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

2/9/2023

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 microalgae 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.). The 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 reuptake zooxanthellae from the water column and recover.

In contrast, when corals bleach in an aquarium setting, the expelled zooxanthellae is removed from the water column via mechanical filtration (e.g., protein skimmers). As such, when a coral bleaches in an aquarium, it cannot reuptake the zooxanthellae that it expelled because that zooxanthellae has been effectively removed. This is where REVIVE comes in! REVIVE adds zooxanthellae back into the aquarium that the coral can reuptake 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 into REVIVE in order to increase the chances that target corals will be receptive to zooxanthellae uptake.

There are at least 25 described species of zooxanthellae (Gomez, 2012), with hundreds of designated subspecies (clades) and sub-clades. In recent years, refinement in zooxanthellae extraction coupled with advances in genetic fingerprinting have allowed researchers to isolate and classify new various sub-clades and their variations. These zooxanthellae are each assigned alpha-numeric designations that indicate which clade and subclade they belong to. For example, the designation “A1” indicates that the zooxanthella belongs to clade “A” and sub-clade “1”. These alpha-numeric designations help to easily classify and categorize the various strains of zooxanthellae.

While clades A – G have been found in corals, the main clades associated with coral symbiosis are clades A, B, and C. As such, we have focused our efforts at Aquaholic Aquaculture on culturing zooxanthellae from clades A, B, and C.

Typically REVIVE contains multiple sub-clades from clades A, B, and/or C. However, the specific sub-clade composition of REVIVE does vary, as it is dependent on which clades 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 Sub-Clades selected for REVIVE

All of the sub-clades that we have selected for REVIVE are from clades A, B, and C. The sub-clades 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 zooxanthellae 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 sub-clades can acclimate to both low and high light levels and are tolerant of both low and high temperatures, with some of them (A1; Symbiodinium microadriaticum) being able to tolerate temperatures as high as almost 90F (Robinson & Warner, 2006).

All of our zooxanthellae cultures are known symbionts of corals found in marine aquaria. Most of our Clade B cultures are from the Caribbean, whereas our Clade A and C 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 native symbionts to corals in the wild and thrive in corals common in the aquarium industry, including: Acropora sp., Capnella sp., Favia sp., Pocillopora sp., Porites sp., Sinularia sp., Stylophora sp., and Zoanthus sp., among others.

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 food 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 a vibrancy and optimal health, corals require regular planktonic feedings in addition to the food created by the zooxanthellae.

Rhodomonas and Phaeodactylum have one 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 can recapture their previously expelled 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 2-3 weeks, 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.

Interested in Purchasing REVIVE?

Do you have a bleached coral that could benefit from REVIVE? Click the button below to visit our online shop.

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References

[1] Gomez, F., 2012. Problematic Biases in the Availability of Molecular Markers in Protists: The Example of the Dinoflagellates. Acta Protozoologica

[2] Robinson, J. and M. Warner, 2006. Differential impacts of photoacclimation and thermal stress on the photobiology of four phylotypes of symbiotic dinoflagellates. Poster presentation, AGU meeting.

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