Preferential consumption of benthic cyanobacterial mats by Caribbean parrotfishes

Abstract

Cyanobacteria are ubiquitous on coral reefs and perform important ecosystem functions. Benthic cyanobacterial mats (BCMs) have become increasingly abundant on degraded reefs. While epilithic and endolithic benthic cyanobacteria are the primary trophic resource for many parrotfishes, mat-forming benthic cyanobacteria are generally considered unpalatable to reef fishes. Regardless, recent studies have documented substantial grazing of BCMs by reef fishes, including parrotfishes. Here, we observed foraging in five Caribbean parrotfishes on the fringing coral reefs of Bonaire, Netherlands, to investigate BCM consumption relative to other benthic substrates. All species overwhelmingly targeted reef substrates composed of algal turfs and crustose coralline algae, which are typically associated with epilithic and endolithic microalgal and cyanobacterial communities. Additionally, three species preferentially consumed BCMs. As such, our work is consistent with and provides direct evidence supporting the recently proposed trophic role for parrotfishes as microphages. Contrasting observations of reef fishes avoiding substrates dominated by BCMs on other reefs suggests variation in the palatability of BCMs to grazing reef fishes, or species-specific differences in preference for these potentially nutritional trophic resources.

Territoriality drives patterns of fixed space use in Caribbean parrotfishes

“…The abundance and biomass of different fish groups, including parrotfishes, are also much higher on Bonaire's coral reefs compared to more heavily fished reefs in the Eastern Caribbean (Hawkins & Roberts, 2003 , 2004 ; Steneck et al, 2019 ). The benthic composition across our study sites was similar, with relatively high coral cover (~20%) and low macroalgal cover (<3%; Manning & McCoy, 2022 ). Additionally, our five focal parrotfish species comprised more than 96% of the parrotfish biomass at our study sites (Manning & McCoy, 2022 ).…”

“…The benthic composition across our study sites was similar, with relatively high coral cover (~20%) and low macroalgal cover (<3%; Manning & McCoy, 2022 ). Additionally, our five focal parrotfish species comprised more than 96% of the parrotfish biomass at our study sites (Manning & McCoy, 2022 ).…”

“…We conducted our research on Scarus iseri, Scarus taeniopterus, Scarus vetula, Sparisoma aurofrenatum, and Sparisoma viride at The abundance and biomass of different fish groups, including parrotfishes, are also much higher on Bonaire's coral reefs compared to more heavily fished reefs in the Eastern Caribbean (Hawkins & Roberts, 2003Steneck et al, 2019). The benthic composition across our study sites was similar, with relatively high coral cover (~20%) and low macroalgal cover (<3%; Manning & McCoy, 2022).…”

“…Parrotfishes are microphages that consume epilithic and endolithic microautotrophs, primarily cyanobacteria (Cissell et al, 2019 ; Clements et al, 2016 ; Manning & McCoy, 2022 ; Nicholson & Clements, 2020 , 2021 ), but some species (i.e., Sparisoma spp.) also consume fleshy macroalgae (Adam et al, 2015 ; Dell et al, 2020 ; Manning & McCoy, 2022 ).…”

“…Parrotfishes are microphages that consume epilithic and endolithic microautotrophs, primarily cyanobacteria (Cissell et al, 2019 ; Clements et al, 2016 ; Manning & McCoy, 2022 ; Nicholson & Clements, 2020 , 2021 ), but some species (i.e., Sparisoma spp.) also consume fleshy macroalgae (Adam et al, 2015 ; Dell et al, 2020 ; Manning & McCoy, 2022 ). Parrotfish grazing is considered important for maintaining cropped, early successional substrates that are conducive to coral larval settlement and recruitment, thereby enhancing reef recovery and resilience (Bonaldo et al, 2014 ; Mumby et al, 2007 ).…”