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Microscopic examination of the surface film sample collected on 17 May from North Yunderup confirm that it was caused by Cricosphaera the same microalgal Genus I mentioned that was present in the Hotham River a few years ago and in the Winslee Canals back in 1993.
The Hotham bloom was discovered when a camper complained that his skin developed a whitish powdery coating after swimming in the River. Presumably left by the drying cells covered with organic scales whose details are necessary for species identification and can only be determined with an electron microscope.
The division of algae that it belongs to contains the related species Prymnesium that is toxic to fish. However Cricosphaera is not one of these toxic species.
The Winslee Canals event in 1993 I recall we issued a nuisance to swimmers recreational warning. That was a denser scum than this one as seen by John's photo of 1993. The density of the alga in then water does not need to be great to produce a thin film as we observed this morning. However one can surmise that given the right wind/tide conditions a thicker scum can develop in embayments and against the side of moored boats. It is not known to be more than an inconvenience and should be washed off if forming a film.
This scum is not to be confused with the Cappuccino-like scum we usually see earlier in the year.
