DOI: 10.5061/dryad.tx95x6b8p
title: Data from: High abundances of crustose coralline algae inside cryptic coral habitats linked to coral reef functioning

description: Cryptic habitats on coral reefs consist of crevices, tunnels, and holes
 that are estimated to comprise 30-75% of the total reef surface area.
 These large habitats are vastly understudied because they are often
 difficult to access. Crustose coralline algae (CCA) are thought to perform
 important ecological functions, including reef accretion and coral
 recruitment, both inside cryptic habitats and on the exposed (top) reef.
 Using GoPro cameras, we surveyed 250 coral crevices from 14 reefs on West
 Maui, Hawai‘i. We documented CCA abundance and distribution, identified
 abiotic and biotic factors that may regulate CCA abundance, and compared
 relative CCA cover between crevices and the well-studied top-reef. We
 found that crevices had 3.1 times more CCA cover on average than the
 top-reef and that CCA cover was highest on the ceilings and entrances of
 crevices that had low sediment and macroalgal cover. These findings
 suggest that crevice openings and ceilings are particularly important for
 reef building and stabilization of reefs, because of CCA’s known
 contribution to calcium accretion. Thus, these findings help to establish
 functional links between coral reef structural complexity, cryptic
 habitats, and reef resilience, and highlight the importance of studying
 cryptic habitats to inform approaches to coral reef conservation.
description: # Data from: High abundances of crustose coralline algae inside cryptic
 coral habitats linked to coral reef functioning Dataset DOI:
 [10.5061/dryad.tx95x6b8p](10.5061/dryad.tx95x6b8p) ## Description of the
 data and file structure **README - 5 August 2025** **Anna Rothstein, Orion
 S. McCarthy, Sophie Luu, Emily L. A. Kelly, Philip Heller, Stuart A.
 Sandin, Jennifer E. Smith, Maya S. deVries. *Royal Society Open Science*.
 “High abundances of crustose coralline algae inside cryptic coral habitats
 linked to coral reef functioning.”** There are four data files associated
 with this manuscript. They are listed here and described in detail below:
 1. **“crevice_data_Rothstein_etal.csv”** 2.
 **“crevice_light_data_Rothstein_etal.csv”** 3.
 “**crevice_topreef_data_Rothstein_etal.csv**” 4.
 **“crevice_benthic_data_Rothstein_etal.csv”** **1. 
 “crevice_data_Rothstein_etal.csv”** This file contains the data for the
 analyses on all 250 coral crevices documented in this study and was used
 to analyze correlations between crustose coralline algae (CCA) abundance
 and crevice depth, microhabitat type, and sedimentation. For detailed
 descriptions of how the data were collected and analyzed, refer to the
 Materials and Methods section in the associated manuscript. Each column
 title in the spreadsheet is described below. Crevice_ID: The unique
 identifier given to each crevice filmed in the study. Each identifier has
 the site abbreviation and a letter denoting the specific crevice. 
 Site_name: The site names for each coral crevice. The abbreviations are
 listed from North to South in West Maui below (see Fig. 1 in associated
 manuscript for a map of the study sites): * Honokowai 1 [HONO1] * Kahekili
 5 [KAH5] * Kahekili 2 [KAH2] * Kahekili 1 [KAH1] * Wahikuli [WAH] *
 Olowalu 1 [OLO1] * Olowalu 2 [OLO2] * Olowalu 3 [OLO3] * Ukumehame 1
 [UKU1] * Keawakapu [KEA] * Molokini Shallow [MOLOS] * Molokini Deep
 [MOLOD] * South La Perouse Bay [SLPB] Depth.m: The depth of each site
 (units: m). Crevice.cm: The crevice depth measured using the telescopic
 extender (selfie stick) when camera was inserted into the crevice (units:
 cm). Microhabitat: Microhabitat of the given screenshot analyzed within
 the specific crevice. The two microhabitats documented were: * WALL: The
 camera was oriented towards the back wall of the crevice * CEILING: The
 camera was oriented towards the ceiling of the crevice SED.TURF: The
 relative abundance of sediment and sediment-laden turf as a measure of
 sedimentation inside crevices (units: %). CCA: Relative CCA abundance
 inside crevices (units: %). ratiocca: Relative CCA abundance as a ratio
 ratiosedturf: relative abundance of sediment and sediment-laden turf as a
 ratio **2.  “crevice_light_data_Rothstein_etal.csv”** This file contains
 the light data collected at one site (KAH 2) and was used to analyzed
 correlations between CCA abundance and light availability, crevice depth,
 microhabitat type, and sedimentation. For detailed descriptions of how the
 data were collected and analyzed, refer to the Materials and Methods
 section in the associated manuscript. Each column title in the spreadsheet
 is described below. Crevice_ID: The unique identifier given to each
 crevice filmed in the study. Light.reading.lumens: Light readings for each
 crevice. Data were taken from the approximately one minute that the probe
 was in the crevice. These data were then used to calculate average light
 readings for each crevice (units: lumens). Microhabitat: Microhabitat of
 the given screenshot analyzed within the specific crevice. The two
 microhabitats documented were: * WALL: The camera was oriented towards the
 back wall of the crevice * CEILING: The camera was oriented towards the
 ceiling of the crevice Crevice.depth.cm: The crevice depth measured using
 the telescopic extender (selfie stick) when camera was inserted into the
 crevice (units: cm). CCA: Relative CCA abundance inside crevices (units:
 %). SED.TURF: The relative abundance of sediment and sediment-laden turf
 as a measure of sedimentation inside crevices (units: %). ratiocca:
 Relative CCA abundance as a ratio ratiosedturf: relative abundance of
 sediment and sediment-laden turf as a ratio **3.
  “crevice_topreef_data_Rothstein_etal.csv**” This file contains crevice
 and top-reef data collected from 8 sites for which there were top-reef
 data available. The data were used to analyze differences in CCA abundance
 and sedimentation between the top reef and crevice ceilings and walls. The
 data were also used to explore potential differences in CCA abundance
 between different coral morphotypes. For detailed descriptions of how the
 data were collected and analyzed, refer to the Materials and Methods
 section in the associated manuscript. Each column title in the spreadsheet
 is described below. Habitat.type: Habitat types documented at a given
 site. The two habitat types documented were: * crevice: coral crevice *
 top-reef: the exposed top of the reef Microhabitat: Microhabitats
 documented at a given site. The three habitat types documented were: *
 ceiling: The camera was oriented towards the ceiling of the crevice *
 wall: The camera was oriented towards the back wall of the crevice *
 top-reef: The whole top of the reef within the 10x10m plot as documented
 from large-area imagery Site_name: The site names for each coral crevice.
 See above for definitions of abbreviations. coral_type: The dominating
 coral morphotype for at each site. The three morphotypes documented were:
 * b: branching coral * m: massive coral * p: plating coral CCA: Relative
 CCA abundance inside crevices (units: %). SED.TURF: The relative abundance
 of sediment and sediment-laden turf as a measure of sedimentation inside
 crevices (units: %). ccaturf: The ratio of CCA:turf algae. ratiocca:
 Relative CCA abundance as a ratio ratioturf: relative abundance of
 sediment and sediment-laden turf as a ratio **4. 
 crevice_benthic_data_Rothstein_etal.csv** This file contains crevice and
 top-reef benthic data collected from 8 sites for which there was top-reef
 data available. The data were used to analyze differences in the relative
 abundances of benthic organisms using a Non-metric MultiDimensional
 Scaling (NMDS) analysis. For detailed descriptions of how the data were
 collected and analyzed, refer to the Materials and Methods section in the
 associated manuscript. Each column title in the spreadsheet is described
 below. Habitat.type: Habitat types documented at a given site. The two
 habitat types documented were: * crevice: coral crevice * top-reef: the
 exposed top of the reef Microhabitat: Microhabitats documented at a given
 site. The three habitat types documented were: * ceiling: The camera was
 oriented towards the ceiling of the crevice * wall: The camera was
 oriented towards the back wall of the crevice * top-reef: The whole top of
 the reef within the 10x10m plot as documented from large-area imagery
 Site_name: The site names for each coral crevice. See above for
 definitions of abbreviations. Category: The category names for organisms
 encountered in the crevices and on the top-reef.  n: The number of
 individuals per category encountered within each documented crevice. ##
 Code/software Data were analyzed using R (v. 4.4.1, 2024). We transformed
 the percent data into proportions and constructed a beta regression model
 (package: betareg) to examine the relationship between relative CCA
 abundance and the microhabitats inside the reef (crevice ceilings vs
 walls), crevice depth, and the abundance of sediment and sediment-laden
 turf across sites to account for differences between sites. To describe
 sediment and turf algal dynamics inside the reef, we examined the
 relationship between the CA:turf algal ratio and microhabitat using a
 generalized linear model (as opposed to a beta regression model) because
 there were ratios that were greater than 1. Finally, we used a Non-metric
 MultiDimensional Scaling (NMDS) analysis to visualize differences in CCA
 percent cover between the top-reef and crevice walls and ceilings.