Project title

Testing different feeding strategies to increase corals resilience to thermal stress

Mentor name

Matthieu Leray, staff scientist, leraym@si.edu
Co-mentor name and position: Laura Marangoni, postdoc fellow
laurafbmarangoni@gmail.com

Location

Naos Marine Laboratory

Project summary and objectives

Food supplements have long been used to improve human health. Enriched food with supplements - the so-called “superfood” – for humans has been developed for decades to provide medical or health benefits, including prevention and treatment of diseases. Some of the major groups of components used in functional food to supplement endogenous levels in the human body include probiotics, lipids, and antioxidant. Antioxidants are molecules that protect a biological target against oxidative damage caused by free radicals (e.g. reactive oxygen species, ROS). A serious imbalance between the generation of ROS and antioxidant protection in favor to the former leads to oxidative stress, a physiological condition where excessive damage occur to biomolecules (e.g. lipids, proteins and DNA) ultimately leading to cell death and diseases. In the coral-algae (Symbiodiniaceae) association, higher quantities of ROS are generated by the algal symbionts, compared to the host coral tissue, due to their photosynthetic nature. Therefore, the maintenance of a good balance has been shown as an important mechanism of acclimation to changing temperature, while redox imbalance (ROS > antioxidants) is intimately linked to the process of coral bleaching - the breakdown of coral-Symbiodiniaceae symbiosis. Importantly, heterotrophic feeding with microcrustaceans has been shown to help the re-establishment of corals health after thermal stress, and feeding corals in early life stages with Artemia salina nauplii can enhance their settlement, and post-settlement survival and growth. Interestingly, few studies have also shown that supplying exogenous antioxidants (e.g. catechin, ascorbate and catalase, dissolved in seawater) can ameliorate the detrimental effects of free in corals and their photosynthetic endosymbionts (Symbiodinaceae) during thermal stress, therefore having the potential to mitigate coral bleaching.

Building up on these findings, the main goal of the present project is to test if enriched food in antioxidants specially developed for corals can turn them more resistant/resilient to thermal stress. For that, a controlled experiment will be conducted at STRI Naos Facilities. Coral species (Pocillopora sp.) collected in the Pacific Gulf of Panama (Islas Las Perlas) will be brought to the experimental facilities, fragmented, distributed in experimental aquaria, and acclimated for 2 weeks. After the acclimation period in the experimental aquaria, corals will be submitted to different feeding treatments (normal food, and enriched food). After two weeks of feeding, corals will be submitted to a thermal stress period (up to two weeks). By the end of thermal stress, the health of corals and their symbionts will be assessed using non-invasive techniques [Pulse amplitude modulated (PAM) fluorometry, Diving PAM, Walz]. After thermal is ceased, corals will be kept in the same aquaria for a four-week recovery period and their health will be assessed again using non-invasive (the same techniques previously mentioned) and other physiological and biochemical techniques to be performed at Naos Marine laboratories, such as quantification of protein biomass and chlorophyll content in corals.

Mentorship goals

The intern will have the opportunity to fully participate in the preparation and development of a controlled experiment designed to test resistance and resilience of corals to thermal stress under different feeding treatments. To name a few, this internship extension will allow the intern to learn: (1) how to set up an aquaria experimental system for symbiotic corals, (2) how to prepare coral nubbins (from mother colonies obtained from the field) to be used in experiments, (3) fundamental practices to conduct a successfully controlled experiment (e.g. how to manipulate and monitor physicochemical traits in the aquaria), and (4) to operate a portable pulse amplitude modulated fluorometer, among other physiological techniques in the laboratory.

Desired Background

The intern will work ~40 hours per week. The product would be a poster presentation at the intern symposium if timing is appropriate and co-authorship in future peer reviewed publications.

List of suggested readings

Marangoni LF de B, Rottier C, Ferrier-Pagès C. 2021. Symbiont regulation in Stylophora pistillata during cold stress: an acclimation mechanism against oxidative stress and severe bleaching. Journal of Experimental Biology 224. (doi:10.1242/jeb.235275)

Hughes TP, Kerry JT, Simpson T. 2018 Large-scale bleaching of corals on the Great Barrier Reef. Ecology 99, 501–501. (doi:10.1002/ecy.2092)

Weis VM. 2008 Cellular mechanisms of Cnidarian bleaching: stress causes the collapse of symbiosis. Journal of Experimental Biology 211, 3059–3066. (doi:10.1242/jeb.009597)

Suggett, D. J., & Smith, D. J. (2020). Coral bleaching patterns are the outcome of complex biological and environmental networking. Global Change Biology, 26(1), 68–79. (doi: 10.1111/gcb.14871)

Tremblay, P., Gori, A., Maguer, J. F., Hoogenboom, M., & Ferrier-Pagès, C. (2016). Heterotrophy promotes the re-establishment of photosynthate translocation in a symbiotic coral after heat stress. Scientific Reports, 6(1), Article 1. (doi: 10.1038/srep38112