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

这项研究将侧重于棕色海藻的生物学，这种具有重要经济意义的海藻是新斯科舍省大部分潮间带和北大西洋寒温带海岸线的优势生物。这项研究的主要目的是更深入地了解由结瘤拟青霉寄生的共生群落及其在潮间带基本生态过程中的作用，以及在加拿大东部收获这种资源的大规模影响。虽然共生群落至少包括七个物种(两种褐藻、一种子囊菌、两种红藻、一种硅藻和一种昆虫)，但这项建议将侧重于该群落的三个关键成员：结节假单胞菌(主要宿主)、假单胞菌(一种普遍存在于结节单胞菌中的专性内生真菌)和绵毛脊椎动物(一种附生的、宿主特有的红藻，典型地丰富于结节单胞菌上)。这项研究将描述根结木霉及其共生体在收获行业中的生长和季节性适应的基本过程。初步数据表明，该行业报告在新斯科舍省西南部收获的20吨ha-1(约占现有作物的25%)严重低估了生物质去除的生物影响至少140%--这种下落不明的物质通常会被贡献到沿海生境的碎屑食物链中。这源于生殖结构的生物量，通过波浪作用移走大叶子，以及新发现的表皮脱落过程，在这个过程中，整个叶子的外层物质以颗粒和溶解有机物的形式定期排放到环境中。这项研究将从生理角度(即，活性氧在这一过程中的潜在作用)及其精细的结构细节，基于共聚焦、透射和扫描电子显微镜，阐明脱落的过程。还将研究真菌在共生中的作用及其作为初级商业产品成分的作用。这将使用两种方法来完成：1)用节瘤曲霉、Pelvetia(也是这种真菌的欧洲近亲)和Fucus(没有霉菌)的商业和实验提取物进行生物检测，以及2)分离真菌本身的培养物，并在类似的生物检测中对提取物进行评估。后一种方法意义重大，因为它可能导致工业生产的提取物在所产生的商业产品中具有更大(或更具体)的活性，并最大限度地减少商业野生云杉收获的程度，这可能对沿海生物多样性和肥力产生负面影响。

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.