Regime shifts in shallow coastal ecosystems: Competition between Floating and Submerged plants

Invasion, competition, and nonlinear feedback, among others, are
phenomena leading to alternating states in complex ecological systems.
Changes of regime have profound consequences on the global ecosystem
structure and its function, and poses dificult problems for remediation
strategies [1,2].
In a class of the above phenomena occurring in lakes and in coastal
shallow areas, free floating plants, which are optimal competitors for
light, interact with rooted submerged macrophytes, which are effcient in
recovering and storing nutrients from the sediments and from the water
column. We introduce a model describing nutrient consumption and
shadowing effects, with parameters adequate to competition among the
rooted seagrass Zostera marina and the macroalga Ulva rigida in coastal
areas such as the Thau lagoon (France) or Sacca di Goro (Italy).
Successions of dominance states, with different resilience
characteristics, are found when changing the input of nutrients and
environmental variables.

1. S. Scheffer, S. Carpenter, J.A. Foley, C. Folkes and B. Walker:
Nature 313, 591 (2001)

2. S. Scheffer, S. Szabo, A. Gragnani, et al.: PNAS 100, 4040 (2003)