Award Abstract # 1636022
Collaborative Research: Stability, flexibility, and functionality of thermally tolerant coral symbioses

NSF Org: OCE
Division Of Ocean Sciences
Recipient: THE PENNSYLVANIA STATE UNIVERSITY
Initial Amendment Date: August 18, 2016
Latest Amendment Date: July 8, 2022
Award Number: 1636022
Award Instrument: Standard Grant
Program Manager: Cynthia Suchman
csuchman@nsf.gov
 (703)292-2092
OCE
 Division Of Ocean Sciences
GEO
 Directorate for Geosciences
Start Date: September 1, 2016
End Date: July 31, 2023 (Estimated)
Total Intended Award Amount: $510,000.00
Total Awarded Amount to Date: $603,500.00
Funds Obligated to Date: FY 2016 = $510,000.00
FY 2021 = $93,500.00
History of Investigator:
  • Todd LaJeunesse (Principal Investigator)
Recipient Sponsored Research Office: Pennsylvania State Univ University Park
201 OLD MAIN
UNIVERSITY PARK
PA  US  16802-1503
(814)865-1372
Sponsor Congressional District: 15
Primary Place of Performance: Pennsylvania State Univ University Park
110 Technology Center Building
University Park
PA  US  16802-1503
Primary Place of Performance
Congressional District:
15
Unique Entity Identifier (UEI): NPM2J7MSCF61
Parent UEI:
NSF Program(s): BIOLOGICAL OCEANOGRAPHY
Primary Program Source: 01001617DB NSF RESEARCH & RELATED ACTIVIT
01002122DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 097Z, 102Z, 1097, 4444, 7657, 8556, 9117
Program Element Code(s): 165000
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

All reef-building corals require large numbers of internal symbiotic microalgae (called Symbiodinium) for their survival and growth. These mutualisms have shown considerable sensitivity to changes in the environment in recent decades, especially due to global increases in ocean temperatures. When exposed to severe thermal stress, corals loose their symbionts and often die. However, recent experiments show that some symbionts may be more stress-tolerant. Corals with these heat-resistant symbionts continue to receive high amounts of algal derived nutrients and grow under elevated temperatures. If the global trend in seawater warming continues to increase, these heat-resistant symbioses may become more ecologically prevalent on reef systems around the world and could play a critical role in maintaining healthy and productive coral communities. This project will examine the ecological and physiological attributes of stress-tolerant symbioses from the Indo Pacific where coral communities are the largest, most diverse, and productive in the world. The researchers will conduct a series of experiments to (1) evaluate host and symbiont attributes that contribute to thermal tolerance and (2) characterize the relative flexibility and functionality of various corals and symbionts exposed to typical ambient and stressful temperatures. Broader impacts of the project include the training of several Ph.D. students, undergraduates, and high school students in the disciplines of physiology and ecology. The researchers will partner with Global Ocean Exploration, Inc. to communicate this research to the general public through short documentary videos, editorials, and podcasts. An interactive K-5 program, "Invertebrates on the Road," will introduce elementary students in Pennsylvania to marine invertebrate diversity. Research results will also be disseminated to the public at the University of Delaware via educational seminars, as well as through hands-on research displays and demonstrations presented at the annual open house "Coast Day" festival in each year of the project.

This project will examine several attributes important to the functional ecology of coral-dinoflagellate symbioses. Specifically, the research team seeks to understand the interplay between coral and symbiont physiologies under different environmental conditions and determine the relative influence of biotic factors crucial to the performance of stress tolerant symbioses. Results from recent experiments on Indo-west Pacific corals found that Clade D (S. trenchii) symbionts are stress-tolerant. These symbionts are able to maintain function and provide nutrients to their hosts under high temperatures that typically elicit the breakdown of symbioses involving many other species of symbiont. A number of questions arise about how enhanced thermal tolerance symbioses may be aided by a combination of factors; for example: Are symbionts physiologically hardier in corals that are routinely feeding? Do host genotypes that are adapted to high temperatures affect the physiology of their symbionts in ways that make the partnership more stress-tolerant? A series of experiments over three years will examine the functionality of different coral-symbiont pairings exposed to ambient and high temperatures. Reciprocal transplants between inshore (stress-tolerant) and offshore (stress-susceptible) reef sites will be used to produce specific host-symbiont parings. Controlled experiments will test the relative importance of coral trophic status (nutrient content) while holding symbiont type constant and how changes in both coral trophic status and symbiont species identity of the resident affect thermal tolerance. Tank experiments on shore will track rates of photosynthesis as well as carbon translocation and assimilation from symbiont to host tissues and skeletons. Long-term growth rates via skeletal density, linear extension, and biomass gain will also be measured. This project will help elucidate how biochemical, physiological and ecological differences among host-symbiont pairings may respond to rising ocean temperatures and enhance the future viability of coral reefs.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

Note:  When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

Turnham, Kira E and Lewis, Allison M and Kemp, Dustin W and Warner, Mark E and Wham, Drew F and Smith, Robin T and Hoadley, Kenneth and Colin, Patrick L and Golbuu, Yimnang and LaJeunesse, Todd C "Limited persistence of the heat-tolerant zooxanthella, Durusdinium trenchii, in corals transplanted to a barrier reef where it is rare among natal colonies" Coral Reefs , 2025 https://doi.org/10.1007/s00338-025-02625-w Citation Details

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

This project was initiated to understand the physiological and ecological mechanisms that reef coral mutualisms cope with environmental change (i.e. global warming). The close relationship between animal corals and internal photosynthetic symbionts is recognized as a major weakness when exposed to severe marine heat waves and the cause of mass coral mortality and reef ecosystem degradation over large geographic scales. Specifically, this research detailed the extent to which the identity of the symbiont contributed to stress sensitivity as well as stress tolerance. Working in the Island nation of Palau provided unique access to a breadth of coral diversity represented by colonies from various reef habitats harboring very different symbiont species in a small geographic area. Once identified, distinct partner combinations were manipulated in field experiments (i.e. reciprocal transplants to different environments/habitats, in situ monitoring) and onshore tank experiments (i.e. artificial thermal stress experiments). Long-term fieldwork of this nature is extremely challenging and while there were several setbacks (e.g. destruction by typhoons; pandemic travel restrictions) the project was an overall success. Highlights of our discoveries (as well as their intellectual merits and impacts) are presented below. Note that this list is not exhaustive. There were many other accomplishments and published discoveries including several manuscripts in preparation, which were omitted for brevity.  

1. Nutritional equivalences among corals from different habitats with different symbionts (Figure 1). Building upon recent findings, which documented inshore colonies better tolerated thermal stress than offshore colonies, we found that most colonies from each habitat contained similar lipid, protein, and carbohydrate content contrary to expectations, and therefore concluded that the symbiont species, not necessarily access to greater amounts of nutrient reserves, was the most consequential feature that explained thermal tolerance among colonies. While host genotypic diversity is also important, these findings further underscore the essential role of symbiont identity in the stability of these mutualisms exposed to physiological stress.

 

2. Corals with thermally tolerant symbionts experience little or no metabolic trade-offs (Figure 2). Colonies harboring symbionts adapted to high temperatures do not necessarily experience physiological trade-offs that compromise the growth and reproductive capabilities of the host. Moreover, the continued maintenance of nutrient assimilation and translocation when subjected to high temperatures largely explains why some mutualisms are tolerant to stress while others are not. These findings dispel the dogma that hosting heat-adapted symbionts has negative consequences and further highlight how these mutualisms may respond on ecological time scales to significant environmental change through partner recombination while maintaining ecosystem productivity.

3. The diversity, distribution, and temporal stability of coral ‘zooxanthellae’ on a Pacific reef: from the scale of individual colonies to across the host community (Figure 3). Complementary to the major objectives of this project, discoveries from coinciding (opportune) research substantiated and advanced our fundamental understanding of these mutualisms. Our continued monitoring of numerous and diverse tagged corals showed conclusively that individual colonies typically maintain long-term stable relationships comprising one symbiont species whose population is genetically homogenous (clonal). This further emphasizes the need to further study genotype-by-genotype interactions and the importance of this diversity under increased natural selection pressure.

 

4. Formal characterization and identification of species (Figure 4). Major progress was made in codifying symbiont taxonomy and systematics critical for use in subsequent scientific correspondence related to this research project and beyond. These supporting works establish that different symbiont species possess different ecological niches. Such fundamental improvement to taxonomy offers new perspectives about the community composition and ecology of these mutualisms and reveals and abundance of new questions for future research.

 

5. Broader Impacts.

Over the course of our project there were numerous public outreach activities and presentations at K-12 schools, National Academy workshops, Scientific conferences and university alumni associations. A few major highlights include:

 

-YouTube/vimeo video about our project. Palau Coral: Glimmer of Hope was produced with funds from this grant (https://www.youtube.com/watch?v=o5M2_tXG5Zo&t=28s).  and has been viewed 25,000 times on YouTube and was featured at the 2019 International Ocean Film Festival in San Francisco.

 

-Feature (cover) Article, “Solar Symbionts,” in Coral Magazine (vol.18 (5) Sept/Oct 2021) a beautiful comprehensive review of coral-algal mutualisms written for lay enthusiasts. This magazine is a high quality bi-monthly periodical for marine aquarists with a circulation of thirty-five thousand international subscribers.

 

Four graduate students (3 women and one male) directly involved in this project received their Ph.D. degrees: 1 from Delaware, 1 from U. of Alabama, Birmingham, and two from Penn State. Several other students also benefitted, albeit somewhat indirectly. Numerous undergraduates at all three institutions received scientific training as well. To date, well over a dozen research papers supported by this grant are published and already well cited.

 


Last Modified: 01/12/2024
Modified by: Todd C Lajeunesse

Please report errors in award information by writing to: awardsearch@nsf.gov.

Print this page

Back to Top of page