If I say algae what comes to your mind? The green color? Slippery stones on a lake shore? Sushi?
Typically autotrophic, and some unicellular, I say they are rather fascinating organisms. I quote,
In the morning, photosynthetic production of ballast carbohydrate increases cell density [compared to water] and the algae begin to sink. […] The carbohydrate ballast is used up overnight by respiration and for the synthesis of new cells. The algae become lighter, and the buoyancy provided by the relatively permanent gas vacuoles causes them [the algae] to float up nearer to the lake surface. [1]
Gas vacuoles are, in essence, compartments filled with nitrogen gas that reside in algae cells (sort of a buoy inside a cell with the effect of keeping the cell afloat). The product of photosynthesis are carbohydrates, basically sugars, stored inside the cell. Those sugars are relatively heavy and, thus, can be considered to be ballast that lets the algae sink (sort of like a cargo ship when it is loaded with containers). So, in the morning thanks to sunshine, i.e. light, photosynthesis starts, sugars are produced, the cell becomes heavier, it sinks well below water surface. With no light, deeper in the water column and during the night when photosynthesis is not an option, cellular activities draw energy through the consumption of sugar reserves, the cell becomes lighter and by the next morning it is back at water surface.
As a phototrophic organism, our algae relies on light for photosynthesis. Thus, it must be at the water surface where light intensity is greatest at least for some time every now and then, especially in turbid waters. The question is why not always? Why does our algae take a daily dive? One of the main reasons is because the afternoon sun is too intense, in particular in UV radiation which may damage, even kill, cells. Thus, just before it gets too hot, the ballast (sugars) accumulated by photosynthesis while at the water surface in the morning, forces the algae to take a dive to escape the dangerous radiation, and guarantees enough energy reserves to survive for the rest of the day. The ballast gets depleted just in time to get back to the water surface, build up new ballast through photosynthesis, and dive again. Note that the rate of photosynthesis correlates positively with light intensity (logarithmic light response curve). Thus, the more intense the light the faster the necessary ballast for the next dive is built (in particular at the lower end of light intensity). On a cloudy day it would simply take longer to build up ballast and, thus, our algae stays longer at the water surface. This is just fine as UV radiation, too, correlates positively with light intensity. Obviously, on a sunny day our algae wants to stay up less.
Fascinating, uh?
The simple and elegant feedback mechanisms are indeed fascinating, in my opinion. We are talking here about cells, vertically moving up and down the water column by increasing and decreasing cell density, perfectly synchronized to be at the water surface when it is safe and to take a dive when it is not.
This made me think about human-built economic systems.
Imagine such well-timed feedback mechanisms implemented in our economic systems. Dangerous bubbles may build up but the system would correct and take a dive well ahead of bubble burst avoiding, thus, damage, crises, losses. You may argue, the bubble burst is the feedback. Perhaps, but the algae seems to get it more timely by diving ahead of damage and resurfacing ahead of death. Further, our algae seems to pefectly balance both increase and decrease in density while our monetary policy pushes for constant inflation, calling deflation a curse. I get that our economic systems are more complex than the activity of an algae yet I keep wondering if we could take some inspiration here.
[1] Alexander J. Horne and Charles R. Goldman. Limnology. McGraw-Hill Inc., 1994