The productivity of aquatic ecosystems depends on the supply of limiting nutrients. The invasion of the Laurentian Great Lakes, the world's largest freshwater ecosystem, by dreissenid (zebra and ...quagga) mussels has dramatically altered the ecology of these lakes. A key open question is how dreissenids affect the cycling of phosphorus (P), the nutrient that limits productivity in the Great Lakes. We show that a single species, the quagga mussel, is now the primary regulator of P cycling in the lower four Great Lakes. By virtue of their enormous biomass, quagga mussels sequester large quantities of P in their tissues and dramatically intensify benthic P exchanges. Mass balance analysis reveals a previously unrecognized sensitivity of the Great Lakes ecosystem, where P availability is now regulated by the dynamics of mussel populations while the role of the external inputs of phosphorus is suppressed. Our results show that a single invasive species can have dramatic consequences for geochemical cycles even in the world's largest aquatic ecosystems. The ongoing spread of dreissenids across a multitude of lakes in North America and Europe is likely to affect carbon and nutrient cycling in these systems for many decades, with important implications for water quality management.
Animal excretion provides nutrients for primary productivity and can be a crucial component of ecosystem nutrient cycling. The concentrations of carbon (C), nitrogen (N), and phosphorus (P) in an ...animal’s excretion are strongly influenced by the C:N:P stoichiometry (molar ratios) of its body and of the food it eats. We measured the C:N:P ratios of quagga mussel (
Dreissena rostriformis bugensis
) tissues and excreta and of seston across wide environmental and spatial gradients in the upper Laurentian Great Lakes. We then investigated how mussel excretion rates were impacted by stoichiometric mismatch—the difference between the C:P ratios of mussel tissues and the C:P ratios their food. Quagga mussel internal C:N:P stoichiometry varied significantly across sites and seasons, driven primarily by changes in tissue P concentrations. When mussel tissues had substantially lower C:P ratios than seston (that is
,
strong stoichiometric mismatch), mussels excreted significantly less N and P relative to C. Excretion C:N ratios varied by nearly threefold, while C:P ratios varied by tenfold. The effect of the stoichiometric mismatch on excretion stoichiometry was more dramatic in the spring, when mussels had higher tissue P concentrations, than in the summer. This suggests seasonality in mussel P demand. Our results challenge the assumption of strict internal homeostasis in consumers and demonstrate that food and tissue stoichiometry need to be considered to predict consumer excretion stoichiometry. These findings help to better understand the impact of consumer-driven nutrient cycling in aquatic environments and quagga mussel contributions to the nutrient budgets of invaded ecosystems.
In the Laurentian Great Lakes, invasive zebra and quagga (dreissenid) mussels have dramatically altered biotic community structure, primary productivity, and biogeochemistry since their introduction ...in the 1980s. Recently, quagga mussel (Dreissena rostriformis bugensis) populations have been expanding deeper into profundal regions of Lakes Michigan, Huron, and Ontario. These dense offshore populations have substantially altered offshore energy and nutrient cycling, but there are key gaps in our understanding of deep-water quagga mussel physiology and their impacts on pelagic biogeochemistry. Specifically, there is a lack of information on (1) quagga mussel tissue nutrient sequestration and regeneration rates, including variability in tissue stoichiometry (C:N:P molar ratios) and its influence on mussel excretion rates and excretion stoichiometry, (2) quagga mussel impact on offshore sediment geochemistry, including sediment mixing rate, sediment oxygen penetration, and dissolved nutrient dynamics at the sediment-water interface, and (3) quagga mussel population dynamics, including size distribution and growth rates, in deep, offshore lake regions. Presented here are the results of field (chapter 2), experimental (chapter 3), and modelling (chapter 4) studies I conducted to address these knowledge gaps about quagga mussel physiology and ecological impacts.To determine variability of quagga mussel tissue stoichiometry and its impact on mussel excretion (chapter 2), I measured mussel tissue and excretion carbon, nitrogen, and phosphorus content along depth (20 – 130m) and trophic gradients in Lakes Michigan and Huron during spring mixing and summer stratification periods of 2019. I found that mussel tissue C:N:P ratios varied substantially in Lakes Michigan and Huron, suggesting that quagga mussels have flexible internal homeostasis. I also found that tissue C:N:P stoichiometry was a significant driver of mussel excretion rates and excretion stoichiometry. When mussels had lower tissue C:P ratios than available seston, excretion C:nutrient (C:N and C:P) ratios decreased. Next, to investigate the influence of quagga mussels on offshore sediment geochemistry (chapter 3), I conducted a sixweek microcosm experiment. I incubated quagga mussels, Diporeia spp. (previously the dominant Great Lakes’ macroinvertebrate), and oligochaete worms (the second most common benthic macroinvertebrate in the Great Lakes). Species were incubated separately and in combination to determine varying organism impacts on sediment mixing and biogeochemistry as well as potential community interaction effects. To simulate deep, offshore conditions, I used low particulate organic matter (POM) sediment in the microcosms and kept them in the dark and at 4°C. I found that sediment mixing depth and intensity varied significantly among species, but that there were no significant differences in sediment oxygen penetration depth or nutrient dynamics. Additionally, I found no evidence for species interaction effects. Finally, I used a Dynamic Energy Budget (DEB) model to explore quagga mussel physiology and growth rates under variable temperatures and food quantities (chapter 4). First, I simulated quagga mussel growth at annual temperatures and food availability representative of oligotrophic, mesotrophic, and eutrophic conditions in nearshore, mid-depth, and offshore regions of the Great Lakes. I then simulated mussel growth under three climate warming scenarios (+0.5°C, +1°C, and +2°C water temperatures). Corresponding changes in lake stratification regime under warming scenarios included an increase in the duration of summer stratification and a decrease in the duration of winter stratification. I found that quagga mussel growth increased with warmer water temperatures and altered stratification regimes. I also found that relative importance of water temperature and food availability varied over trophic status and mussel age, with mussel sensitivity to food limitation increasing as mussels grew larger over time.The combined results from these three studies indicate that quagga mussel impacts on pelagic energy and nutrient dynamics are mostly due to direct mechanisms – including carbon and nutrient ingestion, sequestration, and regeneration – rather than altered sediment geochemistry. My results provide detailed information on quagga mussel physiology, including variability of internal stoichiometry and growth under a wide range of environmental conditions, which strongly influences mussel nutrient recycling. Together, these results improve the current understanding of quagga mussel biology and will help to inform estimates of quagga mussel impacts on biogeochemical cycling in the Great Lakes and other invaded ecosystems.
Abstract Polyphosphate (polyP) is important to phytoplankton ecology, but a unified view of its variability and roles in ecosystem‐scale phosphorus (P) cycling is lacking. We study polyP in the ...world's largest freshwater ecosystem, the Laurentian Great Lakes, covering pelagic to nearshore areas across a wide nutrient gradient. We show that polyP (average 10.99 ± 3.90 nmol L −1 ) constitutes 3.8–30.2% (average 18.1 ± 7.2%) of total particulate P (TPP). PolyP accumulation is higher in low‐P pelagic waters compared with more productive nearshore areas. PolyP is preferentially degraded in the water column of the Great Lakes, enhancing P recycling and relieving the nitrogen (N) : P imbalance. Our data enables a coherent large‐scale freshwater‐to‐oceanic comparison. We show that while different plankton groups accumulate different levels of polyP with smaller plankton accumulating more, P availability is the key driver of polyP variability within and across systems.
Objective
To assess and quantify cleft team practices with regard to nutritional support in the neonatal period
Design
Retrospective review.
Setting
Tertiary pediatric hospital.
Patients
One hundred ...consecutive newborn patients with a diagnosis of cleft lip and/or cleft palate between 2009 and 2012.
Main Outcome Measures
Birth weight, cleft type, initial cleft team weight measurements, initial feeding practices, recommended nutritional interventions, and follow-up nutritional assessments.
Results
All patients in the study were evaluated by a registered dietitian and an occupational feeding therapist. Average birth weight and average age at the first cleft team visit were similar for each cleft type: cleft lip (CL), cleft lip and palate (CLP), and cleft palate (CP). The calculated age (in days) for return to birth weight was significantly different between cleft types: CL = 13.58 days, CLP = 15.88 days, and CP = 21.93 days. Exclusive use of breast milk was 50% for patients with CL, 30.3% for patients with CLP, and 21.4% for patients with CP. Detailed nutritional interventions were made for 31 patients at the first visit: two with CL, 14 with CLP, and 15 with CP.
Conclusions
Distinct differences were seen in neonatal weight gain between cleft types. There was significantly greater total weight gain for patients with CL at their first visit and significantly slower return to birth weight for patients with isolated CP. Patients with CL required far fewer interventions at the initial assessment and were more likely to be provided breast milk exclusively or in combination with formula. Infants with CP were far less likely to receive any breast milk. Patients with CLP and CP required frequent nutritional interventions.
One major advantage of developing large, federally funded networks for clinical research in neurology is the ability to have a trial-ready network that can efficiently conduct scientifically rigorous ...projects to improve the health of people with neurologic disorders.
National Institute of Neurological Disorders and Stroke Network for Excellence in Neuroscience Clinical Trials (NeuroNEXT) was established in 2011 and renewed in 2018 with the goal of being an efficient network to test between 5 and 7 promising new agents in phase II clinical trials. A clinical coordinating center, data coordinating center, and 25 sites were competitively chosen. Common infrastructure was developed to accelerate timelines for clinical trials, including central institutional review board (a first for the National Institute of Neurological Disorders and Stroke), master clinical trial agreements, the use of common data elements, and experienced research sites and coordination centers. During the first 7 years, the network exceeded the goal of conducting 5 to 7 studies, with 9 funded. High interest was evident by receipt of 148 initial applications for potential studies in various neurologic disorders. Across the first 8 studies (the ninth study was funded at end of initial funding period), the central institutional review board approved the initial protocol in a mean (SD) of 59 (21) days, and additional sites were added a mean (SD) of 22 (18) days after submission. The median time from central institutional review board approval to first site activation was 47.5 days (mean, 102.1; range, 1-282) and from first site activation to first participant consent was 27 days (mean, 37.5; range, 0-96). The median time for database readiness was 3.5 months (mean, 4.0; range, 0-8) from funding receipt. In the 4 completed studies, enrollment met or exceeded expectations with 96% overall data accuracy across all sites. Nine peer-reviewed manuscripts were published, and 22 oral presentations or posters and 9 invited presentations were given at regional, national, and international meetings.
NeuroNEXT initiated 8 studies, successfully enrolled participants at or ahead of schedule, collected high-quality data, published primary results in high-impact journals, and provided mentorship, expert statistical, and trial management support to several new investigators. Partnerships were successfully created between government, academia, industry, foundations, and patient advocacy groups. Clinical trial consortia can efficiently and successfully address a range of important neurologic research and therapeutic questions.
Conservation of the 105 species of amphibians, reptiles, and turtles in the northwestern United States and western Canada is represented by a diverse mix of projects and programs across ten states, ...provinces, and territories. In this paper, 29 contributing authors review the status of herpetofauna by state, province or territory, and summarize the key issues, programs, projects, partnerships, and regulations relative to the species and habitats in those areas. Key threats to species across this expansive area include habitat degradation or loss, invasive species, disease, and climate change. Many programs and projects currently address herpetological conservation issues, including numerous small-scale monitoring and research efforts. However, management progress is hindered in many areas by a lack of herpetological expertise and basic knowledge of species' distribution patterns, limited focus within management programs, insufficient funds, and limited communication across the region. Common issues among states and provinces suggest that increased region-wide communication and coordination may aid herpetological conservation. Regional conservation collaboration has begun by the formation of the Northwest working group of Partners in Amphibian and Reptile Conservation.
In a retrospective study we determined the relation between estrogen receptors and the response rate to cytotoxic chemotherapy in 70 patients with metastatic breast cancer. Thirty-four of 45 patients ...with low or absent estrogen-receptor values (less than 10 fmol per milligram of cytoplasmic protein) had objective responses to chemotherapy, whereas only three of 25 patients with higher values (greater than 10 fmol per milligram of cytoplasmic protein) responded (P less than 0.0001). There were no statistically significant differences between the two groups in age, menopausal status, disease-free interval, Karnofsky index or prior therapy. Differences in sites of involvement or type of chemotherapy did not account for the increased response rate in receptor-negative patients. We conclude that estrogen-receptor values are an important predictor of response to cytotoxic chemotherapy in metastatic breast cancer.
The distribution and frequency of steroid hormone receptors are described 329 patients with breast cancer. The distribution of each of the steroid hormone receptors is unimodal with a progressive ...increase in the proportion of patients positive at lower receptor values. Receptor values expressed as fmol/mg cytoplasmic protein are well correlated with values expressed as fmol/mg breast tumor. Estrogen receptor was positive in 53% of the patients; progesterone receptor was positive in 38% of the patients; glucocorticoid receptor was positive in 52% of the patients; and androgen receptor was positive in 31% of the patients. The type of tissue assayed did not affect steroid hormone receptor positivity. For primary tumors, there was no correlation between steroid hormone receptor positivity and location of the tumor in the breast, size of the tumor, or extent of the disease. Each of the steroid hormone receptors was positively associated with each of the other steroid hormone receptors. Estrogen receptor was correlated with menopausal status and axillary nodal status, but these correlations did not exist for the other steroid hormone receptors. Estrogen receptor was not correlated with age after adjustment for menopausal status. The other steroid hormone receptors were not correlated with age.
Estrogen receptor (ER) analyses are widely used in the management of patients with breast cancer. Few data are available concerning variations in ER as a function of time and therapy. We examined ...patients in whom multiple biopsies and receptor analyses were either performed simultaneously or over time with or without intervening chemotherapy or endocrine therapy. In 27 patients with simultaneous assays from different metastatic sites, concordant results were obtained in 23 (85%) with respect to classifying a tumor as ER+ or ER–. In 34 patients, multiple assays were performed over time. The receptor concentrations were concordant in patients receiving no intervening therapy. In 10 patients receiving hormonal therapy, the median receptor concentration changed from 66 femtomoles per mg cytoplasmic protein pretherapy to 8 femtomoles post therapy (P < 0.05). This change suggested that hormonal therapy selectively eliminates ER+ cells. In 19 patients receiving intervening chemotherapy, the median receptor concentrations pre and post therapy were similar. We conclude that simultaneous assays from multiple metastatic sites are highly concordant and unlikely to change over time without intervening therapy, but marked changes occur following therapy with a decrease in receptor concentration after endocrine therapy. Cancer 45:792‐794, 1980.
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