Assessing the potential benefits of learning about environmental issues through a systems thinking pedagogy

Systems thinking is a fundamental learning methodology in sustainability education and in some K-12 standards-based education systems in the United States. However, there is little research and practical application on the use of systems thinking in environmental education, especially at the elementary level. This thesis uses a case study on climate change to assess whether a pedagogy based on systems thinking can fulfill learning objectives derived from the Illinois Learning Standards for Science (ILSS) and provide further insights and understandings on the subject being studied. Three learning modules on climate change consisting of systems thinking habits of mind, concepts, and tools were taught to fourth grade students from the Chicago area as an informal pilot study. It was determined that a systems thinking approach does yield results that suggest fulfillment of the ILSS. A systems thinking approach is also successful in engaging students, creating a fun and interactive learning environment, and making learning more learner-centered and hands-on. More empirical research on the benefits of systems thinking, especially in elementary education, is needed, in both standards-based education and in environmental education

Influences on the oceanic biogeochemical cycling of the hybrid-type metals : cobalt, iron, and manganese

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, February 2012Trace metal cycling is one of many processes that influence ocean ecosystem dynamics. Cobalt, iron, and manganese are redox active trace metal micronutrients with oceanic distributions that are influenced by both biological and abiotic sources and sinks. Their open ocean concentrations range from picomolar to nanomolar, and their bioavailabilities can impact primary production. Understanding the biogeochemical cycling of these hybrid-type metals with an emphasis on cobalt was the focus of this thesis. This was accomplished by determining the dissolved distributions of these metals in oceanic regions that were characterized by different dominant biogeochemistries. A large subsurface plume of dissolved cobalt, iron, and manganese was found in the Eastern South Atlantic. The cause of this plume is a combination of reductive dissolution in coastal sediments, wind-driven upwelling, advection, biological uptake, and remineralization. Additional processes that are discussed as sources of metals to the regions studied during this thesis include isopycnal uplift within cold-core eddies (Hawaii), ice melt (McMurdo Sound, Antarctica), riverine input (Arctic Ocean), and winter mixing (McMurdo Sound). The biological influence on surface ocean distributions of cobalt was apparent by the observation of linear relationships between cobalt and phosphate in mid to low latitudes. The cobalt:phosphate ratios derived from these correlations changed over orders of magnitude, revealing dynamic variability in the utilization, demand, and sources of this micronutrient. Speciation studies suggest that there may be two classes of cobalt binding ligands, and that organic complexation plays an important role in preventing scavenging of cobalt in the ocean. These datasets provided a basis for comparing the biogeochemical cycles of cobalt, iron, and manganese in three oceanic regimes (Hawaii, South Atlantic, McMurdo Sound). The relative rates of scavenging for these metals show environmental variability: in the South Atlantic, cobalt, iron, and manganese were scavenged at very different rates, but in the Ross Sea, mixing and circulation over the shallow sea was fast, scavenging played a minor role, and the cycles of all three metals were coupled. Studying the distributions of these metals in biogeochemically distinct regions is a step toward a better understanding of their oceanic cycles.Funding for this research was provided by the the National Science Foundation Chemical Oceanography (Division of Ocean Sciences OCE-0452883, OCE-0752291, OCE-0928414, OCE-0732665, OCE-0440840, OCE-0327225), the Center for Microbial Research and Education, the WHOI Coastal Ocean Institute, and the WHOI Ocean Life Institute, WHOI Academic Programs Office, and a Fye Teaching Fellowship

Coastal sources, sinks and strong organic complexation of dissolved cobalt within the US North Atlantic GEOTRACES transect GA03

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 14 (2017): 2715-2739, doi:10.5194/bg-14-2715-2017.Cobalt is the scarcest of metallic micronutrients and displays a complex biogeochemical cycle. This study examines the distribution, chemical speciation, and biogeochemistry of dissolved cobalt during the US North Atlantic GEOTRACES transect expeditions (GA03/3_e), which took place in the fall of 2010 and 2011. Two major subsurface sources of cobalt to the North Atlantic were identified. The more prominent of the two was a large plume of cobalt emanating from the African coast off the eastern tropical North Atlantic coincident with the oxygen minimum zone (OMZ) likely due to reductive dissolution, biouptake and remineralization, and aeolian dust deposition. The occurrence of this plume in an OMZ with oxygen above suboxic levels implies a high threshold for persistence of dissolved cobalt plumes. The other major subsurface source came from Upper Labrador Seawater, which may carry high cobalt concentrations due to the interaction of this water mass with resuspended sediment at the western margin or from transport further upstream. Minor sources of cobalt came from dust, coastal surface waters and hydrothermal systems along the Mid-Atlantic Ridge. The full depth section of cobalt chemical speciation revealed near-complete complexation in surface waters, even within regions of high dust deposition. However, labile cobalt observed below the euphotic zone demonstrated that strong cobalt-binding ligands were not present in excess of the total cobalt concentration there, implying that mesopelagic labile cobalt was sourced from the remineralization of sinking organic matter. In the upper water column, correlations were observed between total cobalt and phosphate, and between labile cobalt and phosphate, demonstrating a strong biological influence on cobalt cycling. Along the western margin off the North American coast, this correlation with phosphate was no longer observed and instead a relationship between cobalt and salinity was observed, reflecting the importance of coastal input processes on cobalt distributions. In deep waters, both total and labile cobalt concentrations were lower than in intermediate depth waters, demonstrating that scavenging may remove labile cobalt from the water column. Total and labile cobalt distributions were also compared to a previously published South Atlantic GEOTRACES-compliant zonal transect (CoFeMUG, GAc01) to discern regional biogeochemical differences. Together, these Atlantic sectional studies highlight the dynamic ecological stoichiometry of total and labile cobalt. As increasing anthropogenic use and subsequent release of cobalt poses the potential to overpower natural cobalt signals in the oceans, it is more important than ever to establish a baseline understanding of cobalt distributions in the ocean.We also gratefully acknowledge support of funding agencies on the following grants: the US National Science Foundation (NSF-OCE 0928414, 1233261, 1435056) and the Gordon and Betty Moore Foundation (grant 3738)

A seasonal study of dissolved cobalt in the Ross Sea, Antarctica : micronutrient behavior, absence of scavenging, and relationships with Zn, Cd, and P

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 4059-4082, doi:10.5194/bg-7-4059-2010.We report the distribution of cobalt (Co) in the Ross Sea polynya during austral summer 2005–2006 and the following austral spring 2006. The vertical distribution of total dissolved Co (dCo) was similar to soluble reactive phosphate (PO43−), with dCo and PO43− showing a significant correlation throughout the water column (r2 = 0.87, 164 samples). A strong seasonal signal for dCo was observed, with most spring samples having concentrations ranging from ~45–85 pM, whereas summer dCo values were depleted below these levels by biological activity. Surface transect data from the summer cruise revealed concentrations at the low range of this seasonal variability (~30 pM dCo), with concentrations as low as 20 pM observed in some regions where PO43− was depleted to ~0.1 μM. Both complexed Co, defined as the fraction of dCo bound by strong organic ligands, and labile Co, defined as the fraction of dCo not bound by these ligands, were typically observed in significant concentrations throughout the water column. This contrasts the depletion of labile Co observed in the euphotic zone of other ocean regions, suggesting a much higher bioavailability for Co in the Ross Sea. An ecological stoichiometry of 37.6 μmol Co:mol−1 PO43− calculated from dissolved concentrations was similar to values observed in the subarctic Pacific, but approximately tenfold lower than values in the Eastern Tropical Pacific and Equatorial Atlantic. The ecological stoichiometries for dissolved Co and Zn suggest a greater overall use of Zn relative to Co in the shallow waters of the Ross Sea, with a Co:PO43−/Zn:PO43− ratio of 1:17. Comparison of these observed stoichiometries with values estimated in culture studies suggests that Zn is a key micronutrient that likely influences phytoplankton diversity in the Ross Sea. In contrast, the observed ecological stoichiometries for Co were below values necessary for the growth of eukaryotic phytoplankton in laboratory culture experiments conducted in the absence of added zinc, implying the need for significant Zn nutrition in the Zn-Co cambialistic enzymes. The lack of an obvious kink in the dissolved Co:PO43− relationship was in contrast to Zn:PO43− and Cd:PO43− kinks previously observed in the Ross Sea. An excess uptake mechanism for kink formation is proposed as a major driver of Cd:PO43− kinks, where Zn and Cd uptake in excess of that needed for optimal growth occurs at the base of the euphotic zone, and no clear Co kink occurs because its abundances are too low for excess uptake. An unusual characteristic of Co geochemistry in the Ross Sea is an apparent lack of Co scavenging processes, as inferred from the absence of dCo removal below the euphotic zone. We hypothesize that this vertical distribution reflects a low rate of Co scavenging by Mn oxidizing bacteria, perhaps due to Mn scarcity, relative to the timescale of the annual deep winter mixing in the Ross Sea. Thus Co exhibits nutrient-like behavior in the Ross Sea, in contrast to its hybrid-type behavior in other ocean regions, with implications for the possibility of increased marine Co inventories and utility as a paleooceanographic proxy.This research was supported by the US National Science Foundation through research grants (OPP-0440840, OPP-0338097, OPP-0732665, OCE-0452883, OCE-0752991, OCE-0928414)

FGF and EDA pathways control initiation and branching of distinct subsets of developing nasal glands

Hypertrophy, hyperplasia and altered mucus secretion from the respiratory submucosal glands (SMG) are characteristics of airway diseases such as cystic fibrosis, asthma and chronic bronchitis. More commonly, hyper-secretion of the nasal SMGs contributes to allergic rhinitis and upper airway infection. Considering the role of these glands in disease states, there is a significant dearth in understanding the molecular signals that regulate SMG development and patterning. Due to the imperative role of FGF signalling during the development of other branched structures, we investigated the role of Fgf10 during initiation and branching morphogenesis of murine nasal SMGs. Fgf10 is expressed in the mesenchyme around developing SMGs while expression of its receptor Fgfr2 is seen within glandular epithelial cells. In the Fgf10 null embryo, Steno's gland and the maxillary sinus gland were completely absent while other neighbouring nasal glands showed normal duct elongation but defective branching. Interestingly, the medial nasal glands were present in Fgf10 homozygotes but missing in Fgfr2b mutants, with expression of Fgf7 specifically expressed around these developing glands, indicating that Fgf7 might compensate for loss of Fgf10 in this group of glands. Intriguingly the lateral nasal glands were only mildly affected by loss of FGF signalling, while these glands were missing in Eda mutant mice, where the Steno's and maxillary sinus gland developed as normal. This analysis reveals that regulation of nasal gland development is complex with different subsets of glands being regulated by different signalling pathways. This analysis helps shed light on the nasal gland defects observed in patients with hypohidrotic ectodermal dysplasia (HED) (defect EDA pathway) and LADD syndrome (defect FGFR2b pathway). (C) 2016 Elsevier Inc. All rights reserved.Peer reviewe

Identification of a Homology-Independent Linchpin Domain Controlling Mouse and Bank Vole Prion Protein Conversion

Prions are unorthodox pathogens that cause fatal neurodegenerative diseases in humans and other mammals. Prion propagation occurs through the self-templating of the pathogenic conformer PrPSc, onto the cell-expressed conformer, PrPC. Here we study the conversion of PrPC to PrPSc using a recombinant mouse PrPSc conformer (mouse protein-only recPrPSc) as a unique tool that can convert bank vole but not mouse PrPC substrates in vitro. Thus, its templating ability is not dependent on sequence homology with the substrate. In the present study, we used chimeric bank vole/mouse PrPC substrates to systematically determine the domain that allows for conversion by Mo protein-only recPrPSc. Our results show that that either the presence of the bank vole amino acid residues E227 and S230 or the absence of the second N-linked glycan are sufficient to allow PrPC substrates to be converted by Mo protein-only recPrPSc and several native infectious prion strains. We propose that residues 227 and 230 and the second glycan are part of a C-terminal domain that acts as a linchpin for bank vole and mouse prion conversion

Coastal sources, sinks and strong organic complexation of dissolved cobalt within the US North Atlantic GEOTRACES transect GA03

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 14 (2017): 2715-2739, doi:10.5194/bg-14-2715-2017.Cobalt is the scarcest of metallic micronutrients and displays a complex biogeochemical cycle. This study examines the distribution, chemical speciation, and biogeochemistry of dissolved cobalt during the US North Atlantic GEOTRACES transect expeditions (GA03/3_e), which took place in the fall of 2010 and 2011. Two major subsurface sources of cobalt to the North Atlantic were identified. The more prominent of the two was a large plume of cobalt emanating from the African coast off the eastern tropical North Atlantic coincident with the oxygen minimum zone (OMZ) likely due to reductive dissolution, biouptake and remineralization, and aeolian dust deposition. The occurrence of this plume in an OMZ with oxygen above suboxic levels implies a high threshold for persistence of dissolved cobalt plumes. The other major subsurface source came from Upper Labrador Seawater, which may carry high cobalt concentrations due to the interaction of this water mass with resuspended sediment at the western margin or from transport further upstream. Minor sources of cobalt came from dust, coastal surface waters and hydrothermal systems along the Mid-Atlantic Ridge. The full depth section of cobalt chemical speciation revealed near-complete complexation in surface waters, even within regions of high dust deposition. However, labile cobalt observed below the euphotic zone demonstrated that strong cobalt-binding ligands were not present in excess of the total cobalt concentration there, implying that mesopelagic labile cobalt was sourced from the remineralization of sinking organic matter. In the upper water column, correlations were observed between total cobalt and phosphate, and between labile cobalt and phosphate, demonstrating a strong biological influence on cobalt cycling. Along the western margin off the North American coast, this correlation with phosphate was no longer observed and instead a relationship between cobalt and salinity was observed, reflecting the importance of coastal input processes on cobalt distributions. In deep waters, both total and labile cobalt concentrations were lower than in intermediate depth waters, demonstrating that scavenging may remove labile cobalt from the water column. Total and labile cobalt distributions were also compared to a previously published South Atlantic GEOTRACES-compliant zonal transect (CoFeMUG, GAc01) to discern regional biogeochemical differences. Together, these Atlantic sectional studies highlight the dynamic ecological stoichiometry of total and labile cobalt. As increasing anthropogenic use and subsequent release of cobalt poses the potential to overpower natural cobalt signals in the oceans, it is more important than ever to establish a baseline understanding of cobalt distributions in the ocean.We also gratefully acknowledge support of funding agencies on the following grants: the US National Science Foundation (NSF-OCE 0928414, 1233261, 1435056) and the Gordon and Betty Moore Foundation (grant 3738)

The Angola Gyre is a hotspot of dinitrogen fixation in the South Atlantic Ocean

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marshall, T., Granger, J., Casciotti, K. L., Dahnke, K., Emeis, K.-C., Marconi, D., McIlvin, M. R., Noble, A. E., Saito, M. A., Sigman, D. M., & Fawcett, S. E. The Angola Gyre is a hotspot of dinitrogen fixation in the South Atlantic Ocean. Communications Earth & Environment, 3(1), (2022): 151, https://doi.org/10.1038/s43247-022-00474-x.Biological dinitrogen fixation is the major source of new nitrogen to marine systems and thus essential to the ocean’s biological pump. Constraining the distribution and global rate of dinitrogen fixation has proven challenging owing largely to uncertainty surrounding the controls thereon. Existing South Atlantic dinitrogen fixation rate estimates vary five-fold, with models attributing most dinitrogen fixation to the western basin. From hydrographic properties and nitrate isotope ratios, we show that the Angola Gyre in the eastern tropical South Atlantic supports the fixation of 1.4–5.4 Tg N.a−1, 28-108% of the existing (highly uncertain) estimates for the basin. Our observations contradict model diagnoses, revealing a substantial input of newly-fixed nitrogen to the tropical eastern basin and no dinitrogen fixation west of 7.5˚W. We propose that dinitrogen fixation in the South Atlantic occurs in hotspots controlled by the overlapping biogeography of excess phosphorus relative to nitrogen and bioavailable iron from margin sediments. Similar conditions may promote dinitrogen fixation in analogous ocean regions. Our analysis suggests that local iron availability causes the phosphorus-driven coupling of oceanic dinitrogen fixation to nitrogen loss to vary on a regional basis.This work was supported by the South African National Research Foundation (114673 and 130826 to T.M., 115335, 116142 and 129320 to S.E.F.); the US National Science Foundation (CAREER award, OCE-1554474 to J.G., OCE-1736652 to D.M.S. and K.L.C., OCE-05-26277 to K.L.C.); the German Federal Agency for Education and Research (DAAD-SPACES 57371082 to T.M.); the Royal Society (FLAIR fellowship to S.E.F.); and the University of Cape Town (T.M., J.G., S.E.F.). The authors also recognize the support of the South African Department of Science and Innovation’s Biogeochemistry Research Infrastructure Platform (BIOGRIP)

Basin-scale inputs of cobalt, iron, and manganese from the Benguela-Angola front to the South Atlantic Ocean

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 57 (2012): 989-1010, doi:10.4319/lo.2012.57.4.0989.We present full-depth zonal sections of total dissolved cobalt, iron, manganese, and labile cobalt from the South Atlantic Ocean. A basin-scale plume from the African coast appeared to be a major source of dissolved metals to this region, with high cobalt concentrations in the oxygen minimum zone of the Angola Dome and extending 2500 km into the subtropical gyre. Metal concentrations were elevated along the coastal shelf, likely due to reductive dissolution and resuspension of particulate matter. Linear relationships between cobalt, N2O, and O2, as well as low surface aluminum supported a coastal rather than atmospheric cobalt source. Lateral advection coupled with upwelling, biological uptake, and remineralization delivered these metals to the basin, as evident in two zonal transects with distinct physical processes that exhibited different metal distributions. Scavenging rates within the coastal plume differed for the three metals; iron was removed fastest, manganese removal was 2.5 times slower, and cobalt scavenging could not be discerned from water mass mixing. Because scavenging, biological utilization, and export constantly deplete the oceanic inventories of these three hybrid-type metals, point sources of the scale observed here likely serve as vital drivers of their oceanic cycles. Manganese concentrations were elevated in surface waters across the basin, likely due to coupled redox processes acting to concentrate the dissolved species there. These observations of basin-scale hybrid metal plumes combined with the recent projections of expanding oxygen minimum zones suggest a potential mechanism for effects on ocean primary production and nitrogen fixation via increases in trace metal source inputs.This research was supported US National Science Foundation Chemical Oceanography (Division of Ocean Sciences OCE-0452883, OCE-0752291, OCE-0928414, OCE-1031271), the Center for Microbial Research and Education, the Gordon and Betty Moore Foundation, the WHOI Coastal Ocean Institute, and the WHOI Ocean Life Institute