Investigating Mixotrophic Algal Contribution to Copepod Diet and Reproduction

研究混合营养藻类对桡足类饮食和繁殖的贡献

• 批准号: 2201365
• 负责人: Ann Tarrant
• 金额: $ 89.51万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2201365&HistoricalAwards=false
• 关键词: Investigating; Mixotrophic; Algal; Contribution; Copepod

A primary topic of interest within biological oceanography is the role of algal productivity in the global carbon cycle. Over the past few decades, the traditional planktonic food web has been undergoing revision with a better understanding of the significance of microbes. Many of the single-celled organisms at the base of marine food webs are mixotrophic, meaning they are capable of both photosynthesis and ingestion of prey within a single cell. Though recognized for over a century, this trophic strategy has gone from being considered a physiologically unfavorable oddity to a diverse and widespread adaptation. Despite the prevalence of mixotrophy in marine systems, very few experimental studies have assessed how mixotrophic organisms interact with and impact the zooplankton that ingest them. This project is helping define mixotrophic contributions to higher trophic levels in marine pelagic food webs. The investigators are testing whether mixotrophs can support copepod reproduction under conditions when algal food is of poor quality and assessing mixotrophic contributions to the diet of two abundant copepod species within the Gulf of Maine. Additionally, recent modeling efforts suggest that when incorporated into biogeochemical and food web models, mixotrophy has significant implications for primary productivity and carbon cycling. To facilitate broader consideration of mixotrophy in models, the investigators are participating in a mixotrophy working group and hosting a session at the Ocean Sciences Meeting. In addition, the investigators are hosting undergraduate summer students who are gaining experience with laboratory work, including through the Woods Hole Partnership Education Program (PEP) and guest students recruited from local communities to increase diversity in marine science. The investigators are also partnering with local high school teachers to have students use their art training to contribute to a graphic novel that illustrates the Gulf of Maine food web and potential effects of climate change.Effective transfer of carbon and nutrients to higher trophic levels in the marine environment relies on the planktonic food web. Inclusion of mixotrophy in food web models suggests that it may stabilize fluctuations in the nutritional quality of microbial prey and could be an important pathway for transfer of nutrients into zooplankton However, empirical data have been lacking to parameterize these models adequately. To date, empirical studies of mixotrophs as prey have suffered from testing a limited number of taxa, confounding effects of prey abundance, and a failure to characterize their mixotrophic status. Similarly, few field studies have assessed the diet of mesozooplankton in a way that would allow mixotrophs to be identified, and as in lab studies, the mixotrophic status of prey sources has not been identified. Thus, it has been impossible to provide realistic parameters describing the contribution of mixotrophs to nutrient transfer through the food web, and the issue of whether mixotrophically-growing algae can mitigate the effects of poor-quality photosynthetic food remains largely unresolved. This study is characterizing the role of mixotrophic algae in mitigating deficiencies in phytoplankton food quality with respect to copepod reproduction. Feeding experiments are being conducted that include consistent quantities of actively-mixotrophic prey. Analysis of the nutrient and fatty acid composition of different mixotrophic algae is illustrating a continuum of prey quality that could help inform zooplankton model predictions. The project is exploring effects of nutritional plasticity by contrasting the nutritional quality of heterotrophs reared on bacteria versus phytoplankton. The work is contributing to knowledge of the ability of mixotrophs to supplement or support copepod reproduction, which can coincide with poor phototrophic food availability. Finally, the presence and identity of active mixotrophs in the field is being assessed using labeled-prey ingestion experiments, followed by amplicon sequencing of labeled grazer DNA and environmental water samples. The work is identifying the in situ grazing preferences of copepods in the Gulf of Maine over a growing season, whether it varies with life stage, and how it impacts egg production.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.

生物海洋学中的一个主要主题是藻类生产力在全球碳循环中的作用。在过去的几十年里，随着对微生物重要性的更好理解，传统的浮游生物食物网一直在进行修订。海洋食物网底部的许多单细胞生物是混合营养的，这意味着它们能够在单个细胞内进行光合作用和摄取猎物。虽然认识到超过一个世纪，这种营养策略已经从被认为是一个生理上不利的奇怪的多样性和广泛的适应。尽管在海洋系统中混合营养的流行，很少有实验研究评估混合营养生物如何相互作用，并影响浮游动物摄取它们。该项目正在帮助确定混合营养对海洋中上层食物网中较高营养级的贡献。研究人员正在测试混合营养体是否可以支持桡足类繁殖的条件下，藻类食物质量差，并评估混合营养的贡献饮食的两个丰富的桡足类物种在缅因州的海湾。此外，最近的建模工作表明，当纳入生态地球化学和食物网模型，混合营养初级生产力和碳循环有显着的影响。为了促进更广泛地考虑模型中的混合营养，研究人员正在参加一个混合营养工作组，并在海洋科学会议上主持一次会议。此外，调查人员正在接待正在获得实验室工作经验的本科暑期学生，包括通过伍兹霍尔合作伙伴教育计划（PEP）和从当地社区招募的客座学生，以增加海洋科学的多样性。研究人员还与当地高中教师合作，让学生利用他们的艺术训练来创作一部图画小说，说明缅因州湾的食物网和气候变化的潜在影响。碳和营养物质向海洋环境中更高营养级的有效转移依赖于浮游食物网。混合营养食物网模型的列入表明，它可以稳定微生物猎物的营养质量的波动，并可能是一个重要的途径，营养物质转移到浮游动物，但是，经验数据一直缺乏充分的参数化这些模型。迄今为止，混合营养体作为猎物的实证研究遭受测试数量有限的类群，猎物丰度的混杂效应，以及未能表征其混合营养状态。同样，很少有实地研究评估的饮食的中型浮游动物的方式，将允许mixotrophs被确定，并在实验室研究中，混合营养状态的猎物来源尚未确定。因此，它一直是不可能的，以提供现实的参数描述的营养物质通过食物网的营养转移的贡献，以及混合营养生长的藻类是否可以减轻质量差的光合食物的影响的问题仍然在很大程度上没有得到解决。这项研究的特点是兼养藻类在减轻浮游植物食物质量方面的不足桡足类繁殖的作用。饲养实验正在进行，包括一致数量的积极兼养猎物。不同的兼养藻类的营养和脂肪酸组成的分析说明了一个连续的猎物质量，可以帮助告知浮游动物模型的预测。该项目通过比较细菌和浮游植物饲养的异养生物的营养质量来探索营养可塑性的影响。这项工作有助于了解混合营养体补充或支持桡足类繁殖的能力，这可能与光养食物供应不足相吻合。最后，在该领域的活性mixotrophs的存在和身份正在评估使用标记的猎物摄入实验，然后通过标记的食草动物DNA和环境水样的扩增子测序。这项工作是确定在生长季节的桡足类在缅因州海湾的原位放牧偏好，它是否随生命阶段而变化，以及它如何影响产卵。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。