| Scientific models are numerical substitutes of real world systems, such as an ecosystem, climate or even a brain. They allows scientists to experiment with the different inputs feeding into the system and, by changing a variable like temperature, they can see how the end “product” will be affected. For example, a change in sea surface temperature in a particular region will have a positive or negative impact upon plankton abundance or fish stocks.
An integrated approach is needed in order to meet the goals of policies such as the European Maritime Policy and its ecological pillar the Marine Strategy Framework Directive (MSFD) as well as the Common Fisheries Policy. These policies intended to protect marine resources and support their sustainable exploitation. So an integrative approach that considers multiple drivers and biological interactions in ecosystems is essential.
MEECE has developed end-to-end models which try to represent the entire ecosystem by including all relevant processes in the system, from physics to chemistry, and plankton to fish. To achieve this three types of models have been coupled: hydrodynamic models, lower trophic level (bacteria, phytoplankton and zooplankton) and higher trophic level (mainly fish species) into a single modelling framework.
The models developed and applied in MEECE provide tools for addressing the complex impact of drivers and ecosystem responses. Such numerical models which can simulate and predict changes in the state of marine ecosystem in response to different drivers and management scenarios, and can support the decision-making process.
| This diagram shows the ability of the current models to provide
policy-relevant information, providing an idea of the general
skill of the models for each driver in relation to the knowledge
base to usefully exploit the model information.
What can ecosystem models tell us about different drivers; their scope and limitations
As we move up the foodweb, the implications of change become less clear.
Acidification: Refers to increasing CO2 dissolved in seawater leading to the lowering of pH in the marine environment and impacts at all spatial scales. On one hand increasing CO2 may lead to enhanced phytoplankton growth. On the other hand lowering of pH may have negative impacts on the health and reproduction of a wider range of marine organisms for example plankton, calcareous organisms and fish larvae. At the moment experimental evidence on impacts is often contradictory making it hard to predict what the future may bring.
Currently models are able to provide useful information on the inorganic carbon cycle (e.g. pH, PCo2) at regional scales, this is hampered in coastal regions by the lack of knowledge of alkalinity sources.
At the moment knowledge of the ecological implications of any change is limited, but improving.
Habitats: Models can provide useful information to define pelagic (open-ocean) habitats (e.g. temperature, salinity, nutrients, stratification) at regional scales.
The consequence of changes in these habitats on achieving Good Environmental Status remains an open question.
Eutrophication: This results from the human induced nutrient enrichment of the marine environment leading to a variety of outcomes including greater algal blooms, harmful algal blooms, de-oxygenation and death of seabed creatures. Coupled hydrodynamic ecosystem models can provide useful information of nutrient loads, and chlorophyll concentrations and in some cases summer oxygen levels, but they require the land derived sources to be well known.
The consequences of change are well understood.
Commercial Fishing: Fishing is one of the drivers with most the widespread and substantial impacts on marine ecosystems, particularly on the higher trophic levels. Direct economic interests and needs have motivated the development of management models and related research for decades. There are a wide range of models of commercial fisheries of varying skills which provide information on both fish stocks as well as the wider fish community and their response to changes in fishing pressure at regional scales.
In terms of fisheries impact the end-to-end models are required. Such end-to-end models combine hydrodynamics, nutrient-phytoplankton-zooplankton (NPZ), and higher trophic level (HTL) organisms, into a single modelling framework.
Such models are currently in the proof of principle phase to show that such models can be developed and implemented.
Foodwebs: A key challenge is understanding the potential sensitivities of ecosystems to combinations of top down and bottom up control. For example how the effects of fishing and climate impact through a food web will depend to a large extent on which trophic level the climate and fishing forcing is specifically acting. End-to-end models combine hydrodynamics, nutrient-phytoplankton-zooplankton (NPZ), and higher trophic level (HTL) organisms, into a single modelling framework which can be used to explore these responses.
Such models have been developed in MEECE and used to show that forage fish are perhaps most vulnerable to both driver’s.
Pollution: This covers a wide range of compounds (>100,000) many of which are poorly characterised, particularly in terms of their ecological impacts. New compounds are constantly being developed so there are always unknowns. Similarly, the ecological implications of mixtures of compounds remain a topic of on-going research. The work in MEECE regarding pollution has focused on improving the knowledge base and modelling capabilities, these models are currently in the proof of principle phase.
If the source of a contaminant is well defined then models have the ability to trace its distribution at local and regional scales.
Invasive Species: Non-indigenous species (NIS) introduced by humans, both intentionally and un-intentionally, can have both significant ecological and economic impacts. Currently there are no modelling tools which can usefully predict invasion and colonisation by invasive species. This is partly due to lack of knowledge of the ecology of invasive species and is made worse by the fact that new species appear every so often so there are always unknowns.
Bioclimatic envelope modelling can provide useful information on changes in the distribution of species whose habitat is well characterised.