Table of Contents

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

Fish collection

We sampled 17 species of coral reef fishes (Acanthurus nigricans, Cephalopholis argus, Cephalopholis urodeta, Chromis iomelas, Chromis margaritifer, Ctenochaetus marginatus, Ctenochaetus striatus, Paracirrhites arcatus, Plectroglyphidodon dickii, Pseudanthias bartlettorum, Pseudanthias dispar, Pseudanthias mooreanus, Pseudanthias olivaceous, Pseudianthias pascalus, Pseudanthias spp., Stegastes aureus, Stegastes fasciolatus) across three archipelagos and 19 islands (Jarvis, Kingman, Kiritimati, Palmyra, Tabuaeran, and Teraina in the Northern Line Islands; Flint, Malden, Millennium, Starbuck, and Vostok in the Southern Line Islands; Huahine, Moorea, Raiatea, Rangiroa, Tahiti, Takapoto, Tetiaroa, and Tikehau in French Polynesia), for a total of 5,251 fish. These 17 broadly distributed host species represent a large spectrum of body sizes, including multiple taxonomic and trophic groups. Due to the limitations on the natural geographic ranges of some species, not all species could be sampled on all islands; when we found that a target species was not present on a given island, we sampled a close congener instead (e.g., Stegastes fasciolatus instead of Stegastes aureus). In general, fish greater than 10 cm in total length were collected using three-pronged spears, while hand nets were used to capture fish smaller than 10 cm in length. Most fish were sampled from depths of 8 to 18 m from the leeward forereef of each island. After collection, fish were humanely euthanized using protocols in UC San Diego IACUC protocol #S09392, which provided ethical approval for this study. We then recorded morphometric data, including the total length of each fish (mm), before freezing fish immediately after collection. Fish were transported frozen back to the laboratory and were kept frozen until they were thawed for parasitological examination.

Parasite abundance assessment

We performed a comprehensive examination of each fish, designed to detect most metazoan parasites. We did not count mobile skin parasites or micropredators, as these are easily lost when the host is captured, and we did not search for myxozoan parasites, but all other metazoans should have been detected with our protocol. We adapted the dissection protocol to the morphology of each fish species (keeping the protocol consistent within species); both the generalized dissection protocol and departures from it are detailed elsewhere [see appendix E in Wood, Sandin, et al. (2014)]. Briefly, we examined the following organs individually under a stereomicroscope: fins, gills, eyes, heart, liver, spleen, gonad, gills, muscle, skin, and intestines [after Wood, Sandin, et al. (2014)]. When an organ was missing or damaged (e.g., part of fin was missing), we recorded “n/a,” not “0,”for any parasite species typically found in that organ (e.g., fin metacercariae). Photographs of each parasite species (along with detailed images of diagnostic morphological features) and voucher specimens were archived and are available for examination by request to the corresponding author. We identified parasites to the lowest possible taxonomic level using published keys [see appendix F in Wood, Sandin, et al. (2014)]: Wood CL, Sandin S, Zgliczynski B, Guerra AS, and Micheli F. 2014. Fishing drives declines in fish parasite diversity and has variable effects on parasite abundance. Ecology 95: 1929-46.

Data were originally entered into separate datasheets for each fish species / expedition combination, with separate columns for the number of each parasite species in each organ (e.g., separate columns for Nematode A in the stomach and Nematode A in the intestine). For each of these datasets, we first calculated the total number of parasite individuals for each parasite species across organs, summing across organs and doubling any bilateral organs where only half was counted (e.g., if we found 3 copepods in the buccal cavity and three parasites in the gills, but only counted the right gill arches, the total number of copepods presented in the dataset will be 9). These data therefore reflect the count of each parasite species across all the organs in which they were detected.

For each dataset, we then pivoted longer, such that each row is the count of one parasite species in one fish individual. There are therefore multiple rows for each fish individual, with parasite count as one column and parasite species as a separate column. This allowed us to concatenate datasets across the fish species / expedition combinations.

- imported "psite_group_taxa.csv", "island_locations.csv", "fish_sp_list.csv", and "full_dataset_2025.01.17.csv" into the BCO-DMO system, replacing NAs with blanks
- joined all files into one "945218_v1_parasite_abundance_coral_fish"
- split "fish_LSID" to get "fish_AphiaID"
- renamed fields to comply with BCO-DMO system requirements and to clarify values
- export dataset as "945218_v1_parasite_abundance_coral_fish.csv"

NSF Award Abstract:

Nontechnical explanation of the project's broader significance and importance

As Earth's ecosystems experience rapid biodiversity change, disease ecologists have turned to an urgent question: how might reductions in biodiversity affect the transmission of parasites? In other words, does biodiversity loss increase the abundance of parasites by eroding natural checks and balances on transmission? Alternatively, does it decrease parasite abundance by removing the free-living biodiversity on which parasites depend? This study will constitute the first comprehensive test of these questions in any ecosystem. It will evaluate the relationship between fish biodiversity and parasite abundance across 18 replicate coral reef ecosystems. Not only will the work explore whether reductions in fish biodiversity are associated with increases or decreases in parasite burdens, it will also assess whether parasite and host traits or geographical distance influence the direction and strength of this relationship. The theories that are tested are among the most important and controversial in the rapidly growing field of disease ecology and our work represents a novel, creative approach to a long standing, but unresolved research question. The work will yield transformative insights into the nature of parasite transmission in a changing world. Furthermore, the project will intimately intermingle education with research by launching the Research Internship in Molecular Ecology at California State Monterey Bay, which will place a group of underrepresented undergraduates in a central research role, and by developing and disseminating quality educational tools for teaching about parasite biodiversity through collaboration with the Network of Conservation Educators and Practitioners at the American Museum of Natural History. Parasites are often hidden and can be easy to overlook, but they are ecologically important and affect every population of marine animals.

Technical description of the project

The field of disease ecology is plagued by uncertainty and disagreement over whether biodiversity loss exacerbates parasite transmission, because it lacks the comprehensive, multi-host, multi-parasite, broad-spatial-scale dataset needed to formulate a convincing empirical test.

This project will answer this recalcitrant question, using a dataset of unprecedented replication and taxonomic and spatial resolution, by exploiting the advantages of a marine model system. The project is centered on a natural experiment in which the abundance of parasites across a highly resolved gradient of host biodiversity, for more than 77 parasite species and 18 replicate coral reef ecosystems will be quantified. Dataset will critically test hypotheses for the biodiversity-parasite abundance relationship, revealing how the direction, shape, and scale-dependence of this relationship vary across a diverse array of parasite taxa, and resolving questions of burning interest in the disease ecology literature - and of vital importance to marine conservation. This project will address the following questions: (Q1) For each parasite species detected, what is the direction and shape of the relationship between biodiversity and parasite abundance? (Q2) What factors (e.g., parasite traits like transmission strategy and host specificity, host traits like body size) determine the direction and shape of the relationship between biodiversity and parasite abundance? (Q3) How does spatial scale interact with parasite dispersal capacity to moderate the effects of biodiversity on parasite abundance? The work will integrate an existing dataset on fish biodiversity and abundance of coral reef fish parasites from six equatorial Pacific islands (the Northern Line Islands) with new sampling from 12 additional islands (the Southern Line Islands and French Polynesia). The resulting dataset will reflect the burden of >77 metazoan parasite taxa for seven species of coral reef fishes across18 islands. The work will provide the world's first data on the direction, magnitude, and shape of the biodiversity-disease relationship across a diversity of parasite taxa, host taxa, and spatial scales, and will comprehensively identify conditions under which biodiversity is likely to be important in determining the abundance of parasites - a fundamental contribution to ecology and to biological oceanography. The project will intimately integrate education with research by placing a group of underrepresented minority undergraduates in a central research role: performing the molecular analyses required to estimate parasite dispersal distance. A summer Research Internship in Molecular Ecology will be established at California State University Monterey Bay, a Hispanic-Serving Institution. The project will also underwrite the development of a peer-reviewed learning module on parasite biodiversity, to be developed and disseminated in collaboration with the American Museum of Natural History, and will support the training of two graduate students, one postdoctoral scholar, and several undergraduates.

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.