Resolving resource partitioning in parrotfishes (Scarini) using microhistology of feeding substrata
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Resolving resource partitioning in parrotfishes (Scarini) using microhistology of feeding substrata Georgina M. Nicholson1
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Kendall D. Clements1
Received: 24 February 2020 / Accepted: 26 May 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Parrotfishes (Scarini) are considered key agents in coral reef health and recovery, but the drivers of parrotfish–coral dynamics remain contentious. The prevailing view of parrotfishes as ecosystem engineers is based on the perceived removal of algal turf, macroalgae and sediment, but these are effects of feeding, not causes. The recent proposal that most parrotfishes are ‘microphages’ that target microscopic photoautotrophs (particularly cyanobacteria) identifies the need to resolve dietary targets at a microscopic scale. Here, we investigate parrotfish dietary targets by posing the following two questions: (1) are microscopic photoautotrophs the most consistent and dominant elements of the prey community, and (2) do the prey community and substratum taphonomy vary between parrotfish species? In order to identify and quantify dietary targets, five parrotfish species were followed until focused feeding was observed at Lizard Island on the Great Barrier Reef, Australia. Feeding sites were photographed in situ and extracted as substratum bite cores. Cores were analysed microscopically to identify and quantify all epilithic photoautotrophs. Endolithic photoautotrophs accessible to excavating parrotfish were also investigated by vacuumembedding cores with epoxy resin followed by decalcification to expose endolith microborings. The dominant functional groups of epilithic biota on the cores were tufted cyanobacteria, turfing algae and crustose coralline algae
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00338-020-01964-0) contains supplementary material, which is available to authorized users. & Georgina M. Nicholson [email protected] 1
School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
(CCA). The only consistent feature across all cores was the high density of filamentous cyanobacteria, supporting the view that these parrotfishes target microphotoautotrophs. Macroalgae was absent or a minor component on cores, supporting the hypothesis that parrotfishes avoid larger algae. The microchlorophyte Ostreobium was the dominant photoautotrophic euendolith (true borer) in the cores of the excavating parrotfish Chlorurus microrhinos. Significant differences in CCA coverage, turf height and substrate taphonomy were found among the five parrotfish species, suggesting that interspecific resource partitioning is based on successional stage of feeding substrata. Keywords Parrotfish Coral reef Ostreobium Cyanobacteria Herbivory Algae
Introduction Herbivorous fishes have long been considered integral to the functioning and maintenance of coral reef systems (Odum and Odum 1955; Ogden and Lobel 1978; Steneck 1983, 1995; Choat 1991). Herbivory by par
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