Muri algae clearing say Cook Island authorities

The Cook Islands tourism chief says a drop off in algae growth in the Muri lagoon is no reason to sit back.

Seaweed had been spreading in Rarotonga's tourist hotspot since late 2015 but over the last fortnight the CEO of the Cook Islands Tourism Corporation Halatoa Fua said it's been dying off and sand was returning.

Recent heavy rain is thought to be behind the change.

Groundwater runoff and seepage from surrounding septic tanks as well as a lack of water flow had been blamed for the growth which environmentalists saw spreading around Rarotonga.

Mr Fua said there was reason for optimism now there was a cohesive approach to dealing with the bloom and consultants had been engaged to come up with a solution for the lagoon within 18 months.

"It's one of the most photographed and visited sites in the Cook Islands especially for visitors but now that we've seen a lot of that disappearing it's quite pleasing for us but it doesn't mean that we rest on our laurels," he said.

"There still needs a lot of work to be done for sanitation management here in the Cook Islands.