United they stand: self-organisation makes mussel beds robust
Natural ecosystems often develop distinct spatial patterns. Research from the University of Amsterdam, the Royal Netherlands Institute for Sea Research (NIOZ), the Netherlands Institute of Ecology and the Universities of Groningen and Wageningen has revealed that self-organisation in mussel beds leads not only to beautiful spatial patterns, but also enhances the resilience of these mussel beds and makes them less vulnerable to external disturbances. The team published its findings on 22 October in the leading journal Nature Communications.
Resilient against disturbance
Mussel beds are intriguing ecosystems. If you would study mussel beds from the air, you would see that they show a characteristic banded pattern. Mussel beds on sandy substrates and mudflats form long parallel bands of high mussel density, each with a width of about 2-3 meters. Within these bands, mussels develop a smaller-scale network structure, in which the mussels form long strings of 2-3 mussels thick. ‘These spatial patterns are essential for the resilience of mussel beds against disturbances’, explains Quan-Xing Liu of the University of Amsterdam and the NIOZ. Using mathematical models, he investigated how self-organisation of mussels affects the spatial patterning and functioning of the mussel beds.
Scale and size matter
The models show that pattern formation at multiple spatial scales is essential for the resilience of mussel beds. Without these spatial patterns mussel beds are extremely sensitive for disturbances like storms. Furthermore, spatial patterning facilitates the establishment of mussel beds. Models predict that mussel beds with large-scale banded patterns are stronger: the aggregated mussels help each other with the stabilization of sediment. The small-scale network patterns add to this, as the network structure protects the mussels against erosion while competition for space and food between the mussel individuals remains limited.
Preserving costal ecosystems
'The results of this fundamental research may find application in the preservation of coastal ecosystems such as tidal flats,' says co-author Prof. Jef Huisman. A major threat for many ecosystems, including mussel beds, is the possibility of a sudden collapse when human influence exceeds a critical threshold. 'Our research suggests that the probability of such a collapse is reduced when self-organization and spatial patterning strengthen the function of ecosystems. Stimulation of natural pattern formation makes these ecosystems more robust against external disturbances.'
This research was supported by the Netherlands Organization for Scientific Research (NWO) through the National Program for Sea and Coastal Research (projects WaddenEngine and Optimon).
Quan-Xing Liu, Peter M.J. Herman, Wolf Mooij, Jef Huisman, Marten Scheffer, Han Olff and Johan van de Koppel. 2014. Pattern formation at multiple spatial scales drives the resilience of mussel bed ecosystems, Nature Communications, 2014 (5) 5234, doi: 10.1038/ncomms6234.