Overview

Te Whanganui-a-Tara (Wellington Harbour) is a nationally significant harbour and port environment valued for the range of biodiverse habitats, species, and ecosystem goods and services it provides. Like other coastal environments surrounded by urban areas, the harbour receives inputs of sediment, nutrients, and other contaminants from the surrounding catchments. Such contaminants have the potential to adversely impact on the health and function of its ecosystem.

Why monitor sediments in estuaries and harbours?

  • There is a lot of human activity in and around our harbours and it is Greater Wellington’s job to understand how the activities of people are affecting the marine environment. This will allow us to manage our activities so that we can minimise our impacts through more environmentally conscious actions.
  • Sediments are of particular interest as contaminants (such as heavy metals from zinc roofs, copper from vehicle brake pads, carcinogenic hydrocarbons emitted during combustion) stick easily to fine muddy particles.
  • Sediments also smother marine life and plant communities living on the seafloor. Mapping the extent of muddy areas and the content of mud within marine and estuarine sediment allows us to better understand the effects mud is having on our precious estuarine ecosystems such as shellfish and seagrass beds.
  • Since contamination affects the health of the animal communities living within our marine ecosystems, we analyse samples from the very top layer of harbour sediments to understand whether selected sites within our harbours are becoming more contaminated or whether they are improving over time.

We currently monitor deposition rate, mud content, and oxygenation of intertidal sediments at one site in the Te Awa Kairangi (Hutt River) lower estuary and have been doing so since 2010. Periodically we also monitor macroalgae in this system.

Subtidal sediment surveys are one of the big pieces of monitoring work that we release every four to five years for our main harbours within the Greater Wellington Region. Together with habitat mapping, this information allows us to assess the health of our marine and estuarine invertebrate communities which are indicators of overall ecosystem health.

Our web report may be cited as: Greater Wellington (GW). 2022. Te Whanganui-a-Tara monitoring – Web report. Downloaded from https://www.gw.govt.nz/environment/environmental-data-and-information/water-monitoring/.

A PDF print-version of this report can be viewed and downloaded here.

Te Whanganui-a-Tara monitoring sites
The whole estuary is periodically monitored for changes in: salt marsh cover, macroalgal density, substrate, and mud content. Additionally, three buoys have continuously monitored water quality and wave data. Hover over map circles to see indicators measured at each site. Note that sites and indicators vary across the sampling period.