Molds (Fungi) and Bacteria are something Humans have been at war against with their cleaning and pesticides for decades...
Phytoplankton eat bacteria, correct?
Most published research are rather diplomatic about this phenomenon[0]. However, reading between the lines, the reason appears to be the lack of fecal and insect contamination in food supply, which accidentally eliminated a lot of exogenous micronutrients not present in plants.
[0]:https://www.mayoclinic.org/diseases-conditions/vitamin-defic... [1]:https://www.nhlbi.nih.gov/health-topics/pernicious-anemia
I also wonder to what extent thiamine is recycled in nature, apart from thiaminases, if an predator high up the food chain dies and floats/sinks in the sea, will all the accumulated thiamin be recycled? in what pathways is thiamine consumed in say a human? what would increase or decrease the metabolic consumption (not eating) of thiamine?
>Thiamine in foods can be degraded in a variety of ways. Sulfites, which are added to foods usually as a preservative,[34] will attack thiamine at the methylene bridge in the structure, cleaving the pyrimidine ring from the thiazole ring.[13] The rate of this reaction is increased under acidic conditions. Thiamine is degraded by thermolabile thiaminases (present in raw fish and shellfish[12]). Some thiaminases are produced by bacteria. Bacterial thiaminases are cell surface enzymes that must dissociate from the membrane before being activated; the dissociation can occur in ruminants under acidotic conditions. Rumen bacteria also reduce sulfate to sulfite, therefore high dietary intakes of sulfate can have thiamine-antagonistic activities.
Is this perhaps due to sulfate pollution (bunker oil?) and acidification of the oceans?
No, phytoplankton are basically microscopic plants, they don't eat anything per se, they are autotrophs which use inorganic substances in the environment and get their energy from sunlight.