Ok. So I had a little hiccup with my DIY cryptic 5gal bucket. Lesson: if a container is not designed with seals to hold water under pumping pressure, then trying to DIY the seals to handle it will never be secure. 3 fails is enough for me to get the point. :-(
So gonna have to reset some things and restabilize before any further useful data could be had.
Also going to tighten things up with regards to a few measurements, and more complete documentation in personal notes to give me a better chance of tracking source of any changes.....
In the mean-time I want to circle back to this idea...
You may be able to come up with some interesting results by following this path of "consumption imbalance", but they can be difficult to observe. Most often, when a macroorganism suffers from limitation of an essential nutrient, what occur are developmental delays and some "deficiency diseases", but not necessarily rapid death. For microscopic beings, if a limiting factor causes some to die, their bodies will supply nutrients to the others.
This is very interesting because it matched my assumptions going into it - that seeing chemical evidence of limitation through behavior of tested parameters would be more clear than visual changes in the populations of the tank.
I now think this is wrong though.
While the nutrient evidence of limitations to various organisms during this 3 weeks was hard to see from the data I've posted, some population changes were quite clear.
1. cyanobacteria increase/retreat/disappearance
Pics on day 2, 4, 6 & 10. Cyano never reappeared.
2. Cryptomonas/Rhodomonas disappearance and slight reappearance
Along with the cyano is a tiny protist dude that matches cryptomonas/rhodomonas description.
They were abundant pre-test Mar 23 through Apr 3 (Day 4).
video from that day.
after cyano disappeared, they were entirely absent from sand sampled in the same area on Day 15. They make a reappearance on Day 24 - see sand pigmentation discussion below.
3. Diatom increase, decrease, reappearance
Diatoms increased with silica addition early on, then plateaued, and surprisingly a glass scraping on day 15 showed diatoms had been almost entirely replaced by a mix of green algae, coralline, and a brown film algae - sand samples on the same day showed diatoms to be nearly totally absent there as well. Then they reappeared in force on the glass - Day 24 a scraping was totally diatoms.
This is hard to tie to nutrients because the silica consumption was basically steadily increasing with the increasing dose throughout the whole time frame.
Top 2 - Day 4 diatoms likely at their peak. Bottom 2 - Glass scraping Day 15.
Day 24 - glass film makes a comeback and is near 100% diatoms again.
4. Algae growth.
While hard to quantify, I'd say green algae growth in the display may have stalled/declined for the bulk of the experiment.
Below is a derbesia plug on 3/23 (pre-test), and Days 3,4,6&8
(I never saw signs of a slowdown in the chaeto in the sump.)
5. Sand pigmentation:
Some color to the sand pre-test decreased during the test and stayed as white as I can ever recall it for the bulk of the test with a slight resurgence of brown pigments in the sand by Day 24.
Mar 20 (Pre-Test), Apr 1 - Day2, Days 6,10,19,24.
Inspection of pigmented sand patch on Day 24 showed lots of benthic diatoms, some of the cryptomonads, and a few dinoflagellates.
scope video:
6. Sponges
While I can't say anything conclusively about growth, on day 6 my orange tree sponge opened its siphons showing normal feeding behavior for the first time in many weeks. It had been a long slow degradation process up to that point. (Not 100%, but I think for the last few days - Day 20+ it's been closed again.)
So all that said - I think from the data I do have - I could make a more convincing case for growth limitations in my system by actual observation of the organisms than analysis of the nutrient tests.
Why might that be?
Maybe because to see a sharp drop in consumption of Major nutrients - N, P or Si - in a system that has many classes of organisms that use it - all or nearly all of those organisms would first have to hit a limitation or co-limitations of several scarce resources. If only a few organisms are limited, there are still others that can cover that up by their continued consumption.
For instance: diatom population dropped in the middle of the test with no noticeable decrease in Si consumption - actually Si consumption was still rapidly increasing. Apparently sponges in my system were more than capable of picking up the slack.
