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

海洋动物产卵时会排出大量的卵。这些卵大多被从微小的浮游生物到鱼类等动物吃掉。许多食用鸡蛋的动物比产蛋的动物要小，这与通常的食物网相反。食用鸡蛋为动物提供了高度营养的分子，称为必需脂肪酸，这种分子非常集中在鸡蛋中。这些必需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聚集以协调产卵的时间和地点时，它们会释放数万亿个卵。这就产生了一种“鸡蛋恩惠”——一种巨大但短暂的高营养脂肪酸浓度。该项目将实地取样与实验室实验相结合，以评估卵巢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。该项目的新发现正在推进对水生食物网的认识，并有助于改善海洋资源的管理。例如，鱼类的商业捕捞可以通过减少产卵量，从而从生态系统中去除大量脂肪酸，并对这些生物群落产生连锁反应和不可预见的影响。该项目通过大力推进女性博士后的专业培训，促进了女性对科学的参与。该项目通过针对教师和青年的探究式和基于地点的项目，支持K-12 STEM教育。研究结果正在通过参加公开讲座以及为《科学》和《海洋科学与海洋科学》电台节目、播客和网站做出贡献，向当地和全国公众传播。在时间和空间上离散的斑块中释放的超丰度鸡蛋为鸡蛋消费者创造了脉冲营养资源，称为“蛋肉”，这是海洋食物网的潜在重要组成部分。虽然各种海洋动物都吃卵，但卵在通过食物网转移能量中的作用却很少受到关注。目前正在测试三种假设：1)卵细胞提供了一种途径，通过该途径必需脂肪酸（EFAs）与营养流动的主要方向相反地重新分配；2)鸡蛋消费者体内EFAs的储存量在产卵季节增加，产卵季节结束后仍保持较高水平；3)鸡蛋福利有利于鸡蛋消费者的健康状况。这项拟议中的研究利用了德克萨斯州阿兰萨斯港附近的红鼓鱼（Sciaenops ocellatus）产卵聚集所产生的每年一次的卵恩惠。在野外取样和实验室实验的结合中，脂肪酸谱、脂质含量和体积稳定同位素比值被用来确定卵细胞和选择的低营养水平分类群之间的营养联系。在实验室饲养实验中模拟产卵，旨在通过比较食用鱼卵的分类群与不食用鱼卵的分类群，加强对实地抽样收集的数据的解释。一种核酸生物标志物（RNA/DNA比率）正被用于评估目标分类群中因鸡蛋消耗而导致的状况变化。在环境中，脂肪酸反梯度流动在食物网中的重要性和持久性正在通过对鸡蛋的空间和时间范围内外的样本进行比较来衡量。鸡蛋消费对消费者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志物，这些生物标志物可应用于现场样品。拟议的研究考察了鸡蛋消费如何在食物网中重新分配EFAs，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提供更高的分辨率，并推动多示踪技术在营养调查中的应用。此外，如果鸡蛋确实是对特定消费者群体的重要营养补贴，那么随后的研究调查鸡蛋对海洋食物网二次生产的能量贡献是有根据的。通过捕获产卵聚集的鱼类而减少或去除卵资源如何改变食物网中的营养流动的分析可能对基于生态系统的渔业管理产生影响。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。

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.