Short summary of study:

We present a proof-of-concept of “out-of-season” spawning, utilising aquarium control technology to induce spawning in multiple Great Barrier Reef (GBR) corals held in long-term indoor aquaria. By applying a 6-month offset environmental profile encompassing seasonal temperature, photoperiod, and lunar cues, we induced synchronised coral spawning during austral autumn/winter between 2022-2023. We also “phase-shifted” the hour of sunset by four hours on spawning nights, creating a more favourable time window (i.e., minimising late nights) for gamete fertilisation. Spawning occurred on comparable nights after full moon (NAFM) and at similar times after sunset (TAS) to wild conspecifics, with 2023 cohorts showing the closest alignment. Gamete fertilisation was successful for six species: Acropora millepora, Acropora loripes, Acropora hyacinthus, Acropora elseyi, Acropora austera, and Montipora aequituberculata producing ~1.8 million larvae. We outline physiological insights into environmental regulation of coral spawning synchronicity and discuss the potential for out-of-season spawning to accelerate coral research and enhance reef restoration programs.

Code and Package Versions:

Code/software

R version 4.4.0

libraries required

• library(tidyverse)
• library(readxl)
• library(scales)
• library(car)
• library(lubridate)
• library(emmeans)

sessionInfo()

## R version 4.4.0 (2024-04-24 ucrt)
## Platform: x86_64-w64-mingw32/x64
## Running under: Windows 10 x64 (build 19045)
##
## Matrix products: default
##
##
## locale:
## [1] LC_COLLATE=English_Australia.utf8  LC_CTYPE=English_Australia.utf8  
## [3] LC_MONETARY=English_Australia.utf8 LC_NUMERIC=C                     
## [5] LC_TIME=English_Australia.utf8   
##
## time zone: Australia/Brisbane
## tzcode source: internal
##
## attached base packages:
## [1] stats     graphics  grDevices utils     datasets  methods   base    
##
## other attached packages:
##  [1] emmeans_1.8.8   car_3.1-2       carData_3.0-5   scales_1.4.0  
##  [5] readxl_1.4.5    lubridate_1.9.4 forcats_1.0.0   stringr_1.5.1 
##  [9] dplyr_1.1.4     purrr_1.0.4     readr_2.1.5     tidyr_1.3.1   
## [13] tibble_3.3.0    ggplot2_3.5.2   tidyverse_2.0.0
##
## loaded via a namespace (and not attached):
##  [1] gtable_0.3.6       compiler_4.4.0     tidyselect_1.2.1   yaml_2.3.10      
##  [5] fastmap_1.2.0      R6_2.6.1           generics_0.1.4     knitr_1.50       
##  [9] pillar_1.10.2      RColorBrewer_1.1-3 tzdb_0.5.0         rlang_1.1.6      
## [13] stringi_1.8.7      xfun_0.52          estimability_1.5.1 timechange_0.3.0  
## [17] cli_3.6.5          withr_3.0.2        magrittr_2.0.3     digest_0.6.37    
## [21] grid_4.4.0         mvtnorm_1.3-3      rstudioapi_0.17.1  hms_1.1.3        
## [25] lifecycle_1.0.4    vctrs_0.6.5        evaluate_1.0.3     glue_1.8.0       
## [29] cellranger_1.1.0   farver_2.1.2       abind_1.4-8        rmarkdown_2.29   
## [33] tools_4.4.0        pkgconfig_2.0.3    htmltools_0.5.8.1

Overview of files and their contents:

Files and variables

File: Data_1_Temperature_profiles.csv

Description: Average temperature profile (1998-2015) for Davies Reef and the 6-month offset temperature profile used in the study. Source: AIMS weather station at Davies Reef (18.832° S, 147.635° E), recorded at 4 m depth.

Variables

• Date:
• Davies Reef average (1998 - 2015) temperature (C):
• 6-month offset temperature (C):

File: Data_2_Temperature_entire.csv

Description: Daily temperature setpoint values applied to out-of-season spawning coral systems over the duration of the study

Variables

• Local Date:
• Out-of-season system temperature (C) setpoints:

File: Data_3_Photoperiod_entire.csv

Description: Photoperiod data used to simulate natural dawn and dusk timings, including civil twilight periods, for the out-of-season spawning system. Includes first light and last light times for Townsville, Australia, offset by 6 months.

Variables

• Local Date:
• Lookup Date (Offset 6 months):
• First light (Civil twilight start):
• Phase shifted (4 hours) first light (Civil twilight start):
• Sunset:
• Phase shifted (4 hours) sunset:
• Last light (Civil twilight end):
• Phase shifted (4 hours) last light (Civil twilight end):
• Phase shift (Hours):

File: Data_4_Photoperiod_24_hours.csv

Description: Setpoint values for daily light irradiance (Photosynthetically Active Radiation [PAR]; µmol photons m⁻² s⁻¹) delivered to coral holding systems over a 24-hour period during the inshore full moon (20:00, 7 May 2022 – 19:59, 8 May 2022), as shown in figure S5. First light and last light times were derived from Data 3 – Photoperiod_entire.csv.

Variables

• Local date/time:
• PAR (mmol photons m-2 s --1) setpoint:

File: Data_5_Moonlight_entire.csv

Description: Moonlight settings applied to coral holding tanks, including moonrise and moonset times and illuminance (lux) over the duration of the study. Note: Moonrise and moonset times are phase-shifted by four hours (i.e., advanced by four hours) relative to those listed in the file.

Variables

• Local Date:
• Lookup Date (Offset 6 months):
• Moonrise time:
• Moonset time:
• Peak lux:
• Notes:

File: Data_6_NAFM_TAS_rawdata.xlsx

Description: Raw spawning time data for all coral species used in the out-of-season spawning (OSS) study. Includes individual records for nights after full moon (NAFM) and time after sunset (TAS) for each spawning event across 2022 and 2023. Dataset supports statistical comparisons of temporal spawning synchrony across years and against published wild observations (see Baird et al. [30]).

Variables

• Species
• 2022
• 2023
• Baird.2021

File: Data_7_NAFM_Rdatatable.csv

Description: Formatted input dataset for statistical analysis of nights after full moon (NAFM), used in the Poisson GLM models described in the study. Includes variables for species, dataset (2022, 2023, Baird), and transformed NAFM values (with +1 offset to meet GLM distributional assumptions). Corresponds to results in supplementary tables S8-10.

Variables

• Species:
• Dataset:
• NAFM:
• Species2:
• NAFMt:

File: Data_8_TAS_Rdatatable.csv

Description: Formatted input dataset for statistical analysis of time after sunset (TAS), used in the Poisson GLM models described in the study. Includes variables for species, dataset (2022, 2023, Baird), and TAS values in minutes. Corresponds to results in supplementary tables S9-S11.

Variables

• Species:
• Dataset:
• TAS:
• Species2:
• Min:
• Hr:
• TimeinMin:

File: R_Code_Spawning_Synchrony_Analysis.docx

Description: R script used to analyse coral spawning timing (nights after full moon [NAFM] and time after sunset [TAS]) across datasets from 2022, 2023, and published wild observations (Baird et al. [30]). The code performs data wrangling, assumption checks, and Poisson GLM modelling for each species separately, with post-hoc comparisons using estimated marginal means (emmeans). Outputs include descriptive statistics, model summaries, and pairwise comparisons. Associated input/output files: Data_6_NAFM_TAS_rawdata.xlsx, Data_7_NAFM_Rdatatable.csv, and Data_8_TAS_Rdatatable.csv.

Access information

Other publicly accessible locations of the data:

• https://www.timeanddate.com
• https://weather.aims.gov.au/#/station/4