Table of Contents

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

Sampling and analytical procedures:

Coral Collection: A total of 8 colonies of each species were collected at each site at a depth between 5–10 meters (offshore) or 1–5 meters (Inshore) and at least 10 meters apart. Differences in collection depth were necessary due to the natural distribution of these species at each site and in order to ensure all colonies were collected from similar light conditions (maximal mid-day in situ light of 800-1000-μmol quanta m-2 s-1). Sampling was performed offshore at Rebotel Reef (7.248833, 134.235817) and inshore at Nikko Bay (7.3248, 134.4934). Colonies were transported back to the Palau International Coral Research Center (PICRC) and fragmented into five replicate nubbins and placed into a 1200L flow-through aquarium and held at 27.5°C. Seawater was collected directly off of a nearby pier at a depth of 3 m and then passed through a pressurized sand filter and aquarium filter pads prior to use in flow-through and experimental treatment systems. Coral nubbins were attached to 2-inch square PVC tiles with marine epoxy (Splash zone compound A-788) and held at ambient conditions in flow-through bins as described above for 12-16 days prior to the start of the experiment. Control and experimental bins (see below) were maintained outdoors underneath clear plastic film (Sun Selector, Ginegar Plastic Products) to block periodic rainfall and a 60% shade cloth providing a peak midday light intensity of 800 μmol quanta m-2 s-1, as measured with a light sensor (LiCor LI-192).

Experimental System: Each treatment system consisted of 7–12 (56 L) plastic treatment bins connected to a central (~1200 L) sump. Seawater within each sump was set to either heated or ambient temperature conditions prior to being sent to the treatment bins. Ambient temperature was maintained via a chiller system and a series of titanium heating elements were used for high temperature treatments. For each treatment, three replicate fragments from each colony were placed within separate treatment bins. For the heated treatment, the temperature was gradually ramped from 27.5°C to 32°C over 4 days, and then maintained at 32°C for an additional 10 days for a total of 14 days of heating. Temperature within the control treatment was maintained at 27.5°C throughout the 14-day experiment. Treatment bins and PVC tiles were cleaned every other day to prevent algal fouling, and coral fragments were rotated within their respective bins every other day to ensure a uniform light exposure and minimize possible tank effects.

At the start of the experiment (day 0), one fragment from each coral colony was removed from control and treatment tanks and processed for symbiont photo-physiology and biomass metrics (described below). Additional fragments were then sampled on days 9 (4 days of temperature ramping + 5 days at 32°C) and 14 (4 days of temperature ramping and 10 days at 32°C). Coral tissue was removed by airbrush (100 psi) with filtered (0.22 m) seawater. The resulting slurry was homogenized with a Tissue Tearor (BioSpec products, Inc), and then divided into 2 mL aliquots. One aliquot was preserved with 1% glutaraldehyde for cell enumeration and stored at 4°C. All other aliquots were centrifuged for 2 minutes (5,000×g) and the supernatant was discarded. Algal subsamples from each colony were suspended in DNA preservation buffer (Seutin et al. 1991) and stored at 4°C. The remaining algal samples were immediately frozen (-20°C) and shipped back to the United States and stored at -20°C until further analyses.

Remaining information on procedures can be found in Hoadley et al., 2019.

- Loaded data from two source files
- Combined data from two source files into a single data table
- Added columns for Latitude and Longitude corresponding to coordinates for the offshore site (Rebotel Reef) and the inshore site (Nikko Bay)

NSF Award Abstract
Ocean warming is affecting life on our planet in many ways. High temperature can disrupt the endosymbioses between dinoflagellate algae (Symbiodinium spp.) and reef-building corals (i.e. coral bleaching), thereby risking the global loss of a critical marine ecosystem. The physiological, ecological and evolutionary responses of coral-dinoflagellate symbioses to environmental stress brought on by global climate change are complex. The spread of certain types of symbiotic algae may increase the thermal stress tolerance among corals and help them persist in warmer oceans, but perhaps not without trade-offs to the health of the coral. The dinoflagellate tentatively named Symbiodinium trenchi has become increasingly more common in numerous corals throughout the Caribbean, but is often at low-abundance relative to other symbionts. While S. trenchi can increase in abundance during and after warming, it is often displaced by other symbionts following a return to normal conditions. Genetic evidence indicates that S. trenchi recently invaded and/or expanded in the Caribbean and has developed associations with many corals that seem to be poorly optimized, or mal-adapted, relative to the symbioses it maintains with corals in the Indo-Pacific. This project will investigate the symbiosis ecology and physiology of S. trenchi in corals from the Atlantic and Pacific Oceans. Bleaching experiments will examine the effects of increased temperature on transfer of carbon from the algae to the host coral (via stable isotopic tagging), as well as photosynthesis and growth among colonies harboring S. trenchi compared to colonies harboring other Symbiodinium spp. The potential for symbiont community shifts as well as altered long-term colony growth based on bleaching severity and recovery time will be investigated. A reciprocal transplant study will examine the competitive interaction and stability of symbionts among Pacific corals. These studies will test if the continued spread of S. trenchi will affect coral growth in the Caribbean and whether it might behave similarly in the Indo-Pacific if environmental conditions worsen. The results from this project have the potential to supply transformative information regarding how (or if) a widely distributed symbiotic algal species may influence the resilience of reef-building corals and their potential to survive projected increases in ocean warming due to climate change. In addition to training one postdoctoral scholar and several graduate students, this project will enhance scientific discovery and participation of underrepresented groups via several outreach efforts with the Palau National Aquarium, Palau International Coral Reef Center, and local schools. Educational units in marine symbioses and science will be developed with several local high school teachers and students, and unique research opportunities will be provided to students at the Palau Community College. Likewise, a new educational display addressing how global climate may impact coral reefs, and describing the current research to better understand the physiology of coral-algal symbioses, will be developed and presented at the University of Delaware open house "Coast Day." The display will be donated subsequently to the Palau Aquarium for future use. This award is co-funded by NSF's Office of International and Integrative Activities.