Guam Atlantis Ecosystem Model

A decision support tool for ecosystem-based management

Human well-being is inextricably linked to sustainable use of environmental resources. Ecosystem-based management includes both ecosystem function (biophysical processes) and ecosystem services (socioeconomic processes). Managers are challenged with sustaining ecosystem functions and services under changing environmental conditions and human use. Models can help reveal insights in the economic and ecological tradeoffs of alternative management scenarios. One such model is the Atlantis Ecosystem Model (Atlantis), which can produce realistic simulations of ecosystem dynamics and serve as a strategic management tool for the exploration of ecological hypotheses, simulations of climate scenarios, and testing of human effects on the environment. These human effects include fisheries, tourism, extraction of natural resources, changes in land use, and nonpoint-source pollution. The original Atlantis code was developed by scientists at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia (Fulton et al. 2004a, 2004b).

Atlantis is an effective tool for evaluation of management strategies, particularly for the testing of management policies and methods for coral reef conservation and assessment against simulations that represent a real coral reef ecosystem and its complexities. The model is not intended to replace traditional stock assessments or to make short-term tactical decisions (e.g., total catch limits). Instead, it complements those tools with an ecosystem approach. The Atlantis framework consists of spatially explicit, 3-D "boxes" and, for each box, incorporates information on the biological, geochemical, and physical processes of an identified system. Furthermore, Atlantis integrates these dynamics, includes the effects of different user groups, and dynamically tracks the interaction of these factors over time. It also simulates the important processes of assessment, management, and compliance.

Framework of the Atlantis model, including four submodels that can vary in details depending on the focus of a project. The 
        fisheries submodel also can include other industries.
Framework of the Atlantis model, including four submodels that can vary in details depending on the focus of a project. The fisheries submodel also can include other industries.

Applications of the Atlantis model

Atlantis has been applied both domestically and abroad. Ecosystems that have been modeled vary considerably as have the insights gained from them by resource managers. Recent efforts by NOAA include applications on both the West and East Coasts of the United States.

Atlantis in the United States

On the West Coast, Atlantis has been applied to model the California Current ecosystem (Brand et al., 2007). This work has proven useful for testing ecological indicators, setting federal (both sanctuary and fishery council) management policies for marine protected areas in an ecosystem context, and evaluating effects of individual transferable quotas.

On the East Coast, the tool has been applied to evaluate economic pressures, effort allocation, and gear choice to enhance sustainable fisheries in a context of climate change (Link et al., 2010). The use of Atlantis has provided insights into the consequences and tradeoffs for different monitoring, assessment, and management scenarios. Presently, an Atlantis model is being developed for the Chesapeake Bay to support strategies of ecosystem-based fisheries management.

Atlantis in Australia

The use of the Atlantis model framework is widespread in Australia. In southeastern Australia, where the ecosystem of Port Phillip Bay was examined, model simulations have led to several important general conclusions for that system and potentially for other large estuarine bays as well. Fulton and Smith (2004) concluded that eutrophication can be more important to the health of a bay ecosystem than can fishing, a few key species can capture the major effects of alternative management strategies on an ecosystem, ecosystem models can identify potential impacts that single-species models are unable to recognize, and policies that focus on only the higher trophic levels can fail to achieve management of fisheries on an ecosystem level.

Exploration of Guam's coral reef ecosystems with Atlantis

In 2012, NOAA Pacific Islands Fisheries Science Center Coral Reef Ecosystem Division (CRED) in cooperation with CSIRO, started with the adaptation of the Atlantis framework for (shallow) coral reef ecosystems by incorporating code representing key ecosystem processes. During a workshop (0.6 MB PDF) conducted on Guam in November 2012, participants identified the main stressors to Guam's reefs, various management strategies as well as economic and ecological indicators to include in the Atlantis model for Guam. Based on these stressors and literature reviews of key coral reef ecosystem processes to maintain desired ecosystem functions and services, we included the relevant algorithms and parameters. Additionally, data sets were identified and made available for inclusion in the model.

Spatial model outline of the Guam Atlantis Coral Reef Ecosystem Model (0-54; box 55 is the island Guam), indicated with red lines. 
        Each box can have up to three water layers (0-6; 6-30; >30 m). Blue areas indicate existing marine protected areas (MPAs), light 
        yellow lines represent fishing reporting zones which together with the benthic and oceanographic conditions were taken into account 
        when demarcating the spatial model based on somewhat homogenous conditions per polygon (Atlantis box).
Spatial model outline of the Guam Atlantis Coral Reef Ecosystem Model (0-54; box 55 is the island Guam), indicated with red lines. Each box can have up to three water layers (0-6; 6-30; >30 m). Blue areas indicate existing marine protected areas (MPAs), light yellow lines represent fishing reporting zones which together with the benthic and oceanographic conditions were taken into account when demarcating the spatial model based on somewhat homogenous conditions per polygon (Atlantis box).

A variety of important benefits can come from the development of an Atlantis model for the shallow (0-30 m) coral reef ecosystem around Guam. Such a modeling approach could allow for exploration of the ecosystem effects of environmental changes, policy options, and management strategies. Arguably, the most important benefit of the Atlantis approach is that it lends itself to the evaluation of the simulated outcomes of a wide variety of scenarios of interest to management.

Once the Guam Atlantis model is fully developed, various topical questions can be explored. We can ask, what will be the likely ecosystem effects, for example, of increased or decreased coral cover? Of a larger or smaller population of parrotfishes, sharks, sea stars, or turtles? Of increasing or decreasing nutrient input? Of the increasing size of the human population along the coasts of Guam? Additionally, we can ask questions related to the local economy. Furthermore, because Atlantis has a spatially explicit modeling approach, these types of questions can be explored not just by island but by area (i.e., by identified 3-D boxes).

A conceptual coral reef ecosystem depicting various drivers (coastal development and tourism, fishing, climate) and pressures 
        (land-based sources of pollution, ocean warming and acidification, excessive fishing) which could result in an increase in plankton, 
        crown-of-thorns seastar outbreaks, (over)growth of macroalgae, disruption of trophic balance, decrease of reef complexity, and a 
        shift in benthic and fish community structure. When pressures persist, the reef community may shift to a more degraded ecosystem 
        state with reduced ecosystem functions and services. Figure by Amanda Toperoff and Amanda Dillon PIFSC/JIMAR.
A conceptual coral reef ecosystem depicting various drivers (coastal development and tourism, fishing, climate) and pressures (land-based sources of pollution, ocean warming and acidification, excessive fishing) which could result in an increase in plankton, crown-of-thorns seastar outbreaks, (over)growth of macroalgae, disruption of trophic balance, decrease of reef complexity, and a shift in benthic and fish community structure. When pressures persist, the reef community may shift to a more degraded ecosystem state with reduced ecosystem functions and services. Figure by Amanda Toperoff and Amanda Dillon PIFSC/JIMAR.

As with any model, the usefulness of model forecasts depends on the availability of pertinent data. Therefore, another important use of the development of a Guam Atlantis model is to identify and prioritize the most critical needs for research to support the management of Guam's coral reefs. The majority of the ecological data came from CRED and was augmented with data and expert judgment from the University of Guam Marine Lab, the Coastal Zone Management Program, the Pacific Islands Regional Office in Guam, the War-in-the-Pacific National Historical Park, Guam Environmental Protection Agency, and other organizations.

References

Brand EJ, Kaplan IC, Harvey CJ, Levin PS, Fulton EA, Hermann AJ, Field JC.
2007. A spatially explicit ecosystem model of the California Current's food web and oceanography. NOAA Tech. Memo. NMFS-NWFSC-84, 145 p.
Fulton EA, Parslow JS, Smith ADM, Johnson CR.
2004a. Biogeochemical marine ecosystem models II: the effect of physiological detail on model performance. Ecological Modelling 173:371-406.
Fulton EA, Smith ADM.
2004. Lessons learnt from a comparison of three ecosystem models for Port Phillip Bay, Australia. African Journal of Marine Science 26:219-24.
Fulton EA, Smith ADM, Johnson CR.
2004b. Biogeochemical marine ecosystem models I: IGBEM—a model of marine bay ecosystems. Ecological Modelling 174:267-307.
Link JS, Fulton EA, Gamble RJ.
2010. The northeast US application of Atlantis: a full system model exploring marine ecosystem dynamics in a living marine resource management context. Progress in Oceanography 87:214-234