Inter-habitat variability in parrotfish bioerosion rates and grazing pressure on an indian ocean reef platform (article)

This is the final version. Available on open access from MDPI via the DOI in this recordData Access: The research data supporting this publication are openly available in ORE at https://doi.org/10.24378/exe.2683Parrotfish perform a variety of vital ecological functions on coral reefs, but we have little understanding of how these vary spatially as a result of inter-habitat variability in species assemblages. Here, we examine how two key ecological functions that result from parrotfish feeding, bioerosion and substrate grazing, vary between habitats over a reef scale in the central Maldives. Eight distinct habitats were delineated in early 2015, prior to the 2016 bleaching event, each supporting a unique parrotfish assemblage. Bioerosion rates varied from 0 to 0.84 ± 0.12 kg m−2 yr−1 but were highest in the coral rubble-and Pocillopora spp.-dominated habitat. Grazing pressure also varied markedly between habitats but followed a different inter-habitat pattern from that of bioerosion, with different contributing species. Total parrotfish grazing pressure ranged from 0 to ~264 ± 16% available substrate grazed yr-1 in the branching Acropora spp.-dominated habitat. Despite the importance of these functions in influencing reef-scale physical structure and ecological health, the highest rates occurred over less than 30% of the platform area. The results presented here provide new insights into within-reef variability in parrotfish ecological functions and demonstrate the importance of considering how these interact to influence reef geo-ecology.Natural Environment Research Council (NERC

Bleaching-driven reef community shifts drive pulses of increased reef sediment generation

This is the final version. Available on open access from the Royal Society via the DOI in this recordData accessibility: Benthic ecological data, and parrotfish abundance and biomass data used in this study are deposited at the Dryad Digital Repository: https://doi.org/10.5061/dryad.08kprr4zcThe ecological impacts of coral bleaching on reef communities are well documented, but resultant impacts upon reef-derived sediment supply are poorly quantified. This is an important knowledge gap because these biogenic sediments underpin shoreline and reef island maintenance. Here, we explore the impacts of the 2016 bleaching event on sediment generation by two dominant sediment producers (parrotfish and Halimeda spp.) on southern Maldivian reefs. Our data identifies two pulses of increased sediment generation in the 3 years since bleaching. The first occurred within approximately six months after bleaching as parrotfish biomass and resultant erosion rates increased, probably in response to enhanced food availability. The second pulse occurred 1 to 3 years post-bleaching, after further increases in parrotfish biomass and a major (approx. fourfold) increase in Halimeda spp. abundance. Total estimated sediment generation from these two producers increased from approximately 0.5 kg CaCO3 m−2 yr−1 (pre-bleaching; 2016) to approximately 3.7 kg CaCO3 m−2 yr−1 (post-bleaching; 2019), highlighting the strong links between reef ecology and sediment generation. However, the relevance of this sediment for shoreline maintenance probably diverges with each producer group, with parrotfish-derived sediment a more appropriate size fraction to potentially contribute to local island shorelines.Leverhulme TrustBertarelli Foundatio

Quantifying production rates and size fractions of parrotfish-derived sediment: a key functional role on Maldivian coral reefs (article)

This is the final version. Available on open access from Wiley via the DOI in this recordData Accessibility: Raw data files can be found at https://doi.org/10.24378/exe.3563. Summary data can also be found in the Electronic Supplementary Material.Coral reef fish perform numerous important functional roles on coral reefs. Of these, carbonate sediment production, as a by-product of parrotfish feeding, is especially important for contributing to reef framework construction and reef-associated landform development. However, only limited data exist on: i) how production rates vary among reef habitats as a function of parrotfish assemblages, ii) the relative importance of sediment produced from eroded, reworked, and endogenous sources or iii) the size fractions of sediment generated by different parrotfish species and size classes. These parameters influence not only overall reef29 derived sediment supply, but also influence the transport potential and depositional fate of this sedimentary material. Here, we show that parrotfish sediment production varies significantly between reef-platform habitats on an atoll-margin Maldivian reef. Highest rates of production (over 0.8 kg m-2yr-1) were calculated in three of the eight platform habitats; a rubble-dominated zone, an Acropora spp. dominated zone, and a patch reef zone. Habitat spatial extent and differences in associated parrotfish assemblages strongly influenced the total quantities of sediment generated within each habitat. Nearly half of total parrotfish sediment production occurred in the rubble habitat, which comprised only 8% of the total platform area. Over 90% of this sedimentary material originated from eroded reef framework as opposed to being reworked existing, or endogenously produced, sediment and comprised predominantly coral sands (predominantly 125 to 1000 µm in diameter). This is comparable to the dominant sand types and size fractions found on Maldivian reef islands. By contrast, nearly half of the sediment egested by parrotfish in the Acropora spp. dominated and patch reef habitats resulted from reworked existing sediments. These differences between habitats are a result of the different parrotfish assemblages supported. Endogenous carbonate production was found to be insignificant compared to the quantity of eroded and reworked material. Our findings have important implications for identifying key habitats and species which act as major sources of sediment for reef-island systemsNatural Environment Research Council (NERC

Constraining species-size class variability in rates of parrotfish bioerosion on Maldivian coral reefs: implications for regional-scale bioerosion estimates (dataset)

The article associated with this dataset is located in ORE at: http://hdl.handle.net/10871/32840Dataset for Yarlett et al., (2018) "Constraining species-size class variability in rates of parrotfish bioerosion on Maldivian coral reefs: implications for regional-scale bioerosion estimates" published in MEPSResearch was funded by a Natural Environment Research Council studentship (NE/L002434/1

Constraining species-size class variability in rates of parrotfish bioerosion on Maldivian coral reefs: implications for regional-scale bioerosion estimates (dataset)

The article associated with this dataset is located in ORE at: http://hdl.handle.net/10871/32840Dataset for Yarlett et al., (2018) "Constraining species-size class variability in rates of parrotfish bioerosion on Maldivian coral reefs: implications for regional-scale bioerosion estimates" published in MEPSResearch was funded by a Natural Environment Research Council studentship (NE/L002434/1