Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

A full factorial experiment was completed to determine the survival probability and photochemical efficiency of 25 unique genotypes of Acropora cervicornis in high temperature, high pCO₂ treatment, or the combination of high temperature and high pCO2.

• High temperature was 33 ± 0.6°C and 463 ± 31 µatm
• High pCO₂ treatment was 29 ± 0.2°C and 798 ± 78 µatm
• Combination high temperature and high pCO2 was 33 ± 0.8°C and 823 ± 83 µatm 

Prior to exposure, dark-acclimated photochemical efficiency was measured in all fragments (n=600) using a pulse amplitude modulation chlorophyll fluorometer (I-PAM, Walz GmbH, Effeltrich, Germany). Photochemical efficiency factors include:

• ETR _(max)
• F_v/F_m (max)
• Initial slope of ETR v. PAR plot

Additionally, the starting color index was gathered for each fragment based on the coral health chart provided by CoralWatch.  The starting colors ranged from D1 for bleached to D5 for full color/healthy. During the exposure period, water quality for each tank was measured daily and color index was assessed daily for all fragments. Water samples were collected in acid-washed amber bottles (125 mL) for carbonate chemistry analysis bi-weekly and fixed with mercuric chloride (60 µL). Water samples were filtered (0.2 microns) prior to analysis on the dissolved inorganic carbon (DIC) machine (Apollo SciTech Analyzer).

As replicates started to show signs of stress (paling activity) and subsequent mortality, the following was recorded:

• the date of mortality,
• the time (days) till mortality,
• the mechanism of mortality (i.e. showed signs of Tissue loss, Bleaching, or both occurring simultaneously)

Each replicate coral was categorized as a binomial rank, classified as either 0, no event/alive, or a 1, event occurred/dead, on each day of the study. As coral fragments reached mortality, they were removed from their treatment tank to limit negative effects on the remaining fragments in the tank. Once LD50 was reached for each genotype in each treatment, the dark-acclimated PAM Chlorophyll Fluorometry outputs (ETR _(max), F_v/F_m (max), and initial slope of ETR v. PAR plot) was measured for the remaining fragments of that genotype in that same treatment to derive change of yield over time.

Treatment tank water quality was monitored using a YSI Professional Plus (Pro Plus) Multi-parameter handheld with a quarto containing a Pro Series Galvanic Dissolved Oxygen Sensor, a Pro Series pH Sensor (calibrated using 4, 7, and 10 buffers), Pro Series temperature and conductivity sensor. PAR was measured using the Licor handheld (Li-COR LI-1500) with an underwater quantum senor (Li-Cor LI-192). Dissolved inorganic carbon (DIC) was analyzed using the Apollo SciTech DIC analyzer model AS-C151. Total Alkalinity (TA) was analyzed using the Metrohm 905 Titrando analyzer. Both DIC and TA were standardized each day with certified reference material (CRM) provided by A.G. Dickson. Imaging-PAM Chlorophyll flurometer (Walz GmbH, Effeltrich, Germany) was used to measure photochemical efficiencies and the coral health chart/ color index card was provided by CoralWatch.

Kaplan Meier curves and log rank scores were used to assess the difference in survivorship among genotypes, regions, and treatments. If assumptions were met, ANOVA and Tukeys post-hoc test was used to measure the effect of Genotype, Region, and Treatment (singularly and interaction effect) on photochemical efficiencies; tank number as a random factor. Normality and equality of variances were checked using Shapiro-wilks test and Levene’s test, respectively. If assumptions were not met, a Kruskal Wallis test and Dunn’s post-hoc test was used. Chi squared test was used to assess the independence between the frequency of each mechanism of mortality and Treatment and/or Region. If assumptions were not met, a Fishers exact test was used. All statistical analysis was completed in R version 4.0.3.

NSF Award Abstract:
Caribbean staghorn coral was one of the most common corals within reefs of the Florida Keys several decades ago. Over the last 40 years disease, bleaching, overfishing and habitat degradation caused a 95% reduction of the population. Staghorn coral is now listed as threatened under the U.S. Endangered Species Act of 1973. Within the past few years, millions of dollars have been invested for the purpose of restoring the population of staghorn coral within Florida and the U.S. Virgin Islands. Significant effort has been placed on maintaining and propagating corals of known genotypes within coral nurseries for the purpose of outplanting. However, little is known about the individual genotypes that are currently being outplanted from nurseries onto coral reefs. Are the genotypes being used for outplanting resilient enough to survive the three major stressors affecting the population in the Florida Keys: disease, high water temperatures, and ocean acidification? The research within the present study will be the first step in answering this critically important question. The funded project will additionally develop a research-based afterschool program with K-12 students in the Florida Keys and U.S. Virgin Islands that emphasizes an inquiry-based curriculum, STEM research activities, and peer-to-peer mentoring. The information from the present study will help scientists predict the likelihood of species persistence within the lower Florida Keys under future climate-change and ocean-acidification scenarios. Results of this research will also help guide restoration efforts throughout Florida and the Caribbean, and lead to more informative, science-based restoration activities.

Acropora cervicornis dominated shallow-water reefs within the Florida Keys for at least the last half a million years, but the population has recently declined due to multiple stressors. Understanding the current population level of resilience to three major threats - disease outbreaks, high water temperatures, and ocean acidification conditions - is critical for the preservation of this threatened species. Results from the present study will answer the primary research question: will representative genotypes from the lower Florida Keys provide enough phenotypic variation for this threatened species to survive in the future? The present proposal will couple controlled laboratory challenge experiments with field data and modeling applications, and collaborate with local educators to fulfill five objectives: 1) identify A. cervicornis genotypes resistant to disease, 2) identify A. cervicornis genotypes resilient to high water temperature and ocean acidification conditions, 3) quantify how high water temperature and ocean acidification conditions impact disease dynamics on A. cervicornis; 4) determine tradeoffs in life-history traits because of resilience factors; and 5) apply a trait-based model, which will predict genotypic structure of a population under different environmental scenarios.