Effects of municipal wastewaters on aquatic-nearshore food webs

陆生和水生生态系统通过物质从陆地到水的径流以及这些物质通过新出现的水生昆虫返回到近岸(河岸)捕食者而紧密相连。然而，这些能量联系可能会被污染物破坏，因为它们会影响水生昆虫幼虫的丰度，以及随后河岸捕食者可以获得的猎物。我们对污染物如何破坏水生-河岸联系的理解主要局限于高度污染的工业场所。城市污水是加拿大地表水中最大的人类投入物，含有过量的营养物质和包括抗菌剂(抗生素、消毒剂)在内的多种污染物。我们之前在受废水影响的地点所做的工作显示，鱼、幼虫和河岸蜘蛛改变了微生物群，但尚不清楚这些影响是否发生在其他地点以及这些变化背后的机制(即接触抗菌剂、饮食习惯的改变)。鉴于微生物群对宿主的能量供应、免疫功能等至关重要，其多样性和组成的变化可能会对个体产生不利影响。此外，过量的营养物质和污染物可能会影响水生食物网的结构和水陆联系，这是可以评估的，因为这些流出物中氮的独特同位素值被合并到下游的食物网中。我的探索计划的长期目标是了解水生和河岸环境中的污染物直接或间接构成的生态风险。这将通过确定城市污水及其含有的抗菌剂如何影响的短期目标来实现：1)微生物群、组织抗菌剂和各种水生物种的能源；2)通过新出现的水生昆虫向河岸蜘蛛及其微生物群和抗菌剂水平提供水地补贴；以及3)生物膜、落叶分解和大型无脊椎动物微生物群。为了奥贝。1和2，将在污水排放的上游和下游进行食物网采样，以使用稳定的碳和氮同位素比率评估其结构的变化以及大型无脊椎动物、鱼类和蜘蛛对与废水有关的营养物质的依赖。将对生物样本和地表水进行抗生素分析，以评估它们的命运。使用V3-V4区的16S rRNA基因和Illumina测序来表征宿主微生物群，并评估多样性和相对丰度的变化以及废水来源细菌的存在。中胚层实验(Obj.3)混合使用抗菌剂将确定对大型无脊椎动物的微生物群和生长以及生态系统功能(例如分解)的影响。总体而言，该计划将解决这些大量排放到加拿大地表水中的物质如何影响关键的生态系统过程，并促进对抗菌剂命运和影响的了解。

Terrestrial and aquatic ecosystems are tightly linked through the runoff of materials from land to water and the return of these materials via emergent aquatic insects to nearshore (riparian) predators. However, these energetic links can be disrupted by contaminants because they impact the abundance of aquatic insect larvae and subsequent prey available to riparian predators. Our understanding of how contaminants disrupt aquatic-riparian linkages is mainly limited to highly contaminated, industrial sites. Municipal wastewaters are the largest human inputs by volume to Canadian surface waters and contain excess nutrients and a wide range of contaminants including antimicrobials (antibiotics, disinfectants). Our previous work at wastewater-impacted sites revealed that fish, larval insects and riparian spiders have altered microbiomes but it is unclear whether these effects occur at other sites and the mechanisms behind these shifts (i.e., exposures to antimicrobials, shifts in dietary habits). Given that the microbiome is critical for energy provision, immune function, etc., in their hosts, changes in its diversity and composition may lead to adverse effects in individuals. In addition, the excess nutrients and contaminants may impact aquatic food web structure and aquatic-terrestrial linkages, which can be assessed because the unique isotopic values of nitrogen in these effluents are incorporated into the downstream food web. The long-term objective of my Discovery program is to understand the ecological risks posed directly or indirectly by contaminants in aquatic and riparian environments. This will be met through short-term objectives that determine how municipal wastewater effluents and the antimicrobials they contain affect: 1) microbiomes, tissue antimicrobials, and energy sources of diverse aquatic species; 2) water-land subsidies via emergent aquatic insects to riparian spiders and their microbiomes and antimicrobial levels; and 3) biofilms, leaf litter decomposition and macroinvertebrate microbiomes. For Obj. 1 and 2, food web sampling will be done upstream and downstream of effluent discharges to assess changes in its structure and reliance of macroinvertebrates, fish and spiders on wastewater-associated nutrients using stable C and N isotope ratios. Biological samples and surface water will be analyzed for antibiotics to assess their fate. Host microbiomes are characterized using the 16S rRNA gene of the V3-V4 region and Illumina sequencing and assessed for changes in diversity and relative abundance and the presence of wastewater-derived bacteria. Mesocosm experiments (Obj. 3) using mixtures of antimicrobials will determine effects on the microbiomes and growth of macroinvertebrates and ecosystem functions (e.g., decomposition). Overall, the program will address how these substantial discharges into Canadian surface waters are affecting key ecosystem processes and advance knowledge on the fate and effects of antimicrobials.