The NZ Estuary Trophic Index (ETI) toolkit is to assist regional councils in determining the susceptibility of an estuary to eutrophication, assess its current trophic state, and assess how changes to nutrient load limits may alter its current state.
The Estuary Trophic Index (ETI) toolkit is a series of decision support tools developed with funding from Envirolink Tools Grants for the Regional Councils Coastal Special Interest Group. These tools were developed with the aim of creating a nationally consistent approach to the assessment of estuary eutrophication, including nutrient load thresholds.
In terms of the regional council planning framework, the ETI provides vital supporting guidance for underpinning the ecological health component of regional plans by identifying relevant estuary attributes and outcomes for inclusion in plans, defining methods and indicators to measure ecosystem health attributes, and providing guidelines to assess whether or not the outcomes are being met.
The ETI provides three tools:
Details of when to use each tool and the knowledge underpinning the tools can be found on the Welcome and Background Information tabs, respectively, for each tool. The relationships between the three tools is shown in the concept diagram below.
Tool 1: Determining eutrophication susceptibility using physical and nutrient load data
In Tool 1 two approaches are combined to enable the user to assess estuary susceptibility to eutrophication (i.e., the risk that an estuary will be eutrophic based on its physical characteristics), along with advice about when each approach is applicable.
The two approaches require nutrient load and flow data which is supplied by the model developers for most New Zealand estuaries. If this data is not included for a specific estuary data will need to be provided by the user or added from CLUES modelling.
Tool 2: Assessing Estuary Trophic State using measured trophic indicators
Tool 2 is a monitoring approach which focuses on ecological response indicators (e.g. macroalgal biomass & dissolved oxygen) and how these factors change throughout the ecological gradient of an estuary in question. It then provides a means of translating these ratings into an overall estuarine trophic index based on the response from the monitoring of those indicators.
This tool requires measurement data of primary indicators (e.g. macroalgae & phytoplankton) and secondary indicators (e.g. oxygen, redox potential depth & macrobenthos condition) of eutrophication and trophic state.
Tool 3: Assessing Estuary Trophic State using a Bayesian Belief Network
ETI tool 3 uses knowledge of the ecological connections between drivers of estuary trophic condition (e.g., estuary type, nutrient loads, estuary closure state) and responses of indicators (e.g., macroalgal and macrobenthic health indices) to calculate an ETI score using a Bayesian Belief Network (BBN).
The ETI scoring is identical to that of Tool 2, but the Tool 3 BBN can operate when no or few values are known for primary and secondary indicators. It therefore is most useful when either:
|State of Development||Released and updated|
|Intended End Users||
|Spatial Extents||National, Local (i.e. Catchment or District), Regional|
|Steady State or Dynamic||Steady State|
|Level of Integration||Environmental|
|Key Input Data||Runoff Base data for all esturaties provided - nutrient loads, esturary location shape size etc|
|Input Data Formats||XLS(X)|
|Output Data Formats||XLS(S), Image File(s)|
|Open/Closed Source||Closed Source|
|Licence Type||No Licence|
|Operating Systems||MS Windows, Mac OS X|
|Software Needed||Web Browser, Netica|
|User Interface||Graphical desktop|
|Ease of Use||Easy|
|Use in Policy Process||Plan (Policy Formulation), Review (Issue Identification)|
Instructions, background information and references provided on ETI Tools pages:
|Programming Language||Shiny R, Netica|
|Keywords||estuary, trophic Index, Nutrient loads, eutrophication, susceptibility, health|
|Linkages to other Models||
Plew, D., Zeldis, J., Shankar, U., Elliot,S. (2015) CLUES Estuary – a tool for predicting estuary water quality. Australasian Coasts & Ports Conference, Auckland, New Zealand.
Robertson, B., Stevens, L., Robertson, B., Zeldis, J., Green, M., Madarasz-Smith, A., Plew, D., Storey, R., Hume, T., Oliver, M. (2016) NZ Estuary Trophic Index Screening Tool 1. Determining eutrophication susceptibility using physical and nutrient load data. Prepared for Envirolink Tools Project: Estuarine Trophic Index, MBIE/NIWA Contract No: C01X1420: 47.