Big Bay Wetland: Seaweed Options Assessment

Client: Auckland Council

 Big Bay estuarine wetland where a red seaweed is seasonally deposited with each tide. 

Big Bay estuarine wetland where a red seaweed is seasonally deposited with each tide. 

The seaweed beds of the Manukau Harbour provide important ecosystem services to the marine environment. When large quantities of seaweed wash up on beaches and become trapped in estuarine wetlands, they can become a nuisance to public amenity and recreation with localised impacts. 


In Big Bay, Awhitu Peninsula, a red seaweed seasonally accumulates on the beach and in estuarine mud of the wetland. The seaweed rots, releasing an unpleasant odour and appears to have resulted in a two-meter layer of anoxic sediment. 


Morphum was engaged by Auckland Council to conduct an options and feasibility assessment for innovative engineering design to reduce seaweed accumulation in the wetland. Fish Friendly Tide Gates were proposed to manage the seawater and thus seaweed ingress into the wetland while allowing for environmental flows and fish passage. Morphum facilitated several on site stakeholder workshops with the community to incorporate local ideas into each stage of the project. 


Key deliverables:

  • Working collaboratively with the Big Bay community and Auckland Council Healthy Waters Department to achieve project objectives. 
  • Research into innovative methods for seaweed management. 
  • Seaweed Management Options Assessment Report and Maps. 
     

Cat Davis

Environmental Scientist