Report: TR2005/43

Author: Meg Graeme (Natural Solutions, Marine and Terrestrial Ecologists Ltd.)

Abstract

Aotea Harbour seems relatively sandy which may partly be a result of having the majority of the freshwater wetlands intact. These marsh clubrush and raupo wetlands provide an important filter between the land and harbour. These estuarine-freshwater wetland systems provide significant habitat for wetland birds such as fernbird. It should therefore be a priority to ensure the remaining freshwater-estuarine wetlands around Aotea Harbour are protected from future draining or stock damage.

The extensive seagrass beds are a significant vegetation community in the harbour. Seagrass is at the base of the food chain providing food for herbivores. Seagrass beds also have a diverse in-faunal community; and provide shelter and settlement habitat for benthic and planktonic fauna, which is in turn rich feeding grounds for carnivorous harbour birds and fish. The seagrass is also sustaining a large population of swans.

Weeds are a significant threat to the integrity of the harbour’s estuarine vegetation communities. The Department of Conservation is currently planning to aerial spray the spartina in Aotea Harbour with Gallant herbicide. The other significant estuarine weed is saltwater paspalum. Unlike Kawhia Harbour, saltwater paspalum has spread all around the margins of Aotea Harbour, although it is still generally present only in small patches. This grass has shown itself to be an aggressive competitor throughout the mid and upper tide zones.

The spread of Pacific oyster beds over the harbour flats has the potential to alter sediment and water flow characteristics.

Access by stock to the harbour is generally a problem around the eastern side of the harbour as this is where the majority of the farms are. However, there are isolated problems with stock access on the north and western sides of the harbour as well. Fencing of the eastern side of the harbour will allow the thin pohutukawa fringe that is such a feature of that side, to have the next generation regenerating underneath.

Estuarine Vegetation Survey - Aotea Harbour [PDF, 1.3 MB]

Click on highlighted areas on this map for a zoomed in view.