Drivers, patterns and relationships between estuary health metrics in the Waikato region

Report: TR 2023/18

Author: Dana Clark, Judi Hewitt (Cawthron Institute)

In New Zealand, five macrofauna-based indicators are commonly used to assess estuary health. These include two Regional Benthic Health Models (BHMs), two National BHMs and the Traits Based Index (TBI).

These indicators are underpinned by different formulations, use different taxa to calculate scores and examine different components of estuarine health. While they should not be expected to be highly correlated, there should be some degree of consistency when classifying the health of sites as low, moderate or highly impacted.

Waikato Regional Council uses all five indicators to assess estuarine health in its region. Cawthron Institute (Cawthron) were contracted to investigate the performance of different indicators of estuary health for Waikato estuarine sites compared to stressor gradients and to one another, and to explore drivers of any differences in health scores. This will help the council decide which indicators are best to use in future monitoring.