BEYOND THE HIGH WATER MARK: APPLICATION OF AN ECOSYSTEM MODEL FRAMEWORK FOR INTEGRATED CATCHMENT MANAGEMENT IN LOUGH FOYLE.  

The SMILE project (2004-2006) was one of the first applications of integrated ecological modeling to shellfish carrying capacity assessment, by combining models of water circulation, bivalve individual growth, and biogeochemistry. Building on work by e.g. Raillard and Menesguen (1994), Ferreira et al (1999), and Nunes et al. (2003), the SMILE models included coupling among Irish and Northern Irish sea loughs, a focus on the harvestable fraction of shellfish production, and multi-annual cultivation cycles.

However, a decade ago, the state-of-the-art fell short of integrating catchment processes, and in particular the drivers of particulate organic, and dissolved nutrient discharge to the estuarine and coastal systems where bivalve aquaculture takes place. Integrated catchment management, and the implementation of legislative instruments such as the European Union's Water Framework Directive (2000/60/EC) have created a need for the framework used then to be extended, in order to provide a better understanding of the relationships between pressure and state.

As a consequence of the requirement to identify and quantify management measures, it has become critical for models to include source apportionment for different types of point and diffuse emissions. This (quasi) obligation relates not only to the effects of nutrient control on shellfish production, but on the analysis of the role of multiple uses (and sources), which may include finfish cage culture.

The EASE (Enhanced Application of the SMILE Ecosystem model to Lough Foyle) project, developed over the last two years, provides an example of the use of such an integrated multi-model framework, designed to address the types of questions relevant to present-day water managers.

We exemplify how this approach may be used to analyse changes to the use of the basin, and how those changes affect primary and secondary production within Lough Foyle, an area of great relevance for shellfish production in Ireland. In addition, the linkage of estuarine dynamics with mesoscale shelf processes, taking into account e.g. the development of frontal systems, helps managers understand the extent to which particular activities may be managed.

The EASE models combine and extend key features of the SMILE models, including individual bivalve physiology simulations, and an improved description of population dynamics. There is a much greater focus nowadays on ecosystem services, and these are included in the EASE framework, with an emphasis on top-down eutrophication control by bivalves, and the potential role of shellfish aquaculture in watershed-scale nutrient credit trading (e.g. Rose et al., 2015; Ferreira & Bricker, 2015).  Farm-scale modeling is an additional component of this management suite, more directed at the industry itself, but also of use to managers for licensing purposes.

Finally, we highlight the value of applying a set of different models, each of which is designed to address particular questions-by providing standalone solutions e.g. for catchment or for shelf exchanges, managers are empowered to use segments of the EASE framework to address specific issues, while relying on the combination of different components which is scalable to provide integration as required.

References

Ferreira, J.G., Duarte, P., Ball, B., 1998. Trophic capacity of Carlingford Lough for oyster culture-analysis by ecological modelling. Aquat. Ecol. 31, 361-378.

Ferreira, J.G., S.B. Bricker 2015. Goods and services of extensive aquaculture: shellfish culture and nutrient trading. Aquaculture International. DOI 10.1007/s10499-015-9949-9

Nunes, J.P., Ferreira, J.G., Gazeau, F., Lencart-Silva, J., Zhang, X.L., Zhu, M.Y., Fang, J.G., 2003. A model for sustainable management of shellfish polyculture in coastal bays. Aquaculture 219, 257-277.

Raillard, O. & Ménesguen, A., 1994. An ecosystem box model for estimating the carrying capacity of a macrotidal shellfish system. Mar. Ecol. Prog. Ser. 115: 117-130.

Rose, J.M., S.B. Bricker, J.G. Ferreira, 2015. Comparative analysis of modeled nitrogen removal by shellfish farms. Mar. Pollut. Bull. 91 (1), 185-190.