Thoughts on purposely changing temps over the year

[SDguy]

I'd like to start changing the set temp of my mixed reef. Not really to coincide with any temp variation of a particular region, but just to keep my reef from becoming to accustomed to a very narrow range.

Does anyone do this? How long do you let each "plateau" go for? How long do you take to get to the new temp (days, weeks)? How low/high do you go?

I've thought about this for a while. I remember my very first tanks so many years ago. I took horrible care of them sometimes. Often doing water changes with *just* mixed salt water, not even temp adjusted. Salinity way off. These wtaer changes, however, would often result in spawning events. Hairy mushrooms, limpets, other unidentified spawn. Even anthias! Do our reef creatures then need such changes sometimes?

[murraycamp]

Shimek argues that controlled variability in reef aquaria is a good thing. I too would like to see if anyone has done this and the resulting observations.

Just tagging along.

[DrBDC]

I currently let mine change by the month. I use my aquacontroller and the built-in seasonal tables which let me either use the default settings or change them. I changed mine to ramp between 78 and 80.5. The heater/chiller are on a 1/2 degree setting difference so I don't relly get a daily change.

To be honest though, I think my tank was looking better before the chiller was added and I ran low 80's with a 3 degree daily change. I'm thinking of expanding the heater/chiller varience and upping the temp tables to the 80-83 range. I had also done a tank upgrade in May that coincided with adding the chiller so some of my observations I'm sure are related to that until the sand bed becomes fully functional as my nitrates are still high.

[SDguy]

Hmmm, interesting. I was thinking more than that though...like 78 to 84/85 or so, and back....

[mbbuna]

for the whole year my temp can range between 74/75 up to 84. from day to day its not odd for me to see a 4 or 5 degree shift.

[greenbean36191]

Mine isn't really controlled by anything other than ambient air temp and a heater, but it goes from 78-83 in winter to 80-86 in the summer. Obviously since I'm not really controlling it the change is very gradual with the seasons and there are no real plateaus. I've never seen any noticeable changes from when it was constantly ~80 year round.

As far as the temp changes and spawning, seasonal changes are well documented to be important for priming a lot of animals for spawning. Basically they only start producing gametes or even gonads once the water reaches a certain threshold. After that, shorter term cues take over to actually trigger the spawning. There's also been a lot written on the importance of seasonal acclimatization and shorter term variation on coral resistance to heat stress.

The spawning you saw was most likely just a common stress response rather than an indication of health. Probably the most common way to artificially induce spawning in aquaculture is by dramatically changing the temp of the water (by more than the normal variation they would experience). A lot of animals actually spawn as a stress response.

[SDguy]

Originally posted by greenbean36191
The spawning you saw was most likely just a common stress response rather than an indication of health. Probably the most common way to artificially induce spawning in aquaculture is by dramatically changing the temp of the water (by more than the normal variation they would experience). A lot of animals actually spawn as a stress response.

Yeah, I figured as much on that point

[m2434]

SDGuy, thanks for starting this thread, it's a great topic!

For me I've been letting my temp swing daily... and have been letting my tank flux like this for years. My nano is newer (2+ months) and less stable than my 75g and more extreme in this regard. So far no problems... For example some mornings lately is 77-78ish and can get up to 82+ in the afternoons. I haven't bothered to raise the thermostat on the heater - I just have a hunch it might actually be good in some ways.

Very briefly, my argument might go something like this:

For one, coral genomes appear to be fairly large and if we look at various organism, there seems to be a correlation between gnome size and adaptability. Sometimes however, it takes time for a shift in gene expression patterns. For example, maybe if a coral is in a constant environment, its chromatin structure might become arranged in such a way that it just cant unwind fast enough to adapt to a sudden change – making the coral appear to be sensitive to environmental perturbations. I also suspect that corals are fairly prone to epigenetic changes so I think that there could very well be environmental imprints on the actual genome structure. So if there is going to be some epigenetic changes, I would think we would want the majority of the cells to carry these changes... this would be difficult to accomplish in a large full grown coral, but if we start small, the cellular inheritance should cascade through the organism nicely, leaving only cells that have adapted to the constantly changing environment.

I'm not a biochemist so you likely have much more insight into these processes than me, but it's become one of my favorite topics lately and I hope you share any info and ideas you might come across.

[SDguy]

Interesting stuff. I'm a protein biochemist, not a geneticist, so not sure how much more I would know about such things than you. I'm not sure that type of genetic adaptation is possible on the timescale you are suggesting, especially in such a simple organism like a coral, with really no learning mechanism, like an immune system (someone correct me on that if necessary).

At a local reef club meeting recently, we had a researcher come and talk to us about coral disease that she studies, including all the various bacteria and viruses that can be found on coral. I was hypothesizing, with this whole temp swing issue, that perhaps different temps would favor different bacteria, never allowing one to gain hold on the coral...

[m2434]

Originally posted by SDguy
Interesting stuff. I'm a protein biochemist, not a geneticist, so not sure how much more I would know about such things than you.

I'm sure your still more familiar with genetics than me My experience with genetics and molecular biology is limited to a few semesters as an undergrad, in a Zebrafish neurobiology lab.

I'm not sure that type of genetic adaptation is possible on the timescale you are suggesting, especially in such a simple organism like a coral, with really no learning mechanism, like an immune system (someone correct me on that if necessary).

At a local reef club meeting recently, we had a researcher come and talk to us about coral disease that she studies, including all the various bacteria and viruses that can be found on coral. I was hypothesizing, with this whole temp swing issue, that perhaps different temps would favor different bacteria, never allowing one to gain hold on the coral...

Thats sort of the reason I suspect epigenetics are involved. If you look at things from the typical vertebrate perspective, invert immune systems are almost non-existent. However, the ocean is a harsh place and I don't think inverts would survive long if they didn't have some sort of immune mechanism.

I think on a primitive level, corals and other inverts carry a large amount of genes for immunity and adaptive purposes. The idea is that they can selectively switch genes on and off to adapt to various insults. I believe Epigenetics in humans, has become popular lately largely due to the observations of many genetic adaptive events, which seem to happen too quickly to be explained by conventional genetic theory.

So, lets say that a corals do regulate its genes in order to respond to environmental pathogens. To do this they must turn on and off genes at the appropriate time, but they seem to have these fairly large, cumbersome, variable, almost piecemeal genomes, so how could there be sufficient feedback mechanisms to regulate gene expression? My guess is there isn't – at least not to the extent of a more evolved organism. I think that the there are other mechanisms in place to control gene expression, on a much lower, more fundamental level. We see these mechanisms in all life forms, to some extent and I have no reason to believe they can't occur in the most simple organisms, in fact I believe they may have their roots with them. Also, it may occur even more efficiently, because DNA repair mechanisms are less evolved, from the zebrafish lab, one thing I did learn was that it's really tough to get any genetic change to last more than a generation or two.

This is certainly a controversial topic, and I've only started researching it, but here are a few articles that highlight some key idea I'm finding.

Little TJ, Hultmark D, Read AF.
Invertebrate immunity and the limits of mechanistic immunology.
Nature Immunology. 6, 651 - 654 (2005)

Little TJ, Kraaijeveld AR.
Ecological and evolutionary implications of immunological priming in invertebrates.
Trends Ecol. Evol. 19, 58–60 (2004)

Levenson JM, Sweatt JD.
Epigenetic mechanisms in memory formation.
Nat Rev Neurosci. 6, 108-118 (2005)

Bird A,
DNA methylation patterns and epigenetic memory.
Genes Dev. 1-16, 6-21. (2002)

Marquez LM, Miller DJ, MacKenzie JB, Van Oppen MJ.
Pseudogenes contribute to the extreme diversity of nuclear ribosomal DNA in the hard coral Acropora.
Mol Biol Evol. 20, 1077-1086 (2003)

[m2434]

Of course, right now it's anyones guess. Practically speaking it would be interesting just to show that temp variation is beneficial.

[greenbean36191]

Practically speaking it would be interesting just to show that temp variation is beneficial.

That part has already been shown. It's your questions of the mechanism that allows the adaptability that still need to be answered.

[gatohoser]

Only thing I will add to this conversation is that someone asked whether a change in temperature will change the bacteria present. I would say that's very likely as this is what happens in nature though my experience is with open ocean bacteria, not bacteria that would be in or on corals. So this difference in environments could mean they work differently but I believe it still probably would change. Whether having constantly shifting populations of bacteria is a good thing is a whole other question that I won't pretend to know the answer to.

[greenbean36191]

At a local reef club meeting recently, we had a researcher come and talk to us about coral disease that she studies, including all the various bacteria and viruses that can be found on coral. I was hypothesizing, with this whole temp swing issue, that perhaps different temps would favor different bacteria, never allowing one to gain hold on the coral.

Was that Rohwer? He was here a few weeks ago. He's done some interesting stuff.

On the subject of changing bacterial assemblages, here's an article that relates somewhat, although the types of temps aren't what you would ever see in a reef tank. http://www.pubmedcentral.nih.gov/art...?artid=1538755

[m2434]

Originally posted by greenbean36191
That part has already been shown. It's your questions of the mechanism that allows the adaptability that still need to be answered.

Good point, you have argued this well in the past. I agree that there is strong evidence that temp variation can be beneficial. "Is beneficial" may be a strong word. I think there could be more research on the limits to any beneficial effects. In other words, exactly how much and under what circumstances can we generalize this statement?

Also, I wouldn't doubt that bacterial colonies will flux some with temperature. Certain bacteria will probably get a foothold with certain conditions, when conditions change, of course, the advantage may shift. Of course, bacteria can be fairly adaptive as well...

[SDguy]

Originally posted by greenbean36191
Was that Rohwer? He was here a few weeks ago. He's done some interesting stuff.

It was a woman. I'll have to double check what research group she was with. They do in fact work in Hawaii and the Caribbean though...

[madadi]

im not sure if anyone has mentioned this already, but i have an aquacontroller that controls the temperature in my tank. you can set it to do seasonal temperature changes according to longitude and latitude of the area that you want to simulate. temps run in my tank from 76 in the winter to 81 in the summer, ALSO it simulates daylight duration. the days get shorter in the winter so the lights stay on less and less and backwards in the summer. AND it simulates the moon cycle very accurately, as in the time of night the moon set and rises and the intensity based on the faze of the moon. cant get any better then that.

i read couple articles that such a setup can stimulate corals and fish to spawn. obviously its not necessary for the survival of the critters but its sure cool!

[BeanAnimal]

I am with some of the others here. MY temp swings from 80-85 or so in the summer and from 78-82 or so in the winter. Daily swings can be in the 4-5 degree range over 24-36 hours and depend on evaporation and ambient temps.

The reef appears to be very healthy.

I wrote software to adjust photoperiod according to a selected timezone, including dimming for twilights hours at both ends of the photoperiod. I am not sure that it makes a difference but it makes me feel good