I am thinking the mulch is in large part compost, hence the manure-like smell. I believe the white stuff could be actinomycete(s), part of the microbial community. Google it and see what you think.
L.

Natural mulch products will have fungus and bacteria present and they will work to break that material down. The activity of these wee critters can manifest itself with a whiteish, yelowish, greenish, blackish hue on the surface of the mulch when conditions are right. there can also be slime molds develop (that looks like a dog vomited) that reallly gets people excited but is also harmless.
The manure like odor that was present when the mulch was applied indicated this was stored someplace where it went into anaeerobic digestion, hence the manure like odor. That is not a problem except for the unpleasant, to many people, odor for a time. This mulch will straighten out in time.

Thanks everyone for your comments! My landscaper has now suggested to rake it and spread it around to help it dry out better, which should happen as soon as we have sunnier/drier days. He didn't give it a name, just referred to it as "organism" that can grow due to the combination of excess rain and humidity. I am also starting to think it's some type of bacteria as it clearly has spores and is dusty to the touch (very similar to bread mold) - so nothing to be concerned about? Harmless to plants, pets and people?