Calcification is effected by oxygen?

[Cory]

Quote:

Coral calcification under daily oxygen saturation and pH dynamics reveals the important role of oxygen​

Tim Wijgerde, Catarina IF Silva, Vera Scherders, Judith van Bleijswijk, Ronald Osinga
Biology open 3 (6), 489-493, 2014

Coral reefs are essential to many nations, and are currently in global decline. Although climate models predict decreases in seawater pH (∼0.3 units) and oxygen saturation (∼5 percentage points), these are exceeded by the current daily pH and oxygen fluctuations on many reefs (pH 7.8–8.7 and 27–241% O2 saturation). We investigated the effect of oxygen and pH fluctuations on coral calcification in the laboratory using the model species Acropora millepora. Light calcification rates were greatly enhanced (+178%) by increased seawater pH, but only at normoxia; hyperoxia completely negated this positive effect. Dark calcification rates were significantly inhibited (51–75%) at hypoxia, whereas pH had no effect. Our preliminary results suggest that within the current oxygen and pH range, oxygen has substantial control over coral growth, whereas the role of pH is limited. This has implications for reef formation in this era of rapid climate change, which is accompanied by a decrease in seawater oxygen saturation owing to higher water temperatures and coastal eutrophication.

End quote

Is this saying that corals wont calcify good when oxygen is oversaturated? Would a skimmer prevent oxygen from becoming oversaturated and being more normal?

 

[Garf]

Quote:

Coral calcification under daily oxygen saturation and pH dynamics reveals the important role of oxygen​

Tim Wijgerde, Catarina IF Silva, Vera Scherders, Judith van Bleijswijk, Ronald Osinga
Biology open 3 (6), 489-493, 2014

Coral reefs are essential to many nations, and are currently in global decline. Although climate models predict decreases in seawater pH (∼0.3 units) and oxygen saturation (∼5 percentage points), these are exceeded by the current daily pH and oxygen fluctuations on many reefs (pH 7.8–8.7 and 27–241% O2 saturation). We investigated the effect of oxygen and pH fluctuations on coral calcification in the laboratory using the model species Acropora millepora. Light calcification rates were greatly enhanced (+178%) by increased seawater pH, but only at normoxia; hyperoxia completely negated this positive effect. Dark calcification rates were significantly inhibited (51–75%) at hypoxia, whereas pH had no effect. Our preliminary results suggest that within the current oxygen and pH range, oxygen has substantial control over coral growth, whereas the role of pH is limited. This has implications for reef formation in this era of rapid climate change, which is accompanied by a decrease in seawater oxygen saturation owing to higher water temperatures and coastal eutrophication.

End quote

Is this saying that corals wont calcify good when oxygen is oversaturated? Would a skimmer prevent oxygen from becoming oversaturated and being more normal?

Appears to suggest that high pH increases growth in stonies, but not if that pH is increased by photosynthesis, without adequate aeration. Increased flow helps, as would a skimmer, I reckon.

Coral calcification under daily oxygen saturation and pH dynamics reveals the important role of oxygen

ABSTRACT. Coral reefs are essential to many nations, and are currently in global decline. Although climate models predict decreases in seawater pH (∼0.3 units) and oxygen saturation (∼5 percentage points), these are exceeded by the current daily pH and oxygen fluctuations on many reefs...

journals.biologists.com

 

[taricha]

Is this saying that corals wont calcify good when oxygen is oversaturated? Would a skimmer prevent oxygen from becoming oversaturated and being more normal?

Seems so. the mechanisms for low O2 slowing night calcification and high O2 slowing daytime calcification are given below...

"The limiting role of oxygen in dark calcification rates is probably caused by decreased ATP synthesis in calicoblastic cells via aerobic respiration, resulting in less available energy for calcification (Chalker and Taylor, 1975; Ip et al., 1991)."

Low O2 limits metabolic processes at night, and thus slows calcification.

"A possible explanation for this phenomenon is oxygen intoxication due to reduced oxygen release by the coral (Kühl et al., 1995; Mass et al., 2010), resulting in cellular damage (Wijgerde et al., 2012; and references therein) and photorespiration (Mass et al., 2010). This may coax corals into investing metabolic energy in the production of anti-oxidants rather than calcification."

High water O2 also means high tissue O2 and so mechanisms to protect from oxygen-damage get activated, rather than energy spent on calcification. Seems pretty analogous to high light stress.

This section is tantalizing:

"Interestingly, we did not find evidence for the theory of light-enhanced calcification (Kawaguti and Sakumoto, 1948; Chalker and Taylor, 1975) at baseline conditions of pH 8.1 and normoxia, as light calcification rates were lower than dark calcification rates. This observation is in agreement with a recent study on the growth of Galaxea fascicularis, during which no significant difference between light and dark calcification rates was found when the incubation water was aerated to maintain normoxia (Wijgerde et al., 2012), although it contrasts with several previous studies (reviewed by Gattuso et al., 1999). It seems that light-enhanced calcification is only found when dark calcification rates are impaired due to oxygen limitation and/or reduced oxygen mass transfer at low water flow. "

Calcification at night may be just as fast as daytime IF you can control O2 and pH.
Nice paper.

 

[Miami Reef]

So you’re saying that not having a refugium AND having 20 fish in my 250…is good?

 

[Randy Holmes-Farley]

Thanks for posting the link. Its an interesting paper, but I am somewhat wary of accepting the results as indicative of things that happen in a reef tank.

First, I'll note that the paper is 7 yeas old, but has relatively few more recent papers citing it. That suggests to me that scientists in the field did not find it especially important.

Second, let's look at the actual experiments. Figure 1 appears to show that increased O2 reduced the calcification rate during the day. Note, however, that this result is at 170% of O2 saturation. Such an O2 level seems extraordinarily high, and in studies such as that by Eric Bornemann, is not attained in reef tanks he examined:

http://reefkeeping.com/issues/2005-08/eb/index.php

The same figure looks at low O2, but it is far, far lower in O2 than in any aquarium that Eric examined.

IMO, it's food for thought, not a call to action for reef hobbyists.

 

[taricha]

The same figure looks at low O2, but it is far, far lower in O2 than in any aquarium that Eric examined.

True, except for Eric's originally no-skimmer clownfish tank that had nighttime O2 levels below 20%.

 

[Randy Holmes-Farley]

True, except for Eric's originally no-skimmer clownfish tank that had nighttime O2 levels below 20%.

You're right. Wonder how low that pH got at night. lol

 

[Cory]

Would increased pressure increase oxygen saturation from a skimmer?
My skimmer is a beckett skimmer with a pressure rated pump. Occasionally when the drain in the skimmate cup gets plugged from dry foam or a piece of algae, the water chamber drops from the top all the way to the bottom for up to a minute from increased pressure until the drain unclogs itself in which the water level returns to the normal level inside the skimmer.

 

[ReefGeezer]

We used to build pressurized O2 reactors. Like an ozone reactor but pressurized with O2 from a tank/regulator. Little potential bombs! I can't say for sure if they were very effective. Test kits in those days were difficult to use and I don't know that I got reliable readings.

 

[Randy Holmes-Farley]

Would increased pressure increase oxygen saturation from a skimmer?
My skimmer is a beckett skimmer with a pressure rated pump. Occasionally when the drain in the skimmate cup gets plugged from dry foam or a piece of algae, the water chamber drops from the top all the way to the bottom for up to a minute from increased pressure until the drain unclogs itself in which the water level returns to the normal level inside the skimmer.

Complicated question for something like a skimmer.

In general, higher air pressure within a bubble will lead to more O2 and more CO2 in the water.

But some skimmers create bubbles in a way that may involve cavitation or a venturi, which can involve reduced pressure.

I just don't think it is always possible for these complex devices to easily say what pressure of O2 is attained in contact with the water.

Simple airstones in a water column are easy: deeper means more pressure so possibly more O2 and CO2 at equilibrium.

Downdraft skimmers like the ETS I used are probably always fairly close to room pressure.