Table of Contents

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

A feces addition experiment was conducted three times (Final N = 11 replicates) using fragments of multiple species of Pocillopora in Moorea, French Polynesia. An initial experimental iteration was performed in October 2020 (four replicates); two additional iterations took place in June 2021 (5 replicates each). Coral colonies were collected from the fore reef on the north shore of Mo'orea on Scuba at 4-8 m depth and immediately returned to the research station and placed into flow-through seawater tables. After 24 h, all corals were cut into five ~10 cm long fragments and left to acclimate for 48 hours, and any macrosymbionts (e.g., Trapezia crabs, shrimp) were removed. All fragments were transferred to glass jars containing 500 ml of 0.2 μm-filtered (sterile) seawater with bubblers and air stones to promote aeration and water circulation, and photographed under a dissection microscope with 3.5-180X zoom (AmScope SM-1TSZZ-144S-10M). 

We then blindly assigned each jar containing a coral fragment to one of the following five treatments (such that one fragment from each coral colony was assigned to each treatment, 4 replicate colonies x 5 treatments = 20 coral fragments in separate jars): fresh feces from a corallivorous butterflyfish (FC); fresh feces from a grazer/detritivore (FG); sterilized feces from a corallivorous butterflyfish (SC); sterilized feces from a grazer/detritivore (SG); no-feces control (C). For the fresh feces treatments (FC, FG), we applied 100 µl of fresh feces isolated from the hindgut of the butterflyfish Chaetodon ornatissimus (FC) or the grazer/detritivore Ctenochaetus striatus (FG) directly onto each coral fragment. Fish were collected on the north shore of Mo'orea using a Hawaiian sling and immediately transported on ice to the laboratory. Feces were isolated from the hindgut using sterile tools by making an incision from the anus to the pelvic fin and removing the intestinal tract; feces were then squeezed from the hindgut into sterile collection tubes using sterile tweezers and pipetted onto coral fragments using 1 ml filter tips that were modified to widen the tip opening using a sterilized razor blade. For the sterilized feces treatments (SC, SG), fecal pellets were sterilized in a pressure cooker for 40 minutes at 120 °C and then applied in the same manner as fresh feces. The fresh feces used in the experiment were subsampled for DNA extractions by preservation in DNA/RNA Shield (Zymo Research, CA). No manipulation was conducted on the no-feces control fragments. The experiment ran for ~22 hours; this treatment duration is reflective of time periods over which corals may sometimes be in direct contact with fish feces in situ (up to 48 hours; Ezzat et al., 2019; Ezzat et al., 2021). 

Minor modifications were incorporated into the design of the second and third experimental iterations: for these iterations, five replicate colonies were used instead of four. Additionally, fecal treatments in these iterations were composed of feces from two individuals per fish species that were mixed prior to application (instead of using feces from a single fish individual per treatment as in the first experimental iteration).

To test how microbial communities in fish feces affected coral health, we quantified the frequencies and sizes of coral lesions caused by fecal treatments (in addition to measuring the photosynthetic efficiency of each fragment). In brief, fecal pellets were removed from each fragment and photographs were taken using a dissection microscope. 

Dissection microscope photographs were analyzed in ImageJ (version 1.53f51; Abràmoff, 2004). Each fragment was binned to one of three categories: “apparently healthy” (no change in fragment compared to before fecal application), “lesion” (fragment contains a novel patch of bare calcium carbonate, where coral tissue died and sloughed off following fecal application), or “dead” (fragment no longer contains live tissue; all tissue sloughed off following fecal application). The size of each lesion (excluding fragments binned as “apparently healthy” or “dead”) was measured by determining the average polyp size on each fragment in ImageJ by counting the number of polyps in a polygon of standardized size in triplicate. Then, the size of the lesion was measured (in pixels), and the lesion size was expressed as the estimated number of polyps that had died.

- Imported original files "Lesion frequencies.CSV" and "Lesion sizes.CSV" into the BCO-DMO system.
- Concatenated "graco_iteration", "Treatment", and "Colony" columns into a sample id for each table to join on
- Joined tables into single dataset "933832_v1_coral_lesion_fish_feces.csv"
- Renamed fields to comply with system requirements
- Added month of collection column as indicated in methods section
- Added columns for lat and lon of reef as a general collection location
- Saved final file as "933832_v1_coral_lesion_fish_feces.csv"
- Checked all scientific names referenced in methods section and the methods section of related dataset using World Register of Marine Species (WoRMS) Taxon Match. All scientific names referenced are valid and accepted names as of 2024-09-23
- Included "Identification_in_methods", "matched_AphiaID', "LSID", "AphiaID_accepted", and "ScientificName_accepted" in "taxon_identifiers.csv" supplemental file

NSF Award Abstract:
Climate change and local-scale anthropogenic stressors are degrading coral reefs across the globe. When conditions become too stressful on reefs, corals can lose beneficial microbial symbionts (e.g., dinoflagellates in the family Symbiodiniaceae) that live in their tissues via a process called “bleaching”. Although Symbiodiniaceae play key roles in the health of coral colonies, we know little about the processes that make symbionts available in the environment to prospective host corals. This research test the extent to which coral-eating fish feces, which contain live Symbiodiniaceae, facilitate symbiont acquisition by corals in their early life stages. It will generate seminal knowledge on how corallivore feces impact coral symbioses and health, and will assess the ecological importance of corallivorous fishes as drivers of coral symbiont assemblages. This research also test the extent to which corallivore feces are a source of food and nutrients that impact coral health; this has particular relevance to the survival and recovery of bleached adult corals. This research can ultimately inform intervention strategies to support reef resilience and mitigate reef degradation. Results from this project will be communicated widely in scientific arenas, in undergraduate education programs, and to the public via multimedia content and outreach. The Houston Independent School District (HISD, Houston, TX) is the nation’s 7th largest public school system. This work will enrich environmental science curricula for underrepresented minority students at under-resourced HISD high schools. This work will also support economically disadvantaged and first-generation undergraduate students in pursuing STEM majors and careers through multi-year research experiences.

Symbioses between foundation species (e.g., corals, sponges, trees) and microbiota (e.g., microeukaryotes, bacteria) underpin the biodiversity, productivity, and stability of ecosystems. Consumers, such as predators and herbivores, shape communities of these foundation species through trophic interactions. For instance, grazers contribute to the maintenance of coral dominance on reefs via consumption of macroalgal competitors. However, the indirect effects of other consumers on foundation species are rarely examined. Few studies have tested how consumers affect microbiota assembly in corals, even though coral symbionts (e.g., dinoflagellates in the family Symbiodiniaceae) play key roles in reef function and persistence. Corallivorous (coral-eating) fishes were recently demonstrated to egest large quantities of live Symbiodiniaceae cells as they swim across reefs. This research is testing the hypothesis that corallivore feces promote coral dominance on reefs by supporting coral acquisition of key symbionts and nutrients. The following research objectives will be accomplished: (1) to quantify the contribution of corallivorous fish feces to coral symbiont acquisition; and (2) to test the extent to which corallivorous fish feces influence coral health and recovery from thermal stress. Reefs are being degraded globally due to climate-change induced bleaching and associated mortality. This project is teasing apart the extent to which nutrients and/or live symbionts associated with corallivore feces contribute to the resilience of bleached corals under ambient and heat stress conditions. The research is tightly integrated with two education objectives: (1) to organize a Research Experience for Teachers (RET) program in which rigorous learning modules that high school teachers can incorporate into their Environmental Systems course offerings are developed and tested; and (2) to provide undergraduate students with a multi-year research experience through a partnership with the Rice Emerging Scholars Program (RESP).

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.