The Herring River Estuary: Understanding Salt Marsh Restoration and How to Predict the Response of Phragmites australis to Increased Tidal Flow

My presentation invites you to learn about what is involved in planning a salt marsh restoration project. The Herring River Estuary is a disturbed salt marsh ecosystem at Cape Cod National Seashore which has been diked since 1909. The National Park Service (NPS), in cooperation with many partners, is engaged in efforts to restore the now impacted 1,100 acre estuary by re-introducing tidal flow. There is significant complexity involved in trying to restore such an intricate system- from the multitude of environmental factors to important social and economic consequences. There are also several benefits to restored tidal flow. My thesis project allowed me to assist the National Park Service by mapping the predicted response of Phragmites australis to restoration. P. australis is a key invasive plant species of management interest. Many of the salt marshes in the United States have been significantly altered and disturbed over time. As we have begun to realize the important benefits these ecosystems provide and the negative effects that diking has had on these systems, efforts have begun to restore salt marshes all along the coast. However ecosystems are extremely complex and restoration efforts cannot be done successfully without proper planning. Many of these disturbed systems have been in their existing state for over 100 years and any restoration will cause significant changes to the area. There are many potential consequences that citizens near these salt marshes are legitimately concerned about and the high cost of a restoration can also be prohibitive. However if proper precautions are taken there are significant environmental benefits to such restorations. My role has been to work with the adaptive management team of scientists who are helping to predict the changes that can be expected as the restoration proceeds. Incremental openings to the new dike will allow the estuary to slowly respond to increased tidal flow. By slowly opening the new dike, over the course of several years, the NPS will also be able to monitor system responses and make sure the restoration is proceeding successfully and make adaptive changes if anything is wrong. My specific focus has been on predicting the changes in spread and location of key species as the restoration proceeds. I have focused mostly on Phragmites australis, a tall invasive reed grass that has negative effects on salt marsh ecosystems. As an invasive plant, P. australis is of particular management concern and predicting its response to the restoration is beneficial to helping limit its spread. Using literature on its life history, current data on its occurrence in the estuary, and modeled predictions of restored salinity and tidal levels, I have produced several maps and an associated report on the predicted response of P. australis to the planned restoration. Data analysis and mapping was done using a Geographic Information System (GIS), called ArcGIS 10. The report includes a map of what areas are most likely to see vigorous P. australis growth and a map of areas prone to P. australis seed germination. My analysis has allowed me to consider possible management techniques for P. australis which are also included in my report. Overall, I hope you will find my project to be interesting and informative as it addresses both the complexity of planning a salt marsh restoration and the value of restoring tidal flow

FACTORS INFLUENCING IMPACT OF BIOLOGICAL CONTROL AGENTS OF THE EMERALD ASH BORER

Agrilus planipennis, the emerald ash borer (EAB), is a destructive invasive forest pest decimating North American ash trees. Population-wide management of EAB focuses on biological control, with the introduction of four parasitic wasps; one egg parasitoid, Oobius agrili and three larval parasitoids- Spathius galinae, Spathius agrili and Tetrastichus planipennisi. This thesis examines some of the factors influencing the establishment of these larval biocontrol agents. Chapter 1 examines the relationship between woodpeckers and the parasitoids S. agrili and T. planipennisi. Both woodpeckers and these parasitoids attack the larval stage of EAB, which means their impacts overlap and potentially interact. To examine this relationship, I established parasitized larvae on ash trees and then used screening to exclude woodpeckers from some sections of the tree. Results show that while there is no evidence of discriminatory feeding for or against parasitized larvae, the presence of parasitized larvae changes woodpecker feeding behavior at a stand-level. I hypothesize that this change is due to these larval parasitoids being a low-food reward and that parasitism contributes to a change and decrease in patch quality, causing woodpeckers to quit foraging sooner than usual. My second chapter focuses on Spathius galinae, which was recently approved for release in the north central and northeastern US in 2015, to provide additional population control. Spathius galinae’s long ovipositor (4-5.3mm) is theoretically expected to help target EAB in ash with larger diameters and bark thicknesses. Using experimentally infested logs of varying thicknesses in the laboratory I tested the limits and preferences for oviposition of S. galinae, to understand its potential impact on EAB. My results demonstrated that although parasitism by S. galinae drops significantly when bark thickness reaches 8 mm, this prevents S. galinae only from reaching EAB larvae in my largest ash trees (S. galinae will play a vital role in providing additional control and in supporting ash regeneration in aftermath areas of EAB invasions

Transition from cMyc to L-Myc during dendritic cell development coordinated by rising levels of IRF8

During dendritic cell (DC) development, Myc expression in progenitors is replaced by Mycl in mature DCs, but when and how this transition occurs is unknown. We evaluated DC development using reporters for MYC, MYCL, and cell cycle proteins Geminin and CDT1 in wild-type and various mutant mice. For classical type 1 dendritic cells (cDC1s) and plasmacytoid DCs (pDCs), the transition occurred upon their initial specification from common dendritic cell progenitors (CDPs) or common lymphoid progenitors (CLPs), respectively. This transition required high levels of IRF8 and interaction with PU.1, suggesting the use of EICEs within Mycl enhancers. In pDCs, maximal MYCL induction also required the +41kb Irf8 enhancer that controls pDC IRF8 expression. IRF8 also contributed to repression of MYC. While MYC is expressed only in rapidly dividing DC progenitors, MYCL is most highly expressed in DCs that have exited the cell cycle. Thus, IRF8 levels coordinate the Myc-Mycl transition during DC development

CHANG-ES V: Nuclear Radio Outflow in a Virgo Cluster Spiral after a Tidal Disruption Event

We have observed the Virgo Cluster spiral galaxy, NGC~4845, at 1.6 and 6 GHz using the Karl G. Jansky Very Large Array, as part of the `Continuum Halos in Nearby Galaxies -- an EVLA Survey' (CHANG-ES). The source consists of a bright unresolved core with a surrounding weak central disk (1.8 kpc diameter). The core is variable over the 6 month time scale of the CHANG-ES data and has increased by a factor of $\approx$ 6 since 1995. The wide bandwidths of CHANG-ES have allowed us to determine the spectral evolution of this core which peaks {\it between} 1.6 and 6 GHz (it is a GigaHertz-peaked spectrum source).We show that the spectral turnover is dominated by synchrotron self-absorption and that the spectral evolution can be explained by adiabatic expansion (outflow), likely in the form of a jet or cone. The CHANG-ES observations serendipitously overlap in time with the hard X-ray light curve obtained by Nikolajuk \& Walter (2013) which they interpret as due to a tidal disruption event (TDE) of a super-Jupiter mass object around a $10^5\, M_\odot$ black hole. We outline a standard jet model, provide an explanation for the observed circular polarization, and quantitatively suggest a link between the peak radio and peak X-ray emission via inverse Compton upscattering of the photons emitted by the relativistic electrons. We predict that it should be possible to resolve a young radio jet via VLBI as a result of this nearby TDE.Comment: 45 pages, 10 figures, accepted July 2, 2015 to the Astrophysical Journa

Snail promotes the cell-autonomous generation of Flk1 + endothelial cells through the repression of the microRNA-200 family

Expression of the transcription factor Snail is required for normal vasculogenesis in the developing mouse embryo. In addition, tumors expressing Snail have been associated with a more malignant phenotype, with both increased invasive properties and angiogenesis. Although the relationship between Snail and vasculogenesis has been noted, no mechanistic analysis has been elucidated. Here, we show that in addition to inducing an epithelial mesenchymal transition, Snail promotes the cell-autonomous induction of Flk1(+) endothelial cells in an early subset of differentiating mouse embryonic stem (ES) cells. Cells that become Flk1+ in response to Snail have a transcriptional profile specific to Gata6+primitive endoderm, but not the early Nanog+epiblast. We further show that Snail's ability to promote Flk1(+) endothelium depends on fibroblast growth factor signaling as well as the repression of the microRNA-200 (miR-200) family, which directly targets the 3′ UTRs of Flk1 and Ets1. Together, our results show that Snail is capable of inducing Flk1+ lineage commitment in a subset of differentiating ES cells through the down-regulation of the miR-200 family. We hypothesize that this mechanism of Snail-induced vasculogenesis may be conserved in both the early developing embryo and malignant cancers

Distinct and complementary functions of MDA5 and TLR3 in poly(I:C)-mediated activation of mouse NK cells

The double-stranded RNA (dsRNA) analogue poly(I:C) is a promising adjuvant for cancer vaccines because it activates both dendritic cells (DCs) and natural killer (NK) cells, concurrently promoting adaptive and innate anticancer responses. Poly(I:C) acts through two dsRNA sensors, Toll-like receptor 3 (TLR3) and melanoma differentiation-associated protein-5 (MDA5). Here, we investigated the relative contributions of MDA5 and TLR3 to poly(I:C)-mediated NK cell activation using MDA5−/−, TLR3−/−, and MDA5−/−TLR3−/− mice. MDA5 was crucial for NK cell activation, whereas TLR3 had a minor impact most evident in the absence of MDA5. MDA5 and TLR3 activated NK cells indirectly through accessory cells and induced the distinct stimulatory cytokines interferon-α and interleukin-12, respectively. To identify the relevant accessory cells in vivo, we generated bone marrow chimeras between either wild-type (WT) and MDA5−/− or WT and TLR3−/− mice. Interestingly, multiple accessory cells were implicated, with MDA5 acting primarily in stromal cells and TLR3 predominantly in hematopoietic cells. Furthermore, poly(I:C)-mediated NK cell activation was not notably impaired in mice lacking CD8α DCs, providing further evidence that poly(I:C) acts through diverse accessory cells rather than solely through DCs. These results demonstrate distinct yet complementary roles for MDA5 and TLR3 in poly(I:C)-mediated NK cell activation

Compact Resolved Ejecta in the Nearest Tidal Disruption Event

Tidal disruption events (TDEs) occur when a star or sub-stellar object passes close enough to a galaxy's supermassive black hole to be disrupted by tidal forces. NGC 4845 (d=17 Mpc) was host to a TDE, IGR J12580+0134, detected in November 2010. Its proximity offers us a unique close-up of the TDE and its aftermath. We discuss new Very Long Baseline Array (VLBA) and Karl G. Jansky Very Large Array (JVLA) observations, which show that the radio flux from the active nucleus created by the TDE has decayed in a manner consistent with predictions from a jet-circumnuclear medium interaction model. This model explains the source's broadband spectral evolution, which shows a spectral peak that has moved from the submm (at the end of 2010) to GHz radio frequencies (in 2011-2013) to <1 GHz in 2015. The milliarcsecond-scale core is circularly polarized at 1.5 GHz but not at 5 GHz, consistent with the model. The VLBA images show a complex structure at 1.5 GHz that includes an east west extension ~40 milliarcsec (3 pc) long as well as a resolved component 52 milliarcsec (4.1 pc) northwest of the flat-spectrum core, which is all that can be seen at 5 GHz. If ejected in 2010, the NW component must have had v=0.96 c over five years. However, this is unlikely, as our model suggests strong deceleration to speeds < 0.5c within months and a much smaller, sub-parsec size. In this interpretation, the northwest component could have either a non-nuclear origin or be from an earlier event.Comment: 12 pages, 8 figures, ApJ, in press; v2 includes error corrections and slight additions to the analysi

Reactive oxygen species induce virus-independent MAVS-oligomerization in systemic lupus erythematosus

The increased expression of genes induced by type I interferon (IFN) is characteristic of viral infections and systemic lupus erythematosus (SLE). We showed that mitochondrial antiviral signaling (MAVS) protein, which normally forms a complex with retinoic acid gene I (RIG-I)–like helicases during viral infection, was activated by oxidative stress independently of RIG-I helicases. We found that chemically generated oxidative stress stimulated the formation of MAVS oligomers, which led to mitochondrial hyperpolarization and decreased adenosine triphosphate production and spare respiratory capacity, responses that were not observed in similarly treated cells lacking MAVS. Peripheral blood lymphocytes of SLE patients also showed spontaneous MAVS oligomerization that correlated with the increased secretion of type I IFN and mitochondrial oxidative stress. Furthermore, inhibition of mitochondrial reactive oxygen species (ROS) by the mitochondria-targeted antioxidant MitoQ prevented MAVS oligomerization and type I IFN production. ROS-dependent MAVS oligomerization and type I IFN production were reduced in cells expressing the MAVS-C79F variant, which occurs in 30% of sub-Saharan Africans and is linked with reduced type I IFN secretion and milder disease in SLE patients. Patients expressing the MAVS-C79F variant also had reduced amounts of oligomerized MAVS in their plasma compared to healthy controls. Together, our findings suggest that oxidative stress–induced MAVS oligomerization in SLE patients may contribute to the type I IFN signature that is characteristic of this syndrome