Acceptable Daily Temperature fluctuations
- Thread starter sandgoby
- Start date
Sort of, the main ideas as I see are:
- Animals more or less have absolute thermal limits. They also acclimate to certain temperature ranges within these limits.
- Prolonged exposure outside of the acclimated range can cause stress and mortality or loss of fitness.
- Short or long exposures outside of the organisms' absolute thermal limits can cause stress and mortality or loss of fitness.
- Variation within the acclimated range does not cause stress and mortality, however the potential range of acclimation can vary by organism.
- However, I don't think anyone can say what these absolute limits are, with any generality; it varies by organism. Trying to generalize though, most of the organisms we collect, can probably handle low 70s to upper 80s for example, if acclimated to these ranges.
More for greenbean36191:
Perhaps my last comment was confusing, maybe I can clarify a bit (or maybe not LOL). One area I still have some questions about is the difference between stress due to acclimated ranges vs stress due to absolute ranges. This does not appear to be defined well in the literature and my interpretation is based on my understanding of biological mechanisms and data available from the literature.
I see it as, acclimation can occur due to short bursts in temperature or slow gradual changes. Either sets off a cascade of events that can modify the acclimated range. greenbean36191 seems to be saying acclimation should be slow gradual changes only. However, from what I've seen, quick perturbations seem to lead to fairly immediate changes, perhaps such as changes, such as changes in gene-expression patterns, which control the various protein endpoints.
It seems quick perturbations outside of the acclimated range, only "break" things if excessively prolonged, or if outside of the absolute limits. It takes time for these changes to result in functional changes, capable of handling the prolonged exposure to higher temperatures. So, if the prolonged exposure occurs before the changes are complete, then things can "break"... However, if things revert back before things "break", the cascade is still set into motion and acclimation begins to occur anyway.
I am very interested in any reference on this subject though.
Last edited:
greenbean36191
Premium Member
Sorry, real life has gotten in the way lately, so I've only been able to spend a few minutes online here and there. Obviously it takes a bit more than that to answer such complicated questions.
While it's a bit outdated now, a good review on acclimatization and stress responses in corals is "The Physiological Mechanisms of Acclimatization in Tropical Reef Corals" by Gates and Edmunds (1999). It's got a good section on Hsps in corals.
The gist of the story though is that animals keep around some background level of Hsps essentially all the time (at least in the animals they're known from) to take care of regular maintenance of other proteins which are constantly being damaged. By definition, physiological stress breaks things faster than normal, and in the case of temperature stress one of the hallmarks is the damage to proteins. As a result, you tend to get a spike in Hsp production within hours as the cells attempt to get the damaged proteins under control. Therefore, Hsp levels are sometimes used as a proxy for physiological stress. The key though is that in order to use them as a proxy for stress, you have to have some context about what the normal levels are in the animal you're looking at due to the responses mentioned in Gates and Edmunds.
One type of response is what's seen in Montastrea, in which you get a spike in Hsps and then a decline within a few hours as protein turnover allows acclimation to take place. The HSR is NOT the acclimation- it's an indicator of stress that precedes the acclimation via protein turnover. The acclimation and eventual acclimatization via protein turnover is not considered a continuation of the HSR because under gradual change it can and does occur in the absence of the upregulation of Hsps.
In the other case mentioned with Goniopora, you get a continuous elevation in the "normal" level of Hsps. The cells are essentially keeping more Hsps on demand in anticipation of damage. It is a form of acclimatization, but again it's not usually considered a continuation of the HSR because the high levels of Hsps are simply the background levels, not an indicator of anything going wrong at that moment.
HTH
While it's a bit outdated now, a good review on acclimatization and stress responses in corals is "The Physiological Mechanisms of Acclimatization in Tropical Reef Corals" by Gates and Edmunds (1999). It's got a good section on Hsps in corals.
The gist of the story though is that animals keep around some background level of Hsps essentially all the time (at least in the animals they're known from) to take care of regular maintenance of other proteins which are constantly being damaged. By definition, physiological stress breaks things faster than normal, and in the case of temperature stress one of the hallmarks is the damage to proteins. As a result, you tend to get a spike in Hsp production within hours as the cells attempt to get the damaged proteins under control. Therefore, Hsp levels are sometimes used as a proxy for physiological stress. The key though is that in order to use them as a proxy for stress, you have to have some context about what the normal levels are in the animal you're looking at due to the responses mentioned in Gates and Edmunds.
One type of response is what's seen in Montastrea, in which you get a spike in Hsps and then a decline within a few hours as protein turnover allows acclimation to take place. The HSR is NOT the acclimation- it's an indicator of stress that precedes the acclimation via protein turnover. The acclimation and eventual acclimatization via protein turnover is not considered a continuation of the HSR because under gradual change it can and does occur in the absence of the upregulation of Hsps.
In the other case mentioned with Goniopora, you get a continuous elevation in the "normal" level of Hsps. The cells are essentially keeping more Hsps on demand in anticipation of damage. It is a form of acclimatization, but again it's not usually considered a continuation of the HSR because the high levels of Hsps are simply the background levels, not an indicator of anything going wrong at that moment.
HTH
greenbean36191
Premium Member
Well, it's widely believed that the more thermally tolerant clades of zoox produce less C for the coral and we know that it takes a whole lot of C to produce mucus. Researchers from Hawai'i found that corals with those clades were more susceptible to disease and it's been suggested that that may be because the corals aren't getting enough C to produce a mucus that supports the desirable community of microbes that are associated with healthy corals as seen by Ritchie.
greenbean36191
Premium Member
You almost nailed it. The only changes I would make to your summary is that it doesn't matter whether the limit you exceed is the absolute limit or the limit of acclimatization, the response is the same and the damage occurs on the same time scales.
greenbean36191
Premium Member
Those temperatures would be part of the acceptable range, but not all of it. 86 would be a conservative upper limit for virtually all of our charges (assuming they were acclimatized).
greenbean36191
Premium Member
A negative effect would be increase in disease, decrease in diversity, increase in bleaching, decrease in growth, a spike in Hsp production, a change in P/R ratio, reduction in photosynthetic efficiency, loss of color, reduction in larval recruitment and survival... all of which, except for loss of color, have been examined in the scientific literature and none of which support the line that fluctuations are stressful.
Yes, when I lived in a different house with better climate control, my temp varied only about 2 degrees year-round and it made no discernible difference. Whether the temperature is variable or stable also hasn't made a measurable difference in any of my research systems (working with BTAs, sebae anemones, and clownfish).
Agu
Premium Member
Pulled the heaters a couple of weeks ago as summer is settling into SW Florida. With nanos the thought of a malfunctioning heater scares me. About a week ago the Mrs decided to open all the windows/sliders over night to cool/air out the house. Three of my four nanos were at 69 degrees +/- .5 degrees. I prepared enough water to do substantial water changes but it was wasted effort. My suspicion that they can handle even greater swings was confirmed .
A. Grandis
Active member
I would think that daily fluctuations are fine. 1, 2 and max 3 degrees a day won't hurt. We know that fluctuation in a short period of time would hurt, of course. I would say the danger begins with... perhaps... 2, 3 or more degrees in 1 or 2 hours period.
Grandis.
Grandis.
Ken Hahn
New member
One only needs to observe tropical reefs at low tide with the exposed SPS corals baking for long periods of time under the tropical sun and then being hit with much cooler waves as the tide returns to realize that a few degrees of temp swing over a short period of time is not a big deal for an SPS coral.
--- Ken
--- Ken
Fishinfool
Reefer
Soulsanctu
New member
Gotta agree with ya....here in the desert southwest we don't have air conditioners..we have evaporative coolers on houses. They work great,,except when its humid outside (again...Desert Southwest)
There are so many other things in this hobby to "freak out" over.....When it comes to a few degree variance in temps, you should just....chill out
Well, I'm apparently not the only one to suggest it 
I just recently came across this article... While their research is far from conclusive, it does build on the existing evidence and the authors suggest that short, frequent temperature bursts do help acclimate corals.
It seems to be a pretty well thought out and controlled experiment. There are certainly some loose ends though.
The article is Oliver and Palumbi (2011) "Do fluctuating temperature environments elevate coral thermal tolerance?"
From is "Our work suggests an additional element may be a factor in the hardening of corals to high temperatures: high-frequency, low-duration (HFLD) heating."
Abstract
Do fluctuating temperature environments elevate coral thermal
tolerance?
T. A. Oliver • S. R. Palumbi
Received: 11 March 2010 / Accepted: 3 January 2011
Springer-Verlag 2011
Abstract In reef corals, much research has focused on the
capacity of corals to acclimatize and/or adapt to different
thermal environments, but the majority of work has focused
on distinctions in mean temperature. Across small spatial
scales, distinctions in daily temperature variation are common,
but the role of such environmental variation in setting
coral thermal tolerances has received little attention. Here,
we take advantage of back-reef pools in American Samoa
that differ in thermal variation to investigate the effects of
thermally fluctuating environments on coral thermal tolerance.
We experimentally heat-stressed Acropora hyacinthus
from a thermally moderate lagoon pool (temp range
26.5–33.3C) and from a more thermally variable pool that
naturally experiences 2–3 h high temperature events during
summer low tides (temp range 25.0–35C). We compared
mortality and photosystem II photochemical efficiency of
colony fragments exposed to ambient temperatures (median:
28.0C) or elevated temperatures (median: 31.5C). In the
heated treatment, moderate pool corals showed nearly 50%
mortality whether they hosted heat-sensitive (49.2 ± 6.5%
SE; C2) or heat-resistant (47.0 ± 11.2% SE; D) symbionts.
However, variable pool corals, all of which hosted heatresistant
symbionts, survived well, showing low mortalities
(16.6 ± 8.8% SE) statistically indistinguishable from controls
held at ambient temperatures (5.1–8.3 ± 3.3–8.3%
SE). Similarly, moderate pool corals hosting heat-sensitive
algae showed rapid rates of decline in algal photosystem II
photochemical efficiency in the elevated temperature treatment
(slope = -0.04 day-1 ± 0.007 SE); moderate pool
corals hosting heat-resistant algae showed intermediate
levels of decline (slope = -0.039 day-1 ± 0.007 SE); and
variable pool corals hosting heat-resistant algae showed the
least decline (slope = -0.028 day-1 ± 0.004 SE). High
gene flow among pools suggests that these differences
probably reflect coral acclimatization not local genetic
adaptation. Our results suggest that previous exposure to
an environmentally variable microhabitat adds substantially
to coral–algal thermal tolerance, beyond that provided by
heat-resistant symbionts alone.
I just recently came across this article... While their research is far from conclusive, it does build on the existing evidence and the authors suggest that short, frequent temperature bursts do help acclimate corals.It seems to be a pretty well thought out and controlled experiment. There are certainly some loose ends though.
The article is Oliver and Palumbi (2011) "Do fluctuating temperature environments elevate coral thermal tolerance?"
From is "Our work suggests an additional element may be a factor in the hardening of corals to high temperatures: high-frequency, low-duration (HFLD) heating."
Abstract
Do fluctuating temperature environments elevate coral thermal
tolerance?
T. A. Oliver • S. R. Palumbi
Received: 11 March 2010 / Accepted: 3 January 2011
Springer-Verlag 2011
Abstract In reef corals, much research has focused on the
capacity of corals to acclimatize and/or adapt to different
thermal environments, but the majority of work has focused
on distinctions in mean temperature. Across small spatial
scales, distinctions in daily temperature variation are common,
but the role of such environmental variation in setting
coral thermal tolerances has received little attention. Here,
we take advantage of back-reef pools in American Samoa
that differ in thermal variation to investigate the effects of
thermally fluctuating environments on coral thermal tolerance.
We experimentally heat-stressed Acropora hyacinthus
from a thermally moderate lagoon pool (temp range
26.5–33.3C) and from a more thermally variable pool that
naturally experiences 2–3 h high temperature events during
summer low tides (temp range 25.0–35C). We compared
mortality and photosystem II photochemical efficiency of
colony fragments exposed to ambient temperatures (median:
28.0C) or elevated temperatures (median: 31.5C). In the
heated treatment, moderate pool corals showed nearly 50%
mortality whether they hosted heat-sensitive (49.2 ± 6.5%
SE; C2) or heat-resistant (47.0 ± 11.2% SE; D) symbionts.
However, variable pool corals, all of which hosted heatresistant
symbionts, survived well, showing low mortalities
(16.6 ± 8.8% SE) statistically indistinguishable from controls
held at ambient temperatures (5.1–8.3 ± 3.3–8.3%
SE). Similarly, moderate pool corals hosting heat-sensitive
algae showed rapid rates of decline in algal photosystem II
photochemical efficiency in the elevated temperature treatment
(slope = -0.04 day-1 ± 0.007 SE); moderate pool
corals hosting heat-resistant algae showed intermediate
levels of decline (slope = -0.039 day-1 ± 0.007 SE); and
variable pool corals hosting heat-resistant algae showed the
least decline (slope = -0.028 day-1 ± 0.004 SE). High
gene flow among pools suggests that these differences
probably reflect coral acclimatization not local genetic
adaptation. Our results suggest that previous exposure to
an environmentally variable microhabitat adds substantially
to coral–algal thermal tolerance, beyond that provided by
heat-resistant symbionts alone.
