Tutorial: Ecotracer ZPD

This simulation tutorial is designed to give a basic introduction to the Ecotracer routine within the EwE modelling framework.  It represents a simple model with two living groups (phytoplankton and zooplankton) and a detritus group with all necessary data. The simulations are so simple that they can be solved numerically without the use of EwE.

The tutorial is a simple Zooplankton-Phytoplankton-Detritus (ZPD) model with only three groups for which the Ecopath parameter parameters are given in Table 1. As for diets, zooplankton only eat phytoplankton.

Table 1. Ecopath input data for a simple case simulation.

Group                     Biomass (t km^-2) P/B (year^‐1)    Q/B (year^‐1)

Zooplankton               0.0001                 1.0                    5.0

Phytoplankton           1.0                       2.0                      ‐

Detritus                      1.0                         ‐                        ‐

For Ecotracer, there is an initial environmental concentration, a direct absorption rate (DAR) for phytoplankton, an assimilation efficiency (AE) for zooplankton, and decay rates are lacking (Table 2).

Table 2. Ecotracer input data for a simple case simulation.

Group                  Initial conc.    DAR             AE
                              (Bq∙km^‐2)   (km^‐2∙t^‐1∙year^‐1) (fraction)

The ‘>’ symbol below describes the direction path and what to click, whereas the ‘=’ needs to have data entered including such things as file names that need to be created. In this scenario, it is easy to find the numerical solutions for each group at equilibrium by equations 7 and 8 in the introductory Ecotracer chapter (link).

ToolBar

>File

>New model

=choose directory to save the new model and a file name

Navigator panel

>Ecopath

>Input

>Model parameters

=fill in Model year and No. years (5 years)

>Basic input

>Define groups…

=insert two groups and name (phytoplankton and zooplankton);

set phytoplankton to producer.00 =ok and save changes

=add data from table 2; save

>Diet composition

=put in diet fraction (zooplankton only eat phytoplankton so 1 for diet fraction)

(Message regarding landings and discards, okay to ignore, there are no fisheries) > Output

>Basic estimates

>Tools

>Ecotracer

=Name new Ecosim scenario > create

=Name new Ecotracer scenario > create

>Ecotracer parameters

=enable contaminant tracing for Ecosim

>Ecosim

>lnput

>Ecosim parameters

= Duration of simulation (years): 5

(notice that the contaminant tracing box is checked)

>Tools

>Ecotracer

>Ecotracer input

=input data from table 3

>Ecotracer output

=choose: show data (concentration/biomass or concentration)

=select all groups to display on graph

> Run Ecosim (results show automatically on graph display)

(note that the environment stays at 1.0, but all the other groups are near zero—there is a colored line along the x-axis; to check the functional group values, select them and they will appear on the graph without the environment concentration)