New Strains of Zooxanthellae for 'Reviving' Bleached Aquarium Inhabitants

Enhancing the Efficacy of REVIVE™: Live Zooxanthellae

In the wild when a coral bleaches (i.e., expels its zooxanthellae) it has the opportunity to uptake new zooxanthellae from the water column (via indirect transmission) and heal. In contrast, when corals bleach in aquariums the expelled zooxanthellae are effectively removed via modern mechanical filtration, inhibiting corals from reuptaking the zooxanthellae. The main goal of REVIVE™ is to add live zooxanthellae back into the aquarium, providing corals with the opportunity to uptake the newly introduced zooxanthellae and recover (assuming that the stressor that caused the bleaching event has since been remedied).
 
REVIVE™ currently contains symbiont species from the genera Symbiodinium, Breviolum, and Cladocopium (formerly classified as Clade A, B, and C, respectively). While its current formulation has been undoubtedly successful in ‘reviving’ bleached aquarium inhabitants (see our Testimonials page), at Aquaholic Aquaculture® we are always trying to improve our products, ensuring that we continue to provide aquarists with superior live feeds. The more unique strains from various genera that REVIVE™ contains, the likelier that one (or more) of the strains is a symbiont ‘match’ for the bleached aquarium inhabitant(s). As such, we have spent the last few years searching for new unique strains of zooxanthellae that would be appropriate for us to mass culture and add to our current REVIVE™ blend in order to enhance its overall efficacy.
 
New zooxanthella starter cultures are difficult to acquire, and zooxanthellae are notoriously challenging to grow in a laboratory setting separate from their hosts, making them exceptionally challenging to reliably produce at commercial-scale volumes. Since the release of our product REVIVE™: Live Zooxanthellae in 2017, we have worked to acquire and commercially produce new strains of zooxanthellae, but, despite numerous culture attempts with various species of symbionts, we have had no tangible outcomes until…

Four New Promising Zooxanthella Candidates for REVIVE™

After years of trial-and-error experimentation, we are excited to announce that we finally have four new promising zooxanthella strains for REVIVE™!
 
All four of the new strains of zooxanthellae are theoretically great candidates for aquarium-purposes, as all four of them are known coral symbionts. To date, all four new strains have been responding well to our attempts to gradually scale them up for mass culture. While we are still perfecting our culture protocols for each of them, based on their recorded growth under our current culture methods over the course of the last several months, we feel confident that with patience and further refinement of our protocols that all four of these strains have the capacity for commercial production.

Two New Strains of Cladocopium

Two of the four new strains that we are currently having success with are from the genus Cladocopium (formerly Clade C). One of the new strains is C. goreaui and was isolated from a Rhodactis osculifera (formerly Discosoma sanctithomaei; commonly known as the “St. Thomas Mushroom” in the aquarium hobby) in Jamaica. The other strain of Cladocopium was isolated from a Mastigias papua (i.e., lagoon jellyfish) in Palau. While we have had some prior success commercially producing strains from this genus, Cladocopium is notoriously difficult to culture, so we are thrilled that these two new strains are currently doing so well at our facility.
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Strains of zooxanthellae from Cladocopium are of great interest for use in a product like REVIVE™, as members of this genus are native symbionts of many of the symbiotic host invertebrates found in the aquarium trade. Cladocopium is the most ecologically abundant and broadly distributed genius of Symbiodiniaceae, and is commonly found in symbiosis with a plethora of corals, other cnidarians, clams, etc. (LaJeunesse et al., 2018; Riddle, 2016). This specialist genus of zooxanthellae is adapted for thriving in conditions that mimic a natural coral reef ecosystem, and symbionts of this genus are likely to be selected for uptake by many of the host species found in a typical reef aquarium.

Two New Strains of Durusdinium

The other two promising new symbionts are unique strains of Durusdinium (formerly Clade D). One of the new strains of D. trenchii that we are culturing was isolated from an Acropora sp. in Okinawa, and the other was isolated from an Orbicella faveolata (i.e., Mountainous Star Coral) in the Florida Keys.
 
We have hoped for a while to bring this particular genus of Symbiodiniaceae to the aquarium industry, as research has shown that members of Durusdinium tend to be highly robust and stress-tolerant, bolstering their host’s immunity to environmental stressors (LaJeunesse et al., 2009; LaJeunesse et al., 2018). In the last twenty years, numerous studies have illustrated that Durusdinium is remarkably resilient, with these extremophiles being specially adapted to tolerate harsh conditions including: significant fluctuations in temperature, salinity, nutrients, sediments, turbidity, air exposure, rainfall, and light intensity (LaJeunesse et al., 2018; Mashini et al., 2015; Muller-Parker et al., 2015; Toller et al., 2001a). Research has shown that corals in symbioses primarily with members of Durusdinium are more likely to resist bleaching, survive through bleaching events, and recover from bleaching (Baker, 1999; Baker et al., 2004; LaJeunesse et al., 2009; LaJeunesse et al., 2018; Manzello et al., 2018, Toller et al., 2001a; Toller et al., 2001b; Wang et al., 2022). Theoretically, including strains of Durusdinium in a product like REVIVE™ could be revolutionary, significantly increasing aquarists’ ability to ‘revive’ bleached inhabitants.

Microscopic image of C. goreaui
​© Aquaholic Aquaculture

Microscopic image of Cladocopium sp. 
​© Aquaholic Aquaculture

Microscopic image of D. trenchii 
​© Aquaholic Aquaculture

Microscopic image of D. trenchii 
​© Aquaholic Aquaculture

What's Next?

Reliable Commercial-Scale Volumes & Testing

​Currently we are in the process of further refining our culture protocols for each of these four new strains and gradually ramping up their production. Our goal is to continue to optimize our culture methods and soon be able to reliably produce these new strains in commercial volumes. Once we have achieved consistent commercial-scale volumes, we will begin the extensive ‘Testing Phase’ that each of our strains currently utilized in REVIVE™ has undergone. During the ‘Testing Phase’ we will ensure that these new strains have the potential to be beneficial to reef aquarium inhabitants (and in no way harmful to them). We will also analyze each strain’s ability to withstand periods of prolonged refrigerated storage, as every strain included in REVIVE™ must be able to achieve a minimum four-month shelf life in order to be viable for commercial distribution.

The Road Ahead

In sum, while we are excited that these four new strains are the most promising zooxanthella cultures that we have worked with in a very long time and we are eager to add them to REVIVE™, it will still be a while before any of these new strains will be ready for commercial distribution. However, we feel confident that the wait will be worth it! With every new zooxanthella strain added to REVIVE™, we enhance its overall efficacy and increase the capacity for aquarists’ success maintaining their reef aquariums.
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Stay tuned as we continue to work to bring these new strains to you and your aquarium. Cheers!

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Want to be First to Try the New and Improved REVIVE™?

As we continue to ramp up production of these new zooxanthella strains and approach the ‘Testing Phase’, we will be on the lookout for aquarists who would like to be among the first to test these four new strains of zooxanthellae described above in our newly formulated blend of REVIVE™. Interested in being one of the first to try the new and improved REVIVE™? Reach out to us at [email protected] to join our beta-tester waitlist.

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References

[1] Baker, A. C. (1999). Symbiosis ecology of reef-building corals. Ph.D. dissertation. University of Miami.
 
[2] Baker, A. C., Starger, C. J., McClanahan, T. R., & Glynn, P. W. (2004). Corals' adaptive response to climate change. Nature.
 
[3] LaJeunesse, T. C. (2002). Diversity and community structure of symbiotic dinoflagellates from Caribbean coral reefs. Marine Biology.
 
[4] LaJeunesse, T. C., Smith, R. T., Finney, J., & Oxenford, H. (2009). Outbreak and persistence of opportunistic symbiotic dinoflagellates during the 2005 Caribbean mass coral 'bleaching' event. Proceedings of The Royal Society. 276(1676).
 
[5] LaJeunesse, T. C., Parkinson, J. E., Gabrielson, P. W., Jeong, H. J., Reimer, J. D., Voolstra, C. R., & Santos, S. R. (2018). Systematic revision of Symbiodiniaceae highlights the antiquity and diversity of coral endosymbionts. Current Biology, 28(16).
 
[6] Manzello, D. P., Matz, M. V., Enochs, I. C., Valentino, L., Carlton, R. D., Kolodziej, G., Serrano, X., Towle, E. K., & Jankulak, M. (2019). Role of host genetics and heat-tolerant algal symbionts in sustaining populations of the endangered coral Orbicella faveolata in the Florida Keys with ocean warming. Global Change Biology. 25(3).
 
[7] Mashini, A. G., Parsa, S., & Mostafavi, P. G. (2015). Comparison of Symbiodinium populations in corals from subtidal region and tidal pools of northern coasts of Hengam Island, Iran. Journal of Experimental Marine Biology and Ecology, 473.
 
[8] Muller-Parker, G., D’Elia, C.F., & Cook, C.B. (2015). Interactions between corals and their symbiotic algae. In: Birkeland, C. (eds) Coral Reefs in the Anthropocene.
 
[9] Riddle, D. (2016). An update on Symbiodinium species and their hosts. Advanced Aquarist.
 
[10] Toller, W. W., Rowan, R., & Knowlton, N. (2001a). Zooxanthellae of the Montastraea annularis species complex: patterns of distribution of four taxa of Symbiodinium on different reefs and across depths. Biological Bulletin, 201(3).
 
[11] Toller, W. W., Rowan, R., & Knowlton, N. (2001b). Repopulation of zooxanthellae in the Caribbean corals Montastraea annularis and M. faveolata following experimental and disease-associated bleaching. Biological Bulletin. 201(3).
 
[12] Wang, C., Zheng, X., Li, Y., Sun, D., Huang, W., & Shi, T. (2022). Symbiont shuffling dynamics associated with photodamage during temperature stress in coral symbiosis. Ecological Indicators, 145.