Geology topics

Peter B. McIntyre

Publications and source records attributed to Peter B. McIntyre.

16 recordsLinked to original sources

USGS2025

Quantifying depuration of methylmercury from fish consumption by travelers

During a two-week field sampling expedition in Gabon, two American scientists consumed fish daily from the Ogooué River watershed. We sampled their scalp and facial hair periodically to evaluate hair as a biomarker to track shifts in methylmercury (MeHg) exposure from diet. Each individual differed in the onset and extent of MeHg accumulation but showed similar depuration rates. Pretrip baseline Hg isotope values between participants were distinct from Gabonese fishes allowing us to detect shifts in MeHg sources in the hair of both individuals. δ 202 Hg values tracked the mass-dependent fractionation of MeHg depuration stemming from in vivo metabolism, leading to δ 202 Hg increases of 0.014 ± 0.001 per mille and total Hg losses of 8.3 ± 1.1 ng g –1 daily. While limited in scope due to minimal participants, our findings reveal a complex interaction between prior MeHg burdens, contemporary MeHg intakes, and sources of consumed fishes (locally caught versus market-sourced) in determining the dynamics of MeHg concentrations and δ 202 Hg in human hair. We also suggest that the offset in δ 202 Hg values used in literature between fish and human hair (1.75 ± 0.25‰) may overlook a time domain that increases starting fish-hair δ 202 Hg offsets (0.94‰), through time.

Agence Nationale des Parcs Nationaux↗

USGS2025

Relationship-centered engagement bridges the divide between science and management, and enhances climate adaptation

The rapid pace of climate change demands changes in management practices. Despite abundant climate adaptation research, the implementation of climate adaptation can lag in the management space. In the present article, we argue that relationship-centered engagement—establishing and maintaining relationships among researchers and natural resource managers—is critical for bridging the research–management gap. We evaluated researcher–manager partnerships within the US Northeast Climate Adaptation Science Center and identified three cultural shifts that institutions, funders, researchers, and managers could adopt to boost the odds of translating findings into action: acknowledging and supporting the central role of relationships in creating and implementing actionable science, lengthening funding timelines to better support establishing and maintaining relationships, and aligning institutional rewards to support relationship building. A renewed focus on relationships can lead to more diverse and effective partnerships that bridge knowledge to practice and hasten adaptation to climate change.

BioScience↗

USGS2025

Eradication efforts catalyze rapid evolution in an invasive predatory fish

pecies invasions spur costly and labor-intensive control efforts, yet even local eradication is seldom achieved. When control measures are initially effective, they may drive evolutionary adaptation that prevents full eradication, as has been documented for some chemical and biocontrol approaches. Although the intensity, directionality, and persistence of selection required to increase the frequency of resistant genotypes in complex natural ecosystems remains an open question, theory predicts that high mortality can cause life-history evolution even in the absence of a strong selective agent. Here, we use annually collected ecological and genetic data to show that rapid evolution of introduced smallmouth bass has undermined a 20-y manual suppression effort in a mid-sized lake. Despite nearly doubling annual mortality, our intensive control program produced a larger bass population dominated by young and early-maturing fish. These shifts were accompanied by large allele frequency changes in three genomic regions associated with earlier maturation and increased somatic growth. Our findings bear out the theoretical prediction that high mortality can drive evolutionary adaptation in target species. Controlling species invasions are worldwide practices that typically remove a substantial proportion of a population during each of many successive generations, hence life history adaptation may be commonplace. Such evolutionary responses could be salient in explaining the widespread failure of invasion control efforts. Genetic and phenotypic monitoring to detect cryptic adaptation and preemptive design of invader eradication programs to deliberately disrupt directional selection for resistance could improve invasion control outcomes.

New York↗

USGS2025

Climate-driven deoxygenation of lakes alters the nutrient-toxin profile of a food fish

Climate change is rapidly altering fisheries supporting aquatic ecosystems. The implications for food security depend not only on harvest biomass but also concentrations of nutrients and toxins in fish. Using brook trout from Adirondack lakes (New York, USA), we tested whether ongoing lake deoxygenation trends will affect fish muscle omega-3 fatty acids, selenium, and mercury concentrations. Across space (16 lakes: 1 year) and time (6 years: 1 lake), anoxia decreased selenium and was associated with elevated fish mercury, with no effect on omega-3 content. Because selenium may mitigate some end points of mercury toxicity, highly variable Se:Hg molar ratios (0.70–35.79) in neighboring lakes may have health risk implications. For fish consumers, ongoing lake deoxygenation under climate change could potentially reduce selenium intake while enhancing mercury exposure. Simultaneous alteration of beneficial compounds and toxins by environmental change complicates the development of fish consumption advisories to safeguard public health in a warming world.

New York↗

USGS2024

Human activities shape global patterns of decomposition rates in rivers

Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose decomposition rates, when combined with genus-level litter quality attributes, explain published leaf litter decomposition rates with high accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth and reveals rapid decomposition across continental-scale areas dominated by human activities.

Science↗

USGS2022

Bright spots for inland fish and fisheries to guide future hydropower development

Hydropower production is one of the greatest threats to fluvial ecosystems and freshwater biodiversity. Now that we have entered the Anthropocene , there is an opportunity to reflect on what might constitute a ‘sustainable’ Anthropocene in the context of hydropower and riverine fish populations. Considering elements of existing practices that promote favorable social-ecological outcomes (i.e., ‘bright spots’) is timely given that there are plans to expand hydropower capacity in previously undammed rivers, intensify dam development in some of the world's largest river systems, and re-license existing facilities. We approach this from a pragmatic perspective: for the foreseeable future, hydropower will likely remain an important source of renewable electricity. To offer support for moving toward a more ‘sustainable’ Anthropocene, we provide syntheses of best practices during the siting, design, construction, operation, and compensation phases of hydropower development to minimize impacts on inland fish. For each phase, we offer positive examples (or what might be considered ‘bright spots’) pertaining to some of the approaches described within our syntheses, acknowledging that these projects may not be viewed as without ecological and (or) societal detriment by all stakeholders. Our findings underscore the importance of protecting critical habitat and free-flowing river reaches through careful site selection and basin-scale planning, infrastructure designs that minimize reservoir effects and facilitate safe passage of fish, construction of hydropower plants using best practices that minimize long-term damage, operating guidelines that mimic natural flow conditions, and compensation that is lasting, effective, inclusive, and locally relevant. Learning from these ‘bright spots’ may require engagement of diverse stakeholders, professionals, and governments at scales that extend well beyond a given site, river, or even basin. Indeed, environmental planning that integrates hydropower development into broader discussions of conserving regional biodiversity and ecosystem services will be of utmost importance.

Water Biology and Security↗

USGS2021

Genomic and environmental influences on resilience in a cold-water fish near the edge of its range

Small, isolated populations present a challenge for conservation. The dueling effects of selection and drift in a limited pool of genetic diversity make the responses of small populations to environmental perturbations erratic and difficult to predict. This is particularly true at the edge of a species range, where populations often persist at the limits of their environmental tolerances. Populations of cisco, Coregonus artedi , in inland lakes have experienced numerous extirpations along the southern edge of their range in recent decades, which are thought to result from environmental degradation and loss of cold, well-oxygenated habitat as lakes warm. Yet, cisco extirpations do not show a clear latitudinal pattern, suggesting that local environmental factors and potentially local adaptation may influence resilience. Here, we used genomic tools to investigate the nature of this pattern of resilience. We used restriction site-associated DNA capture (Rapture) sequencing to survey genomic diversity and differentiation in southern inland lake cisco populations and compared the frequency of deleterious mutations that potentially influence fitness across lakes. We also examined haplotype diversity in a region of the major histocompatibility complex involved in stress and immune system response. We correlated these metrics to spatial and environmental factors including latitude, lake size, and measures of oxythermal habitat and found significant relationships between genetic metrics and broad and local factors. High levels of genetic differentiation among populations were punctuated by a phylogeographic break and residual patterns of isolation-by-distance. Although the prevalence of deleterious mutations and inbreeding coefficients was significantly correlated with latitude, neutral and non-neutral genetic diversity were most strongly correlated with lake surface area. Notably, differences among lakes in the availability of estimated oxythermal habitat left no clear population genomic signature. Our results shed light on the complex dynamics influencing these isolated populations and provide valuable information for their conservation.

Wisconsin↗

USGS2020

Outsized nutrient contributions from small tributaries to a Great Lake

Excessive nutrient inputs from tributary streams and rivers contribute to harmful algal blooms and coastal ecosystem degradation worldwide. However, the role that small tributaries play in coastal nutrient dynamics remains unknown because most monitoring and regulatory efforts focus only on the largest tributaries. We combined a 6-d sampling effort with discharge modeling to characterize nutrient inputs from nearly all watersheds draining to the world’s fifth largest lake. We found that streams are particularly likely to promote eutrophication in coastal ecosystems because they deliver water with higher concentrations of nutrients that are readily available to algae. Thus, our findings indicate that efforts to control nutrient loading could be enhanced by looking beyond the largest tributaries to include smaller streams.

Lake Michigan↗

USGS2019

Evidence for interactions among environmental stressors in the Laurentian Great Lakes

Co-occurrence of environmental stressors is ubiquitous in ecosystems, but cumulative effects are difficult to predict for effective indicator development. Individual stressors can amplify (synergies) or lessen (antagonisms) each other's impacts or have fully independent effects (additive). Here we use the Laurentian Great Lakes, where a multitude of stressors have been studied for decades, as a case study for considering insights from both a systematic literature review and an expert elicitation (or structured expert judgment) to identify stressor interactions. In our literature search for pairs of stressors and interaction-related keywords, relatively few studies (9%, or 6/65) supported additive interactions with independent stressor effects. Instead, both antagonisms (42%, or 27/65) and synergies (49%, or 32/65) were common. We found substantial evidence for interactions of invasive dreissenid mussels with nutrient loading and between pairs of invasive species (predominantly dreissenids × round goby), yet both sets of records included mixtures of synergies and antagonisms. Complete quantification of individual and joint effects of stressors was rare, but effect sizes for dreissenid mussels × nutrient loading supported an antagonism. Our expert elicitation included discussion in focus groups and a follow-up survey. This process highlighted the potential for synergies of nutrient loading with dreissenid mussels and climate change as seen from the literature review. The elicitation also identified additional potential interactions less explored in the literature, particularly synergies of nutrient loading with hypoxia and wetland loss. To stimulate future research, we built a conceptual model describing interactions among dreissenid mussels, climate change, and nutrient loading. Our case study illustrates the value of considering results from both elicitations and systematic reviews to overcome data limitations. The simultaneous occurrence of synergies and antagonisms in a single ecosystem underscores the challenge of predicting the cumulative effects of stressors to guide indicator development and other management and restoration decisions.

Ecological Indicators↗

USGS2018

Ratio of mercury concentration to PCB concentration varies with sex of white sucker (Catostomus commersonii)

The whole-fish total mercury (Hg) concentrations were determined in 25 mature female and 26 mature male white suckers ( Catostomus commersonii ) caught during their spawning run in the Kewaunee River, a tributary to Lake Michigan. The age of each fish was estimated using thin-sectioned otoliths, and total length (TL) and weight were determined for each fish. When adjusted for the effect of age, males were found to be 7% higher in Hg concentration than females. Nearly all (about 98%) of the Hg found in the white suckers was determined to be methylmercury. In an earlier study on the same 51 white suckers from the Kewaunee River spawning run, males were found to be 18% higher than females in polychlorinated biphenyl (PCB) concentration. We determined that the ratio of Hg concentration to PCB concentration in females was significantly higher than that in males. Thus, sex significantly interacted with contaminant type (Hg or PCBs) in determining contaminant concentrations. The most plausible explanation for this interaction was that males eliminated Hg at a faster rate than females, most likely due to the boosting of the Hg-elimination rate by certain androgens such as testosterone and 11-ketotestosterone. Hg concentrations in the white suckers were well below federal guidelines for fish consumption.

Environments↗

USGS2018

Distributions of PCB congeners and homologues in white sucker and coho salmon from Lake Michigan

We tested the hypothesis of the proportion of higher chlorinated biphenyl (PCB) congeners increasing with increasing trophic level by comparing the respective PCB homologue distributions in an omnivore, white sucker ( Catostomus commerson i), and a top predator, coho salmon ( Oncorhynchus kisutch ), from Lake Michigan. Adult females had the same congener and homologue proportions of total PCB concentration (ΣPCB) as adult males in both species. Hexachlorinated congeners comprised the largest proportion (32%) found in white sucker, followed by heptachlorinated (21%) and octochlorinated (18%) congeners. In contrast, pentachlorinated congeners comprised the largest proportion (33%) of ΣPCB found in coho salmon, followed by hexachlorinated (26%) and tetrachlorinated (24%) congeners. Coho salmon contained significantly higher proportions of tri-, tetra-, and pentachlorinated congeners, whereas white sucker contained significantly higher proportions of hexa- through decachlorinated congeners. Our results were opposite of the hypothesis of greater degree of PCB chlorination with increasing trophic level, and supported the contention that the PCB congener proportions in fish depends mainly on diet, and does not necessarily reflect the trophic level of the fish. Our results also supported the contention that diets do not vary between the sexes in most fish populations.

Environmental Science & Technology↗

USGS2017

Ecosystem services in the Great Lakes

A comprehensive inventory of ecosystem services across the entire Great Lakes basin is currently lacking and is needed to make informed management decisions. A greater appreciation and understanding of ecosystem services, including both use and non-use services, may have avoided misguided resource management decisions in the past that resulted in negative legacies inherited by future generations. Given the interest in ecosystem services and lack of a coherent approach to addressing this topic in the Great Lakes, a summit was convened involving 28 experts working on various aspects of ecosystem services in the Great Lakes. The invited attendees spanned a variety of social and natural sciences. Given the unique status of the Great Lakes as the world's largest collective repository of surface freshwater, and the numerous stressors threatening this valuable resource, timing was propitious to examine ecosystem services. Several themes and recommendations emerged from the summit. There was general consensus that: 1) a comprehensive inventory of ecosystem services throughout the Great Lakes is a desirable goal but would require considerable resources; 2) more spatially and temporally intensive data are needed to overcome our data gaps, but the arrangement of data networks and observatories must be well-coordinated; 3) trade-offs must be considered as part of ecosystem services analyses; and 4) formation of a Great Lakes Institute for Ecosystem Services, to provide a hub for research, meetings, and training is desirable. Several challenges also emerged during the summit, which are discussed.

Great Lakes↗

USGS2017

Sex difference in PCB concentrations of a catostomid fish

Unraveling the complexities associated with the relative differences in contaminant concentrations between the sexes of mature fish may provide insights into important behavioral and physiological differences between the sexes of not just fish but higher vertebrates as well. Whole-fish polychlorinated biphenyl (PCB) concentrations were determined in 25 mature female white suckers (Catostomus commersoni) and 26 mature male white suckers caught during their spawning run in the Kewaunee River, a tributary to Lake Michigan. Total length and weight were measured for each fish, and age of each fish was estimated from thin-sectioned otoliths. PCB concentration significantly increased with increasing total length, weight, and age. Consequently, three analysis of covariance (ANCOVA) models were fitted to the data to assess the effect of sex on white sucker PCB concentration. Based on model averaging, estimates of mean PCB concentrations in female and male white suckers were 185 and 219 ng/g, respectively. Thus, males were 18% greater in PCB concentration than females. We conclude that this difference between the sexes was most likely mainly driven by a higher rate of energy expenditure in males compared with females. Greater energy expenditure, owing to greater swimming activity and a higher resting metabolic rate , resulted in a higher rate of food consumption, which in turn led to a greater rate of PCB accumulation. Higher whole-fish PCB concentration in males compared with females has now been shown in nine different fish species. Our study represented the first documentation of this type of sex difference in a catostomid fish.

Kewaunee River, Lake Michigan↗

USGS2016

Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems

Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a &sim;1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa’s deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last &sim;150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last &sim;500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika’s extraordinary biodiversity and ecosystem services.

Lake Tanganyika, Mahale Mountains National Park↗

USGS2015

Rapid and highly variable warming of lake surface waters around the globe

In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade −1 ) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors—from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade −1 ) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade −1 ). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.

Geophysical Research Letters↗

USGS2015

A global database of lake surface temperatures collected by in situ and satellite methods from 1985–2009

Global environmental change has influenced lake surface temperatures, a key driver of ecosystem structure and function. Recent studies have suggested significant warming of water temperatures in individual lakes across many different regions around the world. However, the spatial and temporal coherence associated with the magnitude of these trends remains unclear. Thus, a global data set of water temperature is required to understand and synthesize global, long-term trends in surface water temperatures of inland bodies of water. We assembled a database of summer lake surface temperatures for 291 lakes collected in situ and/or by satellites for the period 1985–2009. In addition, corresponding climatic drivers (air temperatures, solar radiation, and cloud cover) and geomorphometric characteristics (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, and volume) that influence lake surface temperatures were compiled for each lake. This unique dataset offers an invaluable baseline perspective on global-scale lake thermal conditions as environmental change continues.

Scientific Data↗