Biogeochemical Cycling of Domoic acid in Natural Waters: The Influence of Bioactive Trace Metal Complexation and Photochemistry

天然水中软骨藻酸的生物地球化学循环：生物活性微量金属络合和光化学的影响

• 批准号: 0326685
• 负责人: Jeffrey Wright
• 金额: $ 48.51万
• 依托单位: University of North Carolina at Wilmington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0326685&HistoricalAwards=false
• 关键词: Biogeochemical; Cycling; Domoic; acid; Natural

ABSTRACTOCE-0326685Domoic acid, a powerful marine toxin produced by Pseudo-nitzschia species, is remarkably pervasive in North American coastal waters. This toxin is a threat to public health and some marine life, and has resulted in severe economic losses in the shellfish and crustacean harvesting industry. Originally discovered as the causative agent in an episode of fatal human poisoning in eastern Canada in 1987, domoic acid has subsequently been linked to other epizootics, particularly on the western coast of North America where it has resulted in the death of seabirds and mammals. Despite the significance of domoic acid to the biogeochemistry of marine systems, virtually nothing is known about the fate of that fraction of the toxin not transferred through the food chain - arguably the vast majority of toxic material produced during harmful algal blooms.In this project, researchers at the University of North Carolina at Wilmington will determine the processes that control the biogeochemical cycling of domoic acid once it is released into the water column. This is significant because preliminary evidence indicates water column concentrations of domoic acid can reach as high as 100 nM during a bloom event. The research team will address the role of light (photochemically-mediated) and dark (microbial and/or chemical degradation) processes and trace metal complexation on the biogeochemical cycling and fate of this powerful toxin in natural waters. They hypothesize that photochemical reactions are particularly important because preliminary data indicates domoic acid is rapidly converted to a series of geometric isomers and decarboxylated derivatives when exposed to short-term irradiations using simulated sunlight. Photochemical degradation of domoic acid is extremely significant because it reduces the lifetime of this powerful toxin in surface seawater where it is produced, but at the same time may also produce more toxic photo-produced byproducts. A second hypothesis, based on recent evidence showing strong complexes are formed by domoic acid with Fe(III) and Cu(II), is that trace metals play an important role in the fate of the toxin once it is released into natural waters. Complexation of domoic acid by these redox-active trace metals is important because the complexes will have different photochemical reactivities than uncomplexed domoic acid (or its photo-isomers) and may therefore have very different residence times and fates in the environment. The experimental approach will be to irradiate domoic acid in seawater to its three geometric isomers and decarboxylated derivatives under a variety of conditions to quantify rates of photochemical degradation and identify the byproducts produced. Similar experiments using dark controls will provide information on kinetics of microbial and chemical degradation in coastal waters. A series of metal- binding studies with the same suite of compounds will determine the degree of metal complexation and the strength of the complexes formed.The proposed research is expected to provide significant new information regarding the chemical and physical factors influencing the residence time and fate of domoic acid and its byproducts in natural waters. This proposal directly addresses fundamental ecological and oceanographic questions related to domoic acid, a powerful and pervasive toxin present in frequent Pseudo-nitzschia blooms in North American coastal waters. A major part of the requested funding will be used to support a post-doctoral researcher, a masters-level graduate student, and four undergraduate students per year. The involvement of undergraduates will be an integral part of the investigators research program. Young students are attracted to this type of study because they perform environmental research of international interest. The proposed research will continue this pattern by allowing undergraduates at a coastal university to become involved in a high profile research question associated with toxic algal blooms.

软骨藻酸是一种由拟菱形藻产生的强效海洋毒素，广泛存在于北美沿海水域。这种毒素对公众健康和一些海洋生物构成威胁，并已导致贝类和甲壳类捕捞业的严重经济损失。软骨藻酸最初是1987年在加拿大东部发生的一起致命的人类中毒事件中被发现的病原体，后来被发现与其他流行病有关，特别是在北美西海岸，它已导致海鸟和哺乳动物死亡。尽管软骨藻酸对海洋系统的生物地球化学具有重要意义，但人们几乎不知道软骨藻酸没有通过食物链转移的那部分毒素的命运--可以说，软骨藻酸是有害藻华期间产生的绝大多数有毒物质。在这个项目中，北卡罗来纳大学威尔明顿分校的研究人员将确定一旦软骨藻酸释放到水体中，控制其生物地球化学循环的过程。这一点意义重大，因为初步证据表明，在水华事件期间，水柱中软骨藻酸的浓度可高达100海里。研究小组将研究光(光化学介导)和暗(微生物和/或化学降解)过程的作用，以及微量金属络合作用对这种强大毒素在自然水域中的生物地球化学循环和命运的影响。他们假设，光化学反应特别重要，因为初步数据表明，软骨藻酸在使用模拟阳光进行短期照射时，会迅速转化为一系列几何异构体和脱羧基衍生物。软骨藻酸的光化学降解极其显著，因为它缩短了这种强烈毒素在其产生的表层海水中的寿命，但同时也可能产生更多有毒的光生副产品。第二种假设基于最近的证据，表明软骨藻酸与铁(III)和铜(II)形成了强大的络合物，即一旦毒素释放到自然水域中，痕量金属对毒素的命运起着重要作用。软骨藻酸与这些氧化还原活性的痕量金属络合是很重要的，因为这些络合物与未络合的软骨藻酸(或其光异构体)具有不同的光化学反应活性，因此在环境中可能有非常不同的停留时间和命运。实验方法将是在各种条件下将海水中的软骨藻酸照射到其三个几何异构体和脱羧基衍生物，以量化光化学降解速率并鉴定产生的副产品。使用黑暗控制的类似实验将提供关于沿海水域微生物和化学降解动力学的信息。对同一组化合物进行的一系列金属结合研究将确定金属络合的程度和形成的络合物的强度。拟议的研究有望提供有关影响软骨藻酸及其副产物在天然水域中停留时间和去向的化学和物理因素的重要新信息。这项建议直接涉及与软骨藻酸有关的基本生态和海洋学问题，软骨藻酸是北美沿海水域频繁出现的伪菱形藻水华中存在的一种强大而普遍的毒素。申请的大部分资金将用于支持每年一名博士后研究员、一名硕士研究生和四名本科生。本科生的参与将是调查人员研究计划不可或缺的一部分。年轻学生之所以被这种类型的学习所吸引，是因为他们从事具有国际兴趣的环境研究。拟议中的研究将继续这一模式，允许沿海大学的本科生参与与有毒藻类水华相关的备受瞩目的研究问题。