1 Introduction
Cockburn Sound in Western Australia is a unique coastal ecosystem renowned for its important economic and environmental values, whilst also being under stress from a range of anthropogenic activities and climate change impacts. Deleterious water quality conditions have been a feature of the system in the past which severely impacted upon the most important ecosystem values, including seagrass and benthic community health, pelagic fisheries, and potentially also apex predators and iconic species. The historically poor water quality has been improving over past decades due to nutrient source control, however, past nutrient enrichment has left a legacy within the system and issues of hypoxia, harmful algae, and lack of water clarity continue to challenge managers and negatively impact upon the range of users of the system (BMT, 2018). Further, there are concerns that some risks associated with hypoxia, harmful algal blooms and excessive turbidity may worsen into the future if they are not actively managed.
As part of the WAMSI Westport Marine Science Program (WWMSP), the Cockburn Sound Integrated Ecosystem Model (hereafter referred to as ‘CSIEM’) has been developed as a tool to quantify water quality and habitat changes within the ecosystem in response to different environmental conditions, and to assist by allowing integrated assessment of management scenarios, and other questions relevant to decision-making. In particular, the model has been developed to allow stakeholders to move towards a more holistic and cumulative assessment of environmental risks, which has been particularly motivated since recent updates to the Environmental Protection Amendment Act (2020) by the State Government of Western Australia.
In building the model the intent has been to develop an ecosystem model able to support the multi-scale prediction needs of both development proponents and environmental regulators seeking to optimise ecosystem use, whilst capturing the latest scientific findings and data from the WWMSP research projects.
The core of the platform is a 3D hydrodynamic-ecological model, termed the Cockburn Sound Integrated Ecosystem Model (CSIEM), which is nested within regional met-ocean predictions and integrated with a variety of other environmental models. CSIEM has been developed as part of Project 1.2 of the WWMSP to undertake hindcast and forecast (scenario) predictions of water mixing and transport, salinity (S), temperature (T), aquatic biogeochemistry and ecology. The model has been implemented as part of an overarching integrated platform designed to coordinate the inter-dependencies between various modelling tools and outputs and model-data workflows, in order to provide a holistic view of the environmental conditions of Cockburn Sound.
Initial phases of the CSIEM development have focused on model setup and testing, and included interim releases (intial versions including v0.9, v1.0, v1.1 and v1.5). This document provides “living-manual” of the model, giving an overview and technical guide of the model design and capability as data and synthesis of the WWMSP research data and findings occurs.