Diatom Frustules as a Mechanical Defense Against Predation by Heterotrophic Dinoflagellates

Diatoms contribute up to 40% of the total primary production in the ocean and heavily influence the cycling of carbon and silica. Much of their success results from their silica frustule, which may provide a mechanical defense against grazers. In this study, I sought to determine the possible defense mechanism of the diatom’s frustule in the presence of one of their dominant grazers, heterotrophic dinoflagellates. I grew two species of diatoms, Thalassiosira rotula and Coscinodiscus radiatus, in semicontinuous culture with 80 μM or 20 μM silicic acid. Based on a 2-fold higher BSi cell-1, BSi:C, and BSi:N, this culture method successfully resulted in diatoms of both species with thick and thin frustules. I performed three predation experiments to determine if frustule thickness would affect predator ingestion, digestion or growth rate. I first fed thick and thin T. rotula to Gyrodinium spirale and measured ingestion and growth rate over 48 hr. I found no difference in ingestion rate between the thick and thin treatments, however G. spirale grew significantly slower on the thick-frustuled diatoms. I then fed thick and thin C. radiatus to Noctiluca scintillans, measuring ingestion rate in one experiment and digestion rate in a second. I found no difference in predator ingestion rate at the end of the 4 hr experiment. However, I did observe a significantly lower predator digestion rate when feeding on the thick-frustuled diatoms. The results strongly suggest that the frustule is providing a defense to the diatoms by slowing the predator’s digestion rate, which then decreases their population growth rate. This is the first reported evidence in favor of diatom frustules as a means of defense against microzooplankton. As such, this proposed mechanism has important implications for diatom bloom dynamics as well as global carbon and silica cycling

Sustaining The Saco Estuary: Final Report 2015

This study focuses on the Saco estuary, the tidal portion of the Saco River, which drains the largest watershed in southern Maine. With headwaters in the White Mountains of New Hampshire, the watershed encompasses more than 4,400 km2, and provides clean healthy drinking water to over 100,000 people living and working in communities in southern Maine. When the study began in 2009, very little was known about the ecology of the Saco estuary. Researchers at the University of New England and the Wells National Estuarine Research Reserve employed the process of collaborative learning to bring together people who care about the estuary in order to identify their concerns. A Stewardship Network composed of people employed by municipal, state and federal governments, water supply organizations and businesses, volunteers from municipal boards making land use decisions, land trusts, property owners and representatives from other organizations that are uniquely focused on the region was formed. The Stewardship Network helped to define the project goals and objectives, and provided input and guidance over the five-year project. This report explains what the researchers discovered about the ecology of the estuary, along with what they learned about its social and economic components. This baseline assessment contributes to the long-term goal of restoring and sustaining the structure and function of the estuary, and supports the efforts of government, businesses and local organizations that value the estuary and depend upon the natural services it provides

Histone Methyltransferase Activity of a Drosophila Polycomb Group Repressor Complex

AbstractPolycomb group (PcG) proteins maintain transcriptional repression during development, likely by creating repressive chromatin states. The Extra Sex Combs (ESC) and Enhancer of Zeste [E(Z)] proteins are partners in an essential PcG complex, but its full composition and biochemical activities are not known. A SET domain in E(Z) suggests this complex might methylate histones. We purified an ESC-E(Z) complex from Drosophila embryos and found four major subunits: ESC, E(Z), NURF-55, and the PcG repressor, SU(Z)12. A recombinant complex reconstituted from these four subunits methylates lysine-27 of histone H3. Mutations in the E(Z) SET domain disrupt methyltransferase activity in vitro and HOX gene repression in vivo. These results identify E(Z) as a PcG protein with enzymatic activity and implicate histone methylation in PcG-mediated silencing

Non-affirmative Theory of Education as a Foundation for Curriculum Studies, Didaktik and Educational Leadership

This chapter presents non-affirmative theory of education as the foundation for a new research program in education, allowing us to bridge educational leadership, curriculum studies and Didaktik. We demonstrate the strengths of this framework by analyzing literature from educational leadership and curriculum theory/didaktik. In contrast to both socialization-oriented explanations locating curriculum and leadership within existing society, and transformation-oriented models viewing education as revolutionary or super-ordinate to society, non-affirmative theory explains the relation between education and politics, economy and culture, respectively, as non-hierarchical. Here critical deliberation and discursive practices mediate between politics, culture, economy and education, driven by individual agency in historically developed cultural and societal institutions. While transformative and socialization models typically result in instrumental notions of leadership and teaching, non-affirmative education theory, previously developed within German and Nordic education, instead views leadership and teaching as relational and hermeneutic, drawing on ontological core concepts of modern education: recognition; summoning to self-activity and Bildsamkeit. Understanding educational leadership, school development and teaching then requires a comparative multi-level approach informed by discursive institutionalism and organization theory, in addition to theorizing leadership and teaching as cultural-historical and critical-hermeneutic activity. Globalisation and contemporary challenges to deliberative democracy also call for rethinking modern nation-state based theorizing of education in a cosmopolitan light. Non-affirmative education theory allows us to understand and promote recognition based democratic citizenship (political, economical and cultural) that respects cultural, ethical and epistemological variations in a globopolitan era. We hope an American-European-Asian comparative dialogue is enhanced by theorizing education with a non-affirmative approach

Transformation of destination leadership networks

This paper investigates the transformation of a destination leadership network within a new funding and governance landscape for Destination Management Organisations (DMOs) and destinations in England. Current longitudinal evidence into the transformation of destination leadership networks and emergent Distributed Leadership (DL) in the literature domain of DMOs and destinations is thin. This study adopts a longitudinal case study and ego-network Social Network Analysis (SNA) approach, drawing on the perspectives of the founding and current Chief Executive Officers (CEOs) of a DMO coupled with semi-structured expert interviews with policy makers from VisitEngland. Longitudinal data findings provide useful insights into the transformation of DMOs and their wider networks through the enactment of DL in order to cope with change and uncertainty.N/