Anthropogenic impacts on the geochemical cycling of nutrients and trace metals within intertidal ecosystems

生态系统功能与群落结构的关系是复杂的、动态的。我的长期研究计划旨在了解这种复杂相互作用的机制，以及生态系统结构和功能之间的相互作用如何随着我们改变环境而变化。现在我们的水生生态系统面临的威胁包括气候变化和污染，其中塑料污染的增加，宏观和微观已经成为本世纪最令人担忧的问题之一。迫切需要了解这些人为污染物如何改变生态系统的结构和功能，以及它们在通过食物网转移有毒化合物（如微量金属）方面所起的作用，以便采取预防和补救行动来保护这些生态系统。传统上，沉积物的特征是由不同的地球化学属性组成，如有机物和淤泥，它们作为金属的吸附点被释放到水生环境中。最近的研究表明，塑料也作为微量金属的吸附点，因此提供了一个尚未量化的来源，因此有毒金属进入底栖动物的食物网。现在人们也认识到，进入水生生态系统的塑料会通过光降解老化。这种老化改变了塑料从原始状态的生物物理特性。因此，了解塑料如何影响潮间带沉积物中微量金属循环的机制的一个重要方面是纳入塑料本身的动态性质，即环境老化的塑料与未老化的塑料。我对未来5年融资周期的目标是：1)表征并确定不同沉积地球化学属性潮间带微塑料的分布，比较潮间带中不同聚合物类型和年龄的微塑料对微量金属（镉、铅、锌、铜）的吸附；2)应用放射性示踪剂109Cd，确定双壳类植物Nuttallia obscurata和Protothacia staminea对镉的富集；从微塑料中回收取决于聚合物的类型和形状，3)决定摄食生态的作用，即摄食、滞留和排出率对从双壳贝和雄蜂中回收微塑料的影响。我的研究项目的成果将增加我们关于塑料如何影响我们的水生生态系统的知识基础，特别是关于微量金属通过食物网的运动。这反过来将提高我们预测生态系统和人类风险的能力，即塑料可能作为有毒金属进入潮间带食物网的载体。

The relationship between ecosystem function and community structure is complex and dynamic. My long term research program is directed at understanding  the mechanisms underlying this complex interplay and how this interplay between ecosystem structure and function changes as we modify our environment. Threats now facing our aquatic ecosystems include a changing climate and pollution, the latter of which the increasing presence of plastics pollution, macro and micro has become arguably one of the greatest concerns of this century. Understanding how these anthropogenic contaminants alter ecosystem structure and function and the role they play in the transfer of toxic compounds such as trace metals, through food webs is urgently needed such that preventative and remediative actions to protect these ecosystems can be put in place. Traditionally, sediments have been characterized as being composed of different geochemical attributes such as organic matter and silt that act as sorption sites for metals that have been released into aquatic environments.  Recent research has indicated that plastics also serve as trace metal sorption sites and as such provide an as yet quantified source and hence entry of toxic metals to benthic food webs.  It is also now recognized that plastics that enter into aquatic ecosystems age through photodegradation. Such aging alters the biophysical properties of the plastics from their virgin state. Hence an important aspect of understanding the mechanisms of how plastics are affecting trace metal cycles within intertidal sediments is to incorporate the dynamic nature of the plastic itself, i.e., environmentally aged plastics versus unaged. My objectives for the next 5 year funding cycle are to; 1) Characterize and determine the distribution of  microplastics within several intertidal regions with different sediment geochemical attributes and  compare the sorption of trace metals (cadmium, lead, zinc, copper) by microplastics of different polymers types and ages, among the intertidal regions, 2) through the application of the radiotracer 109Cd, to determine if the accumulation of cadmium by the bivalves Nuttallia obscurata and Protothacia staminea, from microplastics is dependent on polymer type and shape and 3)determine the role of feeding ecology, i.e., rates of ingestion, retention and egestion in influencing the recovery of microplastics from the bivalves N. obscurata and P. stamenia.  Outcomes of my research programme will add to our knowledge base as to how plastics are impacting our aquatic ecosystems, specifically with respect to the movement of trace metals through food webs. This is turn will improve our ability to predict the risks to both ecosystems and humans, that plastics may present as acting as vectors for the entry of toxic metals into intertidal food webs.