9. Hauraki Gulf/Bay of Plenty estuaries
Map ID Number: 9
Location: Includes Firth of Thames, Coromandel estuaries, and Bay of Plenty estuaries
Approximate area: 217km2(summation of the surface areas of the above estuaries at high water) 8
Description of area:
The Firth of Thames is a large, shallow coastal embayment supporting a range of coastal habitats and plant and animal communities. There are four estuaries (Manaia, Te Kouma, Coromandel, and Colville) on the western coast of the Coromandel Peninsula and several on the eastern coast of the Coromandel Peninsula (e.g., Whangapoua, Tairua, Wharekawa, and Whangamata). There are a number of estuaries along the Bay of Plenty coast (e.g., Tauranga, Maketu, Whakatane, and Ohiwa)
Biological attributes:
The Firth of Thames, Coromandel estuaries, and Bay of Plenty estuaries are highly productive ecosystems, and are of significant environmental and economic importance. A range of habitat types are found in and around these estuaries, including coastal shrublands and forest, freshwater wetlands, saltmarsh, mangroves, seagrass, sand and mud flats, rocky reefs, and tidal channels. The extensive estuarine intertidal flats support abundant and diverse communities of benthic invertebrates – including extensive shellfish beds, which are an important food source for many fish and birds, as well as having other significant ecological functions.
The intertidal sand and mudflats are important feeding grounds, and breeding and roosting sites for large numbers of wading birds, coastal and freshwater birds, including a number of rare and threatened species. The Firth of Thames is one of New Zealand’s most important coastal stretches for wading and shore birds. The area forms a key site for migratory birds from the Arctic Circle to Australasia (the “East Asian-Australasian flyway”).
The estuaries are also important feeding and breeding areas for a number of fish species and are the subject of current Foundation for Research, Science and Technology (FoRST) funded research (conducted by M. Morrison, NIWA).
The Firth of Thames, Coromandel estuaries, and Bay of Plenty estuaries have come under significant threat as a result of catchment activities which, in particular, have been responsible for increased rates of sedimentation. These estuaries are also under threat from coastal development such as marinas and canal developments, subdivisions, aquaculture, reclamation and infilling, foreshore structures, roading, stock grazing, introduced species, and flood control works.
Criteria applied:
Species diversity; species richness; dependency for other species; trophic/ functional diversity; conservation status/ threat classification both nationally and globally; cultural values; degree of disturbance; special conditions and specialised organisms; habitat complexity/ diversity.
Status and management:
The southern Firth of Thames is listed as a wetland of international importance under the Ramsar Convention. The site includes approximately 78km2 of shallow estuarine waters, intertidal mudflats, mangrove and saltmarsh, and graded shell beach ridges. The Firth of Thames is considered to include nationally significant mangrove and mudflat communities.
The Firth of Thames and Coromandel estuaries are included within the Hauraki Gulf Marine Park which was established in 2000 with the aim of enhancing the integrated management of the Hauraki Gulf.
Many of the Coromandel and Bay of Plenty estuaries have been designated as “Areas of Significant Conservation Value” under regional council coastal plans.
Improved catchment management (minimising erosion, reducing runoff and nutrient leaching) will help to protect estuaries. Regional councils, in conjunction with the Minister of Conservation, are responsible under the Resource Management Act 1991 for the management of the effects of activities in the coastal marine area. Territorial authorities are responsible for managing land-use effects above mean high water springs.
State of information:
Variable for the different harbours.
References and further reading:
Auckland Regional Council (2002a, 2002b, 2003b, 2003c, 2003d), Brejaart and Brownell (2001), Cromarty and Scott (1996), Cole et al. (2000), Environment Bay of Plenty (1999, 2000), Hartill et al. (2003), Park (2000), Thrush (1993), Turner and Carter (2004).
8 Source for estuarine areas:http://finz.niwa.co.nz/NewZealand/Whitianga Harbour viewer.htm