LIFECO: Coupled Bio-Physical Modelling: Simulation of lower trophic level dynamics

This work package is part of the LIFECO programme: LInking
Hydrographic Frontal activity to ECOsystem dynamics in the
North Sea and Skagerrak: Importance to fish stock recruitment.

The key to resolving the influence of frontal processes on
the distribution and production of planktonic organisms, the
so-called bottom up processes influencing ecosystem dynamics,
is quantifying the effects of frontal manifestations on intra
and interannual variations in: population growth and production
rates due to fluxes of nutrients limiting primary production
and; rates of aggregation of organisms due to the
interaction between behavioural patterns (e.g. diel migration)
and frontal circulation patterns.
Once these two mechanisms have approximated
realistically the effects of variations of frontal
activity (due to climatic forcing) on the bottom
up processes can be quantified. In order to accomplish
these goals, this work package will couple NORWegian
ECOlogical Model (NORWECOM; a nutrient based 3-D primary
production model previously developed by partner 7 inside
the HAMSOM(WP1) for the estimation of increases in primary
and secondary production due to frontal mixing processes
extend the nested HAMSOM from WP1: Advancement of Hydrodynamic
models, a particle-tracking model for passive tracers to
include the active migration of planktonic organisms observed
during the field component of the program performed in WP 4:
Distribution and Abundance of plankton and fish relative
frontal processes.

Nutrient based primary production models using intermediate
grid scales have been developed for the North Sea ecosystem as
well as for other systems. These models have been used to
estimate rates of primary and secondary production as well as
to examine the effect of variations in climatic forcing on
primary production. However, again the resolution in these
earlier exercises is insufficient for the investigation of
processes in and around fronts. Therefore, the 1-km nested
model developed in WP1 will provide the platform for running
a particle-tracking model on the same grid scale.

The coupling of these two approaches will provide simulated
horizontal and vertical distributions of planktonic biomass
due to nutrient fluxes/enhanced production and aggregation of
organisms in and around the frontal regimes for comparison
with field observations (WP4 & 5) in 2001. Furthermore, this
approach will allow the simulation of intra and inter-annual
variations in the spatial and temporal distributions of primary
and secondary production for the years 2000 to 2002 as well as
years exhibiting anomalous recruitment success in key fish
stocks or climatic conditions. Hence generating hypotheses
and data bases to be utilised in work package 9: Synthesis,
scenario and hypothesis testing.