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USGS2014

Physiological indices of seawater readiness in postspawning steelhead kelts

Management goals to improve the recovery of steelhead (Oncorhynchus mykiss) stocks at risk of extinction include increasing the proportion of postspawning fish that survive and spawn again. To be successful, postspawning steelhead (kelts) migrating downstream to the ocean must prepare physiologically and physically for a seawater transition. We sampled blood, gill filaments, and evaluated the external condition of migrating kelts from an ESA-listed population in the Snake/Columbia River system over two consecutive years to evaluate their physiological readiness for transition to seawater. We chose attributes often considered as measures of preparation for seawater in juveniles, including gill Na + ,K + ATPase activity, plasma electrolytes and hormones to consider factors related to external condition, size and sex. We found kelts in good external condition had plasma profiles similar to downstream-migrating smolts. In addition, we found more than 80% of kelts ranked in good external condition had smolt-like body silvering. We compared measures from migrating kelts with samples obtained from hatchery fish at the time of spawning to confirm that Na + , K + ATPase activity in kelts was significantly elevated over spawning fish. We found significant differences in gill Na + , K + ATPase activity in migrating kelts between the years of sampling, but little indication of influence of fish condition. We conclude that the postspawning steelhead sampled exhibited a suite of behaviours, condition and physiology characteristic of fish prepared for successful transition to a seawater environment.

Idaho;Washington↗

USGS2020

Kelp forest monitoring at Naval Base Ventura County, San Nicolas Island, California: Fall 2018 and Spring 2019, fifth annual report

Introduction Kelp forests and rocky reefs are among the most recognized marine ecosystems and provide the primary habitat for several species of fishes, invertebrates, and algal assemblages (Stephens and others, 2006). In addition, kelp forests have been shown to be important carbon dioxide sinks (Wilmers and others, 2012) and are an important source of nearshore marine primary production (Duggins and others, 1989). These highly dynamic ecosystems are extremely variable, and both top-down and bottom-up ecological controls drive this rich trophic environment. Giant kelp ( Macrocystis pyrifera ) forests and the species that inhabit these ecosystems are influenced by several environmental conditions, such as wave exposure, water temperature, water clarity, bottom depth and composition, species composition, and the density of kelp and other algal assemblages (Schiel and Foster, 2015). However, in addition to “normal” variability, kelp forests can undergo extreme regime shifts from kelp canopy forested areas to barrens characterized by high densities of urchins and encrusting coralline algae (Harrold and Reed, 1985). San Nicolas Island (SNI), outermost of the California Channel Islands, is home to a diverse group of terrestrial and marine organisms and includes kelp bed and rocky reef habitats ( fig. 1 ). The SNI kelp forests not only provide food and shelter for fishes and invertebrates within the habitat, but also they support higher trophic level consumers such as marine birds and several marine mammal species including the southern sea otter ( Enhydra lutris nereis) , a major predator on sea urchins and other marine invertebrates. Owing to concern about the vulnerability of the California population, the U.S. Fish and Wildlife Service (USFWS) translocated 140 southern sea otters from the central California coast to SNI between 1987 and 1990. Although only approximately 14 translocated otters are thought to have remained at SNI (U.S. Fish and Wildlife Service, 2012), their population at the island has increased and is currently greater than 120 individuals (Hatfield and others, 2019). Sea otters are a natural part of the kelp forest ecosystem, but their presence has implications for community dynamics as they repopulate a region from which they were extirpated in the 19th century. At SNI, sea otters have been concentrated mostly around the west end of the island, with some use of the south side and very little, but expanding, use of the northeast side. An ecosystem shift from urchin dominated to kelp dominated, that occurred at a site at the west end of the island in the early 2000s, though initiated by sea urchin disease, was likely facilitated to some degree by sea otter foraging (Kenner and Tinker, 2018). These ecosystems also are the target of many fisheries, including urchin and lobster. Urchin fisheries, which target the larger red sea urchin, may release the smaller but more mobile purple sea urchin from competitive control (Dayton and others, 1998). Lobster fisheries may release purple sea urchins from predatory control (Lafferty, 2004). Owing to the distance from the mainland, however, SNI kelp forests and reefs have been somewhat protected from the degree of harvest and other anthropogenic impacts experienced by the southern California mainland. Invasive species are another issue, and there are a few invasive subtidal macroalgae of concern in southern California waters. Although the brown alga Sargassum muticum has been established at the island for decades, S. horneri has only recently been seen at SNI and, so far, the invasive kelp Undaria pinnatifida and the green alga Caulerpa taxifolia have not been observed there. Sargassum horneri , in particular, has demonstrated a capability to outcompete native kelps at some of the other Channel Islands but it is unclear what indirect effects it may have on community structure (Marks and others, 2015). Because the surrounding kelp forests fall within the management boundary of the SNI Integrated Natural Resources Management Plan (INRMP; U.S. Navy, 2015), USGS works with the Navy to provide surveys of this ecologically important ecosystem that inform natural resource managers of trends in the population abundance of particular species. In addition, long-term surveys allow for an understanding of potential changes in species diversity and community composition as a result of trophic or other interactions. The U.S. Geological Survey (USGS) implemented a kelp forest monitoring program for the U.S. Navy at San Nicolas Island in 2014, building on sites and methods established by USFWS scientists in 1980 ( appendix 1 ). This report focuses on data collected during sampling expeditions to these sites in fall 2018 (October 2–5) and spring 2019 (April 3–6). Together they will be herein referred to as year 5 because, although the trips were made in different calendar years, they were approximately 6 months apart and were conducted under the fifth year of this contract. The previous sampling year (fall 2017 and spring 2018) is referred to as year 4. The year 5 data are compared with data collected during eight trips from fall 2014 through spring 2018. Differences in counts between these expeditions can result from seasonal factors, stochastic variation, or sampling error, but temporal comparison can reveal population trends. Where appropriate, long-term data collected during the 33 years prior to the implementation of these slightly revised protocols will be presented in order to lend some context to the observations reported here. Genus and species names used in this report are those currently recognized as valid in the Integrated Taxonomic Information System (ITIS.gov). Upon first use, the name recognized as valid by the World Register of Marine Species (WoRMS; marinespecies.org) is shown in brackets if different. The exception is Sargassum horneri which does not show up in any discernable form in ITIS.gov.

California↗

USGS2018

Spatial patterns in occupancy and reproduction of Golden Eagles during drought: Prospects for conservation in changing environments

We used a broad-scale sampling design to investigate spatial patterns in occupancy and breeding success of territorial pairs of Golden Eagles ( Aquila chrysaetos ) in the Diablo Range, California, USA, during a period of exceptional drought (2014–2016). We surveyed 138 randomly selected sample sites over 4 occasions each year and identified 199 pairs of eagles, 100 of which were detected in focal sample sites. We then used dynamic multistate modeling to identify relationships between site occupancy and reproduction of Golden Eagles relative to spatial variability in landscape composition and drought conditions. We observed little variability among years in site occupancy (3-yr mean = 0.74), but the estimated annual probability of successful reproduction was relatively low during the study period and declined from 0.39 (± 0.08 SE) to 0.18 (± 0.07 SE). Probabilities of site occupancy and reproduction were substantially greater at sample sites that were occupied by successful breeders in the previous year, indicating the presence of sites that were consistently used by successfully reproducing eagles. We found strong evidence for nonrandom spatial distribution in both occupancy and reproduction: Sites with the greatest potential for occupancy were characterized by rugged terrain conditions with intermediate amounts of grassland interspersed with patches of oak woodland and coniferous forest, whereas successful reproduction was most strongly associated with the amount of precipitation that a site received during the nesting period. Our findings highlight the contribution of consistently occupied and productive breeding sites to overall productivity of the local breeding population, and show that both occupancy and reproduction at these sites were maintained even during a period of exceptional drought. Our approach to quantifying and mapping site quality should be especially useful for the spatial prioritization of compensation measures intended to help offset the impacts of increasing human land use and development on Golden Eagles and their habitats.

California↗

USGS2024

Factors affecting the density of Metabetaeus lohena (Decapoda: Alpheidae) at a high-density anchialine pool environment on the Kona Coast of the Island of Hawai‘i

Caridean shrimps (Caridea) are the dominant macroinvertebrates in most anchialine ecosystems. Hawaiian anchialine ecosystems, primarily composed of shallow surface pools connected to the ocean via hypogeal networks of cracks, tubes, and other voids, support 10 caridean shrimp species, including two federally listed as endangered. Little is known about most of these species. The objective of this study was to identify factors that affect the abundance and distribution of Metabetaeus lohena (Alpheidae), an uncommon species found across the Hawaiian Archipelago, at Kaloko-Honokōhau National Historical Park, Island of Hawai‘i. This park supports the highest concentration of anchialine pools in the State of Hawai‘i and is critical to protecting this threatened ecosystem. During 2017, we measured the density of M. lohena during nighttime surveys, as well as a variety of other biological, physical, and chemical parameters, in 130 pools. Metabetaeus lohena occupied 71.5% of the pools surveyed, with a mean density of 7.32 individuals/m 2 (95% CI = 5.14–9.49). Invasive fish and the endemic shrimp Halocaridina rubra (Atyidae) had the strongest effects on M. lohena density, with negative and positive relations, respectively. In the first estimate of M. lohena density at this scale, our data indicate that Kaloko-Honokōhau supports about 11,480 shrimp (95% CI = 8,054–14,906) in the pools surveyed. Furthermore, our models predict that this park could support an additional 1,695 individuals (95% CI = 955–3,008) for a population of about 13,175 shrimp if fish were removed from 19 pools in which M. lohena are absent.

Hawaii↗

USGS2023

Support for the fasting endurance hypothesis of partial migration in a nearshore seabird

Partial migration occurs when only a fraction of a population migrates instead of all individuals. Considered an evolutionary precursor to full migration, understanding why some individuals choose to undertake migration while others do not may serve to inform general migratory theory. While several hypotheses currently exist for explaining the maintenance of partial migration, empirical support for many is limited. To address this gap, we analyzed GPS data acquired from brown pelicans ( Pelecanus occidentalis ; n = 74), a partially migratory seabird, nesting on six colonies in the South Atlantic Bight over the course of four autumn migrations. We estimated that approximately 74% of pelicans nesting within the study area may be migratory on an annual basis, with the remainder staying within the surrounding marine ecoregion year-round. Mean date of migration initiation was 9 November, although movements occurred from September to December. Results from Cox's proportional hazards modeling indicated significant positive and negative effects of sea surface temperatures and body condition on migration rate, respectively. We suggest that the ontogenetic migration of the primary forage species of brown pelicans from estuarine to pelagic environments causes a seasonal reduction in prey and that pelicans in poor body condition are unable to meet the energetic demands potentially associated with this decrease in prey availability (i.e., the fasting endurance hypothesis of partial migration). Although we did not find evidence for a density-dependent migratory response, the effects of intraspecific competition on migration in pelicans also appear to warrant consideration.

Georgia, South Carolina↗

USGS1993

Possible secondary apatite fission track age standard from altered volcanic ash beds in the middle Jurassic Carmel Formation, Southwestern Utah

Secondary age standards are valuable in intra- and interlaboratory calibration. At present very few such standards are available for fission track dating that is older than Tertiary. Several altered volcanic ash beds occur in the Middle Jurassic Carmel Formation in southwestern Utah. The formation was deposited in a shallow marine/sabhka environment. Near Gunlock, Utah, eight ash beds have been identified. Sanidines from one of the ash beds (GUN-F) give a single-crystal laser-probe 40Ar/39Ar age of 166.3??0.8 Ma (2??). Apatite and zircon fission track ages range from 152-185 Ma with typically 15-20 Ma errors (2??). Track densities in zircons are high and most grains are not countable. Apatites are fairly common in most of the ash beds and have reasonable track densities ranging between 1.2-1.5 ?? 106 tracks/cm2. Track length distributions in apatites are unimodal, have standard deviations <1??m, and mean track lengths of about 14-14.5 ??m. High Cl apatites (F:Cl:OH ratio of 39:33:28) are particularly abundant and large in ash GUN-F, and are fairly easy to concentrate, but the concentrates contain some siderite, most of which can be removed by sieving. GUN-F shows evidence of some reworking and detriaal contamination based on older single grain 40Ar/39Ar analyses and some rounding of grains, but the apatite population appears to be largely uncontaminated. At present BJK has approximately 12 of apatite separate from GUN-F. ?? 1993.

Nuclear Tracks and Radiation Measurements↗

USGS2016

The effects of co-contaminants and native wetland sediments on the activity and dominant transformation mechanisms of a 1,1,2,2-tetrachloroethane (TeCA)-degrading enrichment culture

Bioremediation strategies, including bioaugmentation with chlorinated ethene-degrading enrichment cultures, have been successfully applied in the cleanup of subsurface environments contaminated with tetrachloroethene (PCE) and/or trichloroethene (TCE). However, these compounds are frequently found in the environment as components of mixtures that may also contain chlorinated ethanes and methanes. Under these conditions, the implementation of bioremediation may be complicated by inhibition effects, particularly when multiple dehalorespirers are present. We investigated the ability of the 1,1,2,2-tetrachloroethane (TeCA)-dechlorinating culture WBC-2 to biotransform TeCA alone, or a mixture of TeCA plus PCE and carbon tetrachloride (CT), in microcosms. The microcosms contained electron donors provided to biostimulate the added culture and sediment collected from a wetland where numerous “hotspots” of contamination with chlorinated solvent mixtures exist. The dominant TeCA biodegradation mechanism mediated by the WBC-2 culture in the microcosms was different in the presence of these wetland sediments than in the sediment-free enrichment culture or in previous WBC-2 bioaugmented microcosms and column tests conducted with wetland sediment collected at nearby sites. The co-contaminants and their daughter products also inhibited TeCA biodegradation by WBC-2. These results highlight the need to conduct biodegradability assays at new sites, particularly when multiple contaminants and dehalorespiring populations are present.

Chemosphere↗

USGS2009

Modeling haul-out behavior of walruses in Bering Sea ice

Understanding haul-out behavior of ice-associated pinnipeds is essential for designing and interpreting popula-tion surveys and for assessing effects of potential changes in their ice environments. We used satellite-linked transmitters to obtain sequential information about location and haul-out state for Pacific walruses, Odobenus rosmarus divergens (Il-liger, 1815), in the Bering Sea during April of 2004, 2005, and 2006. We used these data in a generalized mixed model of haul-out bout durations and a hierarchical Bayesian model of haul-out probabilities to assess factors related to walrus haul-out behavior, and provide the first predictive model of walrus haul-out behavior in sea ice habitat. Average haul-out bout duration was 9 h, but durations of haul-out bouts tended to increase with durations of preceding in-water bouts. On aver-age, tagged walruses spent only about 17% of their time hauled out on sea ice. Probability of being hauled out decreased with wind speed, increased with temperature, and followed a diurnal cycle with the highest values in the evening. Our haul-out probability model can be used to estimate the proportion of the population that is unavailable for detection in spring surveys of Pacific walruses on sea ice.

Canadian Journal of Zoology↗

USGS2015

Fire history of Everglades National Park and Big Cypress National Preserve, southern Florida

Fire occurs naturally in the environment on most continents, including Africa (Ryan and Williams, 2011), Asia (Kauhanen, 2008), Australia (Kutt and Woinarski, 2007), Europe (Eshel and others, 2000), South America (Fidelis and others, 2010), and North America (Van Auken, 2000). Antarctica appears to be the only continent that has no reported natural fires, although fire is common in grasslands of Patagonia and on islands in the Subantarctic region (Gonzalez and others, 2005; McGlone and others, 2007). Natural fires also have occurred over thousands of years, and the frequencies of these natural fires have changed (Power and others, 2008). This has resulted in altered ecosystems at landscape scales. Recent evidence suggests that the treeless desert pastures of Tibet once were forests and woodlands, and charcoal deposits indicate that fire was more frequent in the past (Miehe and others, 2006). Human cultural development has been influenced by changes in natural fire frequencies. Zong and others (2007) reported that human suppression of fires in coastal areas of China allowed the development of rice paddy cultivation and, thus, increased the size of human populations. In addition to its almost world-wide occurrence, fire plays a role in a wide variety of ecosystem types. Grassland, savanna, steppe, woodland, forest, and wetland ecosystems all have fire as part of their natural ecology (Veblen and Lorenz, 1988; Chokkalingam and others, 2007; Miller and others, 2009, Keith and others, 2010; Staver and others, 2011). Fires affect these ecosystems in various ways, the most obvious of which is the direct effect on plant biomass (for example, Van Wilgen, 1982; Mack and others, 2008). However, fire has many other effects on ecosystems. Plant species richness, diversity, and functional types can change in response to fire (Peterson and Reich, 2008). All properties of the surface soils (such as bulk density, particle size distribution, pH, and organic carbon and nitrogen content) can be altered by the frequency and severity of fire (Boerner and others, 2009). Faunal communities will respond to fire, with some species increasing (Fuhlendorf and others, 2006) and other species decreasing, after the fire (Vasconcelos and others, 2009).The position of the ecotone between differing ecosystems also is influenced by fire occurrence (Heisler and others, 2003; Briggs and others, 2005; Smith and others, 2013). Fire has been used as a management tool in various ecosystems around the world. Prairies, grasslands, and savannas are fire-maintained ecosystems where fire is used to deter invasion by shrubs and trees (Grant and others, 2009; Scheintaub and others, 2009). Similarly, fire plays an important role in woodlands and forests by influencing species composition and succession such, as the use of fire in coniferous forests to prevent encroachment by hardwoods (Phillippe and others, 2011). Fire also has been used to manage wetland ecosystems for more than 50 years (Lynch, 1941; Frost, 1995). Uses have included returning marshes to early successional states, increasing forage for wildlife (Lynch, 1941). In all fire-influenced ecosystems, prescribed burns are routinely used to reduce fuel loads, reducing the possibility of catastrophic fires.

Florida↗

USGS2025

Desert ecosystems shape diversification in glossy snakes (genus Arizona) requiring a re-alignment of evolutionary and conservation units

Subspecies are often targets for conservation, yet many lack the genetic data necessary to validate their status as distinctive evolutionary lineages. In 2016, conservationists faced this issue when designating the California glossy snake, Arizona elegans occidentalis , as a Species of Special Concern in California, a decision prompted by population declines and habitat loss but absent of genetic information about its evolutionary integrity. To address this knowledge gap, we collected genomic and mitochondrial data from a rangewide sample of the Arizona elegans complex ( n = 257) and characterized genetic structure at varying spatial scales. We confirmed an east–west phyletic division within the A. elegans complex that correlates with an ecotone between the Sonoran and Chihuahuan Deserts and pinpoint the separation to a ∼20 km area in southeastern Arizona, USA. Individuals recognized as A. e. occidentalis do not form a genetically cohesive unit within a more inclusive western clade that is sister to the endemic Arizona pacata in Baja California, México. We synonymize four subspecies circumscribed by the western clade and recognize a new species Arizona occidentalis to re-align the taxonomy with the phylogeographic structure. Most of the diversity within A. occidentalis occurs in California, with three major lineages corresponding separate desert biomes. We revise the conservation units within A. occidentalis to mirror these lineages and address concerns regarding habitat loss in transitional environments along the western edge of its range. This work underscores the importance of aligning taxonomy, evolutionary identity, and management units to design the most effective conservation strategies.

Molecular Phylogenetics and Evolution↗

USGS2026

Fish introductions related to strong and diversifying effects on zooplankton assemblages in high-elevation mountain lakes

Freshwater environments are threatened by multiple anthropogenic stressors. High-elevation mountain lakes are particularly vulnerable to introduced nonnative fish and nutrient deposition because they were historically fishless and typically oligotrophic. To understand the potential effects of fish introduction and nutrient levels on high-elevation lake ecosystems, we assessed differences in zooplankton size, biomass, and density in 76 alpine and subalpine lakes in the Wind River Range, Wyoming, USA, and related those differences to the presence of introduced trout and to food quality (seston nutrient content) and quantity (chlorophyll a concentration). Trout presence, and to a lesser extent trout species, were the strongest predictors of zooplankton composition. Fishless lakes were dominated by low densities of copepods and other large-bodied taxa, and lakes with introduced trout were dominated by high densities of cladocerans, rotifers, and other small-bodied taxa. These assemblage differences are likely because trout reduce or eliminate all large zooplankton taxa by size-selective predation, including predation on Hesperodiaptomus shoshone (S. A. Forbes, 1893), a keystone species that effectively controls populations of rotifers and small crustacean zooplankton taxa. In contrast, the quantity and quality of seston was not associated with zooplankton assemblages. Zooplankton composition in lakes with Rocky Mountain Cutthroat Trout Oncorhynchus virginalis (Girard, 1856) or Golden Trout Oncorhynchus aguabonita (Jordan, 1892) was highly variable, but in lakes with primarily Brook Trout Salvelinus fontinalis (Mitchill, 1814), zooplankton composition was consistently distinct from that in fishless lakes, suggesting that Brook Trout introductions altered the zooplankton assemblage to a greater extent than Cutthroat or Golden trout did. These results contribute to global evidence that predatory fish introductions fundamentally restructure alpine lake food webs. The slow or incomplete recovery of native zooplankton assemblages following fish removal suggests long-term ecological legacies of fish introductions and highlights the importance of understanding factors that promote resilience in high-elevation lake ecosystems.

Wyoming↗

USGS2013

Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon ( Salmo salar ) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater (‘parr’) stage to the migratory stage where they descend streams and enter salt water (‘smolt’) is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes.

Global Change Biology↗

USGS2013

Riverine habitat dynamics

The physical habitat template is a fundamental influence on riverine ecosystem structure and function. Habitat dynamics refers to the variation in habitat through space and time as the result of varying discharge and varying geomorphology. Habitat dynamics can be assessed at spatial scales ranging from the grain (the smallest resolution at which an organism relates to its environment) to the extent (the broadest resolution inclusive of all space occupied during its life cycle). In addition to a potentially broad range of spatial scales, assessments of habitat dynamics may include dynamics of both occupied and nonoccupied habitat patches because of process interactions among patches. Temporal aspects of riverine habitat dynamics can be categorized into hydrodynamics and morphodynamics. Hydrodynamics refers to habitat variation that results from changes in discharge in the absence of significant change of channel morphology and at generally low sediment-transport rates. Hydrodynamic assessments are useful in cases of relatively high flow exceedance (percent of time a flow is equaled or exceeded) or high critical shear stress, conditions that are applicable in many studies of instream flows. Morphodynamics refers to habitat variation resulting from changes to substrate conditions or channel/floodplain morphology. Morphodynamic assessments are necessary when channel and floodplain boundary conditions have been significantly changed, generally by relatively rare flood events or in rivers with low critical shear stress. Morphodynamic habitat variation can be particularly important as disturbance mechanisms that mediate population growth or for providing conditions needed for reproduction, such as channel-migration events that erode cutbanks and provide new pointbar surfaces for germination of riparian trees. Understanding of habitat dynamics is increasing in importance as societal goals shift toward restoration of riverine ecosystems. Effective investment in restoration strategies requires that the role of physical habitat is correctly diagnosed and that restoration activities address true habitat limitations, including the role of dynamic habitats.

Book chapter↗

USGS2002

A Geochemical Trophic Cascade in Yellowstone's Geothermal Environments

We contrast the geochemistry of the Madison drainage, which has high concentrations of geothermal features, with the Lamar drainage of Yellowstone National Park, USA, and trace the consequences of geochemical differences through abiotic and biotic linkages in the ecosystem. Waters in the geothermal-dominated drainage contained anomalously high levels of fluoride (F) and silica (SiO 2 ). Soils, stream sediments, and surface waters that interact or mix with geothermal waters, in turn, had elevated F and SiO 2 concentrations compared to similar samples from the Lamar drainage. The geochemical differences were reflected in the chemistry of forage plants, with some plants from geothermally influenced areas containing four- to eightfold higher concentrations of F and SiO 2 than similar plants in the Lamar drainage. Geothermal heat reduced snowpack, and we found that elk (Cervus elaphus) concentrated in these refugia as snowpack increased each winter. The consequent high dietary intake of F in animals associated with the geothermal areas was confirmed by the finding that bone samples from elk living in the Madison drainage contained sixfold higher concentrations of F than samples collected from animals wintering in the Lamar drainage. High F exposure resulted in compromised dentition due to fluoride toxicosis, which was undoubtedly exacerbated by the abrasive action of silica. The consequent accelerated and aberrant tooth wear resulted in early onset of senescence, reduced life span, and an abbreviated age structure. We speculate that these altered demographics, combined with spatial heterogeneity of snowpack, will result in increased vulnerability of this large herbivore population to wolf predation and less resiliency to compensate demographically for predation.

Wyoming↗

USGS2026

Growth, movement, and survival of precocial shorebird chicks are constrained by their environment.

Young animals are often less mobile than adults, while also having high energetic demands. They may therefore be more vulnerable to local-scale changes in environmental conditions. In particular, when 1 sex must grow more rapidly than the other to achieve a larger adult size, that sex may experience especially dramatic reductions in growth and survival in the face of suboptimal environmental conditions. In order to investigate the flexibility of individuals in response to local-scale environmental variation during development, we studied the sex-specific growth, movement, and survival of Hudsonian Godwit ( Limosa haemastica ) chicks—a sexually dimorphic, precocial shorebird that breeds in the sub-Arctic and exhibits a male-skewed adult sex ratio. We found that female chicks—which must grow to a larger adult size—reached their maximum growth rates at a later age, but had similar growth rates to males before that and survived equally well to 21 days. We also found that, irrespective of sex, chicks had reduced movement rates when they were young and/or temperatures were cold, and only weakly increased their movement rates when invertebrate abundances remained low across an entire week. Early in life, godwit chicks may therefore be constrained from increasing their foraging efforts by local environmental conditions, forcing females to sustain higher growth rates late in the season past the local resource peak. Such sex-specific vulnerabilities could lead to lower early-life survival and, in turn, skewed adult sex ratios, which have important implications for population dynamics and persistence.

Behavioral Ecology↗

USGS2024

Retention of p-Chip microtransponders and posttagging survival of small-bodied stream fishes

Objective Obtaining demographic rates often requires complex open-population capture–mark–recapture (CMR) study designs. Conducting such studies for small-bodied fishes has been limited in part by excessive mortality after tagging procedures and poor tag retention. As new tag types emerge, information regarding fish survival and tag retention over varying time scales may benefit resource managers to effectively plan future CMR studies. The p-Chip microtransponder is a 500- × 500- × 100-μm tag that is inserted subcutaneously and is read with a handheld laser. Each tag contains a nine-digit unique identification number. P-Chip microtransponder tags have been used on a limited number of small-bodied fishes, with relatively high rates observed for fish survival and tag retention. Information on posttagging survival and retention of p-Chip microtransponder tags across a range of small-bodied fish species and tagging locations is needed to inform their effectiveness in future CMR studies. Methods We quantified survival and tag retention after p-Chip microtransponder implantation in Creek Chub Semotilus atromaculatus and Northern Pearl Dace Margariscus nachtriebi in a laboratory environment, and retention of p-Chip microtransponder tags in Northern Pearl Dace was also quantified over a year-long field study. We marked 56 Creek Chub and 9 Northern Pearl Dace in the laboratory with p-Chip microtransponder tags and compared them to an equal number of unmarked individuals over 90 days. We marked 1990 Northern Pearl Dace and conducted recapture events through four seasons (June, September, and October 2022 and June 2023) in four headwater streams of Nebraska. Result Survival for Creek Chub was 85% (standard error [SE] = 5.9) and did not differ from control fish survival (95%; SE = 3.2) in the 90-day laboratory experiment. Survival for Northern Pearl Dace was 89% (SE = 11.0) and did not differ from that of control fish (100%) in the laboratory experiment. Tag retention was 89% (SE = 4.6) for Creek Chub and 100% for Northern Pearl Dace in the laboratory. The p-Chip microtransponder performed well during the CMR field study, with tag retention for Northern Pearl Dace at 94% across 374 days. Conclusion Our results suggest that the p-Chip microtransponder minimally affected small-bodied fish survival and had high tag retention in both the laboratory and field studies. Thus, the p-Chip microtransponder tag may be appropriate for use in small-bodied fishes when individual identification is needed in a CMR study.

North American Journal of Fisheries Management↗

USGS2015

Variability of intertidal foraminferal assemblages in a salt marsh, Oregon, USA

We studied 18 sampling stations along a transect to investigate the similarity between live (rose Bengal stained) foraminiferal populations and dead assemblages, their small-scale spatial variations and the distribution of infaunal foraminifera in a salt marsh (Toms Creek marsh) at the upper end of the South Slough arm of the Coos Bay estuary, Oregon, USA. We aimed to test to what extent taphonomic processes, small-scale variability and infaunal distribution influence the accuracy of sea-level reconstructions based on intertidal foraminifera. Cluster analyses have shown that dead assemblages occur in distinct zones with respect to elevation, a prerequisite for using foraminifera as sea-level indicators. Our nonparametric multivariate analysis of variance showed that small-scale spatial variability has only a small influence on live (rose Bengal stained) populations and dead assemblages. The dissimilarity was higher, however, between live (rose Bengal stained) populations in the middle marsh. We observed early diagenetic dissolution of calcareous tests in the dead assemblages. If comparable post-depositional processes and similar minor spatial variability also characterize fossil assemblages, then dead assemblage are the best modern analogs for paleoenvironmental reconstructions. The Toms Creek tidal flat and low marsh vascular plant zones are dominated by Miliammina fusca , the middle marsh is dominated by Balticammina pseudomacrescens and Trochammina inflata , and the high marsh and upland–marsh transition zone are dominated by Trochamminita irregularis . Analysis of infaunal foraminifera showed that most living specimens are found in the surface sediments and the majority of live (rose Bengal stained) infaunal specimens are restricted to the upper 10 cm, but living individuals are found to depths of 50 cm. The dominant infaunal specimens are similar to those in the corresponding surface samples and no species have been found living solely infaunally. The total numbers of infaunal foraminifera are small compared to the total numbers of dead specimens in the surface samples. This suggests that surface samples adequately represent the modern intertidal environment in Toms Creek.

Oregon↗

USGS2017

Interactive effects of water temperature and salinity on growth and mortality of eastern oysters, Crassostrea virginica: A meta-analysis using 40 years of monitoring data

Despite nearly a century of exploitation and scientific study, predicting growth and mortality rates of the eastern oyster ( Crassostrea virginica ) as a means to inform local harvest and management activities remains difficult. Ensuring that models reflect local population responses to varying salinity and temperature combinations requires locally appropriate models. Using long-term (1988 to 2015) monitoring data from Louisiana's public oyster reefs, we develop regionally specific models of temperature- and salinity-driven mortality (sack oysters only) and growth for spat (<25 mm), seed (25–75 mm), and sack (>75 mm) oyster size classes. The results demonstrate that the optimal combination of temperature and salinity where Louisiana oysters experience reduced mortality and fast growth rates is skewed toward lower salinities and higher water temperatures than previous models have suggested. Outside of that optimal range, oysters are commonly exposed to combinations of temperature and salinity that are correlated with high mortality and reduced growth. How these combinations affect growth, and to a lesser degree mortality, appears to be size class dependent. Given current climate predictions for the region and ongoing large-scale restoration activities in coastal Louisiana, the growth and mortality models are a critical step toward ensuring sustainable oyster reefs for long-term harvest and continued delivery of the ecological services in a changing environment.

Louisiana↗