Perimeter detail of ring at 100x   ( phase contrast )

Possible Bacteria Swarm Ring


I am currently studying the diversity of protozoans and metazoans in water from my rain barrel and keep small sample jars of water and specimens that I collect.
Over time the populations change as some species disappear entirely while other species momentarily bloom and flourish. In one of my jars I let the
water gradually evaporate down into a watery sludge in the bottom of the sample jar.  Tonight I examined slides under my microscope
 and witnessed an eerie quietude with minimal protist activity where there had always been bustling activity. Through the microscope at 100x magnification
using the phase contrast method I noticed a superactive ring of bacteria coalescing, getting denser and in dynamic motion. The ring was unbroken and extended
around the span of most of the cover slip. I made four different slides and each slide duplicated this interesting ring phenomenon.

  : ring perimeter in motion, real time    26 seconds   1.7 Mb movie   ( click image to play )

 :  rotifer, possibly feeding at the ring                25 seconds 1.7 Mb   (click image to play )

 :  bacteria in motion  at 1000x brightfield  11 seconds   819 Kb   (click image to play)     .

Update :  My initial impression of this intense ring of bacteria was that this might be a predatory strategy by the bacteria themselves.
The slide was littered with metazoan carcasses. Upon further dialogue and reading, it appears that my specimen jar became oxygen deprived due to an imbalance
of too much organic matter and not enough oxygen exchange.  The higher "animals" like Chaetonotuses might have died due to lack of oxygen and not predation.
And it is also possible that this bacteria ring itself was oxygen related under the cover slip.  I hope to learn more and update this page with further observations in time.

Any comments, corrections or elucidation on this phenomenon is most welcome.
Thomas Ashcraft
New Mexico

Meiji microscope and objectives
Canon S3 IS camera