consequences for biological integrity and biodiversity. All aquatic organisms move within and among FEM components, but differ in the mode, frequency, distance, and timing of their movements. These movements allow biota to recolonize habitats, avoid inbreeding, escape stressors, locate mates, and acquire resources. Cumulatively, these individual movements connect populations within and among FEMs and contribute to local and regional diversity, resilience to disturbance, and persistence of aquatic species in the face of environmental change. Thus, the biological connections established by movement of biota among streams, wetlands, and downstream waters are critical to the ecological integrity of these systems. Future research will help advance our understanding of the movements that link FEMs and their cumulative effects on downstream waters.

Journal of the American Water Resources Associatio↗
USGS2020

Modeling soil porewater salinity in mangrove forests (Everglades, Florida, USA) impacted by hydrological restoration and a warming climate

Hydrology is a critical driver controlling mangrove wetlands structural and functional attributes at different spatial and temporal scales. Yet, human activities have negatively affected hydrology, causing mangrove diebacks and coverage loss worldwide. In fact, the assessment of mangrove water budgets, impacted by natural and human disturbances, is limited due to a lack of long-term data and information that hinders our understanding of how changes in hydroperiod and salinity control mangrove productivity and spatial distribution. In this study, we implemented a mass balance-based hydrological model (RHYMAN) that explicitly considers groundwater discharge in the Shark River estuary (SRE, southwestern Everglades) located in a karstic geomorphic setting and influenced by regional hydrological restoration. We used long-term hydroperiod and porewater salinity (PWS) datasets obtained from 2004 to 2016 for model calibration and validation and to determine spatiotemporal variability in water levels and PWS at three riverine mangrove sites (downstream, SRS-6; midstream, SRS-5; upstream, SRS-4) along SRE. Model results agree with a distinct PWS pattern along the estuarine salinity gradient where the highest PWS occurs at SRS-6 (mean: 25, range: 22–30 ppt), followed by SRS-5 (17, 14–25 ppt) and SRS-4 (5, 3–13 ppt). A commensurate increase in PWS over a thirteen-year period indicates a long-term reduction in freshwater inflow coupled with sea-level rise (SLR). Increasing freshwater scenario simulation results show a significant reduction (17–27%) in PWS along the estuary in contrast with a high SLR scenario when salinity increases up to 1.1 to 2.5 times that of control values. Model results show that freshwater inflow and SLR are key drivers controlling mangrove wetlands PWS in this karstic coastal region. Given its relatively simple structure, this mass balance-based hydrological model could be used in other environmental settings to evaluate potential habitat and regime shifts due to changes in hydrology and PWS under regional hydrological restoration management.

Florida↗
USGS2011

Chemical ecology of red mangroves, Rhizophora mangle, in the Hawaiian Islands

The coastal red mangrove, Rhizophora mangle L., was introduced to the Hawaiian Islands from Florida 100 yr ago and has spread to cover many shallow intertidal shorelines that once were unvegetated mudflats. We used a field survey approach to test whether mangroves at the land-ocean interface could indicate watershed inputs, especially whether measurements of leaf chemistry could identify coasts with high nutrient inputs and high mangrove productivities. During 2001-2002, we sampled mangroves on dry leeward coasts of southern Moloka'i and O'ahu for 14 leaf variables including stable carbon and nitrogen isotopes (delta 13 C, delta 15 N), macronutrients (C, N, P), trace elements (B, Mn, Fe, Cu, Zn), and cations (Na, Mg, K, Ca). A new modeling approach using leaf Na, N, P, and delta 13 C indicated two times higher productivity for mangroves in urban versus rural settings, with rural mangroves more limited by low N and P nutrients and high-nutrient urban mangroves more limited by freshwater inputs and salt stress. Leaf chemistry also helped identify other aspects of mangrove dynamics: especially leaf delta 15 N values helped identify groundwater N inputs, and a combination of strongly correlated variables (C, N, P, B, Cu, Mg, K, Ca) tracked the mangrove growth response to nutrient loading. Overall, the chemical marker approach is an efficient way to survey watershed forcing of mangrove forest dynamics.

Hawai'i↗
USGS2011

Concentrations, loads, and sources of polychlorinated biphenyls, Neponset River and Neponset River Estuary, eastern Massachusetts

Polychlorinated biphenyls (PCBs) are known to contaminate the Neponset River, which flows through parts of Boston, Massachusetts, and empties into the Neponset River Estuary, an important fish-spawning area. The river is dammed and impassable to fish. The U.S. Geological Survey, in cooperation with the Massachusetts Department of Fish and Game, Division of Ecological Restoration, Riverways Program, collected, analyzed, and interpreted PCB data from bottom-sediment, water, and (or) fish-tissue samples in 2002, 2004-2006. Samples from the Neponset River and Neponset River Estuary were analyzed for 209 PCB congeners, PCB homologs, and Aroclors. In order to better assess the overall health quality of river-bottom sediments, sediment samples were also tested for concentrations of 31 elements. PCB concentrations measured in the top layers of bottom sediment ranged from 28 nanograms per gram (ng/g) just upstream of the Mother Brook confluence to 24,900 ng/g measured in Mother Brook. Concentrations of elements in bottom sediment were generally higher than background concentrations and higher than levels considered toxic to benthic organisms according to freshwater sediment-quality guidelines defined by the U.S. Environmental Protection Agency. Concentrations of dissolved PCBs in water samples collected from the Neponset River (May 13, 2005 to April 28, 2006) averaged about 9.2 nanograms per liter (ng/L) (annual average of monthly values); however, during the months of August (about 16.5 ng/L) and September (about 15.6 ng/L), dissolved PCB concentrations were greater than 14 ng/L, the U.S. Environmental Protection Agency's freshwater continuous chronic criterion for aquatic organisms. Concentrations of PCBs in white sucker (fillets and whole fish) were all greater than 2,000 ng/g wet wt, the U.S. Environmental Protection Agency's guideline for safe consumption of fish: PCB concentrations measured in fish-tissue samples collected from the Tileston and Hollingsworth and Walter Baker Impoundments were 3,490 and 2,450 ng/g wet wt (filleted) and 6,890 and 4,080 ng/g wet wt (whole fish). Total PCB-congener concentrations measured in the whole bodies of estuarine bait fish (common mummichog) averaged 708 ng/g wet wt. PCBs that pass from the Neponset River to the Neponset River Estuary are either dissolved or associated with particulate matter (including living and nonliving material) suspended in the water column. A small proportion of PCBs may also be transported as part of the body burden of fish and wildlife. During the period May 13, 2005 to April 28, 2006, about 5,100 g (3.8 L or 1 gal) of PCBs were transported from the Neponset River to the Neponset River Estuary. Generally, about one-half of these PCBs were dissolved in the water column and the other half were associated with particulate matter; however, the proportion that was either dissolved or particulate varied seasonally. Most PCBs transported from the river to the estuary are composed of four or fewer chlorine atoms per biphenyl molecule. The data suggest that widespread PCB contamination of the lower Neponset River originated from Mother Brook, a Neponset River tributary, starting sometime around the early 1950s or earlier. In 1955, catastrophic dam failure caused by flooding likely released PCB-contaminated sediment downstream and into the Neponset River Estuary. PCBs from this source area likely continued to be released after the flood and during subsequent rebuilding of downstream dams. Today (2007), PCBs are mostly trapped behind these dams; however, some PCBs either diffuse or are entrained back into the water column and are transported downstream by river water into the estuary or volatilize into the atmosphere. In addition to the continuing release of PCBs from historically contaminated bottom sediment, PCBs are still (2007) originating from source areas along Mother and Meadow Brook as well as other sources along the river and Boston Harbor. PCBs from the river (transported by river water) and from the harbor (transported by tidal action) appear to have contaminated parts of the Neponset River Estuary.

Massachusetts↗
USGS2022

Risk assessment of chanchita Cichlasoma dimerus (Heckel, 1840), a newly identified non-native cichlid fish in Florida

The risk of a newly discovered non-native fish species in Florida (USA): Cichlasoma dimerus ([Heckel, 1840]; Family: Cichlidae) is assessed. Its tolerance to cold temperatures was experimentally evaluated and information on its biology and ecology was synthesized. In the cold-temperature tolerance experiment, temperature was lowered from 24 °C by increments of 1 °C per hour, mimicking a typical cold weather front. Fish lost equilibrium at a mean temperature of 7.8 °C and died at 4.7 °C. Those values are lower than most other non-native fishes from the state that have been experimentally evaluated, and it appears C. dimerus is the most cold-tolerant cichlid established in Florida. The combination of cold-temperature tolerance and other biological/ecological factors (e.g., adult size, reproduction and parental care, diet, habitat, and other behaviors) along with the geographic range and habitat diversity of specimens vouchered in museums, indicate C. dimerus may be able to invade many freshwater ecosystems in the state, including environmentally sensitive freshwater springs.

Florida↗
USGS2022

Broad Whitefish (Coregonus nasus) isotopic niches: Stable isotopes reveal diverse foraging strategies and habitat use in Arctic Alaska

Understanding the ecological niche of some fishes is complicated by their frequent use of a broad range of food resources and habitats across space and time. Little is known about Broad Whitefish ( Coregonus nasus ) ecological niches in Arctic landscapes even though they are an important subsistence species for Alaska’s Indigenous communities. We investigated the foraging ecology and habitat use of Broad Whitefish via stable isotope analyses of muscle and liver tissue and otoliths from mature fish migrating in the Colville River within Arctic Alaska. The range of δ 13 C (-31.8– -21.9‰) and δ 15 N (6.6–13.1‰) across tissue types and among individuals overlapped with isotope values previously observed in Arctic lakes and rivers, estuaries, and nearshore marine habitat. The large range of δ 18 O (4.5–10.9‰) and δD (-237.6– -158.9‰) suggests fish utilized a broad spectrum of habitats across elevational and latitudinal gradients. Cluster analysis of muscle δ 13 Cˈ, δ 15 N, δ 18 O, and δD indicated that Broad Whitefish occupied four different foraging niches that relied on marine and land-based (i.e., freshwater and terrestrial) food sources to varying degrees. Most individuals had isotopic signatures representative of coastal freshwater habitat (Group 3; 25%) or coastal lagoon and delta habitat (Group 1; 57%), while individuals that mainly utilized inland freshwater (Group 4; 4%) and nearshore marine habitats (Group 2; 14%) represented smaller proportions. Otolith microchemistry confirmed that individuals with more enriched muscle tissue δ 13 Cˈ, δD, and δ 18 O tended to use marine habitats, while individuals that mainly used freshwater habitats had values that were less enriched. The isotopic niches identified here represent important foraging habitats utilized by Broad Whitefish. To preserve access to these diverse habitats it will be important to limit barriers along nearshore areas and reduce impacts like roads and climate change on natural flow regimes. Maintaining these diverse connected habitats will facilitate long-term population stability, buffering populations from future environmental and anthropogenic perturbations.

Alaska↗
USGS2011

Multi-species attributes as the condition for adaptive sampling of rare species using two-stage sequential sampling with an auxiliary variable

Assessing populations of rare species is challenging because of the large effort required to locate patches of occupied habitat and achieve precise estimates of density and abundance. The presence of a rare species has been shown to be correlated with presence or abundance of more common species. Thus, ecological community richness or abundance can be used to inform sampling of rare species. Adaptive sampling designs have been developed specifically for rare and clustered populations and have been applied to a wide range of rare species. However, adaptive sampling can be logistically challenging, in part, because variation in final sample size introduces uncertainty in survey planning. Two-stage sequential sampling (TSS), a recently developed design, allows for adaptive sampling, but avoids edge units and has an upper bound on final sample size. In this paper we present an extension of two-stage sequential sampling that incorporates an auxiliary variable (TSSAV), such as community attributes, as the condition for adaptive sampling. We develop a set of simulations to approximate sampling of endangered freshwater mussels to evaluate the performance of the TSSAV design. The performance measures that we are interested in are efficiency and probability of sampling a unit occupied by the rare species. Efficiency measures the precision of population estimate from the TSSAV design relative to a standard design, such as simple random sampling (SRS). The simulations indicate that the density and distribution of the auxiliary population is the most important determinant of the performance of the TSSAV design. Of the design factors, such as sample size, the fraction of the primary units sampled was most important. For the best scenarios, the odds of sampling the rare species was approximately 1.5 times higher for TSSAV compared to SRS and efficiency was as high as 2 (i.e., variance from TSSAV was half that of SRS). We have found that design performance, especially for adaptive designs, is often case-specific. Efficiency of adaptive designs is especially sensitive to spatial distribution. We recommend that simulations tailored to the application of interest are highly useful for evaluating designs in preparation for sampling rare and clustered populations.

Conference Paper↗