TY - JOUR

T1 - Atoll-dependent variation in depth zonation of benthic communities on remote reefs

AU - Sannassy Pilly, Jyodee

AU - Richardson, Laura

AU - Turner, John

AU - Roche, Ronan

N1 - Delay in getting Post-print from the author

PY - 2022/1/1

Y1 - 2022/1/1

N2 - HighlightsSignificant depth-by-atoll interactions drove benthic community structure.CCA, turf algae, sponge and soft coral cover were highest on deep reefs.Hard coral, dead coral and bare substrate cover were highest on shallow reefs.Acropora, Stylophora and Pocillopora characterised shallow reefs.Acropora and Porites consistently associated with both shallow and deep reef zones.AbstractThe distribution and organisation of benthic organisms on tropical reefs are typically heterogenous yet display distinct zonation patterns across depth gradients. However, there are few datasets which inform our understanding of how depth zonation in benthic community composition varies spatially among and within different reef systems. Here, we assess the depth zonation in benthic forereef slope communities in the Central Indian Ocean, prior to the back-to-back bleaching events in 2014–2017. We compare benthic communities between shallow (5–10 m) and deep (20–25 m) sites, at two spatial scales: among and within 4 atolls. Our analyses showed the variation in both major functional groups and hard coral assemblages between depth varied among atolls, and within-atoll comparisons revealed distinct differences between shallow and deep forereef slope communities. Indicator taxa analyses characterising the hard coral community between depths revealed a higher number of coral genera characteristic of the deep forereef slopes (10) than the shallow forereef slopes (6). Only two coral genera consistently associated with both depths across all atolls, and these were Acropora and Porites. Our results reveal spatial variation in depth zonation of benthic communities, potentially driven by biophysical processes varying across depths and atolls, and provide a baseline to understand and measure the impacts of future global climate change on benthic communities across depths.

AB - HighlightsSignificant depth-by-atoll interactions drove benthic community structure.CCA, turf algae, sponge and soft coral cover were highest on deep reefs.Hard coral, dead coral and bare substrate cover were highest on shallow reefs.Acropora, Stylophora and Pocillopora characterised shallow reefs.Acropora and Porites consistently associated with both shallow and deep reef zones.AbstractThe distribution and organisation of benthic organisms on tropical reefs are typically heterogenous yet display distinct zonation patterns across depth gradients. However, there are few datasets which inform our understanding of how depth zonation in benthic community composition varies spatially among and within different reef systems. Here, we assess the depth zonation in benthic forereef slope communities in the Central Indian Ocean, prior to the back-to-back bleaching events in 2014–2017. We compare benthic communities between shallow (5–10 m) and deep (20–25 m) sites, at two spatial scales: among and within 4 atolls. Our analyses showed the variation in both major functional groups and hard coral assemblages between depth varied among atolls, and within-atoll comparisons revealed distinct differences between shallow and deep forereef slope communities. Indicator taxa analyses characterising the hard coral community between depths revealed a higher number of coral genera characteristic of the deep forereef slopes (10) than the shallow forereef slopes (6). Only two coral genera consistently associated with both depths across all atolls, and these were Acropora and Porites. Our results reveal spatial variation in depth zonation of benthic communities, potentially driven by biophysical processes varying across depths and atolls, and provide a baseline to understand and measure the impacts of future global climate change on benthic communities across depths.

KW - Depth zonation Coral reefs Remote systems Benthic ecology Community composition Hard coral assemblages

U2 - 10.1016/j.marenvres.2021.105520

DO - 10.1016/j.marenvres.2021.105520

M3 - Article

VL - 173

JO - Marine Environmental Research

JF - Marine Environmental Research

SN - 0141-1136

M1 - 105520

ER -