From a pond water culture. Ceratium looks best possible bet. For more details on setup see
Large swatches of rust/burgandy material in the water here. Not floating on top. Some kind of algal bloom? Iim guessing its a dinoflagellate. I walk here weekly and have never seen this before, but it's been unusually warm.
Only 10um wide
Probably protoperidinium oblongum.
The dinoflagellates (Greek δῖνος dinos "whirling" and Latin flagellum "whip, scourge") are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth. Many dinoflagellates are known to be photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey, (phagotrophy). In terms of number of species, dinoflagellates form one of...