Methods
Full details of methods and guideline comparisons are described in 2019/20 coastal monitoring reports.
Habitat surveys describe and map estuaries according to dominant habitat features combining aerial photography, detailed ground truthing, and Geographic Information System (GIS) data. Changes in the position, size, or type of dominant habitats are monitored over time by repeating the mapping exercise every five years.
Once an estuary has been classified according to its main habitats and their condition, representative habitats can be selected and targeted for sediment quality and ecological monitoring. The National Environmental Management Plan (NEMP) advises monitoring soft sediment in the mid to low tidal range of priority estuaries, but due to the rarity of seagrass habitats in our region, we also include monitoring of these high biodiversity areas within the Porirua Harbour.
The environmental characteristics assessed in fine scale surveys include biological attributes (e.g. macrofauna) and physico-chemical characteristics (e.g. sediment mud content, trace metals, nutrients) to assess ecological condition. We have extended the NEMP to include sedimentation monitoring using plates buried below the soft sediment in select intertidal and subtidal areas to inform the vertical and horizontal spread of mud. Results across all years are assessed using estuarine health metrics or condition ratings, which are used to assign one of four ‘health status’ bands (e.g. ‘poor’, ‘good’) to track changes over time.
