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As summer hits, so do the bleaching and RTN  horror stories from the increase in temperatures. A non-functioning air conditioning unit in your home can possibly lead to the death of sensitive corals such as Acroporas.

If you feel you are at risk from any potential raise in water temperature some simple insurance can be had by turning your heater up. Not down, but up.  By increasing the average temperature, should something happen to cause a drastic spike your corals will be better prepared.

Sounds odd, but fairly logical at the same time. Although I have witnessed this over my years in keeping Acroporids now you don’t have take my word for it…. you can take Middlebrook, Hoegh-Guldberg, and Leggat’s after they found this on their latest scientific study that was published in The Journal of Experimental Biology.

 What was done

The authors collected branches of the reef-building coral Acropora aspera – which contains the dinoflagellate symbiont Symbiodinium (clade C3) — from three large colonies on the reef flat adjacent to the Heron Island Research Station at the southern end of Australia’s Great Barrier Reef. Multiple upward-growing branch tips were placed on racks immersed in running seawater within four 750-liter tanks that were maintained at the mean local ambient temperature (27°C) and exposed to natural reef-flat summer daily light levels. Then, two weeks prior to a simulated bleaching event — where water temperature was raised to a value of 34°C for a period of six days — they boosted the water temperature in one of the tanks to 31°C for 48 hours, while in another tank they boosted it to 31°C for 48 hours one week before the simulated bleaching event. In the third tank they had no pre-heating treatment, while in the fourth tank they had no pre-heating nor any simulated bleaching event. At different points throughout the study, they measured photosystem II efficiency, xanthophyll and chlorophyll a concentrations, and Symbiodinium densities.

What was learned

Middlebrook et al. report that the symbionts of the corals that were exposed to the 48-hour pre-bleaching thermal stress “were found to have more effective photoprotective mechanisms,” including “changes in non-photochemical quenching and xanthophyll cycling,” and they further determined that “these differences in photoprotection were correlated with decreased loss of symbionts, with those corals that were not pre-stressed performing significantly worse, losing over 40% of their symbionts and having a greater reduction in photosynthetic efficiency,” whereas “pre-stressed coral symbiont densities were unchanged at the end of the bleaching.

What it means

In the words of the three researchers, “this study conclusively demonstrates that thermal stress events two weeks and one week prior to a bleaching event provide significantly increased thermal tolerance to the coral holobiont, suggesting that short time-scale thermal adaptation can have profound effects on coral bleaching.” In addition, they say that “both corals and Symbiodinium have been shown to possess a wide variety of genes that encode for stress response proteins, which can impart protection, indicating that a more comprehensive study is required to elucidate all of the underlying mechanisms of thermal bleaching.” All things considered, therefore, it may well be that earth’s reef-building corals are not nearly as helpless before the specter of possible future global warming as the world’s climate alarmists have made them out to be.

So there you go. Before that heat wave comes through your area it may be wise to turn the heater up a degree or two before it hits, as it was found “Symbionts of the corals that were exposed to the 48-hour pre-bleaching thermal stress ‘were found to have more effective photoprotective mechanisms’.”

If you’re contemplating this, care and thought must be given for Deepwater animals. Certain species such as Declivis Butterflies, Bandit Angels, and Borb’s do not care for temperatures over 80F. While other fish and corals can do just fine at 84F given proper acclimation. 84F is not uncommon on natural reefs so do not overly fret if you see your temperatures rise this high.

If you would rather keep your temps low all summer long there are two real options. The first being the effective but costly Chiller. The second being Fans.

Evaporative cooling is very powerful and can drops most tank temps from 1-3F. Fans blowing on the sump work quite well, as water constantly passes through this area. Of course this is not without increased evaporation. Fans blowing on the surface of the tank, or pushing heat from lights away are also effective. If you’re looking for attractive fans, checkout the Aquawind by Tunze.