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背后的机制，以及随着我们改变我们的环境，生态系统结构和功能之间的这种相互作用如何变化。我们的水生生态系统现在面临的威胁包括气候变化和污染，后者日益严重的宏观和微观塑料污染已经成为本世纪最大的担忧之一。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微量金属等有毒化合物方面所起的作用，以便能够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性质组成，如有机质和泥沙，它们是释放到水环境中的金属的吸附场所。最近的研究表明，塑料也是痕量金属的吸附场所，因此提供了一个尚未量化的来源，因此有毒金属进入海底食物网。现在还认识到，通过光降解进入水生生态系统的塑料。这种老化改变了塑料的生物物理性质，使其处于原始状态。因此，了解塑料如何影响潮间带沉积物中痕量金属循环的机制的一个重要方面是结合塑料本身的动态性质，即环境老化的塑料与未老化的塑料。我对下一个5年筹资周期的目标是；1)表征和确定微塑料在几个具有不同沉积物地球化学属性的潮间带区域内的分布，并比较不同聚合物类型和年龄的微塑料在潮间带区域对痕量金属(镉、铅、锌、铜)的吸附；2)通过应用放射性示踪剂109Cd，确定微塑料对镉的积累是否取决于聚合物类型和形状；3)确定摄食生态的作用，即摄食率，我的研究方案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，特别是关于痕量金属通过食物网的移动。这反过来将提高我们预测生态系统和人类面临的风险的能力，塑料可能会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.