Toxic algae has been found in the Waihopai River in Southland ... flows and can be identified as dark brown or green slime on rocks or dark brown/black mats at the water's edge.

"You can identify toxic algae by looking out for leathery dark green or black mats clinging to rocks, or clumps of brown at the river's edge. The best antidote for toxic algae is to avoid it all ...

Have you ever seen brown or green goo floating on a river or in the ocean? Or have you noticed how the walls ... Sargassum floats near the water’s surface, while kelp is anchored to rocks on the ocean ...