Physiological data for Montipora capitata and Porites compressa: endosymbiont cell density (cells cm-2), Contribution of Total Carbon to Animal Respiration (CTAR, %), calcification (mg day-1 cm-2), biomass (g cm-2), total lipids (J gdw-1), photosynthesis and respiration (µmol hr-1 cm-2), Contribution of Zooxanthellae (Symbiodiniaceae) to Animal Respiration (CZAR, %), feeding rate (brine shrimp hr-1 cm-2), and Contribution of Heterotrophy to Animal Respiration (CHAR, %). Measurements for experimental corals were taken from one of three time points (November 2015, June 2014, or December 2015).

Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
  • Problem Description
• Data Files
• Supplemental Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

Sampling Details

Between 10–12 November 2014, three weeks following the peak of the 2014 thermal stress event, six visibly non-bleached and six visibly bleached parent colonies of Montipora capitata and Porites compressa were collected from 1–3m depth from the fringing reefs surrounding Moku o Loʻe in Kāneʻohe Bay (centered at 21°26’6” N, 157°47’12” W) and in Waimānalo Bay (centered at 21°19’36” N, 157°40’54” W) using a hammer and chisel.

One ramet from each colony was immediately placed in a -20 °C freezer to evaluate the initial physiology of the parent colonies prior to experimental manipulation. An additional twelve ramets were collected from each parent colony of each species from each location (totaling 576 fragments) and mounted on pre-labeled plastic tiles for use in the manipulative experiment.

Experimental Tank Conditions

All experimental ramets were returned to the Hawai‘i Institute of Marine Biology and allowed to recover under ambient seawater conditions in outdoor, unfiltered, flow-through seawater tanks for three days. Natural light levels were reduced using 40% neutral density shade cloth such that photosynthetically active radiation levels mimicked that at collection depth.

On 15 November 2014, ramets were equally divided among eight outdoor, 38 L experimental tanks supplied with unfiltered, flow-through seawater. Though the incoming seawater was unfiltered, virtually no zooplankton is delivered to experimental tanks at HIMB due to scouring of the inflowing seawater by in-line invertebrates. Two experimental tanks were randomly assigned to each of the following four treatments: 1) Control (ambient seawater of pH 7.97 and unfed), 2) Fed (ambient seawater of pH 7.97 and fed), 3) OA (acidified seawater of pH 7.74 and unfed), and 4) OA+Fed (acidified seawater pH 7.74 and fed).

Coral holobiont physiology was assessed for parent colonies (i.e., in situ reef controls) and a subset of experimental corals in December 2014 (2 months after 2014 peak thermal stress; 1 month in experimental tanks), June 2015 (8 months after 2014 peak thermal stress; 7 months in experimental tanks), and November 2015 (one month after 2015 peak thermal stress; 13 months in experimental tanks). At each experimental time point, physiological trait measurements were conducted (calcification, photosynthesis, respiration, and zooplankton feeding rate capacity). Once all live measurements were completed, these ramets were frozen for further analyses (endosymbiont cell density, tissue biomass, and total lipids).

The seawater pH was reduced in the simulated OA treatments by bubbling CO gas into the tanks. To ensure tanks remained within target pH range, all tanks were spot-checked with a calibrated pH probe every 1–2 days throughout the experiment. This data was recorded during periods when physiological measurements were being made. Small adjustments to the CO2 bubbling rate were made as needed to maintain the desired 0.2 pH offset between ambient and simulated OA treatments.

Weekly, pH and total alkalinity measurements were made on seawater samples collected from each tank at18:00 h. Total alkalinity was measured using a modified Gran titration and checked for accuracy and precision (~5 μmol kg) using certified reference materials obtained from A. Dickson (Scripps Institution of Oceanography). pH was measured spectrophotometrically at 25 °C with m-cresol purple (precision ~0.002 pH units).

These parameters were then entered into CO2Sys to calculate pH in situ. The CO bubbling rate was then adjusted as necessary, pH was measured again using a calibrated pH probe, and any further adjustments were made until the desired pH was consistently read. In December 2014, March 2015, and June2015, diel cycle chemistry was measured over a 24-hour period across all tanks using the same method.

 

Differences in the physiological profiles (including endosymbiont cell density, CTAR, calcification, tissue biomass, and total lipids) between species, sites, and sites within species was assessed with a multivariate analysis of similarity (ANOSIM).

Physiological profiles of experimental ramets in December 2014 and June 2015 were evaluated using both multivariate and univariate analyses.

Additional details of statistical analyses are outlined in the associated results publication (Dobson et al.).

- Time_point (date) field converted from %d-%y (e.g., Nov-14) to %m-%Y (e.g., 11-2014) format

- Converted latitude and longitude fields from degrees, minutes, seconds to decimal degree format, and rounded these fields to six degrees of precision

- Empty cells represent "No data" within the dataset

Following the 2015 thermal stress event, almost all P. compressa ramets died, resulting in sample sizes too small for analysis in December 2015.

Coverage: Oahu, HI; Hawaii Institute of Marine Biology

Following the second hottest month on record since the 1940s, water temperatures on O'ahu reached 30 degrees C. The result of this ~2 degree C increase above summer mean temperatures has been a severe bleaching event across the entire length of the Hawaiian Archipelago, with as many as 75% of the dominant coral species in Kane'ohe Bay losing color or bleaching completely white. This event exceeds the magnitude of the only major bleaching event previously documented for Hawaii in 1996. Although tragic, this event provides a rare natural experiment to understand the impact of coral bleaching on the ability of Hawaiian corals to recovery from high temperature stress in the context of climate change and ocean acidification. The proposed will leverage previous work by the PIs to compare recovery following this event and the 1996 mass bleaching event to the recovery rates of Hawaiian corals under future climate change scenarios. Results from this work will provide data on coral resistance and recovery potential from bleaching events of the future.

Coral reefs are among the most diverse ecosystems on the planet, housing an estimated 25% of marine species. But, that diversity appears particularly susceptible to the effects of global change. Massive coral bleaching poses a substantial threat to the integrity of coral reef habitat in US waters, and is predicted to be the major source of mortality for reefs under future climate scenarios. Although previous work on the recovery of corals from bleaching sets the groundwork for this project, it remains to be seen how recovery from bleaching will be impacted by climate change and ocean acidification. To address this fundamental question, we take advantage of the natural difference in baseline temperature and pCO2 conditions between Kane'ohe Bay and Waimanalo Bay, HI, both of which are currently impacted by the massive bleaching event in the Hawaiian Archipelago. This natural experiment makes possible a rare opportunity to test three basic questions about the rates of recovery of bleached and unbleached corals under future climate change scenarios:
1) Will ocean acidification slow rates of recovery from bleaching?;
2) Does zooplankton feeding minimize the impact?; and
3) Do corals acclimated to warmer, more acidic baseline conditions (Kane'ohe Bay) recover more quickly under future conditions than corals from present day mean oceanic conditions (Waimanalo Bay)?

This research addresses broad scientific questions relating to the ability of corals to acclimate or adapt to both local environments and future climate conditions, and to help identify coral populations that may be resilient to the predicted impacts of climate change on the reefs of the future.