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Das A.J.,Western Ecological Research Center | Stephenson N.L.,Western Ecological Research Center | Flint A.,California Water Science Center | Das T.,University of California at San Diego | van Mantgem P.J.,Western Ecological Research Center
PLoS ONE | Year: 2013

Recent increases in tree mortality rates across the western USA are correlated with increasing temperatures, but mechanisms remain unresolved. Specifically, increasing mortality could predominantly be a consequence of temperature-induced increases in either (1) drought stress, or (2) the effectiveness of tree-killing insects and pathogens. Using long-term data from California's Sierra Nevada mountain range, we found that in water-limited (low-elevation) forests mortality was unambiguously best modeled by climatic water deficit, consistent with the first mechanism. In energy-limited (high-elevation) forests deficit models were only equivocally better than temperature models, suggesting that the second mechanism is increasingly important in these forests. We could not distinguish between models predicting mortality using absolute versus relative changes in water deficit, and these two model types led to different forecasts of mortality vulnerability under future climate scenarios. Our results provide evidence for differing climatic controls of tree mortality in water- and energy-limited forests, while highlighting the need for an improved understanding of tree mortality processes.


Zamani K.,University of California at Davis | Bombardelli F.A.,University of California at Davis | Wuertz S.,University of California at Davis | Smith P.E.,California Water Science Center
World Environmental and Water Resources Congress 2010: Challenges of Change - Proceedings of the World Environmental and Water Resources Congress 2010 | Year: 2010

A deterministic 3D model for simulating hydrodynamics and salinity, based on the code Si3D, was implemented for San Francisco Bay. Several scenarios were modeled involving different months with varying estuarine conditions between October 2007 and June 2008. Bay bathymetry, coastal and river water levels, and salinity were used as input. This paper presents preliminary results of the modeling project. The paper discusses results obtained with two meshes and addresses the effects of boundary conditions on the numerical results. Predictions of tidal current patterns were developed for a study of water quality and quantitative pathogen monitoring in the sub-embayment of San Pablo Bay. © 2010 ASCE.


PubMed | University of Texas at Austin, California Water Science Center, National Oceanic and Atmospheric Administration and University of California at Davis
Type: Journal Article | Journal: PloS one | Year: 2016

Climate change is driving rapid changes in environmental conditions and affecting population and species persistence across spatial and temporal scales. Integrating climate change assessments into biological resource management, such as conserving endangered species, is a substantial challenge, partly due to a mismatch between global climate forecasts and local or regional conservation planning. Here, we demonstrate how outputs of global climate change models can be downscaled to the watershed scale, and then coupled with ecophysiological metrics to assess climate change effects on organisms of conservation concern. We employed models to estimate future water temperatures (2010-2099) under several climate change scenarios within the large heterogeneous San Francisco Estuary. We then assessed the warming effects on the endangered, endemic Delta Smelt, Hypomesus transpacificus, by integrating localized projected water temperatures with thermal sensitivity metrics (tolerance, spawning and maturation windows, and sublethal stress thresholds) across life stages. Lethal temperatures occurred under several scenarios, but sublethal effects resulting from chronic stressful temperatures were more common across the estuary (median >60 days above threshold for >50% locations by the end of the century). Behavioral avoidance of such stressful temperatures would make a large portion of the potential range of Delta Smelt unavailable during the summer and fall. Since Delta Smelt are not likely to migrate to other estuaries, these changes are likely to result in substantial habitat compression. Additionally, the Delta Smelt maturation window was shortened by 18-85 days, revealing cumulative effects of stressful summer and fall temperatures with early initiation of spring spawning that may negatively impact fitness. Our findings highlight the value of integrating sublethal thresholds, life history, and in situ thermal heterogeneity into global change impact assessments. As downscaled climate models are becoming widely available, we conclude that similar assessments at management-relevant scales will improve the scientific basis for resource management decisions.


Nowell L.H.,California Water Science Center | Moran P.W.,Washington Water Science Center | Gilliom R.J.,California Water Science Center | Calhoun D.L.,Georgia Water Science Center | And 4 more authors.
Archives of Environmental Contamination and Toxicology | Year: 2013

Organic contaminants and trace elements were measured in bed sediments collected from streams in seven metropolitan study areas across the United States to assess concentrations in relation to urbanization. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, the pyrethroid insecticide bifenthrin, and several trace elements were significantly related to urbanization across study areas. Most contaminants (except bifenthrin, chromium, nickel) were significantly related to the total organic carbon (TOC) content of the sediments. Regression models explained 45-80 % of the variability in individual contaminant concentrations using degree of urbanization, sediment-TOC, and study-area indicator variables (which represent the combined influence of unknown factors, such as chemical use or release, that are not captured by available explanatory variables). The significance of one or more study-area indicator variables in all models indicates marked differences in contaminant levels among some study areas, even after accounting for the nationally modeled effects of urbanization and sediment-TOC. Mean probable effect concentration quotients (PECQs) were significantly related to urbanization. Trace elements were the major contributors to mean PECQs at undeveloped sites, whereas organic contaminants, especially bifenthrin, were the major contributors at highly urban sites. Pyrethroids, where detected, accounted for the largest share of the mean PECQ. Part 2 of this series (Kemble et al. 2012) evaluates sediment toxicity to amphipods and midge in relation to sediment chemistry. © 2012 Springer Science+Business Media New York (outside the USA).


Kemble N.E.,Columbia Environmental Research Center | Hardesty D.K.,Columbia Environmental Research Center | Ingersoll C.G.,Columbia Environmental Research Center | Kunz J.L.,Columbia Environmental Research Center | And 6 more authors.
Archives of Environmental Contamination and Toxicology | Year: 2013

Relationships between sediment toxicity and sediment chemistry were evaluated for 98 samples collected from seven metropolitan study areas across the United States. Sediment-toxicity tests were conducted with the amphipod Hyalella azteca (28 day exposures) and with the midge Chironomus dilutus (10 day exposures). Overall, 33 % of the samples were toxic to amphipods and 12 % of the samples were toxic to midge based on comparisons with reference conditions within each study area. Significant correlations were observed between toxicity end points and sediment concentrations of trace elements, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), or organochlorine (OC) pesticides; however, these correlations were typically weak, and contaminant concentrations were usually below sediment-toxicity thresholds. Concentrations of the pyrethroid bifenthrin exceeded an estimated threshold of 0.49 ng/g (at 1 % total organic carbon) in 14 % of the samples. Of the samples that exceeded this bifenthrin toxicity threshold, 79 % were toxic to amphipods compared with 25 % toxicity for the samples below this threshold. Application of mean probable effect concentration quotients (PECQs) based on measures of groups of contaminants (trace elements, total PAHs, total PCBs, OC pesticides, and pyrethroid pesticides [bifenthrin in particular]) improved the correct classification of samples as toxic or not toxic to amphipods compared with measures of individual groups of contaminants. © 2012 Springer Science+Business Media New York (outside the USA).


Carpenter K.D.,Oregon Water Science Center | Kuivila K.M.,Oregon Water Science Center | Hladik M.L.,California Water Science Center | Haluska T.,Oregon Water Science Center | Cole M.B.,Cole Ecological Inc.
Environmental Monitoring and Assessment | Year: 2016

Insecticide use in urban areas results in the detection of these compounds in streams following stormwater runoff at concentrations likely to cause toxicity for stream invertebrates. In this 2013 study, stormwater runoff and streambed sediments were analyzed for 91 pesticides dissolved in water and 118 pesticides on sediment. Detections included 33 pesticides, including insecticides, fungicides, herbicides, degradates, and a synergist. Patterns in pesticide occurrence reveal transport of dissolved and sediment-bound pesticides, including pyrethroids, from upland areas through stormwater outfalls to receiving streams. Nearly all streams contained at least one insecticide at levels exceeding an aquatic-life benchmark, most often for bifenthrin and (or) fipronil. Multiple U.S. EPA benchmark or criterion exceedances occurred in 40 % of urban streams sampled. Bed sediment concentrations of bifenthrin were highly correlated (p < 0.001) with benthic invertebrate assemblages. Non-insects and tolerant invertebrates such as amphipods, flatworms, nematodes, and oligochaetes dominated streams with relatively high concentrations of bifenthrin in bed sediments, whereas insects, sensitive invertebrates, and mayflies were much more abundant at sites with no or low bifenthrin concentrations. The abundance of sensitive invertebrates, % EPT, and select mayfly taxa were strongly negatively correlated with organic-carbon normalized bifenthrin concentrations in streambed sediments. Our findings from western Clackamas County, Oregon (USA), expand upon previous research demonstrating the transport of pesticides from urban landscapes and linking impaired benthic invertebrate assemblages in urban streams with exposure to pyrethroid insecticides. © 2016, The Author(s).


Deeds D.A.,California Water Science Center | Kulongoski J.T.,California Water Science Center | Muhle J.,University of California at San Diego | Weiss R.F.,University of California at San Diego
Earth and Planetary Science Letters | Year: 2015

Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge (Cre; ~30 fmolkg-1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1-9 times Cre), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10-980 times Cre) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20-100 km) suggests that the SAFS potentially emits (0.3-1)×10-1 kg CF4 yr-1 to the Earth's surface. For comparison, the chemical weathering of ~7.5×104 km2 of granitic rock in California is estimated to release (0.019-3.2)×10-1 kg CF4 yr-1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial-interglacial transitions. © 2014 Elsevier B.V.All rights reserved.


Torregrosa A.,Western Geographic Science Center | Taylor M.D.,Western Geographic Science Center | Flint L.E.,California Water Science Center | Flint A.L.,California Water Science Center
PLoS ONE | Year: 2013

Bioclimates are syntheses of climatic variables into biologically relevant categories that facilitate comparative studies of biotic responses to climate conditions. Isobioclimates, unique combinations of bioclimatic indices (continentality, ombrotype, and thermotype), were constructed for northern California coastal ranges based on the Rivas-Martinez worldwide bioclimatic classification system for the end of the 20th century climatology (1971-2000) and end of the 21st century climatology (2070-2099) using two models, Geophysical Fluid Dynamics Laboratory (GFDL) model and the Parallel Climate Model (PCM), under the medium-high A2 emission scenario. The digitally mapped results were used to 1) assess the relative redistribution of isobioclimates and their magnitude of change, 2) quantify the loss of isobioclimates into the future, 3) identify and locate novel isobioclimates projected to appear, and 4) explore compositional change in vegetation types among analog isobioclimate patches. This study used downscaled climate variables to map the isobioclimates at a fine spatial resolution -270 m grid cells. Common to both models of future climate was a large change in thermotype. Changes in ombrotype differed among the two models. The end of 20th century climatology has 83 isobioclimates covering the 63,000 km2 study area. In both future projections 51 of those isobioclimates disappear over 40,000 km2. The ordination of vegetation-bioclimate relationships shows very strong correlation of Rivas-Martinez indices with vegetation distribution and composition. Comparisons of vegetation composition among analog patches suggest that vegetation change will be a local rearrangement of species already in place rather than one requiring long distance dispersal. The digitally mapped results facilitate comparison with other Mediterranean regions. Major remaining challenges include predicting vegetation composition of novel isobioclimates and developing metrics to compare differences in climate space.


PubMed | Cole Ecological Inc., California Water Science Center and Oregon Water Science Center
Type: Journal Article | Journal: Environmental monitoring and assessment | Year: 2016

Insecticide use in urban areas results in the detection of these compounds in streams following stormwater runoff at concentrations likely to cause toxicity for stream invertebrates. In this 2013 study, stormwater runoff and streambed sediments were analyzed for 91 pesticides dissolved in water and 118 pesticides on sediment. Detections included 33 pesticides, including insecticides, fungicides, herbicides, degradates, and a synergist. Patterns in pesticide occurrence reveal transport of dissolved and sediment-bound pesticides, including pyrethroids, from upland areas through stormwater outfalls to receiving streams. Nearly all streams contained at least one insecticide at levels exceeding an aquatic-life benchmark, most often for bifenthrin and (or) fipronil. Multiple U.S. EPA benchmark or criterion exceedances occurred in 40% of urban streams sampled. Bed sediment concentrations of bifenthrin were highly correlated (p<0.001) with benthic invertebrate assemblages. Non-insects and tolerant invertebrates such as amphipods, flatworms, nematodes, and oligochaetes dominated streams with relatively high concentrations of bifenthrin in bed sediments, whereas insects, sensitive invertebrates, and mayflies were much more abundant at sites with no or low bifenthrin concentrations. The abundance of sensitive invertebrates, % EPT, and select mayfly taxa were strongly negatively correlated with organic-carbon normalized bifenthrin concentrations in streambed sediments. Our findings from western Clackamas County, Oregon (USA), expand upon previous research demonstrating the transport of pesticides from urban landscapes and linking impaired benthic invertebrate assemblages in urban streams with exposure to pyrethroid insecticides.


News Article | February 15, 2017
Site: www.nature.com

Every few days, Alan Flint plucks a gardenia from outside the building where his wife, Lorraine, works in Sacramento, California. He replaces the fading flower on her desk and refills the glass with fresh water. It's an easy romantic gesture, given that Alan's office is right down the hall. The Flints are both research hydrologists with the US Geological Survey California Water Science Center. It's the farthest apart their offices have been for years: they met during secondary school, married in 1975 and have been next door to each other throughout much of their careers in soil science. There are many couples in science similar to the Flints — and this Valentine's Day, Alan might not be the only one delivering flowers to an office down the hall. For researcher couples, obvious advantages can range from reviewing each other's writing to carpooling. Yet there are potential downsides, from navigating the challenge of finding and holding dual jobs to concerns about potential or existing conflicts of interest — such as when one partner sits on a promotions committee that discusses the other — or what might happen if the romance collapses (see 'Science soldiers on'). According to a 2008 report by the Clayman Institute for Gender Research at Stanford University in California, which collected data on around 9,000 faculty members at 13 universities, 36% of US faculty members were part of an academic couple1. Of those, 38% worked in the same department as their partner. Professors in the natural sciences were particularly likely to work in similar fields or the same department: 83% of female scientists and 54% of male scientists in academic couples had another scientist as a partner. A report released by the US National Science Foundation in 2015 found that 73% of scientists were married, and 24% of their employed spouses worked in engineering, computing, mathematics or the natural sciences2. “I know so many of my colleagues here who are married to another scientist on this campus,” says Alexis Templeton, a geologist at the University of Colorado Boulder. In Europe, too, it's common for scientists to marry another scientist, says Phil Stanier, a geneticist at University College London — although it's less common for them to work as closely as he does with his wife, geneticist Gudrun Moore, with whom he's co-authored dozens of papers. A 2016 report by the European Commission (EC) similarly found that 72% of surveyed researchers were in a relationship, and, of those, 54% were partnered with a person who was also pursuing a demanding career (although not necessarily in science)3. Some couples deliberately keep their careers separate and don't talk much shop on evenings and weekends. Others, such as the Flints, are driven by a shared goal, and seamlessly integrate their work and home lives. Ultimately, navigating a relationship and career as a member of a scientist couple requires mutual respect, effort to carve out two distinct niches and a hearty dose of cooperation. Married wildlife biologists Paula MacKay and Robert Long laugh at the idea of setting boundaries between personal and professional activities. The pair was once halfway up a mountain, carrying odorous bear-scent lures, when MacKay realized that it was their wedding anniversary. Long, a senior conservation scientist at Woodland Park Zoo in Seattle, Washington, and MacKay, a contract field biologist whose clients include the zoo, had been so involved in planning their trip that they had both forgotten the date. “I feel like I'm always out there with my best friend,” MacKay says. “When we approach a remote camera site or a place where we had set out a station before, it's really exciting to be there with Rob.” That shared joy is one of the myriad benefits of dual employment as researchers. Those might be as simple as grabbing lunch for one's partner on a busy day, as Frances Rena Bahjat and Keith Bahjat of Bristol-Myers Squibb in Redwood City, California, frequently do for each other. Frances Rena is senior director of in vivo studies and Keith directs cellular immunology at the company. To keep up with the literature, they also play a 'Who can find the best papers?' game each week, and they recommend potential collaborators to each other. “The two of us have much more reach than a single scientist, that's for sure,” says Frances Rena. One partner's enthusiasm for science, or for a particular field, can be contagious. Frances Rena says that she probably wouldn't have become a scientist if she hadn't met her husband (and now, colleague) when both were undergraduates. She didn't understand how science could be a career until she met Keith, whose father was a geophysicist. Similarly, Alan Flint started his career in soil science before Lorraine followed, and their couple status has even helped in a job search. As Alan was finishing his PhD and Lorraine her master's, their adviser heard about a lab that was looking for two soil scientists — one at the PhD level and one at the master's level. They got the jobs. This situation is not uncommon: in the Clayman Institute report1, 10% of faculty members were hired as a couple, and as of 2008, that rate was on the rise. Usually, one partner was hired first and negotiated for the other. Men were more often the first hire at that time, and the second hire was more likely to be in a junior faculty position. For many couples, such as geneticists Moore and Stanier of University College London, working together enhances both the relationship and research. The pair met during the 1980s at St Mary's Hospital in London. After a series of lecturer and postdoc positions, both worked at Imperial College London for a time, sharing equipment, working on each other's grants and co-authoring papers. They tried working apart, but didn't like it. “We're stronger together,” says Moore. For example, the pair was able to productively combine Moore's background in protein chemistry and Stanier's in molecular cloning when they searched for a gene associated with X-linked cleft palate. Working together and being able to continue the discussion at home is a big advantage for the research, agrees Shin-ichi Horike, a geneticist at Kanazawa University in Japan whose wife, Makiko Meguro, works in his lab. When a grant deadline is coming up, science is a major item on the conversation agenda at their house, albeit after the children have gone to bed. They discuss results of their experiments on those evenings. For partners who collaborate closely, division of expertise is crucial. “You have to develop complementary skills so that you're not in competition with each other,” says Lorraine Flint. And it's important, for the relationship, to take a bit of time away from science, say the Flints. They've set aside a daily cocktail hour. Ethologists Rick D'Eath and Susan Jarvis of Scotland's Rural College in Easter Bush, UK, don't work on exactly the same science, but they use each other as a sounding board to practise major presentations. Both can approach other colleagues for feedback, but are fully — even brutally — honest with each other. Jarvis feels perfectly comfortable telling her husband that his points are “a bit rubbish”. Whether scientist couples work closely or just share an employer, many say that they appreciate the ability to provide mutual support through tough times at work. Allison Mattheis, an educational researcher at California State University (Cal State) in Los Angeles, met her partner, Valerie Wong, when they were both at the University of Minnesota — Mattheis at the Minneapolis campus and Wong in St Paul. Now, Wong is an adjunct faculty member at Cal State. “You get frustrated by all the same bureaucratic hurdles of the institution,” says Mattheis. Who better to commiserate with over Mattheis's struggles to add her partner to her health insurance than Wong? The two talk about how best to design lessons, address students' misconceptions or advise students. Wong also refers biology students with an interest in teaching to Mattheis. The two have started a project to connect secondary-school teachers with university instructors to improve early science education. These relationships are of value to scientists still in training, too. Erin Zimmerman of London, Canada, misses this kind of connection now that she and her husband, Eric Chevalier, no longer work in science. Although they met as graduate students in the Plant Biology Research Institute at the University of Montreal, Canada, she's now a freelance science writer; he, an optometrist at Old South Optometry in London. When they began dating, it was easy to keep in contact. Chevalier once placed a picture of a hand-drawn flower into a beaker on Zimmerman's desk, because he knew she hated how real cut flowers die. They co-authored a review, and related to each other's dealings with academic culture, funding woes and other frustrations. “It was nice being able to have someone at home who really understood that,” says Zimmerman. “Now,” she jokes, “we bore each other.” There are potential pitfalls to such a relationship. For one, those determined to work together might limit their options. One-fifth of researchers in a relationship surveyed by the EC3 had refused or left a job owing to the challenge of maintaining both careers. Moore advises: “You have to be seen as one, so when they want you, they want both of you.” Scientist couples who work together need to be aware of how they present themselves, and must always maintain an image of two distinct professionals. “Your relationship is living in a fishbowl,” says MacKay. And they must take care to avoid even the possible appearance of favouritism. Intern architect Donna Marion and her husband, Mike Grosskopf, a statistics graduate student at Simon Fraser University in Vancouver, Canada, met as undergraduates in an astrophysics lab at the University of Michigan in Ann Arbor. Both joined the lab as employees once they graduated, and, for a time, Grosskopf was Marion's supervisor. But when romance blossomed, he warned his boss, who changed Marion's supervisor. Similarly, mathematician Piper Harron, a temporary faculty member at the University of Hawaii at Manoa, avoided selecting her husband, Robert Harron, as an academic mentor when she was applying for grant support. “If we weren't related, I would be the natural choice,” says her husband, a maths faculty member at the university, but he knew that any reports or letters of recommendation that he might write about her would be suspect. Nonetheless, they contribute to each other's work, reading and editing their writing. Piper excels at bits that sell the projects, and Robert is good at converting text into more maths-oriented language. Sharing a last name might also raise eyebrows, adds biochemist Edith Sim of Oxford, UK, who met her husband, Bob Sim, when they were undergraduate laboratory partners. They worked in each other's labs at times. Once, a grant application that she had submitted came back with the comment, “Was this hers or was this her husband's?” From then on, she left her husband's name off any papers that she produced. By contrast, colleagues of Moore and Stanier didn't always catch on that they were married. “We didn't hide it, but we didn't particularly flaunt it,” explains Stanier. One visiting student spent a few months in Moore's lab while Stanier was a postdoc there, and thought the two were engaged in a scandalous affair. (His adviser set him straight.) Another issue that couples may want to consider, points out Keith Bahjat, is that when a couple works for the same employer, both members depend on that employer for their wages. That's a particular concern in industry, he says, where companies might impose layoffs at any time. D'Eath and Jarvis had the same concern, which they've mitigated in part by Jarvis taking a second position as director of a master's programme at the University of Edinburgh, UK, in addition to her work at Scotland's Rural College. Now they feel safer, because it's unlikely that both institutions would falter at the same time. Despite these challenges, scientist couples know that they enjoy significant good fortune. “Finding a situation where you both have great opportunity is really rare,” says Frances Rena Bahjat.

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