Estuarine Trophic Index Toolkit (ETI)

Purpose

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.

Description

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.

ETI Toolkit

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:

  1. you have little or no knowledge of the state of indicators for an estuary;
  2. you wish to test the response of estuary trophic condition to changes in loads resulting from altered land use or point sources;
  3. you wish to test the response of estuary trophic condition to load limit-setting scenarios in upstream catchments.

State of Development Released and updated

Development Contact

NIWA
eti-tools@niwa.co.nz
NIWA

Main Developers

  • National Institute of Water and Atmospheric Research (NIWA)

Scope

Outcome Areas Environmental
Management Domains Coastal
Subdomains Land Use
Intended End Users
  • Researcher
  • Regional Council Scientist
  • General Usability
Spatial Extents National, Local (i.e. Catchment or District), Regional
Steady State or Dynamic Steady State
Level of Integration Environmental

Input & Output Data

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)

Accessibility

Open/Closed Source Closed Source
Licence Type No Licence

User Information

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)
Documentation

Instructions, background information and references provided on ETI Tools pages:

Tool 1 Eutrophication Susceptibility

Tool 2: Trophic state assessment - measured indicators

Tool 3: Trophic state assessment - Bayesian Belief Network

Technical Considerations

Programming Language Shiny R, Netica
Keywords estuary, trophic Index, Nutrient loads, eutrophication, susceptibility, health
Linkages to other Models
Links

CLUES Estuary

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.

Key References

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.


Robertson, B.M, Stevens, L., Robertson, B., Zeldis, J., Green, M., Madarasz-Smith, A., Plew, D., Storey, R., Oliver, M. 2016. NZ Estuary Trophic Index Screening Tool 2. Determining Monitoring Indicators and Assessing Estuary Trophic State. Prepared for Envirolink Tools Project: Estuarine Trophic Index, MBIE/NIWA Contract No: C01X1420. 68p.