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At least 1,261 records · Page 70Linked to original sources
USGS2022

Climatic drivers and ecological impacts of a rapid range expansion by non-native smallmouth bass

Smallmouth bass ( Micropterus dolomieu ) are a globally introduced fish species that have experienced widespread range expansions in recent decades and which can have deleterious effects on native fish communities. Rapidly assessing their expansions will aid conservation and management actions geared towards controlling their spread and mitigating their impacts. Smallmouth bass have recently experienced a rapid upstream expansion in a Great Plains river (Laramie River, Wyoming, USA), which provided an opportunity to evaluate the drivers and impacts of this expansion by using a modified before-after, control-impact (BACI) design. Our objectives were to test whether climatic drivers (temperature, precipitation, flow) were related to this range expansion and subsequent effects of the expansion on native fish communities. Smallmouth bass population size in Grayrocks Reservoir increased following a climatically extreme wet year, with statistically extreme amounts of spring-time and June precipitation creating high discharge events that coincided with the upstream expansion. Unlike previous studies highlighting the invasive nature of smallmouth bass, the modified BACI analysis revealed no declines in species richness induced by the expansion. However, there was evidence that native small-bodied minnow species (family Leuciscidae ) declined in relative abundance and that community-level and species-level trophic niches were compressed for invaded sites. Our findings provide important insight into how climatic extremes can prompt biological invasions that can alter community composition and food web structure even if local extirpations do not occur.

Wyoming↗
USGS2022

High densities of conspecifics buffer native fish from negative interactions with an ecologically similar invasive

Invasive species are a leading cause for native species declines, but it remains unclear whether maintenance of high native densities influence native persistence in freshwater systems. We designed complementary laboratory and field experiments to test whether high native cutthroat trout (Oncorhynchus clarkii) densities affect competition with invasive brown trout (Salmo trutta). We manipulated density of native cutthroat trout while holding brown trout density constant. Interspecific aggressive interactions towards native cutthroat trout were 66% fewer in the highest cutthroat trout density treatment compared to the lowest density treatment. At high densities of conspecifics, cutthroat trout, sympatric with brown trout, lost 33-81% less weight and demonstrated 1.5 times greater survival in both experiments than at low conspecific densities. Cutthroat trout held at low densities in laboratory experiments experienced greater stress-related disease virulence and negative effects of harassment, apparently owing to more frequent aggressive interactions with brown trout. These results support the hypothesis that reduced per capita effects of invaders on native fish at high densities buffers native species from negative effects of invaders, reducing the potential for invasive fish to displace high density native fish populations.

Utah↗
USGS2008

Delayed genetic effects of habitat fragmentation on the ecologically specialized Florida sand skink ( Plestiodon reynoldsi )

Populations rarely show immediate genetic responses to habitat fragmentation, even in taxa that possess suites of traits known to increase their vulnerability to extinction. Thus conservation geneticists must consider the time scale over which contemporary evolutionary processes operate to accurately portray the effects of habitat isolation. Here, we examine the genetic impacts of fragmentation on the Florida sand skink Plestiodon reynoldsi , a sand swimming lizard that is highly adapted to the upland scrub habitat of central Florida. We studied fragments located on the southern Lake Wales Ridge, where human activity in the latter half of the 20th century has modified the natural patchiness of the landscape. Based on a relaxed molecular clock method, we estimate that sand skinks have persisted in this region for approximately 1.5 million years and that the time frame of human disturbance is equivalent to fewer than 30 skink generations. Using genotypes from eight microsatellite loci, we screened for molecular signatures of this disturbance by assessing congruence between population structure, as inferred from spatially-informed Bayesian assignment tests, and the current geography of scrub fragments. We also tested for potential intrapopulation genetic effects of inbreeding in isolated populations by comparing the average pairwise relatedness of individuals within fragments of different areas and isolation. Our results indicate that although some patches show a higher degree of relatedness than expected under random mating, the genetic effects of recent isolation are not evident in this part of the species’ range. We argue that this result is an artefact of a time-lag in the response to disturbance, and that species-typical demographic features may explain the genetic inertia observed in these populations.

Conservation Genetics↗
USGS2025

Regional high-frequency monitoring revealed chloride concentrations in exceedance of ecological benchmarks in urban streams across the Delaware River Basin, USA

Rising chloride concentrations pose critical risks to freshwater stream ecosystems in temperate regions like the Delaware River Basin (DRB), USA, where winter deicer applications ( i.e. , road salt) are common. Increasing chloride concentrations have been documented in the region, but the extent to which chloride exceeds regulatory benchmarks remains unclear because detection of exceedances requires continuous monitoring of chloride ( i.e. , hourly or daily). A network of 82 non-tidal continuous specific conductance (SC) monitoring sites, spanning varied land use and geological settings, was established across the DRB to address this research need. First, a cluster analysis was conducted to group sites based on their watershed characteristics. Next, regression models for sites and clusters were developed to predict chloride using SC as a proxy. Finally, daily mean and hourly mean chloride concentration predictions were made for a three-year period (2020–2022) at the 82 study sites and analyzed to determine where and when chloride exceeded federal regulatory benchmarks. Chloride exceedance events occurred at 35% of the sites, all of which had 5% impervious cover or greater. Seasonally elevated chloride also was predicted at sites with less than 5% impervious cover. Variability in chloride patterns likely was influenced by deicer material types, winter weather patterns, geological settings, and gaps in data coverage. This study demonstrated the value of SC as a proxy for predicting chloride concentrations and showed how SC-chloride regression relationships vary across settings. More broadly, this study highlighted the value of continuous water quality monitoring to assess effects of freshwater salinization at a regional scale.

Delaware, Maryland, New Jersey, New York, Pennsylv↗
USGS2015

A chronicle of a killer alga in the west: Ecology, assessment, and management of Prymnesium parvum blooms

Since the mid-1980s, fish-killing blooms of Prymnesium parvum spread throughout the USA. In the south central USA, P. parvum blooms have commonly spanned hundreds of kilometers. There is much evidence that physiological stress brought on by inorganic nutrient limitation enhances toxicity. Other factors influence toxin production as well, such as stress experienced at low salinity and temperature. A better understanding of toxin production by P. parvum remains elusive and the identities and functions of chemicals produced are unclear. This limits our understanding of factors that facilitated the spread of P. parvum blooms. In the south central USA, not only is there evidence that the spread of blooms was controlled, in part, by migration limitation. But there are also observations that suggest changed environmental conditions, primarily salinity, facilitated the spread of blooms. Other factors that might have played a role include altered hydrology and nutrient loading. Changes in water hardness, herbicide use, system pH, and the presence of toxin-resistant and/or P. parvum -inhibiting plankton may also have played a role. Management of P. parvum in natural systems has yet to be attempted, but may be guided by successes achieved in small impoundments and mesocosm experiments that employed various chemical and hydraulic control approaches.

Hydrobiologia↗
USGS2021

A socio-ecological imperative for broadening participation in coastal and estuarine research and management

For most of the scientific disciplines associated with coastal and estuarine research, workforce representation does not match the demographics of communities we serve, especially for Black, Hispanic or Latino, and Indigenous peoples. This essay provides an overview of this inequity and identifies how a scientific society can catalyze representational, structural, and interactional diversity to achieve greater inclusion. Needed changes go beyond representational diversity and require an intentional commitment to build capacity through inclusivity and community engagement by supporting anti-racist policies and actions. We want to realize a sense of belonging on the part of scientists in society at large and enable research pursuits through a lens of social justice in service of coastal communities. Minimally, this framework offers an avenue for increased recruitment of individuals from more diverse racial and ethnic identities. More broadly, the mechanisms described here aim to create a culture in scientific societies in which social justice, driven by anti-racist actions, produces systemic change in how members of scientific societies approach, discuss, and address issues of inequity. We have written this essay for members of the coastal and marine science community who are interested in change. We aim to call in new voices, allies, and champions to this work.

Estuaries and Coasts↗
USGS2024

Projecting mangrove forest resilience to sea-level rise on a Pacific Island: Species dynamics and ecological thresholds

Mangroves can increase their elevation relative to tidal flooding through biogeomorphic feedbacks but can submerge if rates of sea-level rise are too great. There is an urgent need to understand the vulnerability of mangroves to sea-level rise so local communities and resource managers can implement and prioritize actions. The need is especially pressing for small islands, which have been identified as an area of concern by the IPCC. We developed a generalizable modeling framework for tidal wetlands (WARMER-3) that accounts for species interactions and the belowground processes that dictate soil elevation building relative to sea levels. The model was calibrated with extensive field datasets, including accretion rates derived from 29 soil cores, over 300 forest inventory plots, water level, and elevation. The model included five mangrove tree species and was applied across seven regions around the Pacific Island of Pohnpei, Federated States of Micronesia, where mangrove forest is a critical ecosystem that supports subsistence living for local communities. We explored mangrove resilience and carbon accumulation under six sea-level rise scenarios. We also conducted an analysis to determine the sea-level rise rate threshold above which mangroves would be lost. The results suggest that Pohnpei mangroves can build their elevations relative to low and moderate rates of sea-level rise to prevent submergence, with limited loss of mangrove area through 2150. Under higher sea-level rise rates, however, forest elevation decreased substantially relative to mean sea level and there was extensive loss of mangrove area by that year. Regarding mangrove community composition, for all sea-level rise scenarios, the model predicted a change to increasing relative abundance of flood tolerant species and decreasing relative abundance of high-elevation species, which started to being realized by 2100. Variation in sediment supply, water levels, and elevation capital led to differential vulnerability around the island. We identified a threshold for Pohnpei mangroves where if local sea-level rise rates exceed 7.8 ± 2.2 mm/year they are projected to eventually submerge and be lost. Our modeling framework is novel by addressing both species interactions and critical belowground processes to better understand potential tidal ecosystem responses to sea-level rise.

Pohnpei↗
USGS2025

Bridging social and ecological science to create spatially-explicit models of human-caused mortality of carnivores

Research indicates that human-caused mortality (HCM) is a key factor limiting numerous large carnivore populations. However, efforts to represent HCM in spatially explicit models have generally been limited in scope—often relying on proxies, such as road or human density. Yet such efforts fail to distinguish different sources of HCM, which can arise from different antecedent processes. We offer a systems-based conceptual framework for understanding the antecedents of HCMs that is grounded in theory from the social and behavioral sciences. Specifically, we first explain how HCMs are usefully distinguished into four types (e.g., accidental, harvest, illicit, control actions), then discuss how these different types tend to be driven by different sets of psychological and sociopolitical processes. We contend that improvements in understanding the spatial variation in HCMs would rise from more explicit attention to the various antecedent processes that precede each mortality type.

Ambio↗
USGS2012

Ecology and evolution of pine life histories

Introduction - Pinus is a diverse genus of trees widely distributed throughout the Northern Hemisphere. Understanding pine life history is critical to both conservation and fire management. Objectives - Here I lay out the different pathways of pine life history adaptation and a brief overview of pine evolution and the very significant role that fire has played. Results - Pinus originated ~150 Ma in the mid-Mesozoic Era and radiated across the northern continent of Laurasia during the Cretaceous Period. Pines have followed two evolutionary strategies interpreted as responses to competition by the newly emerging angiosperms. The Strobus lineage mostly has radiated into stressful sites of low nutrient soils and extremes in cold or heat. The Pinus (subgenus) lineage has radiated into fire-prone landscapes with diverse fire regimes. Examination of life history traits illustrates syndromes associated with fire-avoider, fire-tolerater, fire-embracer, and fire-refuge strategies. Conclusion - Understanding the current pattern of pine distribution requires interpreting their evolution in terms of climate, geology, and fire. All three of these factors have played a role since the Mesozoic origin of the genus. All are important to the appropriate management of these resources.

Annals of Forest Science↗
USGS2019

Records of engagement and decision making for environmental and socio-ecological challenges

We propose creating and maintaining records of engagement and decision-making (RoED) to help us and our communities better understand ourselves, our goals, our decisions, and the dynamic systems in which we all live. The purpose of RoED is to go well beyond noting that dialogue occurred or a decision was reached. The records should, in ways appropriate to the context and participants, document interactions and note biases, beliefs, emotions, behaviors, norms, and values. These crucial aspects are generally absent in academic papers and formal reports, yet they always play a role in decision-making processes. While not a panacea for addressing critical biophysical and social challenges, we propose that a comprehensive framework for promoting realistic, legitimate and inclusive engagement could enhance trust, establish institutional memory, and when and where appropriate, ensure greater transparency. The aim is to create and maintain RoED to collect significant information and share insights from multi-stakeholder decision-making processes from diverse institutions, contexts, and disciplinary domains. In the long-term RoED could promote more effective adaptive management or governance approaches. This paper describes an exploratory phase intended to catalyze collaborative efforts worldwide.

EURO Journal on Decision Processes↗
USGS1984

Distribution and ecology of deep-water benthic foraminifera in the Gulf of Mexico

Bathyal and abyssal foraminifera in the Gulf of Mexico are distributed among thirteen generic predominance facies. Five predominance facies nearly encircle the Gulf basin along the slope and rise; a sixth predominance facies blankets the Sigsbee Plain, and a seventh is restricted to the Mississippi Fan. The remaining eight predominance facies have more restricted distributions. The areal patterns of these predominance facies can be related chiefly to water mass and substrate characteristics; modifications are brought about by calcite dissolution, upwelling, and sill depth. Analysis of ancient generic predominance facies is useful in predicting relative paleobathymetry and other paleoenvironmental properties.

Alabama, Florida, Louisiana, Mississippi, Texas↗
USGS2022

Rainforest carnivore ecology in a managed forest reserve: Differential seasonal correlates between habitat components and relative abundance

Studies of relationships between seasons and Neotropical carnivore distributions tend to focus on water and prey availability without considering other habitat components such as escape, foraging, and resting cover. Our goal was to evaluate habitat characteristics that may be important for predicting the seasonal (dry or rainy) relative abundance of four commonly captured Neotropical carnivores (i.e., jaguar [ Panthera onca ], puma [ Puma concolor ], ocelot [ Leopardus pardalis ], and grey fox [ Urocyon cinereoargenteus ]) in Chiquibul Forest Reserve in Belize, Central America. We used trail camera data and random-effect Poisson models to investigate how prey ratios (number of prey detections/total detections), cover (e.g., logs and stumps used for hiding cover from predators), vegetation structure, and environmental site characteristics (e.g., site harvest-history, slope, aspect) were related to carnivore relative abundance. Both prey ratios and vegetation structure appeared in supported models more frequently than other environmental site characteristics and were negatively correlated with carnivore relative abundance. Supported models differed for each season for all species except jaguars for which mammalian prey ratios and prey cover at sites was always negatively correlated with jaguar relative abundance. Carnivores appeared to avoid sites where vegetation created ideal escape and hiding cover for prey even though prey may be less abundant. Our data suggest that vegetation structure and composition can create conditions conducive to carnivore foraging and that these characteristics can differ by season in the tropics.

Biological Conservation↗
USGS2006

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3-4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12-15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

Catena↗
USGS2019

Ecological effects of establishing a 40-year oasis protection system in a Northwestern China Desert

Aims: Desertification around oasis areas is a serious problem in semi-arid and arid regions, which is expected to continue into the future due to a rapidly increasing human population. Oasis protection systems are created to reverse desertification by recovering degraded soil and vegetation properties and improving ecosystem services. Most research has focused on the short-term effects of a single restoration practice using an individual vegetation or soil metric, while more complete assessments along a gradient of an entire oasis protection system have seldom been studied. In this study, soil and vegetation properties were measured along a 40-year oasis-protection system to assess the effectiveness of increasing land protection belts along a gradient from prohibiting grazing, to fencing shrubland, to establishing shrub- and tree-plantations in northwestern China. Methods: Three sites in each belt of the oasis-protection system were selected to measure soil texture, soil organic carbon, total nitrogen, total phosphorus, pH, electrical conductivity, and eight ions under the plant canopy and in the inter-canopy area, as well as to investigate plant community composition, diversity and productivity. Wind velocity and sand transportation rates were measured in each of the five belts during storm events. Results: Compared with shifting dunes in unprotected desert settings, the wind velocity and sand transportation rate decreased by 75 and 98%, respectively, when spring storms passed through the most protected plantation belts in the oasis system. Soil organic carbon, total nitrogen, total phosphorus significantly increased, along with the silt and clay contents, across the protection gradient, and reached their highest levels at the shrub- and tree-plantation belts. Similarly, the density, cover, and biomass of herbaceous plants also increased along the gradient. Despite these positive effects, there was a significant increase in soil salinity, sodicity, and desiccation at the shrub- and tree-plantation belts, which may negatively affect the future sustainability of the oasis-protection system under a predicted future drier and warming climate. Conclusions Although shrub and tree plantations improve soil fertility and favor the development of the herbaceous plant community, their environmental consequences (i.e., soil salinization and desiccation) need to be evaluated in the context of ecosystem restoration over the long-term, especially in arid regions.

Catena↗