A novel model approach to bridge the gap between box models and classic 3D models in estuarine systems

The multiple hydrodynamic and ecological processes characterizing estuarine systems make ecological modelling an essential tool for ecosystem-based management by increasing the understanding of the complex interactions and by quantifying the effects of various natural and anthropogenic pressures. The modelling technique used is dominated by computational simple box model approaches with a low spatial resolution and coupled 3D hydrodynamic-ecological models with high computational requirements. In this paper we present a novel concept (Flexsem) which combines the computational simplicity and condensed hydrodynamics from box models with a high spatial resolution characterizing coupled 3D models. The modelling framework Flexsem is a fast, flexible and user-friendly tool specifically targeted towards scientific and management challenges of the complex biogeochemical processes in coastal zone ecosystems. We use Flexsem to simulate the physical conditions in a typical Danish estuary, Horsens Fjord utilizing unstructured computational meshes to vary the complexity of grid geometry and resolution. The results showed that the model was able to reproduce the physical conditions in the estuary and provide reliable estimates for the tracer residence time.

[1]  T. Neumann,et al.  Introduction to the Modelling of Marine Ecosystems , 2014 .

[2]  L. M. Svendsen,et al.  Coastal eutrophication and the Danish national aquatic monitoring and assessment program , 2002 .

[3]  R. Díaz.  Overview of hypoxia around the world. , 2001, Journal of environmental quality.

[4]  J. Bendtsen,et al.  Elucidating the dynamics and mixing agents of a shallow fjord through age tracer modelling , 2007 .

[5]  R. Garvine,et al.  An estuarine box model of freshwater delivery to the coastal ocean for use in climate models , 2006 .

[6]  Morten Søndergaard,et al.  Dissolved organic matter (DOM) export to a temperate estuary: seasonal variations and implications of land use , 2006 .

[7]  Michel Carreau,et al.  A physical-biogeochemical coupling scheme for modeling marine coastal ecosystems , 2012, Ecol. Informatics.

[8]  Jamie Pittock,et al.  National Climate Change Policies and Sustainable Water Management: Conflicts and Synergies , 2011 .

[9]  J. Carstensen,et al.  Hypoxia Is Increasing in the Coastal Zone of the Baltic Sea , 2011, Environmental science & technology.

[10]  A. Josefson,et al.  Nutrient retention by benthic macrofaunal biomass of Danish estuaries: importance of nutrient load and residence time , 2000 .

[11]  J. Støttrup,et al.  A Systems Approach Framework for Coastal Zones , 2011 .

[12]  W. Kemp,et al.  Variability of biogeochemical processes and physical transport in a partially stratified estuary: a box-modeling analysis , 2008 .

[13]  J. Støttrup,et al.  Research, part of a Special Feature on A Systems Approach for Sustainable Development in Coastal Zones Mussel Production and Water Framework Directive Targets in the Limfjord, Denmark: an Integrated Assessment for Use in System-Based Management , 2011 .

[14]  W. Boynton,et al.  The fate of nitrogen and phosphorus at the land-sea margin of the North Atlantic Ocean , 1996 .

[15]  G. Grell,et al.  A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5) , 1994 .

[16]  Matthew A. Peeples,et al.  Sustainable Small-Scale Agriculture in Semi-Arid Environments , 2011 .

[17]  Elizabeth A. Fulton,et al.  Effects of spatial resolution on the performance and interpretation of marine ecosystem models , 2004 .

[18]  J. Austin.  Estimating the Mean Ocean-Bay Exchange Rate of the Chesapeake Bay , 2002 .

[19]  C. Hearn,et al.  On the effects of wind and tides on the hydrodynamics of a shallow mediterranean estuary , 2002 .

[20]  Edward H. Dettmann,et al.  Effect of water residence time on annual export and denitrification of nitrogen in estuaries: A model analysis , 2001 .

[22]  C. Stedmon,et al.  Seasonal dynamics and conservative mixing of dissolved organic matter in the temperate eutrophic estuary Horsens Fjord , 2011 .

[23]  John R. Kelly,et al.  Nitrogen flow and the interaction of Boston harbor with Massachusetts Bay , 1997 .

[24]  M. Alber,et al.  A comparison of residence time calculations using simple compartment models of the Altamaha River estuary, Georgia , 2002 .

[25]  D. Conley,et al.  Characteristics of Danish estuaries , 2000 .

[26]  J. Therriault,et al.  Box model analysis of bacterial fluxes in the St. Lawrence Estuary , 1987 .

[27]  R. Filgueira,et al.  A Box Model for Ecosystem-Level Management of Mussel Culture Carrying Capacity in a Coastal Bay , 2009, Ecosystems.

[28]  K. Timmermann,et al.  Streams or open sea? Tracing sources and effects of nutrient loadings in a shallow estuary with a 3D hydrodynamic–ecological model , 2010 .

[29]  B. Müller-Karulis,et al.  Hypoxia in future climates: A model ensemble study for the Baltic Sea , 2011 .

[30]  Y. Monbet,et al.  Control of phytoplankton biomass in estuaries: A comparative analysis of microtidal and macrotidal estuaries , 1992 .