Clarifying functional roles: algal removal by the surgeonfishes Ctenochaetus striatus and Acanthurus nigrofuscus

Tebbett, Sterling B.; Goatley, Christopher H. R.; Bellwood, David R.

doi:10.1007/s00338-017-1571-z

Cited by 69 publications

(75 citation statements)

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“…Other species significant in delineating differences in assemblage structure are highlighted here because they may serve as useful indicators for reef type and health. These included the detritivorous Ctenochaetus striatus, which was most the abundant species throughout the region and is known to prefer low sediment levels on reefs (Tebbett, Goatley, & Bellwood, ). We recorded exceptionally high densities at some sites such as Shomoni, Grande Comore (1,452 ± 832 SD indiv./ha), and Tekamaji, Mozambique (1,224 ± 872 SD indiv./ha), suggesting these sites may represent reefs with crystalline waters.…”

Section: Discussionmentioning

confidence: 99%

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Samoilys

Halford

Osuka

2019

Ecology and Evolution

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Aim Understanding the drivers of the structure of coral reef fish assemblages is vital for their future conservation. Quantifying the separate roles of natural drivers from the increasing influence of anthropogenic factors, such as fishing and climate change, is a key component of this understanding. It follows that the intrinsic role of historical biogeographical and geomorphological factors must be accounted for when trying to understand the effects of contemporary disturbances such as fishing. Location Comoros, Madagascar, Mozambique and Tanzania, Western Indian Ocean (WIO). Methods We modeled patterns in the density and biomass of an assemblage of reef‐associated fish species from 11 families, and their association with 16 biophysical variables. Results Canonical analysis of principal coordinates revealed strong country affiliations of reef fish assemblages and distance‐based linear modeling confirmed geographic location and reef geomorphology were the most significant correlates, explaining 32% of the observed variation in fish assemblage structure. Another 6%–8% of variation was explained by productivity gradients (chl_ a ), and reef exposure or slope. Where spatial effects were not significant between mainland continental locations, fishing effects became evident explaining 6% of the variation in data. No correlation with live coral was detected. Only 37 species, predominantly lower trophic level taxa, were significant in explaining differences in assemblages between sites. Main Conclusions Spatial and geomorphological histories remain a major influence on the structure of reef fish assemblages in the WIO. Reef geomorphology was closely linked to standing biomass, with “ocean‐exposed” fringing reefs supporting high average biomass of ~1,000 kg/ha, while “lagoon‐exposed fringing” reefs and “inner seas patch complex” reefs yielded substantially less at ~500kg/ha. Further, the results indicate the influence of benthic communities on fish assemblages is scale dependent. Such insights will be pivotal for managers seeking to balance long‐term sustainability of artisanal reef fisheries with conservation of coral reef systems.

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Section: Discussionmentioning

confidence: 99%

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Samoilys

Halford

Osuka

2019

Ecology and Evolution

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“…Specialist species that eat particulates (e.g., Ctenochaetus striatus ) and those that eat the whole EAM (i.e., parrotfishes) appear to be most deterred by sediments (Bellwood & Fulton, ; Gordon, Goatley, & Bellwood, ; Tebbett, Goatley, & Bellwood, ; Tebbett et al., ). By contrast, grazing Acanthurus eat algae above the sediment layer and are thus not as constrained by sediments (Tebbett et al., , ). The answer to the sediment paradox, therefore, may be that for fish species that are able to avoid ingesting sediments, the reef flat is a highly advantageous and productive feeding location.…”

Section: Discussionmentioning

confidence: 99%

“…The species are identified as predominantly EAM feeders (following Brandl et al., ; Choat, Clements, & Robbins, ; Green & Bellwood, ; Hoey, Brandl, & Bellwood, ; Kelly et al., ; Russ, ). We excluded specialist detritivores (Tebbett, Goatley, & Bellwood, ), acanthurids which feed over mixed or soft substrata, that is, “sediment suckers” (sensu Russ, ), excavating parrotfishes that may target corals (Bellwood, Hoey, & Choat, ) or endolithic material (Clements, German, Piché, Tribollet, & Choat, ), macroalgal browsers (Streit, Hoey, & Bellwood, ), and planktivores, as these species are not necessarily feeding on EAM productivity per se. The feeding locations of macroalgal browsers are hard to determine and may include interreefal habitats (Lim, Wilson, Holmes, Noble, & Fulton, ; Marshell, Mills, Rhodes, & McIlwain, ; Pillans et al., ).…”

Section: Methodsmentioning

confidence: 99%

The role of the reef flat in coral reef trophodynamics: Past, present, and future

Bellwood

Tebbett

Bellwood

et al. 2018

Ecology and Evolution

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The reef flat is one of the largest and most distinctive habitats on coral reefs, yet its role in reef trophodynamics is poorly understood. Evolutionary evidence suggests that reef flat colonization by grazing fishes was a major innovation that permitted the exploitation of new space and trophic resources. However, the reef flat is hydrodynamically challenging, subject to high predation risks and covered with sediments that inhibit feeding by grazers. To explore these opposing influences, we examine the Great Barrier Reef (GBR) as a model system. We focus on grazing herbivores that directly access algal primary productivity in the epilithic algal matrix (EAM). By assessing abundance, biomass, and potential fish productivity, we explore the potential of the reef flat to support key ecosystem processes and its ability to maintain fisheries yields. On the GBR, the reef flat is, by far, the most important habitat for turf‐grazing fishes, supporting an estimated 79% of individuals and 58% of the total biomass of grazing surgeonfishes, parrotfishes, and rabbitfishes. Approximately 59% of all (reef‐wide) turf algal productivity is removed by reef flat grazers. The flat also supports approximately 75% of all grazer biomass growth. Our results highlight the evolutionary and ecological benefits of occupying shallow‐water habitats (permitting a ninefold population increase). The acquisition of key locomotor and feeding traits has enabled fishes to access the trophic benefits of the reef flat, outweighing the costs imposed by water movement, predation, and sediments. Benthic assemblages on reefs in the future may increasingly resemble those seen on reef flats today, with low coral cover, limited topographic complexity, and extensive EAM. Reef flat grazing fishes may therefore play an increasingly important role in key ecosystem processes and in sustaining future fisheries yields.

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“…Furthermore, recent evaluations of these groups have discovered serious shortcomings in our ability to capture the complexity of the ecological processes under examination (e.g. Adam et al, ; Brandl & Bellwood, ; Kelly et al, ; Tebbett, Goatley, & Bellwood, ). It is clear that the basic FGs have significant limitations.…”

Section: Functional Traits and Ecosystem Functions In A Changing Worldmentioning

confidence: 99%

The meaning of the term ‘function’ in ecology: A coral reef perspective

et al. 2019

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The inherent complexity of high‐diversity systems can make them particularly difficult to understand. The relatively recent introduction of functional approaches, which seek to infer ecosystem functioning based on species’ ecological traits, has revolutionized our understanding of these high‐diversity systems. Today, the functional structure of an assemblage is widely regarded as a key indicator of the status or resilience of an ecosystem. Indeed, functional evaluations have become a mainstay of monitoring and management approaches. But is the heavy focus on broad metrics of functional structure grounded in empirical research? On tropical coral reefs, the ocean’s most diverse ecosystems, remarkably few studies directly quantify ecosystem functions and the term ‘function’ is widely used but rarely defined, especially when applied to reef fishes. Our review suggests that most ‘functional’ studies do not study function as it relates to ecological processes. Rather, they look at easy‐to‐measure traits or proxies that are thought to have functional significance. However, these links are rarely tested empirically, severely limiting our capacity to extend results from community structure to the dynamic processes operating within high‐diversity ecosystems such as coral reefs. With rapid changes in global ecosystems, and in their capacity to deliver ecosystem services, there is an urgent need to understand and empirically measure the role of organisms in various ecosystem functions. We suggest that if we are to understand and manage transitioning coral reefs in the Anthropocene, a broad definition of the word ‘function’ is needed along with a focus on ecological processes and the empirical quantification of functional roles. In this review, we propose a universal operational definition of the term ‘function’ that works from a cellular to a global level. Specifically, it is the movement or storage of energy or material. Within this broad definitional framework, all functions are part of a continuum that is tied together by the process‐based unifier of material fluxes. With this universal definition at hand, we then present a path forward that will allow us to fully harness the power of functional approaches in understanding and managing high‐diversity systems such as coral reefs. A plain language summary is available for this article.

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Clarifying functional roles: algal removal by the surgeonfishes Ctenochaetus striatus and Acanthurus nigrofuscus

Cited by 69 publications

References 68 publications

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

The role of the reef flat in coral reef trophodynamics: Past, present, and future

The meaning of the term ‘function’ in ecology: A coral reef perspective

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