Why would you ever want a refugium?

[i_declare_bankruptcy]

Let me preface this by saying that I'm starting a refugium right now. Also, I studied computer science and physics in school and I can't balance a chemical equation; I'm not sharp there.

I've been reading about coral reefs (at my mortal level of intelligence, mind you) and have encountered some contradicting information. Primarily, the role of algae in the reef ecosystem. As we know, algae abundance is bad -- it can smother corals, look ugly, and clog up equipment. One way some combat algae is through refugiums on the premise that they "out compete" the algae in the display tank. A seemingly unnatural (though our tanks are inherently unnatural) part of the ecosystem based on my reading. However, from my understanding of reefs, this could actually be a detriment in some circumstances. According to Coral Reefs in the Microbial Seas (Forrest Rohwer, Merry Youle), DDAM (DOC, Death, Algae, and Microbes) is responsible for a large amount of reef bleaching events. The theory states that the overgrowth of algae can potentially release excess DOC (dissolved organic carbon) into the water column, thus providing a wealth of nutrients for microbes to consume and grow. If the microbes in the coral encounter these nutrients and grow too quickly, they could potentially consume the local oxygen at such a rate that the coral is asphyxiated. Additionally, some turf algae has been shown to carry specific pathogens that can cause white-band disease in corals through the means of physical contact. Sources: Coral Reefs in the Microbial Seas 104-115; additional sources used by the text are cited there as well.

Based on this understanding, could popular refugium algae such as Chaetomorpha, provide the conditions necessary to harm coral health?

The text continues to describe the importance of herbivores (and the entire upper food chain) of a reef. Without the herbivores, the algae can grow excessively, consuming the nutrients and elements (hope I'm not butchering this) needed for growth (phosphorous, iron, nitrogen) disproportionately quickly. However, the algae can continue to photosynthesize without growing -- by releasing excess DOC into the water. Taking this point quite a bit out of context, could it be reasonable to assume that you can have too large of a Fuge which can have these effects; too much chaeto starving the corals not only for nutrients but also CO2 AND producing excess DOCs? Can this reinforce the importance of managing algal blooms (especially GHA) on the grounds that they can not only starve the corals, but produce microbe-feeding DOCs and potentially harbor bacteria and phages (this might be stretching it) that can harm corals? Sources: Coral Reefs in the Microbial Seas 104-110; additional sources used by the text are cited there as well.

What about in a mature reef? It seems lots of mature reefs can handle excess feeding / nutrients better than younger reefs. Many attribute this to bacterial diversity and population (probably right); but what about surface area? If the algae can't grow anywhere because everything is covered by coral colonies, it cannot take hold, and thus those excess nutrients fuel coral growth instead of DOC-releasing algae? OR, the excess nutrients prevent algae from releasing DOC because it is always able to create biomass from photosynthesis VS extra DOC because of the availability of nitrogen and phosphorous; so even if it did take hold in a mature or high nutrient reef, it wouldn't have as devastating of an impact?

Lastly, could the distance from refugium to coral have an impact? Can DOCs released from Chaetomorpha or others breakdown quickly so they can't make it to a coral / could proximity of turf algae to coral be a factor in coral health we haven't thought of as much from a reef hobbyist perspective?

If you're still with me and don't hate me for butchering that, I'd love to hear your thoughts! I really want to learn more about how reefs work and the biochemistry behind it. Maybe it's time I tried to learn some basic chemistry.

 

[OREGONIC]

Over my head, but following!

 

[EmdeReef]

It’s an interesting topic that could be debated forever. Fwiw IMO most refugiums are too small to cause issues described in many studies on “microbialization.” I would say the biggest risk comes from certain macroalgae that can take plague proportions in your DT. It’s usually pretty rare and in many cases a foxface will solve the problem.

One long thread with good info:

Algae release "useful proteins, carbohydrates and metabolites."

That is from your Triton method description: https://www.triton.de/en/products-services/triton-method/ "A healthy algae refuge will consume animal waste by-products and some metals while exporting useful proteins, carbohydrates and metabolites." What is the basis for saying these these...

www.reef2reef.com

 

[TheHarold]

My understanding is that only dying algae releases mentioned DOCs. Healthy algae (clearly; given it grows) uses and uptakes more nutrients than it releases. Then we trash a good portion of it, and repeat the cycle.

 

[i_declare_bankruptcy]

It’s an interesting topic that could be debated forever. Fwiw IMO most refugiums are too small to cause issues described in many studies on “microbialization.” I would say the biggest risk comes from certain macroalgae that can take plague proportions in your DT. It’s usually pretty rare and in many cases a foxface will solve the problem.

One long thread with good info:

Algae release "useful proteins, carbohydrates and metabolites."

That is from your Triton method description: https://www.triton.de/en/products-services/triton-method/ "A healthy algae refuge will consume animal waste by-products and some metals while exporting useful proteins, carbohydrates and metabolites." What is the basis for saying these these...

www.reef2reef.com

Thank you, going to read through that. I was thinking the same -- fuges are often pretty small and often pruned so likely would not be an issue (but I wanted to make these points to understand the concepts anyways). If you have any other studies/literature that a n00b can understand I'd love to see it!

My understanding is that only dying algae releases mentioned DOCs. Healthy algae (clearly; given it grows) uses and uptakes more nutrients than it releases. Then we trash a good portion of it, and repeat the cycle.

Any sources for dying algae releasing DOCs? I'd love to read. I would have though dying algae would be POC (particulate organic carbon) but perhaps as it decomposes, small enough particles (like, smaller than POC), are released?

 

[EmdeReef]

My understanding is that only dying algae releases mentioned DOCs. Healthy algae (clearly; given it grows) uses and uptakes more nutrients than it releases. Then we trash a good portion of it, and repeat the cycle.

DOC is released through metabolism/photosynthesis

 

[i_declare_bankruptcy]

I think I missed a point in my OP as well. Part of why I titled my thread this way is because I don't understand: if refugiums are indeed small enough or trimmed enough to prevent this from being an issue, wouldn't they be less or potentially completely ineffective at outcompeting display algae? I understand we use lighting that is preferred by the algae in the Fuge; but surely it can't fully outcompete the display algae in our small fuges?

 

[EmdeReef]

I think I missed a point in my OP as well. Part of why I titled my thread this way is because I don't understand: if refugiums are indeed small enough or trimmed enough to prevent this from being an issue, wouldn't they be less or potentially completely ineffective at outcompeting display algae? I understand we use lighting that is preferred by the algae in the Fuge; but surely it can't fully outcompete the display algae in our small fuges?

We usually grow macroalgae which are always going to be slower than microalgae found in the water column where you can have a million cells per ml of water. I think that theory was started by one of the YouTube series and is quite frankly pure fantasy.

The benefit of a refugium is nutrient export, some O2 production, and a ph boost - the effect will be correlated to the growth area, lighting, nutrients etc.

 

[EmdeReef]

Thank you, going to read through that. I was thinking the same -- fuges are often pretty small and often pruned so likely would not be an issue (but I wanted to make these points to understand the concepts anyways). If you have any other studies/literature that a n00b can understand I'd love to see it!



Any sources for dying algae releasing DOCs? I'd love to read. I would have though dying algae would be POC (particulate organic carbon) but perhaps as it decomposes, small enough particles (like, smaller than POC), are released?

I’ll look through my files tomorrow to send you some studies I find helpful.

 

[aqua_code]

I find this interesting because it contradicts research I've been doing recently on sea grass. From the articles I've been reading - sea grass is greatly beneficial to reefs and reduces pathogens. One added benefit that isn't really discussed in the OP is the copepod population and biodiversity within the refugium.

I've seen several studies like this referencing better coral health when macroalgae is present in the system.

Science | AAAS

science.sciencemag.org

 

[Jacked Reefer]

In a properly run fuge you don't need to worry about many of these issues. Providing correct amounts of light? Avoid excess CO2. Removing algae when needed? Avoid major die offs and the replenishment of nutrients into the water. Really all the algae in a fuge does is make it easier to remove excess organic compounds and gives you a longer time. The premise of a reef tank is keeping everything balanced. Growing algae under your tank instead of in it is no exception. And your topic about mature reefs. Algae can and will grow on coral. It is the same maintenance that allowed it to get mature that allows it to stay balanced.
You do bring up some good points in your reasoning. But ocean does not translate to fish tank though they may both be salt water. Maybe your theories would be applicable if there was a large tank which received no care with a massive refugium.

edit: Sorry if i came off as stand off-ish, Am in the process of writing an argumentative essay for school lol

 

[i_declare_bankruptcy]

Perhaps an important fact I missed is that we grow macroalgae which is different from the micro algae such as turf algae that I'm referencing. I don't know how much of a difference, but perhaps that is an important distinction. Also, to your point @EmdeReef, the primary benefit of a refugium is nutrient export and pH balancing, NOT outcompeting algae as some believe -- though that can be a beneficial side effect of the nutrient export. I think I let that get in my head and put myself down this train of thought.

I did take things to an extreme -- but that was so I could understand and repeat the concepts. I do wonder if it still poses an increased risk of infection via pathogen or asphyxiation due to increased DOC on a smaller scale purely from a conceptual / theoretical point of view.

Thanks for all the good info everyone If anyone has more suggested readings I'm all ears/eyes!

 

[i_declare_bankruptcy]

I find this interesting because it contradicts research I've been doing recently on sea grass. From the articles I've been reading - sea grass is greatly beneficial to reefs and reduces pathogens. One added benefit that isn't really discussed in the OP is the copepod population and biodiversity within the refugium.

I've seen several studies like this referencing better coral health when macroalgae is present in the system.

Science | AAAS

science.sciencemag.org

I have heard some theorize that the macro algae can provide amino acids/proteins that can benefit the corals? These kinds of things make me wish I was a marine biologist; I'd love to test these hypotheses!

 

[aqua_code]

I think another interesting connection is how mangroves benefit coral populations.

Mangroves protecting corals from climate change

Corals are finding refuge within the red mangroves at Hurricane Hole, a mangrove habitat in the US Virgin Islands, from threats such as warming ocean temperatures, solar radiation and increased ocean acidification.

www.sciencedaily.com

Sea grass and macroalgae is seeded within these mangrove roots and forests. This helps with the sustainability and balance within the ecosystem. It also helps oxygenate the sand bed and provides phosphate/nitrate benefits. This creates a more stable environment for the corals by acting as a buffer when parameters go through swings. Mangroves are not very popular in the hobby, because they are super slow to grow.

Chaeto however - is definitely showing positive results for many reefers. There are alot of successful tanks using the Triton method which is meant to be a closed system with no water changes and a refugium. If the macro was releasing toxins I think people using this methodology would not be successful.

 

[ScottR]

A bit off topic but some people keep macro for the sake of housing and growing pod numbers.

 

[KrisReef]

Great thread.
The only difficulty in trying to copy the handiwork of God is that we don't have enough information to replicate god. There is one great reference book that indicates this but most people only read the Ten Commandments and think they've got it all figured out.
Still, It's in our nature to try and sometimes we kind of succeed.

What I have often wondered about is when was the last time the ocean had a water change? The coral and fish that live there seem to have been thriving for a while since the last one.

"Algae abundance is bad" in a reef tank? I like the healthy growth of symbiotic algae in mine.

I will also admit I can't balance my checkbook or complicated chemical equations and rarely are my comments not a bit snarky but I do hope they are helpful in stimulating thought. Our tanks and the equipment attached to them can be successful in keeping coral and fish for very short times in relation to the time that reefs and the ocean have been chugging along without a protein skimmer or a refuge or even a QT dip for all of the planktonic drift. It certainly does provide a lot to ponder and a keen challenge to imitate.

 

[Hermie]

it's a bit late and I admit I did not read through the whole thread, but the premise of DOC fueling microbes which damage corals is based on algae being within a very close proximity to algae from what I recall. That means, unless your algae is growing literally centimeters away from your corals (at most, IIRC), then any microbe-fueling DOCs will disperse into the water column before they can cause problems with the coral tissues.

 

[edgewater]

Following!

 

[sixty_reefer]

Interesting thread, I have been playing with the idea of DOC in phytoplankton to fuel my aerobic bacteria, only seen good things so far.

 

[Dan_P]

Let me preface this by saying that I'm starting a refugium right now. Also, I studied computer science and physics in school and I can't balance a chemical equation; I'm not sharp there.

I've been reading about coral reefs (at my mortal level of intelligence, mind you) and have encountered some contradicting information. Primarily, the role of algae in the reef ecosystem. As we know, algae abundance is bad -- it can smother corals, look ugly, and clog up equipment. One way some combat algae is through refugiums on the premise that they "out compete" the algae in the display tank. A seemingly unnatural (though our tanks are inherently unnatural) part of the ecosystem based on my reading. However, from my understanding of reefs, this could actually be a detriment in some circumstances. According to Coral Reefs in the Microbial Seas (Forrest Rohwer, Merry Youle), DDAM (DOC, Death, Algae, and Microbes) is responsible for a large amount of reef bleaching events. The theory states that the overgrowth of algae can potentially release excess DOC (dissolved organic carbon) into the water column, thus providing a wealth of nutrients for microbes to consume and grow. If the microbes in the coral encounter these nutrients and grow too quickly, they could potentially consume the local oxygen at such a rate that the coral is asphyxiated. Additionally, some turf algae has been shown to carry specific pathogens that can cause white-band disease in corals through the means of physical contact. Sources: Coral Reefs in the Microbial Seas 104-115; additional sources used by the text are cited there as well.

Based on this understanding, could popular refugium algae such as Chaetomorpha, provide the conditions necessary to harm coral health?

The text continues to describe the importance of herbivores (and the entire upper food chain) of a reef. Without the herbivores, the algae can grow excessively, consuming the nutrients and elements (hope I'm not butchering this) needed for growth (phosphorous, iron, nitrogen) disproportionately quickly. However, the algae can continue to photosynthesize without growing -- by releasing excess DOC into the water. Taking this point quite a bit out of context, could it be reasonable to assume that you can have too large of a Fuge which can have these effects; too much chaeto starving the corals not only for nutrients but also CO2 AND producing excess DOCs? Can this reinforce the importance of managing algal blooms (especially GHA) on the grounds that they can not only starve the corals, but produce microbe-feeding DOCs and potentially harbor bacteria and phages (this might be stretching it) that can harm corals? Sources: Coral Reefs in the Microbial Seas 104-110; additional sources used by the text are cited there as well.

What about in a mature reef? It seems lots of mature reefs can handle excess feeding / nutrients better than younger reefs. Many attribute this to bacterial diversity and population (probably right); but what about surface area? If the algae can't grow anywhere because everything is covered by coral colonies, it cannot take hold, and thus those excess nutrients fuel coral growth instead of DOC-releasing algae? OR, the excess nutrients prevent algae from releasing DOC because it is always able to create biomass from photosynthesis VS extra DOC because of the availability of nitrogen and phosphorous; so even if it did take hold in a mature or high nutrient reef, it wouldn't have as devastating of an impact?

Lastly, could the distance from refugium to coral have an impact? Can DOCs released from Chaetomorpha or others breakdown quickly so they can't make it to a coral / could proximity of turf algae to coral be a factor in coral health we haven't thought of as much from a reef hobbyist perspective?

If you're still with me and don't hate me for butchering that, I'd love to hear your thoughts! I really want to learn more about how reefs work and the biochemistry behind it. Maybe it's time I tried to learn some basic chemistry.

These very interesting questions and difficult to answer with certainty, but here some thoughts.

After rereading the chapter you mentioned, I remember thinking the same thing, “why would anyone want to grow macro algae in the presence of coral”. I then wondered whether growing macro algae was an indirect way of carbon dosing and that both bacteria and the algae were consuming nitrate and phosphate. And therein lies one possible explanation why growing macro algae does not harm coral. Bacteria in the aquarium keep macro algae exudate concentration low and prevent the overfeeding of bacteria associated with coral.

I think that you offer a second explanation for macro algae not harming coral. If nitrate and phosphate are sufficiently high, then algae are able to use their photosynthetic products to build mass rather than dumping them to the water.

Another thought is that we are harming coral but the progression of the illness is such that we cannot make the connection between the difficulty growing coral and macro algae growth. Similarly, the average aquarist is not able to see a connection between the DOC level in the aquarium and coral health.

I suspect these three explanations or mechanisms, and more, are probably in play.