Ascophyllum and its symbionts: cell biology, ecology and resource management

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The research will focus on the biology of the brown, economically important seaweed, Ascophyllum nodosum, the dominant organism of the intertidal zone of much of Nova Scotia and cold-temperate coastlines of the North Atlantic Ocean.  The primary thrust of the research is to gain a deeper understanding of the symbiotic community hosted by A. nodosum and its role both in fundamental ecological processes operating in the intertidal zone, and the large-scale impact of  harvesting of this resource in eastern Canada.  While the symbiotic community comprises at least seven species (two brown algae, an ascomycete, two red algae, a diatom and an insect), this proposal will focus on three key members of the community: A. nodosum (the primary host), Mycophycias ascophylli (an obligate endophytic fungus universally present in A. nodosum) and Vertebrata lanosa (an epiphytic, host-specific red alga typically abundant on A. nodosum).  The research will characterize basic processes of growth and seasonal adaptations of A. nodosum and its symbionts in the context of the harvesting industry. Preliminary data suggests that the industry reported 20 tons ha-1 (ca. 25% of standing crop) harvested in southwestern Nova Scotia is a major underrepresentation of the biological impact of the biomass removal by at least 140% - this unaccounted for material is what would normally be contributed to the detrital food chain of coastal habitats.  This is derived from the biomass of reproductive structures, the removal of large fronds by wave action, and a newly discovered process of epidermal shedding in which an outer layer of material from the entire frond is shed at regular intervals into the environment as particulate and dissolved organic matter. The research will clarify the process of shedding from a physiological standpoint (i.e., the potential role of reactive oxygen species in the process) and its fine structural details, based on confocal, and transmission and scanning electron microscopy. The role of Mycophycias in the symbiosis and its role as a component in the primary commercial product will also be studied. This will be accomplished using two approaches: 1) bioassays with commercial and experimental extracts of A. nodosum, Pelvetia (a European relative that also hosts the fungus) and Fucus (without Mycophycias), and 2)  isolating cultures of the fungus itself, and evaluating extracts in similar bioassays. The latter approach is significant in that it may lead to industrially produced extracts with greater (or more specific) activity in resulting commercial products, and minimize the extent of the commercial wild harvest of Ascophyllum, which may be having a negative impact on coastal biodiversity and fertility.