Conceptual model of ecosystem (focus on elements and processes)
  1. identify bio-ecological receptors and their relationships
  2. Relate the model to the concept of ecosystem health
3)A conceptual model  is key component in the development of an integrated monitoring program to assess trends in the ecologic status of a system, highlighting its most relevant interaction. In \citet{2011} an example of such model shows how all the elements are correlated in the reef. To be able to identify and list which are the predominant negative factors affecting the barrier reef, we also have to recognise which element in the system are best suited to promptly detect them. In the case of the GBR corals are the obvious choice to indicate these changes, because their presence and structure underpins the entire ecosystem. It is also useful to recognise those species that thrive under certain conditions which will also cause an imbalance disrupting  the ecosystem stability.  As an example, in  \citealt{Cooper_2009}, a study with the purpose of undertaking a monitoring program to assess water quality on coral reefs, scientific literature was used to rank the suitability of bioindicators according to a framework that assessed weather responses to changes in water quality were  specific (to the stressor of interest and not to other environmental stressors),  monotonic (the magnitude of the biological response should reflect the intensity and duration of the stressor of interest),  variable (biological responses should be consistent at a range of spatial and temporal scales),  practical (Measurements of biological responses should be cost effective, easy to measure, non-destructive and observer independent) and relevant (Biological response should be ecologically relevant and important in public perception to assist communication) to management goals for long- and short-term monitoring programmes. At the end of this process, 11 indicators were chosen for long-term  and 8 for short-term monitoring useful to assess areas with acute disturbances on coral communities. The assessment framework developed in the article, provides the basis for the selection of a suite of bioindicators to be used when assessing the consequences of changes in water quality around coral reefs.