akindbro4u
New member
I don't worry about the daily swings, just the highs, and the lows. Gotta play the over under.
Acceptable Daily Temperature fluctuations
- Thread starter sandgoby
- Start date
Cozmo4
Member
So if the thought it that a temp fluctuation is good for coral resilience, would anyone suggest forcing a temp swing if it doesn't naturally occur? I'm running LEDs on my 210g with Vortechs. I've got very little heat being generated. My other tank swings about 4 degrees naturally from heat from the lighting. Should I set my controllers to gradually increase temp through the day and allow it to fall at night?
Very informative posts. Thanks
therealshark
New member
good info, i was worried about this awhile back when my tank would swing 4 to 5 degrees and have since made it abit better. now only about 2.5 degree swing daily. i guess i really didnt have to worry about it.
greenbean36191
Premium Member
There's no need to force a larger swing than what already occurs. Generally, my advice is to let the temp swing as much as it wants to on its own as long as you keep the high temp consistent. If it goes from 76-84 during the day, that's ok, but so is a tank that stays 83 all day long without a chiller or heater since none of the common modes of failure (power goes out or heater or chiller dies/sticks on) is going to give you a stress-inducing spike.
The main concern is that people don't use their heaters and chillers to try to keep their tank +/-0.5 degrees, creating a situation where if their equipment fails or the power goes out, they're going to get a temp spike/drop of several degrees as the tank settles on its natural temp.
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Based upon Greenbean's advice I have been running my reefs for the past 6 months with as little heater/cooling intervention as possible with daily swings from 75-82 with no adverse affects on fish or inverts, soft or hard (sps) corals. Thanks for the energy savings Greenbean!
LOL, well it's difficult to find a "not too scientific" review of scientific research. I don't want to summarize it all, so I'll take it. While it has it's flaws, I think that, as far as that criteria goes it's pretty good.
I agree some of the research may or may not be directly relevant to the hobby. And they may spend too much time on certain research. However, at a minimum it does provide strong evidence that corals are not as intolerant of thermal perturbations as some have suggested. That really was my point. I certainly realize that you are more trained in this area than I am and really respect your input. I'm sure your comments are fair, valid and well thought out. I do certainly think that while the situations described in the research, may not all be directly applicable to our systems, I still feel that it's worth poking a bit further into some of your assumptions.
You mentioned that "responses they're talking about don't occur in closed systems and those that do, occur only as a result of exposure to stress, which fluctuations (as opposed to spikes) aren't known to induce."
However, it seems to me that there is a fine line between a spike and a fluctuation. If it's the beginning of summer and you have a hot day, the temp can rise quickly, add to that MHs turning on at mid day and you have a rapid increase in temp. There is more reason to believe that this situation would result in a stress induced response than to believe that this would simply be biologically equivalent to a temperature fluctuation. These types of events happen often here in the Northeast and I strongly believe are related to the temperature resilience I have observed latter during the warmer months of the summer.
You also discuss "selective mortality" and suggest that this was the "most likely" reason for some given observations. While it's likely true that certain individual organisms may be more adapted to a given environment. And these individuals may pass on certain selected traits to surviving offspring, there are certainly other documented mechanisms that could just as likely explain these observations which you are referring to. For example, there are many phenotypic adaptations that could easily account for this as well, such as gene regulation and switching, which are certainly know to occur in cnidarians.
Also, you discuss symbiont shuffling, I don't think this is a primary means by which corals adapt to thermal stress in our systems, but I do believe this happens. You suggest that there is not enough "free-floating cells in the water to inoculate" and use the example of phytoplankton. However, while that may be true of many components of phytoplankton, dinoflagellates seem to survive quite well in our systems. This seems to be supported by some research such as Littman et al 2008, who suggest that free-living Symbiodinium appears to be primarily benithic and therefore I do not see why you would expect it to be skimmed out.
Additionally, we import corals from all over the world, so there is likely to be a diverse set of symbionts in our system. I think going back to selective mortality, it's also reasonable to believe that the corals that thrive in our systems are the ones ones best adapted to our systems. As we progress in the hobby, inevitably some specimens die, and some stagnate, we however, trade and purchase new species to replace these with ones that do better in the artificial environments we have created. These specimens have the potential to share symbiotic resources with other inhabitants.
Also, most of our systems are not perfect reproductions of the natural environments most of our inhabitants come from. Therefore it seems reasonable to assume that expulsion of zooxanthellae will be a reasonably common event in our closed systems. It seems that this mechanism would be perfectly capable of spreading more tolerant strains of symbiodinium to other hosts. And finally, just because a host may revert back, primarily to the original clade, we know these organisms often host multiple clades. I'm not familiar with any research that definitively shows the more heat tolerant clades are latter replaced with the original clade and not that the original clad instead regains dominance. I would be interested in this information though if you have a reference.
Anyways, this goes beyond my original point, but these topics are of interest to me. I appreciate you input.
greenbean36191
Premium Member
I agree, but whether corals tolerate temperature fluctuations is a separate question from whether they can survive and adapt to extreme temperatures. The mechanisms are different and mostly unrelated.
No. When a coral or other organism acclimatizes to the temperature range of its habitat, there are changes to its biochemistry such as the restructuring of lipid membranes and the production of different forms of enzymes that are suited to the temperatures most likely to be experienced. Basically, those changes set the tolerance limits, and as long as you stay within those limits, it makes very little difference how much or how quickly temperature changes. Once you go outside of those limits (i.e. a temp spike), things start to break and different mechanisms take over in response to stress. You get increased protein turnover, heat shock protein production, an inflection in the respiration curve, etc. which you don't see in response to changes within the range of acclimatization.
A 10 degree change within 15 minutes might not elicit any measurable response from corals acclimatized to that range, whereas exceeding the maximum temperature they had been acclimatized to by just 2 degrees, even if it took all day could have dramatic effects.
An analogy might be a car's engine being over-revved vs. operating within the normal range of rpm. Even if you floor the accelerator, the engine functions the same across the entire range from idle to redline. However, it you rev it past the redline, even if you do it gradually, things start to break and new processes govern how the engine functions (or doesn't).
Well, we do know for sure that corals that survive stress events can adapt in ways that better prepare them for future insults- e.g. HSP up-regulation in Acropora- and that probably did play some role at Cocos (though again, since it takes a stressful event to trigger that, it's something hobbyists should avoid). However, at Cocos the authors noted that the damage was selective and that there were major changes in the species composition. In addition. This is important because it indicates adaptation at the level of the reef rather than by individual corals- i.e. there was less damage from subsequent bleaching events because the corals that were left were the strongest ones which survived the initial bleaching (or were descended from them), not necessarily because the first bleaching event toughened-up those corals.
Whether the adaptation was at the level of the individual coral or at the level of the reef might seem like nitpicking, but it makes a huge difference as far as what we expect for the future of reefs. Aside from the fact that mortality, selective or otherwise, isn't acceptable to most hobbyists, my main point was that the Idso's summary article suggests that the corals at Cocos are adapting to increasing temperature, therefore things will be just fine for reefs (if you have any doubt that this is their position, just have a look around the rest of their site). The Cocos example they lean so heavily on on doesn't actually support that very well because the survival and recovery of particular corals doesn't imply the survival of the reef as a functional community.
While there is a lot of research which has found large amounts of Symbiodinium in the sand, most researchers haven't looked at whether these are the same strains that are symbionts of corals. In the few cases I know of where the strains have actually been identified (Carlos et al., 1999 and another one Scott Santos was an author on- don't know where it was published), they were either strains not known to form natural associations with corals or strains not known to be symbiotic at all. In other words, there's a lot of Symbiodinium in the sand and it probably gives rise to the waterborne cells, but most of that algae isn't actually useful as zoox for corals. Also, even if the sand is a reservoir for potential zoox, it's of no use for symbiont shuffling if it doesn't contain more heat tolerant clades. Again, because in most parts of the world the heat tolerant strains are among the least common strains, probably the majority of tanks have never been inoculated with them.
In addition, if the corals are shuffling by actually taking up new zoox rather than simply repopulating with residual populations of a clade they actually held before bleaching, all indications are that the zoox are taken up from the water column. While the sand might act as a reservoir, the algae need to be waterborne to make it to the coral and that is the problem in closed systems. Yes, benthic dinoflagellates do just fine in our system, but that's because they're benthic rather than planktonic. The same can be said for diatoms. They're probably the most successful group of unicellular microalgae in our tanks, but if you feed your tank the planktonic diatom Phaeodactylum (one of the components of DT's phytoplankton) into a reef tank, it will quickly die, get eaten, or get skimmed out. There's too much equipment, too many filter feeders, and too few nutrients to sustain live phytoplankton in most tanks. This is probably a good thing though since benthic dino outbreaks are bad enough without having to worry about having red tides in our tanks.
Diverse, yes. Useful for symbiont shuffling, in most case, probably not.
Clades A and B are restricted almost exclusively to the Caribbean and the few subclades that are found in the Pacific and northern Red Sea tend to only be found in one or two species of coral, so don't make for very good zoox donors. A is also only moderately temperature tolerant and B tends rank near the bottom, so neither is particularly useful for adaptation.
Clade C is far and away the most common clade. It's the dominant clade throughout almost the entire Indo-Pacific. Although there is a lot of diversity within clade C, only a small handful of subclades are more thermally tolerant than C1 and C3 which are the most common symbionts of all, and those thermally tolerant subclades are only found in a very small proportion of corals.
Clade D is the most thermally tolerant, but it doesn't tend to form stable associations and is only found in a small proportion of corals as well.
C15 (the most common heat tolerant C subclade) and clade D typically account for 5-15% of corals in the Indo-Pacific except shortly after a bleaching event.
The diversity in most tanks is probably comprised almost entirely of a lot of different
Clade C with a few A1, B, and D in some tanks.
There's actually an almost constant shedding of zoox even in nature. It was actually thought for a while that this rather than the sand was the reservoir that provided the waterborne zoox that inoculate corals. Whether they're coming from corals or from the sand the same obstacles apply though.
Wow, is this an awesome thread, and very opportune for me. I had a heater just explode in my sump. (I run 2 heaters all the time for redundancey and I run them attached to 2 different outlets on the controller for additional redundancy). However, this weekend's fry of one heater. (Got out of the sump water too long during a water change and it had kicked on, my bad for not checking it...)
I was worried if one heater was enough to keep it stable. This post relieves my fears. I'll go with one heater now and program the controller to have it kick on at lower temps. e.g. <76.5 instead of 78.5.
I did have a 12 hour power outtage. Temp got down to 75 degrees. I was worried about temp more than oxygen, but, even with that decline, there was not a single loss or even a sign of stress. The fish were more confused about where the flow went.
So, if my ambient room temp is around 70 degrees. I run halides so, during the day it would stay warmer, but, is there harm if by morning the tank is down to 72 and then the tank warms up to 75 or 76 during the day? I thought the tropics were warmer and the ideal "healthy' temp for fish and corals to get along in was the upper 70s. variations, o.k. but to have a temp steadily lower than say 75 would lead to issues with acclimating new fish and corals, etc.
I also was told when I first started that a high temp over 83 was the "max" and death would start occuring at 84-86 degrees.
I'd love to remove the insecurity of the heater from my tank. But I live in the north and heating is generally a requirement almost year round. When temps outside get to -40 degrees, inside is hard to keep it at 70 room temp.
Are heaters neccessary is the real question?
I was worried if one heater was enough to keep it stable. This post relieves my fears. I'll go with one heater now and program the controller to have it kick on at lower temps. e.g. <76.5 instead of 78.5.
I did have a 12 hour power outtage. Temp got down to 75 degrees. I was worried about temp more than oxygen, but, even with that decline, there was not a single loss or even a sign of stress. The fish were more confused about where the flow went.
So, if my ambient room temp is around 70 degrees. I run halides so, during the day it would stay warmer, but, is there harm if by morning the tank is down to 72 and then the tank warms up to 75 or 76 during the day? I thought the tropics were warmer and the ideal "healthy' temp for fish and corals to get along in was the upper 70s. variations, o.k. but to have a temp steadily lower than say 75 would lead to issues with acclimating new fish and corals, etc.
I also was told when I first started that a high temp over 83 was the "max" and death would start occuring at 84-86 degrees.
I'd love to remove the insecurity of the heater from my tank. But I live in the north and heating is generally a requirement almost year round. When temps outside get to -40 degrees, inside is hard to keep it at 70 room temp.
Are heaters neccessary is the real question?
thecoralreefer
New member
I have had shipments get stuck in Pitt for 3 days on the dock there.
When they arrived here in fl they were 61 degrees in the bags.
I only lost 46% of this shipment and could not believe it at first.
At the other end in the summer I had fish come in @ 86 degrees and do just fine.
My 29 Bio sweeps daily from 4 to 6 degrees byt the end of the light cycle.
And Ph drops almost a full 2 points by the end of cycle But it still grows !
When they arrived here in fl they were 61 degrees in the bags.
I only lost 46% of this shipment and could not believe it at first.
At the other end in the summer I had fish come in @ 86 degrees and do just fine.
My 29 Bio sweeps daily from 4 to 6 degrees byt the end of the light cycle.
And Ph drops almost a full 2 points by the end of cycle But it still grows !
Thanks greenbean36191, great info! There are certainly a lot of unknowns, but a lot of useful info too.
Just to go back to "stress vs. acclimation" though. I guess first I should probably make sure we are on the same page, defining "stress". I'm referring to stress to indicate temperature fluctuations outside of the currently acclimated range.
I have a few questions regarding these processes though. For one, how are you reaching the conclusion that stress and acclimation separate processes? HSR as viewed from the perspective of HSP appears to be somewhat independent from other processes, such as those you have referred to as "acclimation" processes. However, even HSP response seems to have some physiological connection to acclimation. The onset and range of HSR seems to vary based on the currently acclimated temperature range. This is described in Tomanek (2008) for example. So, sort of additional information, it seems reasonable to think that these mechanisms are part of the same larger cascade.
Other than HSP though, there doesn't seem to be much definitive information in the literature regarding the physiology of acclimation and thermal stress. Most of the mechanisms you mention, recently, were briefly reviewed in Hofmann and Todgham (2010) for example. However it appears that many of these mechanisms also act effectively, within short time-scales and it still seems that many may also help prime organisms for latter shifts of the thermal environment. Even HSP is a gradual process in most organisms; the response is not just on or off. And it doesn't appear that things necessarily break because HSR is activated.
While there doesn't appear to be much info regarding what defines temperature limits. HSP does seem to be an indicator that the organism is getting closer to these thermal limits, in many organisms, at least, so I'd certainly expect it to be correlated with metabolic dysfunction and failure. However, from what I can find, the mechanisms for priming a marine organism for future temperature shifts, within its thermal limits, appears to be part of a larger, more general process.
So, I'm still having trouble understanding why stress response and acclimation need be thought of as mutually exclusive and could not be considered to be varying magnitudes of the same underlying chain of events? It seems however that whether or not things break from a spike, depends more on how far things are being pushed to begin with, than whether or not there is a spike outside of the acclimated range.
However, it also seems that HSP/HSR isn't necessarily prime mechanism for setting the acclimated range. Again, from what I've found, it is only a protective response, and is not directly associated with changes the acclimated temperature range. Again though, it does seem reasonable to me that it is part of a larger signaling cascade. If I recall correctly this is true in other organisms, but I have not found much specific info on marine organisms in this regards. It would be nice to see a good microarray study for sure However, are there any good references you could recommend, that would explain discrepancies in our in our interpretations? Its certainly possible I missed something.
Just to go back to "stress vs. acclimation" though. I guess first I should probably make sure we are on the same page, defining "stress". I'm referring to stress to indicate temperature fluctuations outside of the currently acclimated range.
I have a few questions regarding these processes though. For one, how are you reaching the conclusion that stress and acclimation separate processes? HSR as viewed from the perspective of HSP appears to be somewhat independent from other processes, such as those you have referred to as "acclimation" processes. However, even HSP response seems to have some physiological connection to acclimation. The onset and range of HSR seems to vary based on the currently acclimated temperature range. This is described in Tomanek (2008) for example. So, sort of additional information, it seems reasonable to think that these mechanisms are part of the same larger cascade.
Other than HSP though, there doesn't seem to be much definitive information in the literature regarding the physiology of acclimation and thermal stress. Most of the mechanisms you mention, recently, were briefly reviewed in Hofmann and Todgham (2010) for example. However it appears that many of these mechanisms also act effectively, within short time-scales and it still seems that many may also help prime organisms for latter shifts of the thermal environment. Even HSP is a gradual process in most organisms; the response is not just on or off. And it doesn't appear that things necessarily break because HSR is activated.
While there doesn't appear to be much info regarding what defines temperature limits. HSP does seem to be an indicator that the organism is getting closer to these thermal limits, in many organisms, at least, so I'd certainly expect it to be correlated with metabolic dysfunction and failure. However, from what I can find, the mechanisms for priming a marine organism for future temperature shifts, within its thermal limits, appears to be part of a larger, more general process.
So, I'm still having trouble understanding why stress response and acclimation need be thought of as mutually exclusive and could not be considered to be varying magnitudes of the same underlying chain of events? It seems however that whether or not things break from a spike, depends more on how far things are being pushed to begin with, than whether or not there is a spike outside of the acclimated range.
However, it also seems that HSP/HSR isn't necessarily prime mechanism for setting the acclimated range. Again, from what I've found, it is only a protective response, and is not directly associated with changes the acclimated temperature range. Again though, it does seem reasonable to me that it is part of a larger signaling cascade. If I recall correctly this is true in other organisms, but I have not found much specific info on marine organisms in this regards. It would be nice to see a good microarray study for sure
However, are there any good references you could recommend, that would explain discrepancies in our in our interpretations? Its certainly possible I missed something.
acropora1981
New member
Great thread... makes me wonder why I've been trying so hard to maintain < or = 1F variations for so many years...
greenbean, hi,some great information you've posted in this thread,though Ive found the above quote a little vague,perhaps Im not quite understanding part of the interpretation.
At your leisure,could you take alook at this article...I'm not sure what you think about it,but if corals take up clade D "through acute thermol flunctuations" as you've stated is this now something to consider as a secondary consequence? http://imars.usf.edu/~carib/Public/RitchieMEPS322.pdf
Thanks for your time.-Steve
fwiw- thanks for pm back on the other.(polyp bailout)
acropora1981
New member
As a result of this thread I've changed my controller to have a 0.8F hysteresis, and for it to only turn on the fans after the temp has risen about 1F. Its made a big difference - the fans are no longer annoyingly clicking on and off, and my corals don't see to mind at all, and growth and coloration are unnaffected a week later. I'm still only getting a ~2-2.5F swing in a day; tank is much quieter.
stevie-o
New member
this is a very interesting thread I use to have 6 degree swings, but i recently put a big fan over my tank took the lid off, and added my old heater now i only have about 2-3 degree swings, and my acros, monti, and birdsnest are doing the same as when I had the 6 degree swing. The reason I got worried about temp swings is because I heard temp swings are the number one cause for bleaching.
acropora1981
New member
The main idea here seems to be that temp swings outside of the acceptable range (generally into the mid to high 80's) causes bleaching, instead of the actual swing itself. As long as the swing stays within the acceptable range (75-82F or thereabouts), no damage is caused.
