Trophic transfer of fatty acids in marine food webs

我小组的研究兴趣集中在利用脂质和脂肪酸（FA）作为工具来研究海洋环境中的碳流和食物网动态。FA非常适合此类研究，因为许多膳食FA仅在结构上进行了轻微修改就被纳入消费者体内，这使得FA作为其来源的指示器或生物标志物非常有用。在这里，我们建议通过研究FA的营养转移效率，继续研究低营养水平FA从猎物到捕食者的转移。这是对沉积在捕食者组织中的FA的量与饮食中可获得的FA的量的测量，我们相信这些会随着捕食者、FA的浓度和FA的结构而变化。一些FA，如长链omega-3 FA，是所有生物生长和生存所必需的营养物质。在海洋食物网中，这些必需脂肪酸大部分仅由浮游植物合成；因此，了解这些营养物质从饮食中转移到消费者身上的效率就显得尤为重要。营养转移效率也可以纳入我们正在开发的方法，通过比较捕食者和猎物的FA模式或概况来估计消费者的饮食。它们在这个应用中很重要，因为它们使我们能够补偿由分解代谢和捕食者的其他过程引起的饮食FA谱的变化。******我们提出了三个具体目标：1)以类calanoid桡足类（Calanus finmarchicus）、大西洋鳕鱼（Pollachius virens）和大西洋鲑鱼（Salmo salar）为模型种，研究FA结构、饲料浓度、组织和种类对FA转移效率的影响；2)通过对大西洋鲑鱼饲喂不同饵料混合物的研究，检验统计模型中营养转移效率对饵料估计准确性的影响；3)将FA的营养转移效率纳入我们的统计模型，并应用巴芬岛和白令海的现有数据集来估计大西洋和北极鳕鱼的饮食（Gadus morhua和Boreogadus saida）。这些生态系统最容易受到气候变化的影响，是检测碳循环随时间变化的良好候选者。在更大的范围内，我们将利用营养转移效率，结合从浮游植物遥感得到的FA生产水平，来估计海洋的基本FA预算。从根本上说，我们相信将这些必需的营养物质纳入机制模型将提高生态系统特性和变化预测的准确性，最终导致更好的决策管理和保护我们的海洋资源。正如我们在这里提出的那样，测量必需FA的营养转移效率是将其纳入此类模型的必要的第一步。

The research interests of my group are focused on the use of lipids and fatty acids (FA) as tools to study carbon flow and food web dynamics in the marine environment. FA are well suited to such studies because many dietary FA are incorporated into consumers with only minor modifications to structure, making FA useful as indicators or biomarkers of their source. Here, we propose to continue our ongoing work investigating the transfer of FA from prey to predators at low trophic levels by examining trophic transfer efficiencies of FA. This is a measure of the amount of FA deposited in a predator's tissue relative to the amount available in its diet, and we believe these will vary with consumer, concentration of FA and FA structure. Several FA, such as long chain omega-3 FA, are essential nutrients, required for growth and survival by all organisms. In the marine food web, the majority of these essential FA are synthesized only by phytoplankton; thus, it is particularly important to understand the efficiency with which such nutrients are transferred from diet to consumer. Trophic transfer efficiencies can also be incorporated into methods we are developing to estimate consumer diets by comparison of FA patterns, or profiles, in predator and prey. They are important in that application because they allow us to compensate for changes made to the diet FA profile by catabolism and other processes in the predator. ******We are proposing three specific objectives: 1) examine the influence of FA structure, dietary concentration, tissue and species on transfer efficiency of FA, using calanoid copepods (Calanus finmarchicus), Atlantic pollock (Pollachius virens) and Atlantic salmon (Salmo salar) as model species; 2) test the influence of trophic transfer efficiencies in our statistical models on the accuracy of diet estimates by conducting feeding studies with Atlantic salmon fed different diet mixtures; and 3) incorporate trophic transfer efficiencies of FA into our statistical models and apply to existing datasets from Baffin Island and the Bering Sea to estimate diets of Atlantic and Arctic cod (Gadus morhua and Boreogadus saida). These are ecosystems that are most susceptible to the effects of climate change and make good candidates to detect variation in carbon cycling over time. At larger scope, we will use trophic transfer efficiencies, combined with production levels of FA derived from remote sensing of phytoplankton, to estimate the essential FA budget of the ocean. Fundamentally, we believe that incorporation of these essential nutrients into mechanistic models will improve the accuracy of predictions of ecosystem properties and shifts, ultimately leading to better decision-making regarding management and conservation of our marine resources. Measurement of trophic transfer efficiencies of essential FA, as we have proposed here, is a necessary first step for their inclusion in such models.