Effects of Wind Waves versus Ship Waves on Tidal Marsh Plants: A Flume Study on Different Life Stages of Scirpus maritimus

Abstract : Recent research indicates that many ecosystems, including intertidal marshes, follow the alternative stable states theory. This theory implies that thresholds of environmental factors can mark a limit between two opposing stable ecosystem states, e.g. vegetated marshes and bare mudflats. While elevation relative to mean sea level is considered as the overall threshold condition for colonization of mudflats by vegetation, little is known about the indi- vidual driving mechanisms, in particular the impact of waves, and more specifically of wave period. We studied the impact of different wave regimes on plants in a full scale flume exper- iment. Seedlings and adult shoots of the pioneer Scirpus maritimus were subjected to two wave periods at two water levels. Drag forces acting on, and sediment scouring occurring around the plants were quantified, as these are the two main mechanisms determining plant establishment and survival. Depending on life stage, two distinct survival strategies emerge: seedlings present a stress avoidance strategy by being extremely flexible, thus lim- iting the drag forces and thereby the risk of breaking. Adult shoots present a stress toler- ance strategy by having stiffer stems, which gives them a higher resistance to breaking. These strategies work well under natural, short period wind wave conditions. For long peri- od waves, however, caused e.g. by ships, these survival strategies have a high chance to fail as the flexibility of seedlings and stiffness of adults lead to plant tissue failure and ex- treme drag forces respectively. This results in both cases in strongly bent plant stems, po- tentially limiting their survival.
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PLoS ONE, Public Library of Science, 2015, 10 (3 : e0118687), pp.1-16. 〈10.1371/journal.pone.0118687〉
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Soumis le : mercredi 25 mars 2015 - 11:07:50
Dernière modification le : mardi 16 janvier 2018 - 16:12:14

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Alexandra Silinski, Maike Heuner, Jonas Schoelynck, Sara Puijalon, Uwe Schröder, et al.. Effects of Wind Waves versus Ship Waves on Tidal Marsh Plants: A Flume Study on Different Life Stages of Scirpus maritimus. PLoS ONE, Public Library of Science, 2015, 10 (3 : e0118687), pp.1-16. 〈10.1371/journal.pone.0118687〉. 〈hal-01135329〉

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