Table of Contents

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

We collected images from three UCH sites and surrounding coral reefs in Palau (Micronesia, western Pacific). Sites were selected based on accessibility, depth (≤ 6 m), and proximity to naturally-occurring coral reefs. All UCH dated from WWII, meaning that at the time of sampling, structures had rested on the seafloor for approximately 80 years. In May 2022, we collected images from two World War II shipwrecks: the “Fish N Fins shipwreck” (henceforth FNF) was located near a dive shop by the same name, and the “Taoch shipwreck” was located in the Taoch region of Palau’s Rock Island Southern Lagoon. Unfortunately, the identity of these two shipwrecks is unknown. In November 2022, we collected images from an Aichi E13A “Jake” sea plane wreck (henceforth Plane) near Ngermid.

We collected images of the sessile invertebrate fauna at each site using a Nikon D850 camera with a wide-angle lens, a GoPro Hero 7 with a wide-angle lens, and two Olympus TG-6 cameras. Wide-angle photography was used to record adult corals or other sessile invertebrates (≤ 5 cm diameter) in quadrats (0.34 ± 0.01 m2, mean ± SE). Olympus cameras were used for macro photography of young coral recruits (< 5 cm diameter), with each recruit being photographed individually to enable identification. A size scale was included in images to show colony size and quadrat area.

Images were recorded in transects at each site. The FNF shipwreck was oriented in an upright position, was 30 m long, and stretched from the seafloor (4 m depth) to above the sea surface. Images were recorded in three transects on the starboard hull (4, 3, and 2 m depth), one transect along the starboard gunnel (1 m depth), one transect on the port side (2 - 4 m depth), and one transect on the deck of the ship (2 m depth). Each transect stretched the length of the ship, ~30 m. A coral reef interspersed with sandy sediment surrounded the FNF shipwreck on both sides. Coral heads and coral rubble occurred on the seafloor within 1 m of the shipwreck, so there was almost no gap between the shipwreck and the adjacent natural reef. Quadrats were recorded from the coral reef (4 m depth) in three transects, each 20 – 30 m in length: near the starboard side, near the port side, and near the bow of the shipwreck.

The Taoch shipwreck was oriented on its side and 30 m long. It rested on the seafloor at 6 m depth and stretched to 1 m depth. Images were collected in transects that stretched the length of the ship: three transects on the hull (6 m, 3 m, 1 m depth) and 2 transects on the deck (6 m, 4 m depth). The seafloor on the deck side of the shipwreck was blanketed by sand and punctuated by sparse coral heads. On the hull side of the wreck, there was an area of sand ~2–5 m wide, and then a dense coral reef sloped upward to shore. Quadrats were recorded from this sloping coral reef in transects running the length of the ship: two transects (6 m, 3 m) on the hull side of the shipwreck and one transect (6 m depth) on the deck side of the shipwreck.

The seaplane rested approximately in flight orientation on the seafloor at 2 m depth. Quadrats from this aircraft were photographed in 2 transects: along the fuselage (12 m long), and along the wings (15 m). A coral reef covered the limestone walls of the U-shaped bay where the plane wreck rested, with a gap of 1 – 5 m from the airplane. This surrounding coral reef was photographed in a single transect stretching around the tail of the aircraft (~20 m long, 2 m depth).  

Images were used to visually identify and count sessile invertebrates living on each wreck and the adjacent coral reefs. Coral colonies were delineated based on margins – all polyps enclosed within contiguous, visible margins were counted as one colony, regardless of colony size. In a few cases, large coral colonies appeared in adjacent images, but these colonies were only counted in one image. Coral species were identified to the genus level by comparison to published guides (Erhardt and Knop, 2005; Veron et al., 2016; Kelley, 2022). All coral identifications were updated to match the most recent available taxonomic revisions (Kelley, 2022). Other sessile invertebrate species were identified to broad taxonomic categories (e.g., wire coral, sponge, tube worm). 

We also recorded metadata for each photo including its site, transect, and organism type (UCH adult, UCH juvenile, or Reef adult). We analyzed 493 photos from the FNF site (shipwreck and natural reef), 472 photos from the Taoch site, and 232 photos from the Plane site. Altogether, 5835 individuals were identified.

* Converted Date field from "%d-%b-%y" format to "%Y-%m-%d" string format
* Converted Lat field from degrees-decimal_minutes format (with N/S directional) to decimal degrees
* Converted Long field from degrees-decimal_minutes format (with E/W directional) to decimal degrees
* Rounded Long field to 7 decimal places
* Renamed fields by replacing spaces with underscores across specified fields
* Organism names checked in World Register of Marine Species (WoRMS)
* Zipped images and added to landing page

NSF Award Abstract:
Coral reefs host thousands of marine species, help protect coastlines from storm damage, generate tourism, and house fish used for human consumption. However, corals are vulnerable to increasing water temperatures, which can lead to coral death. One way for reefs to survive in warming oceans is for corals that are well-suited to warmer waters to repopulate reefs that have less temperature-tolerant individuals. For this strategy to succeed, however, the more temperature-tolerant corals need to be able to disperse to and survive in these different environments. This project takes advantage of reef systems in the Pacific nation of Palau that naturally experience a wide range in temperatures across short geographic distances. Using cutting-edge ecological and genomic techniques, the team of investigators is directly testing whether young corals from Palau’s warmest reefs can successfully be carried by ocean currents to Palau’s currently cooler reefs and subsequently survive and thrive in these habitats. Given the relevance of this research for the local ecology, the team is disseminating results to the Palauan government through a written report in conjunction with Palauan scientists who are interning with the team, and to the Palauan people through public presentations. As part of this work, the investigators are maintaining a blog and are organizing a music-lecture series combining dance, music, and science to promote awareness of the coral reef crisis across English and Spanish-speaking communities in the US. Results from this project are informing restoration and conservation practices of the Coral Conservation Consortium as well as other efforts worldwide.

A major question in evolutionary biology is how plasticity and adaptation interact to influence survival under novel environments. Understanding these processes is increasingly important as rising temperatures associated with climate change influence species globally. For marine organisms with pelagic larval phases, including reef-building corals, the post-settlement period constitutes a critical bottleneck for adaptation and plasticity, with the added complexity that the conditions experienced and time spent as larvae can incur carryover effects. This project leverages reefs in Palau that span a steep environmental gradient to study how environmental variation drives selection and plasticity and to examine if dispersal between reefs limits success across habitats due to carryover effects. The investigators are testing the overarching hypothesis that corals from warmer and more variable environments are adapted to warmer temperatures and exhibit increased plasticity, but that dispersal between reefs incurs a fitness cost. The team integrates field and molecular techniques to: 1) investigate the degree of selection occurring on warmer and more variable reefs, 2) test whether corals transplanted to more variable environments improve their thermal tolerance through developmental plasticity, and 3) examine whether delays in metamorphosis required for dispersal across reefs comes at a fitness cost due to carryover effects.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.