Authorities have escalated their health advice amid South Australia's algal bloom, and are recommending people with asthma carry their medication on the state's beaches when foam is present.

The advice, which was updated last week, was discussed on the opening day of a Senate inquiry into the bloom which heard South Australia was "unprepared" for the ongoing disaster.

A group of scientists told the parliamentary committee the full extent of the damage remained unknown because environmental monitoring was "underfunded and fragmented".

Marine scientist Stefan Andrews, co-founder of the Great Southern Reef Foundation, said the bloom was "the most extensive marine mortality recorded in South Australia", having affected "at least 500 species".

"The bloom is a warning of what climate-driven

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