Counter-gradient Flow of Fatty Acids in Marine Food Webs Through Egg Boons

海洋动物在产卵时会释放极大量的卵。这些卵中的大多数被从微型浮游生物到鱼类的动物吃掉。许多鸡蛋消费者比释放鸡蛋的动物要小，这代表着通常的食物链的逆转。鸡蛋的消费为动物提供了被称为必需脂肪酸的高度营养的分子，这些分子非常集中在鸡蛋中。这些必需的脂肪酸对动物的健康和整个生态系统的健康都很重要。当海洋鱼类形成产卵群体以协调产卵的时间和位置时，它们会释放数万亿个卵。这就产生了一种“蛋的恩惠”--一种大量但暂时的高营养脂肪酸。该项目将现场采样与实验室实验相结合，以评估卵子中的脂肪酸如何影响食物网。该项目正在确定食用鸡蛋是否有利于鸡蛋消费者的状况。该项目的新发现促进了对水生食物网的了解，并有助于改善海洋资源的管理。例如，商业捕捞鱼类可以减少卵的惠益，并导致对这些生物群落的级联和不可预见的影响，从而从生态系统中移除数以吨计的脂肪酸。该项目通过大力推进对一名女性博士后的专业培训，促进妇女参与科学。该项目通过面向教师和青年的基于探究和基于地点的方案来支持K-12 STEM教育。通过参加公众讲座和向科学和海洋TM广播节目、播客和网站投稿，研究结果正在当地和全国范围内向公众传达。在时间和空间上离散的区域中释放的大量鸡蛋为鸡蛋消费者创造了脉冲营养资源，称为“鸡蛋恩惠”，这可能是海洋食物网的重要组成部分。虽然各种海洋动物已经被证明吃蛋，但卵的恩惠在通过食物网进行能量转移中的作用几乎没有受到关注。目前正在测试三个假设：1)产卵提供了一条途径，使必需脂肪酸(EFA)与营养流动的主要方向背道而驰；2)鸡蛋消费者体内必需脂肪酸的储存量在产卵期间增加，并在产卵季节后保持较高水平；以及3)产卵有利于鸡蛋消费者的状况。这项拟议的研究利用了德克萨斯州阿兰萨斯港附近的赤鼓鱼产卵所产生的年度产卵恩惠。在野外采样和实验室实验相结合的情况下，脂肪酸分布、脂肪含量和整体稳定同位素比率是用来确定卵子和一些营养水平较低的分类群之间的营养联系的指标。在实验室饲养实验中模拟了卵子的有利条件，这些实验旨在通过比较消耗鱼卵的分类群和不消耗鱼卵的分类群来增强对田间采样收集的数据的解释。一种核酸生物标记物(RNA/DNA比率)正被用来评估可归因于目标类群中鸡蛋消费的条件变化。在环境中，食物网中脂肪酸逆梯度流动的重要性和持久性是通过比较在卵子恩惠的空间和时间范围内外采集的样本来衡量的。消费者食用鸡蛋的影响正在通过对照实验进行量化，以确定消费者组织中鸡蛋消费的饮食生物标记物，这些标记物可以应用于现场样本。这项拟议的研究考察了鸡蛋消费如何重新分配食物网中的EFA，并为考虑传统元素限制模型无法解释的潜在控制和营养瓶颈提供了背景。脂肪酸和稳定同位素方法的结合有望为通过食物网追踪有机物质提供更高的分辨率，并推动多种示踪剂技术在营养调查中的应用。此外，如果蛋的恩惠确实是对选定的消费者群体的一种重要的营养补贴，那么后续调查蛋恩惠对海洋食物网中二次生产的能量贡献的研究是有必要的。一项关于如何通过捕捞产卵群中的鱼类减少或移除卵资源改变食物网中营养物质流动的分析可能会对基于生态系统的渔业管理产生影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Marine animals release extremely large numbers of eggs when they spawn. Most of these eggs are eaten by animals ranging from microscopic plankton to fish. Many egg consumers are smaller than the animals that released the eggs, representing a reversal of the usual food web. The consumption of eggs provides animals with highly nutritious molecules called essential fatty acids which are very concentrated in eggs. These essential fatty acids are important for the health of animals and the health of the whole ecosystem. When marine fishes form spawning aggregations to coordinate the timing and location of spawning, they release trillions of eggs. This results in an “egg boon” – an immense but temporary concentration of highly nutritious fatty acids. This project combines field-based sampling with laboratory experiments to assess how fatty acids in the egg boons affect food webs. The project is determining whether consumption of eggs is beneficial to the condition of the egg consumers. New findings from this project are advancing the understanding of aquatic food webs and contributing to improved management of marine resources. For example, commercial harvest of fish can remove tons of fatty acids from an ecosystem by reducing egg boons and leading to cascading and unforeseen effects on those biological communities. The project is fostering the participation of women in science by substantially advancing the professional training of a female postdoctoral fellow. The project is supporting K-12 STEM education through inquiry-based and place-based programs for teachers and youth. Findings are being communicated to the public locally and nationally through participation in public lectures and contributions to the Science and the SeaTM radio program, podcast, and website.Super-abundances of eggs released in temporally and spatially discrete patches create pulsed nutritional resources for egg consumers, called “egg boons,” which are potentially important components of marine food webs. While various marine animals have been shown to consume eggs, the role of egg boons in energy transfer through food webs has received little attention. Three hypotheses are being tested: 1) egg boons provide a pathway through which essential fatty acids (EFAs) are redistributed counter to the main direction of trophic flow; 2) stores of EFAs in egg consumers increase during egg boons and remain elevated after the spawning season; and 3) egg boons are beneficial to the condition of egg consumers. The proposed research takes advantage of an annual egg boon produced by a spawning aggregation of the marine fish, red drum (Sciaenops ocellatus) near Port Aransas, Texas. In a combination of field sampling and laboratory experiments, fatty acid profiles, lipid content, and bulk stable isotope ratios are measures used to define trophic links between the egg boon and a selection of lower-trophic-level taxa. Egg boons are simulated in laboratory feeding experiments that are designed to enhance interpretation of data collected from field based sampling by comparing taxa that consume fish eggs with those that do not. A nucleic acid biomarker (RNA/DNA ratios) is being used to assess changes in condition that can be attributed to egg consumption in target taxa. In the environment, the importance and persistence of counter-gradient flow of fatty acids in the food web is being gauged through comparisons of samples taken inside and outside the spatial and temporal extent of the egg boon. The effects of egg consumption on consumers is being quantified in controlled experiments to identify dietary biomarkers of egg consumption in consumer tissues that can be applied to field samples. The proposed research examines how egg consumption redistributes EFAs within food webs and provides a context for considering potential controls and trophic bottlenecks that cannot be explained from the traditional element-limitation models. The integration of fatty acid and stable isotope approaches is expected to provide greater resolution for tracking organic matter through food webs and to advance the application of multi-tracer techniques in trophic investigations. Further, if egg boons are indeed an important nutritional subsidy to select groups of consumers, then subsequent studies investigating the energetic contribution of egg boons to secondary production in marine food webs are warranted. An analysis of how reduction or removal of egg resources through the harvest of fishes in spawning aggregations changes nutrient flow in food webs could have implications for ecosystem-based fisheries management.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.