A Closer Look at REEFreshments®: REVIVE™ – Reviving Bleached Corals via Zooxanthellae and Proper Nutrition

One of the most interesting live feed products that we produce at Aquaholic Aquaculture is our REEFreshments: REVIVE™. Like our Live Phytoplankton, REVIVE™ is a blend of several species of microalgae. However, REVIVE™ is unique in that it not only provides a nutritious feed for corals (and other filter-feeding invertebrates), but REVIVE™ also contains zooxanthellae that can help ‘revive’ bleached corals when reintroduced into the aquarium. In this blog post, we will delve into the microalga ingredients that comprise REVIVE™ and how these specific microalgae work together to help return bleached corals to their former glory.

REEFreshments: REVIVE (32 oz. Bottle)
​© Aquaholic Aquaculture

What are Zooxanthellae? And What is Coral Bleaching?

Zooxanthellae are special microalgae that form a symbiotic relationship with corals (as well as certain other invertebrates, including: anemones, clams, jellyfish, sea fans, etc.). On a taxonomic level, the colloquial term "zooxanthellae" is synonymous to members of the family Symbiodiniaceae. These zooxanthellae live within the host’s tissue and provide the host with oxygen, food, and its iridescent colors. When a host is stressed, it expels its zooxanthellae and ‘bleaches’, losing its color. The symbiotic relationship that these hosts have with their zooxanthellae is necessary for the host’s growth and survival; without their zooxanthellae, hosts lose their color and eventually starve to death.

Microscopic image of zooxanthellae (Symbiodinium tridacnidorum)
​© Aquaholic Aquaculture

How Does REVIVE Work?

Corals expel their zooxanthellae when exposed to intolerable environmental stressors (e.g., extreme temperatures, sudden changes in water quality, etc.).
 
In the ocean when corals bleach and expel their zooxanthellae, the zooxanthellae remain in the water column. If the stressor that caused the coral to originally bleach is removed, the coral can uptake zooxanthellae from the water column and recover.
 
In contrast, when corals bleach in an aquarium setting, the expelled zooxanthellae are removed from the water column via mechanical filtration (e.g., protein skimmers). As such, when a coral bleaches in an aquarium, it cannot uptake the zooxanthellae that it expelled because those zooxanthellae have been effectively removed. This is where REVIVE™ comes in! REVIVE™ adds zooxanthellae back into the aquarium that the coral can uptake once the stressor that caused the bleaching event has been corrected.

Microscopic image of S. tridacnidorum
​© Aquaholic Aquaculture

How to Use REVIVE

REVIVE™ can be broadcast-fed or target-fed depending on the extent of the bleaching event. The necessary quantity and frequency of dosage is dependent on the severity and extent of the bleaching event as well as the water volume of the aquarium housing the affected corals.
 
When using REVIVE™ as a broadcast-feed, we recommend a starting dosage of ¼ oz per 10 gallons added every day to the aquarium in a high flow area. Mechanical filtration should be disabled for approximately 2 hours after dosing REVIVE™ to allow the corals time to uptake the microalgae.

Which Zooxanthellae were chosen for REVIVE?

Corals can be selective as to which zooxanthellae they will form a symbiotic relationship with. Because of this, we try to incorporate a variety of zooxanthellae species into REVIVE™ in order to increase the chances that target corals will be receptive to zooxanthellae uptake.
 
There are seven genera (formerly known as "clades") of Symbiodiniaceae, and numerous species (formerly referred to as "sub-clades") of zooxanthellae within each genus (LaJeunesse et al., 2018). 
 
Of the seven genera of Symbiodiniaceae, the genera Symbiodinium, Breviolum, Cladocopium, and Durusdinium (formerly clades A-D) are the main genera associated with coral symbiosis. As such, we have focused our efforts at Aquaholic Aquaculture on culturing zooxanthellae from these genera.
 
Typically REVIVE™ contains multiple species from either Symbiodinium, Breviolum, and/or Cladocopium. However, the specific zooxanthella composition of REVIVE™ does vary, as it is dependent on which species are thriving at the time that we bottle the product.

Microscopic image of S. tridacnidorum
​© Aquaholic Aquaculture

Microscopic image of Breviolum minutum
​© Aquaholic Aquaculture

A Closer Look at the Genera Selected for REVIVE™

All of the species that we have selected thus far for REVIVE™ are from either the genus Symbiodinium, Breviolum, or Cladocopium. The species that we culture were selected because of their relative hardiness and because they are known symbionts of corals kept in marine aquaria.
 
Most of our zooxanthella cultures have been isolated from motile hosts (e.g., jellyfish), and, as such, are able to adapt to various environments as well as rapid shifts in environmental conditions. These species can acclimate to both low and high light levels and are tolerant of both low and high temperatures, with some of them (e.g., Symbiodinium microadriaticum) being able to tolerate temperatures as high as almost 90F (Robinson & Warner, 2006).
 
All of our zooxanthella cultures are known symbionts of corals found in marine aquaria. Most of our Breviolum cultures are from the Caribbean, whereas our Symbiodinium and Cladocopium cultures are Indo-Pacific based. While some of our cultures were isolated from corals, most of our cultures were isolated from jellyfish (Cassiopeia), anemones (Aiptasia), and clams (Tridacna). However, despite being isolated from non-coral hosts, these zooxanthellae are also symbionts of corals in the wild and thrive in corals common in the aquarium industry, including but not limited to: Acropora sp., Capnella sp., Favia sp., Pocillopora sp., Porites sp., Sinularia sp., Stylophora sp., and Zoanthus sp.

Microscopic image of Symbiodinium microadriaticum
​© Aquaholic Aquaculture

Microscopic image of S. microadriaticum
​© Aquaholic Aquaculture

REVIVE™ and Nourish

In addition to zooxanthellae, REVIVE™ also contains the microalgae Rhodomonas sp. and Phaeodactylum tricornutum. Rhodomonas and Phaeodactylum are added to REVIVE™ as a supplemental live coral feed intended to aid with the recovery of bleached corals through providing high quality nutrition.
 
Aquarists often overlook the important role that live feeds play in the growth, coloration, and overall health of corals. While the zooxanthellae that reside within the tissues of the coral provide the coral with food, these zooxanthellae are only one component of nourishment for the coral. In order to sustain vibrancy and optimal health, corals require regular planktonic feedings in addition to the food created by the zooxanthellae.
 
Rhodomonas and Phaeodactylum have some of the highest microalgal polyunsaturated fatty acid concentrations making them a perfect addition to REVIVE™ for the purpose of nourishing your livestock back to health. Through dosing REVIVE™, bleached corals have the opportunity to uptake newly introduced zooxanthellae, and then these corals can feed on Rhodomonas and Phaeodactylum receiving the nourishment that they need to thrive.

How Fast Does REVIVE™ Work?

Recovery time for most corals fed REVIVE™ is at least one month, so do not expect a miracle overnight. It takes time for these corals to heal after being stressed. Removal of the initial stressor, consistent dosage of REVIVE™, and patience is key to successful coral recovery.
 
To read testimonials from customers who swear by our REVIVE™, please visit our Testimonials page.

Pearlberry Acropora
​© Aquaholic Aquaculture

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Interested in Purchasing REVIVE™?

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REEFreshments: REVIVE™ (64 oz. Pump Jug)
​© Aquaholic Aquaculture

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References

[1] LaJeunesse, T. C., Parkinson, J. E., Gabrielson, P. W., Jeong, H. J., Reimer, J. D., Voolsrra, C. R., & Santos, S. R. (2018). Systematic revision of Symbiodiniaceae highlights the antiquity and diversity of coral endosymbionts. Current Biology, 28(16).

[2] Robinson, J. D., & Warner, M. E. (2006).  Differential impacts of photoacclimation and thermal stress on the photobiology of four phylotypes of symbiodinium (pyrrhophyta). Journal of Phycology, 42​(3), 568-579.

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