Caulerpa Update March 2026

After a period of reducing caulerpa presence for much of 2025, recent surveillance across the Bay of Islands and at Aotea Great Barrier Island indicates exotic caulerpa biomass is increasing, with regrowth in known areas and some new detections. We have several research, surveillance and removal projects underway to track these changes in biomass and minimisee, particularly Opito and Paroa Bays, where multiple areas of patchy caulerpa have been confirmed and prioritised for treatment to control biomass and reduce the risk of spread.

In Paroa Bay, areas of low density have spread across the bay with some larger patches around 1-2m. Paroa Bay has been identified as a preferred location for early intervention as it represents the western edge of the known population, most of the exotic caulerpa is on soft sediment which has lower diversity than rocky reef, and is easier to treat with the current tools.

At Omakiwi Cove, surveys have identified that most of the exotic caulerpa is still confined to reef on the northern and southern side of the bay. There have been no reports of the ‘large carpets’ or extensive monocultures of exotic caulerpa we saw in the past.

On Aotea, re-growth has been seen in known areas including Whangaparapara, Broken Islands, and at Okupu Bay, where only sparse mats were seen in October – December 2025.

Algae species like exotic caulerpa often undergo cycles of reduction and growth. It is likely that the survey results are the result of a summer growth period. We have several research, surveillance and removal projects underway to track these changes in biomass and minimise impacts in high priority sites.