Mussel bed pattern formation
Mussel beds are a prominent feature of intertidal ecosystems. They often occur on the seaward edge of tidal flat. Here, the filter feeding mussels can make optimal use of the algae in the seawater when in enters the tidal flat area during the flood tides.
When a mussel bed is viewed from the air, they reveal a remarkable spatial organisation. Mussel beds are strongly banded, with elongated mussel patches of 2-3 meters across alternating the open, bare areas of 3-4 meters. To explain pattern formation in mussels, one needs to take into account the two most basic processes that determine mussel live: they need to eat, and they need to be safe.
The life of a mussel
Mussels make a living by consuming the microalgae – diatoms for the most – from the lower water layers of the water column. In dense beds, this can lead to fierce competition among the mussels for the algal food. Luckily for the mussels, the water flow, bringing fresh food for a long as the incoming tides flow.
There are two imminent dangers threatening the life of a mussel. The first is being eaten by birds or sea stars, the second is being washed away from their favourite habitat. They protect themselves against the danger by attaching themselves to other mussels using byssal threads, forming extensive mats of mussels. This means that mussels are more safe as there are more fellow mussels around.
A simple model suffices to show that the interaction of algal competition and density- dependent mortality can explain the formation patterns in mussels. This model describes the interaction of the concentration of algae in the lower water layer, and the biomass of mussels on the tidal flat.
How to use
To use and run this model, click on the image above. A new secure webpage opens which runs the model, and allows you to set the parameters. If you don’t see anything appearing (for instance on an phone or tablet), then the computer is too light to run the applets.