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，珊瑚礁正在经历人类造成的干扰，强度和速度都在不断增加。珊瑚在受到干扰后的恢复，在一定程度上取决于食草动物是否能阻止有害藻类的繁殖并占领珊瑚礁。这一重要的放牧活动是由一组共存的草食性鱼类进行的，如鹦鹉鱼和刺尾鱼，它们共同控制藻类，从而促进珊瑚恢复。然而，这些鱼中的许多以哪种藻类为食在很大程度上是未知的。这些食草动物的觅食行为是恒定的，还是取决于珊瑚礁条件，如珊瑚的丧失，也是未知的。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，并为现代珊瑚礁上的关键生态系统过程奠定基础。因此，该项目的目的是：(A)确定食草性鱼类在健康的珊瑚礁上的摄食行为和食物--使用传统和尖端技术--以更好地量化这些草食动物之间的资源分配，以及(B)确定每种草食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，研究小组将重点放在珊瑚礁食草性鱼类群体的核心成员上，并量化它们在珊瑚礁上的摄食生态，范围从受影响最小到严重退化。通过揭示食草动物觅食的隐藏方面，以及哪些草食性鱼类发挥着独特的生态作用，这个项目将重塑我们对珊瑚礁生态的理解。更广泛地说，这个项目是：(1)对不同的本科生和研究生群体进行尖端科学方法的交叉培训；(2)扩大公共数据库，以促进更广泛的科学界的科学发现；(3)与资源管理者分享结果，以加强决策过程；(4)通过共同开发视觉艺术，提高公众的科学素养和参与度。在珊瑚礁上，许多草食性鱼类物种共存，并通过自上而下控制不同的藻类组合对底栖群落产生强烈影响。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。每个食草动物的摄食活动和饮食(即“营养生态位”)如何随着生态系统环境的变化而变化，例如珊瑚的丧失，也是未知的。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，并为现代珊瑚礁上的关键生态系统过程奠定基础。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，极大地改善了草食性鱼类的生态位描述。这项技术揭示了物种之间的细微差异，从而补充了以前的方法，尽管这些方法比较粗略，但在更大的空间和时间尺度上量化了生态位。该项目的目的是：(A)结合实地观察、传统食物追踪方法、化合物特定同位素和肠道内容物高分辨率DNA元生物编码，确定健康珊瑚礁上主要食草性鱼类的营养生态位，以更好地量化这类生态系统中营养生态位分配的类型和程度，以及(B)确定食草动物生态位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，研究人员正在研究珊瑚礁食草性鱼类协会主要成员的营养生态位(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、物种水平生态位的扩张或收缩作为珊瑚礁衰退的函数，以及由此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消费者的理解，对同时管理渔业和珊瑚礁过程产生影响。更广泛地说，这项研究为生态位提供了新的见解-这是生态学中的一个基本概念，涉及从物种共存到生物多样性和生态系统功能之间的关系等主题。该奖项反映了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。

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.