Chart Description:
Blue shaded area in back is CO2 level, orange line is entrance temperature, green line is temperature above cluster, light blue line is RH% and dark blue line is the outside temperature. Temp and rh use the right Y axis and CO2 uses the left Y axis. It’s a visual way to see how things relate to each other. You look for leading events and observe what happened subsequently. Examples here are human disturbances (i.e. adding a sensor), rapidly warming temperatures as well as steady state periods where nothing major is happening (used as baselines). I collected data from mid-October to March 12. The entrance sensor was added late December to add another data point (indicates entrance activity, cluster movement, is one parameter of natural ventilation).
Hive Setup:
The bees are hived in a deep plus and medium super. Top has R40 and sides and back of the hive are about R20, front side of hive has about R10 (condensing wall). It has a fully open screen bottom board which opens into a protected cavity used to drain excess condensation.
General Comments:
The orange line is the temperature 3" inside the entrance, so when that spikes it tells me the bees are bearding or coming out the entrance!!! It resulted in 2 high mortality events where bees likely got chilled after coming out of the hive. The two main events actually show the outside temperature rising above the entrance temperature. This would stall/slows natural convection (ventilation). The bees quickly heated up the inside of the hive, likely spiking CO2 inside, and rushed to the entrance to fan and exit hive. A side note: I tested 25 of these bees (fresh dead bees), no Nosema or Amoeba observed. I observed one of these events where the bees just rush out (puke out) a couple of years ago. Removing the entrance guard helped them quickly quiet down again. At this time of year the open screen board is littered with about 3/4" of dead bees likely preventing much air exchange with the crawl space. The other thing associated with these warming spells (Chinooks) is the air is much wetter (Gulf of Alaska) vs dry cold interior. (0.4 g/m3 absolute humidity vs 3 to 4 g/m3). 20C at 60RH% is 9-10g/m3. So the bees moisture needs just instantly dropped by 30-40%.
My entrance is likely too small and I will need make it larger to prevent this from happening in future. My other 3 colonies have large entrances and did not experience this type of event during the 2 chinooks. In past years, regardless of entrance size (I have two styles of poly hives), colonies with Nosema and Amoeba (co-infection) would show high levels of dead bee out front. Happily, all 4 colonies have made it through so far, they have decent cluster sizes. My runty experiment hive (small cluster) with a queen (3 years old) that I moved from a severely infect colony last year that was collapsing, has survived. This tells me the queens in these Nosema/Amoeba infected colonies are likely ok and it is the infected workers that are unable to raise brood. Also all my gut sampling shows very low Nosema with a few bees showing infected tubules or odd floating Amoeba cyst. None of the 20+ bees dissected had dual infection.
The other major change was to treat all my spare gear with 80% Acetic acid fumes for about 2 weeks before re-using any of the gear. Last year I tested my spare gear and found Nosema and Ameoba on most of my spare (small feces and bottom of cells) drawn frames and threw out anything that was too "dirty".
I am currently putting together list of observations and hypothesis to attempt to explain what is happening. I am also listing out a list of relationships between weather, physical and biological that would drive them.
Feel free to comment and theorize
Example:
Observations on CO2 levels:
At temperatures above approximately -10C, CO2 levels drop below 10,000 ppm.
Much of the winter CO2 levels are above 10,000 ppm (>23 times higher than atmospheric).
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