Biological wastes as plant growth substrate amendments

Globally, agriculture is being intensified with mechanization and increased use of synthetic fertilizers and pesticides. There has been a scaling up of production to satisfy the demands of supermarket distribution. Problems associated with intensification of production, trade globalisation and a larger market demand for greater volumes of fresh produce, include consumers' concern about pesticide residues and leaching of nutrients and pesticides into the environment, as well as increases in the transmission of human food-poisoning pathogens on raw vegetables and in fruit juices. The first part of this research was concerned with the evaluation of a biological control strategy for soil-borne pathogens, these are difficult to eliminate and the chemicals of which the most effective fumigants e.g. methyl bromide, are being withdrawn form use. Chitin-containing crustaceans shellfish waste was investigated as a selective growth substrate amendment in the field, in glasshouse and in storage trials against Sclerotinia disease of Helianthus tuberosus, Phytophthora fragariae disease of Fragaria vesca and Fusarium disease of Dianthus. Results showed that addition to shellfish waste stimulated substrate microbial populations and lytic activity and induced plant defense proteins, namely chitinases and cellulases. Protective effects were seen in all crop models but the results indicate that further trials are required to confirm long-term efficacy. The second part of the research investigated the persistence of enteric bacteria in raw salad vegetables using model food poisoning isolates. In clinical investigations plants are sampled for bacterial contamination but no attempt is made to differentiate between epiphytes and endophytes. Results here indicate that the mode isolates persist endophytically thereby escaping conventional chlorine washes and they may also induce host defenses, which results in their suppression and in negative results in conventional plate count screening. Finally a discussion of criteria that should be considered for a HACCP plan for safe raw salad vegetable production is presented.

Ecotoxicology of marine biotoxins in bivalve shellfish

A small proportion of harmful algae produce toxins which are harmful to human health. Strict monitoring programmes are in place within Ireland and the EU to effectively manage risk to human consumers of shellfish species that have accumulated marine biotoxins in their tissues. However, little is known about the impacts of HABs on shellfish health. This study used Solid Phase Adsorption and Toxin Tracking (SPATT) for the passive sampling of algal biotoxins at Lough Hyne Marine Nature Reserve in West Cork, Ireland. Spatial and temporal monitoring of the incidence of a wide range of lipophilic toxins was assessed over a 4-month period. Active sampling accumulated sufficient quantities of toxin for use in subsequent experimentation. In addition to commonly occurring Diarrhetic Shellfish Poisoning (DSP) toxins, Dinophysis toxin-1 and Pinnatoxin-G were both detected in the samples. This is the first identification of these latter two toxins in Irish waters. The effects of the DSP toxin okadaic acid (OA) were investigated on three shellfish species: Mytilus edulis, Ruditapes philippinarum and Crassostrea gigas. Histological examination of the gill, mantle and hepatopancreas tissues revealed varying intensity of damage depending both on the tissue type and the species involved. At the cellular level, flow cytometric analysis of the differential cell population distribution was assessed. No change in cell population distribution was observed in Mytilus edulis or Ruditapes philippinarum, however significant changes were observed in Crassostrea gigas granulocytes at the lower levels of toxin exposure. This indicated a chemically-induced response to OA. DNA fragmentation was measured in the haemolymph and hepatopancreas cells post OA-exposure in Mytilus edulis and Crassostrea gigas. A significant increase in DNA fragmentation was observed in both species over time, even at the lowest OA concentrations. DNA fragmentation could be due to genotoxicity of OA and/or to the induction of cell apoptosis.

The contribution of warlordism to the disintegration of the western Roman army (c. AD 395-480)

My thesis investigates the dynamics behind the changing nature of the leadership of the western Roman army in the fifth century through the concept of ‘warlordism’. I carried this out by analyzing those cases of insubordination and military unrest in the officer class of the western Roman army, which can be shown to be linked to the slow decline of central authority and the imperial office in the period 395-480. My thesis demonstrates that theories of ‘Warlordism’, as developed in social sciences, can be useful for both the late Imperial west as for other eras of ancient history, such as the late Roman republic. Warlordism was a way of continuing politics, if necessary by military means, when commanders found themselves outside the legitimate framework. Unlike the case of usurpation of the imperial office, when there was little hope of achieving permanent recognition and acceptance, it offered insubordinate officers a chance of returning to the ruling imperial regime depending on circumstances and the success of their resistance. I propose that warlordism functioned as an alternative to usurpation, a tool for military dissidence, fuelled by an economy of violence. Contrary to modern warlordism, the warlordism of the fifth century AD represented a transient phase which no imperial commander was willing to prolong indefinitely. At some stage, given the means, warlords in the western Roman army wanted to become part of the imperial echelon again. Yet these alternative methods of violent opposition, and the acquisition of force through private means, ensured the breakdown of the state’s monopoly on violence and the disintegration of centralized armies. What started as an accidental revolution became a new form of military rule.