Simulating regimes of chemical disturbance and testing impacts in the ecosystem using a novel programmable dosing system

Pollution is a global issue at the frontier between ecology, environmental science, management, engineering and policy. Legislation requires experiments to determine how much contamination an ecosystem can absorb before there are structural or functional changes. Yet, existing methods cannot realistically simulate regimes of chemical disturbance and determine impacts to assemblages in ecosystems. This is because they lack ecologically relevant species and biotic interactions, are logistically difficult to set-up, and lack environmentally relevant regimes of chemical and abiotic disturbance that organisms experience in polluted areas. We solved these long-standing environmental, logistical, experimental and ecological problems by developing a programmable dosing-system. This dosing-system simulates, in situ, regimes of chemical disturbance to assemblages by manipulating the concentration, duration, timing and frequency of pollutants to which they are exposed. Experiments with priority pollutants (the metal copper and the biocide Chlorpyrifos) and mussel assemblages revealed consistent plumes of contamination within patches of mussel. Mussels at the sources of experimental plumes of copper created by the dosing-system, accumulated 670% more copper in their tissues compared to mussels 0.5-50 m away. In addition, when mussels were exposed to increasing concentrations of copper there was a concomitant increase in the amount of copper in the tissues of mussels. Combining the dosing-system with an established hierarchy of ecotoxicological assays revealed mussel assemblages exposed to copper and/or Chlorpyrifos had 40-70% fewer worms, whilst Chlorpyrifos alone caused an 81% reduction in the number of amphipods and caused mussels to filter 48% fewer particles from the water. Combinations of copper and/or Chlorpyrifos had no effects on the abundance of crabs, the respiratory functions of assemblages or the viability of molluscan haemocytes. As global contamination accelerates we discuss how this technological advance will enable a diverse array of ecologists, mangers and policy-makers to understand and reduce pollution.

污染是横跨生态学、环境科学、管理学、工程学与政策学的前沿全球性议题。立法机构要求开展相关实验，以明确生态系统在发生结构或功能改变前所能承受的最大污染负荷。然而现有方法无法真实模拟化学扰动模式，亦难以量化其对生态群落的影响。究其根源，此类方法既未纳入具备生态学相关性的物种与生物相互作用，实地部署难度极大，且无法复现污染区域中生物所经历的化学与非生物扰动模式。本研究通过开发一套可编程投加系统（programmable dosing-system），解决了长期存在的环境、后勤、实验与生态学层面的诸多难题。该系统可原位模拟生态群落所承受的化学扰动模式，通过精准调控污染物的暴露浓度、持续时长、施加时机与作用频率实现上述目标。以优先污染物（priority pollutants）——金属铜与杀菌剂毒死蜱（Chlorpyrifos）——及贻贝群落为对象开展的实验显示，贻贝斑块内会形成稳定的污染羽流。由该投加系统产生的铜污染羽流源头处的贻贝，其组织内铜的富集量较0.5至50米外的贻贝高出670%。此外，当贻贝暴露于浓度逐步升高的铜环境中时，其组织内的铜富集量亦随之同步上升。将该投加系统与成熟的生态毒理学实验（ecotoxicological assays）体系相结合后发现，暴露于铜和/或毒死蜱环境中的贻贝群落，其伴生蠕虫的数量减少了40%至70%；仅暴露于毒死蜱的组别中，端足类动物（amphipods）的数量下降了81%，同时贻贝的滤水率降低了48%。铜与毒死蜱的联合暴露则未对蟹类丰度、群落呼吸功能以及软体动物血细胞存活率产生显著影响。随着全球污染态势持续加剧，本研究还探讨了这项技术突破将如何帮助广大生态学家、管理者与政策制定者更好地理解并治理污染问题。