Polyunsaturated aldehyde production by a temporally varying field assemblage of diatoms in the San Juan Island Archipelago: can diatom metabolites affect microzooplankton grazing?

The success of diatoms in a wide range of global habitats, together with common observations of the post-bloom sinking of diatom biomass, indicates that this taxon has evolved a mechanism to reduce the largest loss process for phytoplankton in the ocean, microzooplankton grazing. Recent research has shown that polyunsaturated aldehydes (PUAs), lipid oxidation products generated by various species of diatoms, can reduce copepod fecundity and egg hatching success. This leads to the question of whether PUAs adversely affect the major global consumers of phytoplankton, microzooplankton. In the late spring to early fall 2007, I used the seawater dilution technique to quantify phytoplankton growth and microzooplankton grazing; at the same time I determined diatom and microzooplankton abundances and biomasses at Rosario Point, Orcas Island, WA (N 48° 38.614, W 122°52.750). In addition, I measured production of PUAs by the phytoplankton community to assess whether these chemicals functioned as chemical grazing deterrents, to look for novel PUA-producing diatom genera, and to evaluate environmental factors that potentially influenced PUA production. Four hydrographic structural change (HSC) events in the water column were identified during the spring-summer sampling period that probably reflected flushing by outside water masses. These events altered environmental conditions with distinct planktonic communities (termed community states) emerging during post-event water column stabilization. The first two community states were characterized by low nutrient concentrations with chlorophyll a between 6.5 and 13.1μg L-1 and several instances of negative growth and grazing rates. This suggested the release of an unidentified chemical by the Pseudo-nitzschia spp. dominated first community state that additionally had moderately high PUA production levels of 771-1520 μg PUA g C-1. Harmful algal bloom species Heterosigma akashiwo dominated the mid-summer community state with chlorophyll a reaching 10.45 μg chl L-1 and microzooplankton grazing rates reduced to nearly zero. Lastly, the diatom dominated mid-to-late summer community state reached 15.84 μg chl L-1 with Thalassiosira spp, Chaetoceros spp., and Skeletonema sp. all present as major constituents of the community that produced high PUA levels (1280- 3410 μg PUA g C-1). Each of the genera found in this study contain species that have previously been identified as producing PUA. Low phosphate concentrations within each of the PUA-producing communities appeared to influence production, as well as the presence of low light levels in the first community state that possibly increased PUAprecursor molecule formation. Furthermore, changes to growth rates in the \u3e20-μm (diatom) community with nutrient addition often occurred during PUA production, however this response by sampled diatom communities did not preclude PUA production. Community grazing on the \u3e20-μm size fraction was observed to decrease when PUA production was high. During the spring state negative grazing along with low microzooplankton biomass made interpretation difficult. During the mid-to-late summer state grazing was reduced to -0.02 to 0.08 d-1 with a large biomass of 143 to 180 μg C L-1 of non-feeding microzooplankton that included known diatom-feeding dinoflagellates Protoperidinium sp., 40 to 59 μm Gyro/Gymnodinium, and \u3e60-μm Gyro/Gymnodinium. With this reduced grazing, diatoms grew from 23.2 to 244 μg C L-1. Since diatom grazing genera of microzooplankton did not feed during the initiation and maintenance of the August bloom, my data suggests that PUA played a role in bloom initiation and allowed the diatom community to avoid predation

Analysis and quantification of the benefits of interconnected distribution system operation

In the UK, the Capacity to Customers (C2C) project is underway to determine the potential benefits of increased interconnection in distribution systems, combined with demand side response technology. Managed contracts with customers, i.e., the agreement that certain loads are interruptible following system faults, allows distribution circuits to be loaded beyond the limits presently required for security of supply. This potentially permits load growth but avoids the cost and environmental impact of conventional network reinforcement. This paper provides the results of electrical system modelling to quantify the benefits of the C2C operation, using actual circuit data and typical load distributions. Based upon simulations of these circuits, it is shown that increased interconnection generally leads to minor improvements in electrical losses and system voltage. By connecting managed (i.e., interruptible) loads, circuits typically can be loaded significantly further than the present practice in the UK—an average increase of 66% for radial operation and 74% for interconnected systems

Models in the Cloud: Exploring Next Generation Environmental Software Systems

There is growing interest in the application of the latest trends in computing and data science methods to improve environmental science. However we found the penetration of best practice from computing domains such as software engineering and cloud computing into supporting every day environmental science to be poor. We take from this work a real need to re-evaluate the complexity of software tools and bring these to the right level of abstraction for environmental scientists to be able to leverage the latest developments in computing. In the Models in the Cloud project, we look at the role of model driven engineering, software frameworks and cloud computing in achieving this abstraction. As a case study we deployed a complex weather model to the cloud and developed a collaborative notebook interface for orchestrating the deployment and analysis of results. We navigate relatively poor support for complex high performance computing in the cloud to develop abstractions from complexity in cloud deployment and model configuration. We found great potential in cloud computing to transform science by enabling models to leverage elastic, flexible computing infrastructure and support new ways to deliver collaborative and open science

Development of a Reference Design for a Cyber-Physical System

The purpose of this thesis is to develop a reference design to assist in the selection of security practices in power electronics design. A prototype will be developed from this reference design for evaluation. This evaluation will include a brief cost/benefit analysis to gauge the efficacy of implementing each layer of security throughout the power electronics design process. This thesis will also describe the obstacles and effectiveness of integrating a Trusted Platform Module (TPM) into a cyber-hardened grid-connected device. The TPM device is a secured crypto processor that assists in generating, storing, and restricting the use of cryptographic keys. The emphasis of this research is to establish integrity, authenticity, and confidentiality within a system by providing a baseline of security concerns for segments of the system. This research considers communication, control, and hardware level securities. The scope of this thesis will review the necessary security methods as well as consider the effects these methods have on the embedded system, to assess the desired security to responsiveness trade off. Applying this approach to a design process will alleviate various unknowns of appending security to a power electronics design. This thesis describes the specific vulnerabilities introduced within this grid-edge environment, and how the liabilities within the system can be mitigated. Initially, common security techniques will be considered to establish a guideline to benchmark performance and resource costs of the system. The foundation will be a non-hardened power electronic system platform with industry standard communication protocols. Several security techniques and attack vectors will then be evaluated to contribute to the base level platform. Other fail-safe features take place to gauge progress of the selected approach, non-inclusive to the TPM. Collectively, this investigation will determine a valid experiment by appraising and categorizing resource allocation, performance overhead, and monetary cost analysis results into a reference design. The prototype will then demonstrate methods to relieve common threats that are purposefully implemented into the design