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At least 361 records · Page 20Linked to original sources
USGS2012

Sediment mobility and bed armoring in the St Clair River: insights from hydrodynamic modeling

The lake levels in Lake Michigan-Huron have recently fallen to near historical lows, as has the elevation difference between Lake Michigan-Huron compared to Lake Erie. This decline in lake levels has the potential to cause detrimental impacts on the lake ecosystems, together with social and economic impacts on communities in the entire Great Lakes region. Results from past work suggest that morphological changes in the St Clair River, which is the only natural outlet for Lake Michigan-Huron, could be an appreciable factor in the recent trends of lake level decline. A key research question is whether bed erosion within the river has caused an increase in water conveyance, therefore, contributed to the falling lake level. In this paper, a numerical modeling approach with field data is used to investigate the possibility of sediment movement in the St Clair River and assess the likelihood of morphological change under the current flow regime. A two-dimensional numerical model was used to study flow structure, bed shear stress, and sediment mobility/armoring over a range of flow discharges. Boundary conditions for the numerical model were provided by detailed field measurements that included high-resolution bathymetry and three-dimensional flow velocities. The results indicate that, without considering other effects, under the current range of flow conditions, the shear stresses produced by the river flow are too low to transport most of the coarse bed sediment within the reach and are too low to cause substantial bed erosion or bed scour. However, the detailed maps of the bed show mobile bedforms in the upper St Clair River that are indicative of sediment transport. Relatively high shear stresses near a constriction at the upstream end of the river and at channel bends could cause local scour and deposition. Ship-induced propeller wake erosion also is a likely cause of sediment movement in the entire reach. Other factors that may promote sediment movement, such as ice cover and dredging in the lower river, require further investigation.

St. Clair River↗
USGS2010

High mangrove density enhances surface accretion, surface elevation change, and tree survival in coastal areas susceptible to sea-level rise

Survival, growth, aboveground biomass accumulation, sediment surface elevation dynamics and nitrogen accumulation in sediments were studied in experimental treatments planted with four different densities (6.96, 3.26, 1.93 and 0.95 seedlings m −2 ) of the mangrove Rhizophora mucronata in Puttalam Lagoon, Sri Lanka. Measurements were taken over a period of 1,171 days and were compared with those from unplanted controls. Trees at the lowest density showed significantly reduced survival, whilst measures of individual tree growth did not differ among treatments. Rates of surface sediment accretion (means ± SE) were 13.0 (±1.3), 10.5 (±0.9), 8.4 (±0.3), 6.9 (±0.5) and 5.7 (±0.3) mm year −1 at planting densities of 6.96, 3.26, 1.93, 0.95, and 0 (unplanted control) seedlings m −2 , respectively, showing highly significant differences among treatments. Mean (±SE) rates of surface elevation change were much lower than rates of accretion at 2.8 (±0.2), 1.6 (±0.1), 1.1 (±0.2), 0.6 (±0.2) and −0.3 (±0.1) mm year −1 for 6.96, 3.26, 1.93, 0.95, and 0 seedlings m −2 , respectively. All planted treatments accumulated greater nitrogen concentrations in the sediment compared to the unplanted control. Sediment %N was significantly different among densities which suggests one potential causal mechanism for the facilitatory effects observed: high densities of plants potentially contribute to the accretion of greater amounts of nutrient rich sediment. While this potential process needs further research, this study demonstrated how higher densities of mangroves enhance rates of sediment accretion and surface elevation processes that may be crucial in mangrove ecosystem adaptation to sea-level rise. There was no evidence that increasing plant density evoked a trade-off with growth and survival of the planted trees. Rather, facilitatory effects enhanced survival at high densities, suggesting that managers may be able to take advantage of high plantation densities to help mitigate sea-level rise effects by encouraging positive sediment surface elevation.

Puttalam Lagoon↗
USGS2019

Canals, backfilling and wetland loss in the Mississippi Delta

Canals and spoil banks have contributed significantly to high rates of wetland loss in the Mississippi delta. There has been relatively little research on management of canals and spoil banks and this needs to be a significant component of restoration of the delta. We analyze research on the role of backfilling canals in the context of delta restoration with special reference to Turner and McClenachan (2018) who state that if all canals were backfilled, it could significantly reduce or even reverse wetland loss and that most wetland loss is caused by canals. We agree with T&M that canals have been a significant cause of wetland loss in the Mississippi Delta and that removing spoil banks and backfilling canals should be an integral part of delta restoration. However, a number of factors need to be considered when choosing which canals to backfill including possible enhanced erosion due to exposure to wave action for newly created and remnant marsh, the current and future production history of oil and natural gas from canals, and other restoration activities in oil and gas fields. Turner and McClenachan’s analysis using wetland loss patterns in 15-minute quadrangles suggesting that canal density can explain most wetland loss in coastal Louisiana is flawed because of scale problems and other impacts of oil and gas activity. These impacts include subsurface induced subsidence and the impact of produced water and toxins on wetlands that are largely unrelated to surface alteration due to canals and spoil banks.

Louisiana↗
USGS2020

Expert assessment of future vulnerability of the global peatland carbon sink

The carbon balance of peatlands is predicted to shift from a sink to a source this century. However, peatland ecosystems are still omitted from the main Earth system models that are used for future climate change projections, and they are not considered in integrated assessment models that are used in impact and mitigation studies. By using evidence synthesized from the literature and an expert elicitation, we define and quantify the leading drivers of change that have impacted peatland carbon stocks during the Holocene and predict their effect during this century and in the far future. We also identify uncertainties and knowledge gaps in the scientific community and provide insight towards better integration of peatlands into modelling frameworks. Given the importance of the contribution by peatlands to the global carbon cycle, this study shows that peatland science is a critical research area and that we still have a long way to go to fully understand the peatland–carbon–climate nexus.

Nature Climate Change↗
USGS2015

Fire effects on aquatic ecosystems: An assessment of the current state of the science

Fire is a prevalent feature of many landscapes and has numerous and complex effects on geological, hydrological, ecological, and economic systems. In some regions, the frequency and intensity of wildfire have increased in recent years and are projected to escalate with predicted climatic and landuse changes. In addition, prescribed burns continue to be used in many parts of the world to clear vegetation for development projects, encourage desired vegetation, and reduce fuel loads. Given the prevalence of fire on the landscape, authors of papers in this special series examine the complexities of fire as a disturbance shaping freshwater ecosystems and highlight the state of the science. These papers cover key aspects of fire effects that range from vegetation loss and recovery in watersheds to effects on hydrology and water quality with consequences for communities (from algae to fish), food webs, and ecosystem processes (e.g., organic matter subsidies, nutrient cycling) across a range of scales. The results presented in this special series of articles expand our knowledge of fire effects in different biomes, water bodies, and geographic regions, encompassing aquatic population, community, and ecosystem responses. In this overview, we summarize each paper and emphasize its contributions to knowledge on fire ecology and freshwater ecosystems. This overview concludes with a list of 7 research foci that are needed to further our knowledge of fire effects on aquatic ecosystems, including research on: 1) additional biomes and geographic regions; 2) additional habitats, including wetlands and lacustrine ecosystems; 3) different fire severities, sizes, and spatial configurations; and 4) additional response variables (e.g., ecosystem processes) 5) over long (>5 y) time scales 6) with more rigorous study designs and data analyses, and 7) consideration of the effects of fire management practices and policies on aquatic ecosystems.

Freshwater Science↗
USGS2022

A framework to integrate innovations in invasion science for proactive management

Invasive alien species (IAS) are a rising threat to biodiversity, national security, and regional economies, with impacts in the hundreds of billions of U.S. dollars annually. Proactive or predictive approaches guided by scientific knowledge are essential to keeping pace with growing impacts of invasions under climate change. Although the rapid development of diverse technologies and approaches has produced tools with the potential to greatly accelerate invasion research and management, innovation has far outpaced implementation and coordination. Technological and methodological syntheses are urgently needed to close the growing implementation gap and facilitate interdisciplinary collaboration and synergy among evolving disciplines. A broad review is necessary to demonstrate the utility and relevance of work in diverse fields to generate actionable science for the ongoing invasion crisis. Here, we review such advances in relevant fields including remote sensing, epidemiology, big data analytics, environmental DNA (eDNA) sampling, genomics, and others, and present a generalized framework for distilling existing and emerging data into products for proactive IAS research and management. This integrated workflow provides a pathway for scientists and practitioners in diverse disciplines to contribute to applied invasion biology in a coordinated, synergistic, and scalable manner.

Biological Reviews↗
USGS2019

A general model of temporary aquatic habitat use: Water phenology as a life history filter

Temporary aquatic habitats are not widely appreciated fish habitat. However, fish navigate the transient waters of intertidal zones, floodplains, intermittent and ephemeral streams, lake margins, seasonally frozen lakes and streams, and anthropogenic aquatic habitats across the globe to access important resources. The selective pressures imposed by water impermanence (i.e., freezing, drying, tidal fluctuations), however, operate similarly across taxa and ecosystems. These similarities are formalized into a conceptual model relating habitat use to surface water phenology. Whereas all necessary life history functions (spawning, foraging, refuge, and dispersal) can be accomplished in temporary habitats, the timing, duration, and predictability of water act as a “life history filter” to which habitats can be used and for what purpose. Habitats wet from minutes to months may all be important—albeit in different ways, for different species. If life history needs co-occur with accessibility, temporary habitats can contribute substantially to individual fitness, overall production and important metapopulation processes. This heuristic is intended to promote research, recognition and conservation of these frequently overlooked habitats that can be disproportionately important relative to their size or brevity of existence. There is a pressing need to quantify how use of temporary aquatic habitats translates to individual fitness benefits, population size and temporal stability, and ecosystem-level consequences. Temporary aquatic habitats are being impacted at an alarming rate by anthropogenic activities altering their existence, phenology, and connectivity. It is timely that scientists, managers and policymakers consider the role these habitats play in global fish production.

Fish and Fisheries↗
USGS2008

Recent damaging earthquakes in Japan, 2003-2008

During the last six years, from 2003-2008, Japan has been struck by three significant and damaging earthquakes: The most recent M6.6 Niigata Chuetsu Oki earthquake of July 16, 2007 off the coast of Kashiwazaki City, Japan; The M6.6 Niigata Chuetsu earthquake of October 23, 2004, located in Niigata Prefecture in the central Uonuma Hills; and the M8.0 Tokachi Oki Earthquake of September 26, 2003 effecting southeastern Hokkaido Prefecture. These earthquakes stand out among many in a very active period of seismicity in Japan. Within the upper 100 km of the crust during this period, Japan experienced 472 earthquakes of magnitude 6, or greater. Both Niigata events affected the south-central region of Tohoku Japan, and the Tokachi-Oki earthquake affected a broad region of the continental shelf and slope southeast of the Island of Hokkaido. This report is synthesized from the work of scores of Japanese and US researchers who led and participated in post-earthquake reconnaissance of these earthquakes: their noteworthy and valuable contributions are listed in an extended acknowledgements section at the end of the paper. During the Niigata Chuetsu Oki event of 2007, damage to the Kashiwazaki-Kariwa nuclear power plant, structures, infrastructure, and ground were primarily the product of two factors: (1) high intensity motions from this moderate-sized shallow event, and (2) soft, poor performing, or liquefiable soils in the coastal region of southwestern Niigata Prefecture. Structural and geotechnical damage along the slopes of dunes was ubiquitous in the Kashiwazaki-Kariwa region. The 2004 Niigata Chuetsu Earthquake was the most significant to affect Japan since the 1995 Kobe earthquake. Forty people were killed, almost 3,000 were injured, and many hundreds of landslides destroyed entire upland villages. Landslides were of all types; some dammed streams, temporarily creating lakes threatening to overtop their new embankments and cause flash floods and mudslides. The numerous landslides resulted, in part, from heavy rain associated with Typhoon Tokage. The earthquake forced more than 100,000 people into temporary shelters, and as many as 10,000 displaced from their upland homes for several years. Total damages was estimated by Japanese authorities at US$40 billion, making this the second most costly disaster in history, after the 1995 Kobe earth-quake. The 2003 Tokachi-Oki earthquake was the third event of magnitude 8.0+ to strike the southeastern portion of Hokkaido in the last 50 years. The event produced tsunami run-ups along the shoreline of southern Hokkaido that reached maximum heights of 4 meters. Accelerations recorded by seismic networks of Hokkaido indicated a high intensity motion region from Hiroo area to Kushiro City, with a PGA values in the range of 0.35 to 0.6g. Despite high acceleration levels, the observed ground failure, liquefaction, structural, port, and lifeline damages were remarkably light.

Conference Paper↗
USGS2000

Data and applications for study of the water cycle in Africa

There are a number data set development, data dissemination, and applications activities at the U.S. Geological Survey (USGS) that contribute to the study of the water cycle in Africa. Some of these stem from global change research initiatives, while others are the result of technical assistance provided to international development and humanitarian assistance projects. Data themes include topography and related hydrological derivatives, land cover, satellite rainfall estimates, and vegetation indices. Some data sets are USGS products, while others originate from cooperating agencies like NASA and NOAA and are distributed secondarily. In Africa, applications include agrometeorological estimates, drought and flood monitoring. Many of the data sets are available to the user community without charge by internet, or at cost of reproduction on CDROM and tape media.

Conference Paper↗
USGS2020

Research priorities for migratory birds under climate change—A qualitative value of information assessment

The mission of the U.S. Geological Survey National Climate Adaptation Science Center is to provide actionable, management-relevant research on climate change effects on ecosystems and wildlife to U.S. Department of the Interior bureaus. Providing this kind of useful scientific information requires understanding how natural-resource managers make decisions and identifying research priorities that support those decision-making processes. Migratory bird management and conservation of migratory bird habitat are central components of the U.S. Department of the Interior’s mission. In particular, the U.S. Fish and Wildlife Service has an intensive, complex decision-making process for identifying high-priority parcels of land that will contribute to migratory bird conservation through permanent acquisition or easement. Climate change introduces several uncertainties into this decision-making process, and additional climate change research should help to support more informed decision making regarding habitat acquisition. Not all climate change related uncertainties, however, will have a meaningful effect on acquisition decisions; therefore, understanding which uncertainties have the most potential to alter decision making is crucial. This document summarizes a multiyear effort to clarify the major sources of climate change uncertainty that affect migratory bird management and to articulate related research priorities. We worked with U.S. Fish and Wildlife Service staff to assess the primary ways in which climate change is likely to affect migratory birds and their habitats; to clarify uncertainties surrounding these effects; and to assess how uncertainties may affect habitat acquisition decisions. Using a modified structured decision-making approach, we assessed a set of hypotheses about how climate change will affect migratory birds and their habitats. Then, we used a qualitative value of information assessment to rank the most important topics for future research. The ranking process was built on an assessment of three primary characteristics: the magnitude of uncertainty, the topic’s relevance to habitat acquisition decision making, and the feasibility of reducing the uncertainty. Based on the results of this process, high-priority topics for future research include the following: The effects of rising temperatures on spatial distributions of migratory birds during the breeding and nonbreeding seasons; Climate-driven changes to avian community composition through homogenization and loss of specialists; The effects of decreased precipitation on abundance in the breeding season; and The effects of rising temperatures on abundance in the nonbreeding season. In addition to describing high-priority research needs, this document provides a summary of the methodology used to identify, assess, and rank uncertainties. This method was developed for a climate change related topic where a full quantitative value of information approach may not be feasible. The results and methodology described here may be useful for U.S. Geological Survey and other science-funding agencies interested in improving the applicability of their research to natural-resource management decision making.

Circular↗
USGS2024

Spatial distribution and diet of Lake Michigan juvenile lake trout

Most studies of Lake Michigan lake trout ( Salvelinus namaycush ) have focused on adults, with scant attention to juveniles (<400 mm). We explored the spatial distribution and diet of juvenile lake trout using U.S. Geological Survey September bottom trawl data (2015–2022) and stomach content information opportunistically collected since 2012 by various agencies using multiple gear types. Most juvenile lake trout in the September bottom trawl survey were caught at 37–64 m bottom depths. Length frequency data from the bottom trawl survey identified three size classes likely associated with wild juvenile lake trout age: < 85 mm (∼age-0), 85–170 mm (∼age-1) and > 170 mm (∼age-2+). Largest catches of wild lake trout < 170 mm occurred along a northeastern transect (near Frankfort, Michigan), whereas most > 170 mm were collected along southern transects. Mysis diluviana was the dominant prey for juvenile lake trout < 170 mm, and > 250 mm were primarily piscivorous, while 170–250 mm appeared to be a transitional period of switching from Mysis to fish. Species composition of prey fishes consumed by lake trout varied spatially and we found evidence of seasonal and annual diet variation within Grand Traverse Bay. Diporeia , once an important component of juvenile lake trout diet, appears to no longer be consumed by juvenile lake trout in Lake Michigan to any measurable degree. Continued research on the ecology of juvenile lake trout may provide insight into the effects of a changing ecosystem on juvenile lake trout diet and growth, thereby contributing to the effort to rehabilitate the Lake Michigan lake trout population.

Lake Michigan↗
USGS2015

Citizen science contributes to our knowledge of invasive plant species distributions

Citizen science is commonly cited as an effective approach to expand the scale of invasive species data collection and monitoring. However, researchers often hesitate to use these data due to concerns over data quality. In light of recent research on the quality of data collected by volunteers, we aimed to demonstrate the extent to which citizen science data can increase sampling coverage, fill gaps in species distributions, and improve habitat suitability models compared to professionally generated data sets used in isolation. We combined data sets from professionals and volunteers for five invasive plant species ( Alliaria petiolata , Berberis thunbergii , Cirsium palustre , Pastinaca sativa , Polygonum cuspidatum ) in portions of Wisconsin. Volunteers sampled counties not sampled by professionals for three of the five species. Volunteers also added presence locations within counties not included in professional data sets, especially in southern portions of the state where professional monitoring activities had been minimal. Volunteers made a significant contribution to the known distribution, environmental gradients sampled, and the habitat suitability of P. cuspidatum . Models generated with professional data sets for the other four species performed reasonably well according to AUC values (>0.76). The addition of volunteer data did not greatly change model performance (AUC > 0.79) but did change the suitability surface generated by the models, making them more realistic. Our findings underscore the need to merge data from multiple sources to improve knowledge of current species distributions, and to predict their movement under present and future environmental conditions. The efficiency and success of these approaches require that monitoring efforts involve multiple stakeholders in continuous collaboration via established monitoring networks.

Wisconsin↗
USGS2018

Land use diversification and intensification on elk winter range in Greater Yellowstone: A framework and agenda for social-ecological research

Amenity migration describes the movement of peoples to rural landscapes and the transition toward tourism and recreation and away from production-oriented land uses (ranching, timber harvesting). The resulting mosaic of land uses and community structures has important consequences for wildlife and their management. This research note examines amenity-driven changes to social-ecological systems in the Greater Yellowstone Ecosystem, specifically in lower elevations that serve as winter habitat for elk. We present a research agenda informed by a preliminary and exploratory mixed-methods investigation: the creation of a “social-impact” index of land use change on elk winter range and a focus group with wildlife management experts. Our findings suggest that elk are encountering an increasingly diverse landscape with respect to land use, while new ownership patterns increase the complexity of social and community dynamics. These factors, in turn, contribute to increasing difficulty meeting wildlife management objectives. To deal with rising complexity across social and ecological landscapes of the Greater Yellowstone Ecosystem, future research will focus on property life cycle dynamics, as well as systems approaches.

Rangeland Ecology and Management↗
USGS2022

Global genetic diversity status and trends: Towards a suite of Essential Biodiversity Variables (EBVs) for genetic composition

Biodiversity underlies ecosystem resilience, ecosystem function, sustainable economies, and human well-being. Understanding how biodiversity sustains ecosystems under anthropogenic stressors and global environmental change will require new ways of deriving and applying biodiversity data. A major challenge is that biodiversity data and knowledge are scattered, biased, collected with numerous methods, and stored in inconsistent ways. The Group on Earth Observations Biodiversity Observation Network (GEO BON) has developed the Essential Biodiversity Variables (EBVs) as fundamental metrics to help aggregate, harmonize, and interpret biodiversity observation data from diverse sources. Mapping and analyzing EBVs can help to evaluate how aspects of biodiversity are distributed geographically and how they change over time. EBVs are also intended to serve as inputs and validation to forecast the status and trends of biodiversity, and to support policy and decision making. Here, we assess the feasibility of implementing Genetic Composition EBVs (Genetic EBVs), which are metrics of within-species genetic variation. We review and bring together numerous areas of the field of genetics and evaluate how each contributes to global and regional genetic biodiversity monitoring with respect to theory, sampling logistics, metadata, archiving, data aggregation, modeling, and technological advances. We propose four Genetic EBVs: ( i ) Genetic Diversity; ( ii ) Genetic Differentiation; ( iii ) Inbreeding; and ( iv ) Effective Population Size ( N e ). We rank Genetic EBVs according to their relevance, sensitivity to change, generalizability, scalability, feasibility and data availability. We outline the workflow for generating genetic data underlying the Genetic EBVs, and review advances and needs in archiving genetic composition data and metadata. We discuss how Genetic EBVs can be operationalized by visualizing EBVs in space and time across species and by forecasting Genetic EBVs beyond current observations using various modeling approaches. Our review then explores challenges of aggregation, standardization, and costs of operationalizing the Genetic EBVs, as well as future directions and opportunities to maximize their uptake globally in research and policy. The collection, annotation, and availability of genetic data has made major advances in the past decade, each of which contributes to the practical and standardized framework for large-scale genetic observation reporting. Rapid advances in DNA sequencing technology present new opportunities, but also challenges for operationalizing Genetic EBVs for biodiversity monitoring regionally and globally. With these advances, genetic composition monitoring is starting to be integrated into global conservation policy, which can help support the foundation of all biodiversity and species' long-term persistence in the face of environmental change. We conclude with a summary of concrete steps for researchers and policy makers for advancing operationalization of Genetic EBVs. The technical and analytical foundations of Genetic EBVs are well developed, and conservation practitioners should anticipate their increasing application as efforts emerge to scale up genetic biodiversity monitoring regionally and globally.

Biological Reviews↗
USGS2025

The Center for the Advancement of Population Assessment Methodology (CAPAM): A perspective on the first 10 years

The Center for the Advancement of Population Assessment Methodology (CAPAM) was established in 2013, envisioned as an institute that could conduct, organize, and communicate stock assessment research with the aim of benefiting fisheries assessment efforts internationally. CAPAM’s activities have focused on its workshop series and consequent special issues in Fisheries Research . The information generated through CAPAM and its permanent recording as journal articles has greatly benefited the stock assessment community and can potentially contribute to modelling in general. We discuss what has made CAPAM successful, its future, and what could be done to reach the ultimate goal of producing a good practices guide for fisheries stock assessment.

Fisheries Research↗
USGS2017

Fracture propagation and stability of ice shelves governed by ice shelf heterogeneity

Tabular iceberg calving and ice shelf retreat occurs after full‐thickness fractures, known as rifts, propagate across an ice shelf. A quickly evolving rift signals a threat to the stability of Larsen C, the Antarctic Peninsula's largest ice shelf. Here we reveal the influence of ice shelf heterogeneity on the growth of this rift, with implications that challenge existing notions of ice shelf stability. Most of the rift extension has occurred in bursts after overcoming the resistance of suture zones that bind together neighboring glacier inflows. We model the stresses in the ice shelf to determine potential rift trajectories. Calving perturbations to ice flow will likely reach the grounding line. The stability of Larsen C may hinge on a single suture zone that stabilizes numerous upstream rifts. Elevated fracture toughness of suture zones may be the most important property that allows ice shelves to modulate Antarctica's contribution to sea level rise.

Larsen C Ice Shelf↗
USGS1984

The toxicity of chlorine to a common vascular aquatic plant

Myriophyllum spicatum was exposed to various chlorine concentrations on a continuous and intermittent basis in 96-h toxicity studies utilizing a proportional diluter. Continuous exposure to chlorine concentrations as low as 0.05 mg l −1 total residual chlorine (TRC) depressed shoot and total plant dry weights approx. 30% relative to controls. Shoot length was depressed approx. 16% at this concentration. Chlorophyll a was depressed 25% at 0.1 mg l −1 TRC. However, intermittent exposure of plants to chlorine for three 2-h periods daily for 96 h indicated an insensitivity to repeated short term chlorine exposure at all concentrations but 1.0 mg l −1 TRC. These results indicate that high level chlorine discharges from waste water facilities and electric generating plants could be a contributing factor impacting nearby submerged aquatic vegetation.

Water Research↗
USGS2003

Protecting embryos from stress: Corticosterone effects and the corticosterone response to capture and confinement during pregnancy in a live-bearing lizard (Hoplodactylus maculatus)

Hormones in the embryonic environment, including those of the hypothalamo-pituitary-adrenal (HPA) axis, have profound effects on development in eutherian mammals. However, little is known about their effects in reptiles that have independently evolved viviparity. We investigated whether exogenous corticosterone affected embryonic development in the viviparous gecko Hoplodactylus maculatus, and whether pregnant geckos have a corticosterone response to capture and confinement that is suppressed relative to that in non-pregnant (vitellogenic) females and males. Corticosterone implants (5 mg, slow-release) administered to females in mid-pregnancy caused a large elevation of corticosterone in maternal plasma (P<0.001), probable reductions in embryonic growth and development (P=0.069-0.073), developmental abnormalities and eventual abortions. Cool temperature produced similar reductions in embryonic growth and development (P???0.036 cf. warm controls), but pregnancies were eventually successful. Despite the potentially harmful effects of elevated plasma corticosterone, pregnant females did not suppress their corticosterone response to capture and confinement relative to vitellogenic females, and both groups of females had higher responses than males. Future research should address whether lower maternal doses of corticosterone produce non-lethal effects on development that could contribute to phenotypic plasticity. Corticosterone implants also led to increased basking in pregnant females (P<0.001), and basal corticosterone in wild geckos (independent of reproductive condition) was positively correlated with body temperature (P<0.001). Interactions between temperature and corticosterone may have broad significance to other terrestrial ectotherms, and body temperature should be considered as a variable influencing plasma corticosterone concentrations in all future studies on reptiles. ?? 2003 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗