Is nutrient control an effective method of treating algae in a reef?

[Subsea]

As I listen to you scientist talk, I realize just how complex biochemistry is in the coral holobiont. Corals crosstalking with bacteria. Bacteria cross talking with algae.

In a distant, but similar analogy in physics, the Boson sub atomic particle gives credulance to, “what holds everything together”.

 

[Belgian Anthias]

Regarding the bacteria the excretions of corals support different bacteria than the excretions of algae as this article shows. While algae excrete labile sugars that are very rapidly degraded by bacteria corals excrete semi-labile substances that are degraded more slowly by different kinds of bacteria. The bacteria that live on the labile sugars are potential pathogens of corals and maybe fish and crustaceans.

In my experience the bacteria that grow with glucose or other labile forms of organic carbon dosing excrete more slime than the slower growing bacteria. This can be seen on the glasses of the tank. This slime forms foam with air and feeds the skimmer. Maybe bacteria that excrete more slime are skimmed better and in this way the selective skimming of slime forming bacteria is a great advantage. Maybe because of this the skimmer is such a proven device for water treatment.

Within the bacterial population there are also K and R strategists. I suppose you are talking about r strategists when it comes to carbon dosing. But most r-strategists are very small. One may need 1000000 r-cells to replace one K-strategist, which will not be removed by a skimmer as K-strategists are often bounded to a substrate. Production of slime by r-strategists? The first time I hear about this. I think the visual is caused by the numbers. Of coarse they may become part of bio-flocks in combination with phyto plankton.
The skimmer may be a general used device but it is not a good device for water treatment, certainly not for removing organics, which I think is its main task. An efficiency of only +- 35% is not what I would call an effective device. But the worse is that the removal of organics is selective, the same kind of organics are removed, the 65% organics left behind may accumulate as they will not be skimmed, also not at a second passage if they remain in the same form. At the very low bio-load reef systems are operated this is not a disadvantage as organics remain available to support live. And the evolution issue caused by the operation of closed systems does not influence the filtration capacity, so for most this is no issue at all. Except for those exceptional cases where people are hospitalized with very strange symptoms. The issue is taken seriously for managing closed aqua culture systems and a lot of research is going on concerning the issue of selective evolution. And it is very easily avoided in reef aquaria.

 

[Hans-Werner]

I find both articles a bit hard to compare except for bacterial growth efficiency (bge). Bge was high in the control and Halimeda and reduced to the half and lower in Turbinaria and Amansia. Concluding from the newer article this means Turbinaria and Amansia support "the less efficient Entner–Doudoroff and pentose phosphate pathways" of the copiotrophic facultatively pathogen bacteria.
The DOC and the nocturne oxygen consumption as second factor endangering corals is highest in turf algae.

Only turf algae are typically used for filtration purposes. In aquaria Halimeda competes with corals for calcium and carbonates.

 

[Hans-Werner]

But most r-strategists are very small. One may need 1000000 r-cells to replace one K-strategist, which will not be removed by a skimmer as K-strategists are often bounded to a substrate.

Are you sure? As far as I know bacteria in oceanic waters low in nutrients are especially small and hard to cultivate. They can hardly be r-strategists. On the other side fast growing bacteria that can be cultivated easily are often quite big, shouldn't these be the r-strategists?

I think small bacteria grow slowly on low nutrient concentations while large bacteria take up nutrients fast and store them in their voluminous cells for rapid growth. Which one is the r-strategist?

I don´t use skimmers but practical knowledge seems to proof the skimmer as a good device. It is used for decades and one of the oldest devices in marine aquarium care.

 

[Belgian Anthias]

Makes UV treatment organics more hydrophobic?

 

[Belgian Anthias]

Are you sure? As far as I know bacteria in oceanic waters low in nutrients are especially small and hard to cultivate. They can hardly be r-strategists. On the other side fast growing bacteria that can be cultivated easily are often quite big, shouldn't these be the r-strategists?

I don´t use skimmers but practical knowledge seems to proof the skimmer as a good device. It is used for decades and one of the oldest devices in marine aquarium care.

r-strategists are the ones able to react very fast on changing conditions. There lag phase is short and there log phase may be explosive.

My first system, in the early seventies, had a big BIO, a counter current protein skimmer and a UV unit. The only thing I knew about the skimmer was the fact it removed proteins. So it removed proteins for many years. Until it was proven that the skimmer does not remove much proteins. A skimmer seems to be good in removing toxins. Now its mean purpose is removing toxins.

 

[Scrubber_steve]

The DOC and the nocturne oxygen consumption as second factor endangering corals is highest in turf algae.

Only turf algae are typically used for filtration purposes.

No! Turf algae are not typically used for filtration purposes!

"Turf algae (or “algal turfs”) are dense, multi-species assemblages of filamentous benthic algae,
including small individuals of macroalgae and cyanobacteria, that are typically less than 1 cm in height (Connell, Foster & Airoldi, 2014)."
"Compared to other algal groups such as macroalgae and crustose coralline algae (CCA), turf algae occupy available space quicker (Diaz-Pulido & McCook, 2002)

Competitive interactions between corals and turf algae depend on coral colony form
https://peerj.com/articles/1984/



Neither macroalgae - various ulva species that typically take up on scrubber screens, nor the chaetomorpha used in refugia, fall into the category "turf algae"!

 

[Hans-Werner]

I think a skimmer removes slime and other exudates of algae and bacteria. If you look for "transparent exopolymer particles" (TEP) you will find what I mean. TEP are collected from oceanic waters by bubbling, finally just another expression for skimming if you look at the construction of the device that is used.

 

[Belgian Anthias]

I think a skimmer removes slime and other exudates of algae and bacteria. If you look for "transparent exopolymer particles" (TEP) you will find what I mean. TEP are collected from oceanic waters by bubbling, finally just another expression for skimming if you look at the construction of the device that is used.

A skimmer removes hydrophobic compounds. At least part of the molecule must be hydrophobic to be skim able. Carried by the foam is not a chemical process and has nothing to do with the skimming process. Toxins are exudate's of algae and bacteria and the only reason I would keep on using a skimmer, fed by UV treated water!

 

[Hans-Werner]

A skimmer removes hydrophobic compounds. At least part of the molecule must be hydrophobic to be skim able.

Sure? I thought it removes amphiphilic compounds, compounds that have a hydrophilic and a hydrophobic part. I think also molecules with charged groups like alginate can adhere to air bubbles which also have a charged surface (due to the orientation of the water molecules), if I am not wrong.

 

[mcarroll]

In an isolated laboratory experiment, it was shown that coral selectively harvested only certain bacteria (I assume by size), then produced a growth enzyme to target feed that specific bacteria species. Did coral just manipulate its environment?

A well adapted coral would be balanced between manipulating and being manipulated by its environment, right?

Now its mean purpose is removing toxins.

I think aeration is the main and only predictable function across all protein skimmers in use.

Removal of "dirt" is without a doubt an incomplete matter in all skimmers and must vary – according to what goes into the tank, as well as with the possibility of long term selectivity trends.

If removing cells or dirt from the water is a real priority, then a real mechanical filter – a micron filter a la the Marineland Polishing filter or the classic Vortex XL diatom filter – with an appropriate maintenance routine would without doubt be the way to go.

Aeration should be a real priority, but may only be critical on tanks that are densely stocked AND brightly lit.

Corals in these tanks are likely to be CO2-limited during the day. I forget the how of it, but corals also benefit from good aeration at night.

 

[Randy Holmes-Farley]

There is nothing to prove. When proven it is to late. It is a question of responsible reef keeping and common sense. By using UV sterilized water for feeding the skimmer selective removal of live bacteria is avoided. Not using a skimmer avoids the necessity for UV.

OK, You can be a believe in nonevolution is good. I also think a UV probably causes evolution/species selection of planktonic bacteria to be more resistant to UV, but again, I don't see a reason to think that is good or bad. It just happens.

 

[Randy Holmes-Farley]

Makes UV treatment organics more hydrophobic?

Not usually. If anything it will make organic molecules more hydrophilic and more easily metabolized. Same as oxidation with ozone.

 

[Belgian Anthias]

Sure? I thought it removes amphiphilic compounds, compounds that have a hydrophilic and a hydrophobic part. I think also molecules with charged groups like alginate can adhere to air bubbles which also have a charged surface (due to the orientation of the water molecules), if I am not wrong.

That is what I have said.

 

[ca1ore]

Aeration should be a real priority, but may only be critical on tanks that are densely stocked AND brightly lit.

...... AND poorly circulated (particularly at night).

 

[mcarroll]

(Late reply/old post)

It complicates things that some individual tangs, for example, decide they don't like algae versus others that do. My scopas, for example, eats no algae at all, ever. Mud brown lump of useless.

One of the more fascinating things I've found in reading about algae is that herbivores have picky tastes in food that aligns exactly with our picky human palate.

When tested, there appears to be a general preference among herbivores for foods in this order:
prepared foods (ie. flake or pellet) > meaty whole foods (ie. mysis shrimp) > their preferred algae > less palatable algae.

(Translate to us: pizza > lobster/chicken/fish > lettuce > kale)

 

[mcarroll]

...... AND poorly circulated (particularly at night).

Very true as that potentially slows every exchange the coral has to make with the outside water!

Some corals probably adapt by growing thinner slime coats or other action...it's hard to predict the extent possible/healthy for any particular coral though.

 

[ca1ore]

One of the more fascinating things I've found in reading about algae is that herbivores have picky tastes in food that aligns exactly with our picky human palate.

I think that is exactly true. I've probably had a dozen yellow tangs in my time in the hobby. Of those that stick in my memory. three of them were very good GHA consumers, four were not good at all, and the remaining only when there was an extended period of no pizza .

 

[Randy Holmes-Farley]

Corals in these tanks are likely to be CO2-limited during the day. I forget the how of it, but corals also benefit from good aeration at night.

CO2 limitation to what? photosynthesis, or growth? CO2 limitation implies that the thing will do better at lower pH, and I've not seen any data suggesting that corals grow better at lower pH. Maybe they photosynthesize better, but grow slower, I don't know.

 

[mcarroll]

Photosynthesis.

Long-term effects of nutrient and CO2 enrichment on the temperate coral Astrangia poculata (Ellis and Solander, 1786)

and

The response of the scleractinian coral Turbinaria reniformis to thermal stress depends on the nitrogen status of the coral holobiont

...are two I saved that speak to this.

I saved these quotes from the first article:

Coral calcification rates[…]were not significantly affected by moderately elevated nutrients at ambient CO2 and were negatively affected by elevated CO2 at ambient nutrient levels.

However, calcification by corals reared under elevated nutrients combined with elevated CO2 was not significantly different from that of corals reared under ambient conditions, suggesting that CO2 enrichment can lead to nutrient limitation in zooxanthellate corals.

Nutrient limited corals are unable to utilize an increase in dissolved inorganic carbon (DIC) as nutrients are already limiting growth, thus the effect of elevated CO2 on saturation state drives the calcification response. Under nutrient replete conditions, corals may have the ability to utilize more DIC, thus the calcification response to CO2 becomes the product of a negative effect on saturation state and a positive effect on gross carbon fixation, depending upon which dominates, the calcification response can be either positive or negative.

And from the article, also minimally edited for clarity:

[…]the saturation state of the surrounding seawater alone does not control coral calcification as corals can continue to calcify in under-saturated conditions (e.g. Marubini and Atkinson, 1999; Cohen et al., 2009) or dissolve in super-saturated conditions (e.g. Herfort et al., 2008).