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Light and it's effects on algae


A few threads have been addressing lighting and algae over the last few
days/weeks and light is the "throttle" to many of our tanks generally that
determines uptake rates of nutrients. Therefore some might find this of
interest:

Algae processes that change as irradiance (light) changes:

1) Xanthophyll cycle takes about 1 minute to change.(think about clouds etc)

2) Rubisco  takes about 10 minutes to change.(think about O2 levels)

3) Changes in max Productivity(measured as O2 production) 6hr-1 day.(think
about O2 levels)

4) Changes in the amount of Chlorophyll A  about 1-7days.(think about
blackout)

You can screw with algae(an plants in most cases) playing with these
processes. O2 toxicity in No3# from excess plant growth(plants have a
cuticle protecting them internally from the high levels of O2) seems that it
can damage and harm most nuisance algae since they lack the cuticle
protective layer in many species. The O2 competes with Rubisco for CO2 and
lowers it's efficiency(also in no#2). By separating the internal portion
from the high O2 environment, especially in the later parts of the day the
plant have a "reserve" of CO2 still available to them within the larger
structure of the plant and also better protection from the high O2
environment keeping the Rubisco running at top speeds/efficiencies. Algae in
most cases do not. High algae such as Charaophytes (Nitella and Chara) and
some Cladophora (algae balls and that hair algae everyone cannot get rid of)
are larger and have better protection from this O2 competition.
Maybe not.

The changes in CHL A, at 1-7 days seems to fall in line with a blackout
method for eradication of most algae. They will produce spores etc that will
come back if things are left the same after the light is turned back on but
it will get rid of them for the moment so you can correct conditions within
the tank and help get the plants going again. Plants also are effected by
this and perhaps the lower light from GW blockage is simply a rebound effect
since the plant has produced more CHL A to make up for the decrease in
light. More CHL A generally means more production of O2. We often see a
noticeable clearer tank after the GW is removed and also low presence of
other algae.

Food for thought. Some of these "gear switching" lighting ideas might work
better if we know what happens to the algae and also the times it takes for
each process to occur.

Regards, 
Tom Barr