Date Published: July 20, 2018
Publisher: Public Library of Science
Author(s): Sieme Bossier, Artur P. Palacz, J. Rasmus Nielsen, Asbjørn Christensen, Ayoe Hoff, Marie Maar, Henrik Gislason, François Bastardie, Rebecca Gorton, Elizabeth A. Fulton, Geir Ottersen.
Achieving good environmental status in the Baltic Sea region requires decision support tools which are based on scientific knowledge across multiple disciplines. Such tools should integrate the complexity of the ecosystem and enable exploration of different natural and anthropogenic pressures such as climate change, eutrophication and fishing pressures in order to compare alternative management strategies. We present a new framework, with a Baltic implementation of the spatially-explicit end-to-end Atlantis ecosystem model linked to two external models, to explore the different pressures on the marine ecosystem. The HBM-ERGOM initializes the Atlantis model with high-resolution physical-chemical-biological and hydrodynamic information while the FISHRENT model analyses the fisheries economics of the output of commercial fish biomass for the Atlantis terminal projection year. The Baltic Atlantis model composes 29 sub-areas, 9 vertical layers and 30 biological functional groups. The balanced calibration provides realistic levels of biomass for, among others, known stock sizes of top predators and of key fish species. Furthermore, it gives realistic levels of phytoplankton biomass and shows reasonable diet compositions and geographical distribution patterns for the functional groups. By simulating several scenarios of nutrient load reductions on the ecosystem and testing sensitivity to different fishing pressures, we show that the model is sensitive to those changes and capable of evaluating the impacts on different trophic levels, fish stocks, and fisheries associated with changed benthic oxygen conditions. We conclude that the Baltic Atlantis forms an initial basis for strategic management evaluation suited for conducting medium to long term ecosystem assessments which are of importance for a number of pan-Baltic stakeholders in relation to anthropogenic pressures such as eutrophication, climate change and fishing pressure, as well as changed biological interactions between functional groups.
A Baltic Atlantis model was implemented to integrate and better comprehend the complexity of the marine ecosystem when exploring effects of changes in different pressures on the marine ecosystem. Here we evaluated eutrophication and fishery pressures on the whole ecosystem on a spatial explicit scale. This established model framework will help us to evaluate the performance of alternative management strategies on mitigating human and natural pressures in the long term. We discuss the current model calibration and the realism of the baseline given the model uncertainty, as well as the application to nutrient load reduction scenarios and sensitivity analyses to fishing pressure levels to test the ability of the model to capture the dynamics in the ecosystem according to the changes. As the model is only for strategic use and due to the many assumptions, limitations and overall uncertainty, we only focus on the direction of changes in the relative evaluations rather than short term absolute predictions.
In this paper we have introduced a new calibrated Baltic Atlantis model and an integrated end-to-end modelling framework to examine ecosystem-wide responses under scenarios of human-induced changes in the Kattegat, Western Baltic Sea and southern Baltic proper regions with a focus on eutrophication, nutrient load reductions, and sensitivity to fishing pressure and climate factors. The Baltic Sea Atlantis model presented here for the first time forms the core of the established integrated framework. We have described the current setup of the framework with focus on the sensitivity of the Atlantis model to nutrient load reduction scenarios and fishing pressure changes; this demonstrates how the framework can be used to evaluate ecosystem and economic impacts: HBM-ERGOM, Baltic Atlantis and FISHRENT (noting that the FISHRENT KWB component of the framework only covers the Kattegat and the Western Baltic). Using four hypothetical eutrophication scenarios we demonstrated the capability of Atlantis and the framework to evaluate resulting changes in biological production and their long term biological consequences and economic impacts on the fishing catch sector, also taking into consideration fishing pressure as another anthropogenic impact. In light of the current assumptions and model limitations, we also have discussed the current and envisaged future improvements to the Atlantis model and the framework. The models have the potential to help evaluate conflicting objectives and alternative management strategies for better strategic management of human and natural pressures in relation to impacts on marine resources and in relation to an ecosystem based approach to management taking into consideration a sufficient complexity of processes and biological interactions in the ecosystem and the technical interactions in the fishery. They can also help with identifying knowledge gaps and recommendations for addressing them, e.g. regular benthos monitoring, and integrated data management for Baltic States.