Collaborative Research: Revealing the changing trophic niches of large herbivorous fish on modern coral reefs using an interdisciplinary approach

在全球范围内，珊瑚礁正经历着日益严重和迅速的人为干扰。 珊瑚在受到干扰后的恢复，部分取决于食草动物是否能阻止有害藻类繁殖并接管珊瑚礁。这一重要的放牧活动是由各种共存的食草鱼类物种进行的，如鹦嘴鱼和外科鱼，它们共同控制藻类，从而促进珊瑚的恢复。然而，这些鱼类中许多以藻类为食的具体类型在很大程度上是未知的。也不知道这些食草动物的进食行为是恒定的，还是取决于珊瑚礁的状况，如珊瑚的损失。需要对食草动物的饮食进行更详细的研究，以了解这些物种如何共存，以及哪些物种具有独特的作用，并支持现代珊瑚礁的关键生态系统过程。因此，本项目的目的是（a）确定健康珊瑚礁上食草鱼类的摄食行为和饮食-使用传统和尖端技术-以更好地量化这些食草动物之间的资源分配，以及（B）确定每种食草动物的摄食生态是否以及如何随着珊瑚礁条件的变化而变化。为了实现这些目标，研究小组正在关注珊瑚礁草食性鱼类组合的核心成员，并量化它们在受影响最小到严重退化的珊瑚礁上的摄食生态。通过揭示食草动物进食的隐藏方面，以及食草鱼类发挥独特的生态作用，该项目将重塑我们对珊瑚礁生态的理解。更广泛地说，该项目是：（1）交叉培训一批不同的本科生和研究生掌握尖端的科学方法，（2）扩大公共数据库，以促进更广泛的科学界的科学发现，（3）与资源管理人员分享成果，以加强决策过程，以及（4）通过视觉艺术的共同发展，提高公众的科学素养和参与度。在珊瑚礁方面，许多食草鱼类物种共存，通过自上而下控制各种藻类组合，对底栖生物群落产生强烈影响。然而，这些物种之间的资源分配还没有完全了解，草食性鱼类之间存在的生态位重叠的程度仍然未知。目前还不清楚进食活动和饮食（即，每种食草动物的“营养生态位”（trophic niche）随着生态系统环境的变化而变化，如珊瑚的消失。因此，需要进行更广泛、更高分辨率的研究，以了解这些物种如何共存，以及哪些物种在功能上是独特的，并支撑着现代珊瑚礁的关键生态系统过程。研究人员的初步工作表明，肠道内容物的DNA元编码是一种尖端工具，极大地改善了食草鱼类的生态位描述。这种技术阐明了物种之间的精细尺度差异，从而补充了以前的方法，虽然粗糙，量化生态位在更大的空间和时间尺度。该项目的目标是：（a）结合实地观察、传统的饮食追踪方法、特定化合物同位素和肠道内容物的高分辨率DNA元编码，确定健康珊瑚礁上主要食草鱼类的营养生态位，以便更好地量化这种生态系统中营养生态位划分的类型和程度，和（B）确定草食动物生态位是否以及如何随礁体条件的变化而变化。为了实现这些目标，研究人员正在描述珊瑚礁草食性鱼类协会关键成员的营养生态位（通过上述方法），这些研究地点跨越了珊瑚礁条件的梯度。通过量化健康珊瑚礁上的食草动物生态位重叠，物种水平的生态位扩张或收缩作为珊瑚礁衰退的函数，以及由此产生的对总营养生态位宽度的影响，这项研究正在重塑我们对珊瑚礁大型消费者的理解，同时对渔业和珊瑚礁过程的管理产生影响。更广泛地说，这项研究为生态位提供了新的见解-生态位是生态学中的一个基本概念，其主题涵盖从物种共存到生物多样性和生态系统功能之间的关系。该奖项反映了NSF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。

Globally, coral reefs are experiencing human-induced disturbances with growing intensity and pace. Coral recovery after a disturbance is shaped, in part, by whether grazing herbivores prevent harmful algae from blooming and taking over the reef. This important grazing activity is carried out by a diverse group of co-existing herbivorous fish species, such as parrotfishes and surgeonfishes, which collectively control algae and thereby facilitate coral recovery. However, the specific types of algae that many of these fish feed on is largely unknown. It is also unknown if the feeding behaviors of these herbivores are constant, or instead depend on reef condition such as loss of coral. More detailed studies of herbivore diets are needed to understand how these species co-exist, as well as which species have unique roles and underpin key ecosystem processes on modern reefs. The aims of this project are thus to (a) define the feeding behaviors and diets of herbivorous fishes on healthy coral reefs – using both traditional and cutting-edge techniques – to better quantify resource partitioning among these herbivores, and (b) determine whether and how the feeding ecology of each herbivore shifts with changing reef conditions. To accomplish these objectives, the research team is focusing on core members of the coral reef herbivorous fish assemblage and quantifying their feeding ecology on reefs that range from minimally impacted to heavily degraded. By revealing hidden aspects of herbivore feeding, as well as which herbivorous fishes serve unique ecological roles, this project stands to reshape our understanding of coral reef ecology. More broadly, this project is: (1) cross-training a diverse group of undergraduate and graduate students in cutting-edge scientific methods, (2) augmenting public data repositories to foster scientific discovery across the wider scientific community, (3) sharing results with resource managers to enhance decision-making processes, and (4) increasing public science literacy and engagement via the co-development of visual art.On coral reefs, many herbivorous fish species co-exist and exert strong impacts on benthic communities via top-down control of a diverse algal assemblage. However, resource partitioning among these species is not fully understood and the extent of niche overlaps that exist among herbivorous fishes remains unknown. It also remains unknown how the feeding activities and diet (i.e., the “trophic niche”) of each herbivore shifts in response to changing ecosystem context, such as the loss of coral. Broad, higher-resolution studies are thus needed to understand how these species co-exist, as well as which species are functionally unique and underpin key ecosystem processes on modern reefs. The researchers’ preliminary work showed that DNA metabarcoding of gut contents, a cutting-edge tool, vastly improves niche descriptions for herbivorous fishes. This technique illuminates fine-scale differences among species, thus complementing previous approaches that, albeit coarser, quantify the niche at larger scales of space and time. The aims of this project are to (a) define the trophic niches of key herbivorous fishes on healthy reefs – using a combination of field observations, traditional diet tracing methods, compound-specific isotopes, and high-resolution DNA metabarcoding of gut contents – to better quantify the types and degree of trophic niche partitioning in such ecosystems, and (b) determine whether and how herbivore niches shift with changing reef condition. To meet these objectives, the researchers are characterizing the trophic niches of key members of the coral reef herbivorous fish guild (via the aforementioned methods) at numerous study sites that span a gradient of reef condition. By quantifying herbivore niche overlaps on healthy reefs, species-level niche expansions or contractions as a function of reef decline, and resultant impacts to total trophic niche breadth, this research is reshaping our understanding of large consumers on coral reefs, with implications for managing fisheries and reef processes simultaneously. More broadly, this study provides new insights into the niche – a fundamental concept in ecology that underlies topics ranging from species coexistence to the relationship between biodiversity and ecosystem function.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.