Red or green substance appearing in waterways

The substance is Trichodesmium, which is a bright green naturally occurring algae that releases a pink substance.

What is Trichodesmium and how does it occur?

Subtropical climates provide warm and sunny conditions. These conditions can assist Trichodesmium to bloom in our waters.

Trichodesmium are cyanobacteria (blue-green algae) that appear naturally in tropical and subtropical ocean waters and are commonly known as sea sawdust, whale sperm, whale food and sea scum.

Trichodesmium is a member of the phytoplankton family, and plays an important role in the aquatic food chain. Normally Trichodesmium are barely visible to the naked eye, but in water that has been calm for long periods it begins to float like sawdust on the surface.

Combinations of calm conditions, northerly currents and warm water temperatures can increase growth and even discolour the water.

What to look for

Blooms are most common between August and December. You may have noticed a bloom washed up on a beach, in an estuary area or in the Broadwater. There may also be an unpleasant ‘fishy’ smell. Wind and current conditions often cause large amounts of Trichodesmium to group together.

Trichodesmium blooms can cause water to appear rust- coloured but traces of grey, green and purple streaks can also be visible. In stagnant conditions, Trichodesmium blooms can release a clear toxin that changes the blooms’ colour from rust brown to green and also releases a pigment that colours the water pink.

The concentration of the toxin in a natural system, like the ocean, is generally not high enough to be harmful to human health. However to be certain it is best to avoid affected areas.

Don’t panic

Blooms generally disappear in a few days. Please remember if you have come in contact
with Trichodesmium it can easily be rinsed off the skin.

For further information on this topic, please contact us on 3829 8999 or view the fact sheet.