Planktonic Omnivores and Stable Isotopes: Developing, Validating and Field-testing a Multi-species Functional Response Model

食物网的图表通常用方框来表示捕食者和猎物之间的联系。虽然这些都是关于能量如何沿着食物链传递的有用模型，但真正的食物网要复杂得多。捕食者的饮食通常是多变的，这使得在海洋群落中建立捕食者-猎物联系变得困难。这个项目正在调查沿海食物网的一个关键成员，虾状的mysid， Neomysis americana的猎物转换。猎物转换会影响群落结构和生物体对环境扰动的适应能力，但不容易量化。该项目采用实验室实验和实地抽样相结合的方法，开发出一个食物网模型，预测mysid在环境中的摄食模式。这种现实和预测的食物网模型使用传统的肠道分析和分析技术，跟踪碳和氮，因为它被纳入蚕蛹的身体。此外，mysid的食物偏好正在实验室中通过一系列的饮食可能性来确定。将校正后的肠道分析和化学标记数据与饲养实验相结合纳入模型，然后预测不同环境条件下mysid对混合饲料的摄食。根据现场数据验证了这些预测。更广泛的影响包括对社会的好处，使人们更好地了解沿海食物网的运作方式。对博士生和本科生进行实验和实地研究培训。通过与两所社区学院（南马里兰学院、切萨皮克学院）合作，招募暑期实习生进行研究经验，STEM领域的多样性正在增加。外联活动包括为适合年级的动手实验室实验编写教材，并为初中和高中教师团体提供在课堂上使用这些教材的培训机会。该项目正在开发和实地测试一种可推广的方法，以了解和预测海洋食物网中复杂的捕食者-猎物关系。研究计划包括建立和验证一个杂食性消费者的多物种功能反应（MSFR）模型，mysid Neomysis americana。这些模型预测了在不同猎物浓度下以多种猎物为食的消费者的饮食，并确定了在环境中猎物转换发生的条件。利用肠道内容物、体积稳定同位素（SI）和化合物特异性氨基酸稳定同位素（AA-CSI）分析进行近期和时间整合的饮食跟踪，并在实验室中进行验证，并用于野外重建新松鱼的饮食。本研究旨在验证关于Neomysis的消耗率和猎物偏好的特定假设，以及将SI和AA-CSI整合到MSFR模型中的有效性。实验室实验通过放牧实验确定了Neomysis在不同猎物浓度和环境（温度）条件下对猎物的特异性功能反应曲线。实验结果被纳入一个温度依赖的MSFR模型，该模型适用于5室简化食物网（新生动物、成年桡足动物、nauplii桡足动物、浮游植物、碎屑）。该项目的一个补充要素是实验测定Neomysis和每种猎物类型的体积SI（𝛿13C和𝛿15N）和caa - csi（𝛿15N）平衡率和营养富集因子。利用实验室验证的MSFR方法和现场数据，包括猎物浓度、肠道内容物、猎物和Neomysis SI和AA-CSI数据，对环境中Neomysis的捕食者-猎物动态进行了建模。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Diagrams of food webs are typically drawn as boxes that show linkages between predators and prey. While these are useful models of how energy is transferred along a food chain, real food webs are more complex. Predator diets are often variable making it difficult to establish predator-prey links in marine communities. This project is investigating prey switching in a key member of coastal food webs, the shrimp-like mysid, Neomysis americana. Prey switching affects community structure and an organism’s resilience to environmental perturbation, but it is not easy to quantify. This project is using a combination of laboratory experiments and field sampling to develop a food web model that predicts mysid feeding patterns in the environment. This realistic and predictive food web model uses traditional gut analysis and analytical techniques that follow carbon and nitrogen as it is incorporated into the bodies of the mysids. In addition, mysid food preferences are being determined in the laboratory across a full range of diet possibilities. The calibrated gut analysis and chemical marker data in combination with feeding experiments are incorporated into the model, which then predicts mysid feeding on mixed diets under different environmental conditions. These predictions are validated against field data. Broader impacts include benefits to society for a better understanding of how coastal food webs work. Doctoral students and undergraduate students are being trained in experimental and field research. Increasing diversity in STEM fields is occurring through a partnership with two community colleges (College of Southern Maryland, Chesapeake College) to recruit summer interns for research experiences. Outreach activities include the development of educational materials for grade-appropriate hands-on laboratory experiments and training opportunities for middle and high school teacher groups in the use of these materials in their classrooms. This project is developing and field-testing a generalizable approach to understand and predict complex predator-prey relationships in marine food webs. The research plan involves building and validating a multispecies functional response (MSFR) model for an omnivorous consumer, the mysid Neomysis americana. These models predict diet for consumers that feed on multiple types of prey under differing prey concentrations and identify conditions under which prey switching occurs in the environment. Recent and time-integrated diet tracking with gut contents, bulk stable isotope (SI) and compound-specific amino acid stable isotope (AA-CSI) analysis are validated in the lab and used to reconstruct diet of Neomysis in the field. The proposed research is testing specific hypotheses about Neomysis’ consumption rates and prey preferences and the effectiveness of integrating SI and AA-CSI into MSFR models. Laboratory experiments are determining prey-specific functional response curves by Neomysis under varying prey concentrations and environmental (temperature) conditions using grazing experiments. Experimental results are incorporated into a temperature-dependent MSFR model for a 5-compartment simplified food web (Neomysis, adult copepod, copepod nauplii, phytoplankton, detritus). A complementary element of the project is the experimental determination of bulk SI (𝛿13C and 𝛿15N) and AA-CSI (𝛿15N) equilibration rates and trophic enrichment factors for Neomysis and each prey type. The predator-prey dynamics of Neomysis in the environment are being modeled using the lab-validated MSFR approach and field data, including prey concentrations, gut contents, and prey and Neomysis SI and AA-CSI data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.