Life Strategies of Aquatic Soft Bottom Macrophytes

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Abstract
The R-C-S theory, which assumes three basic strategies for terrestrial plants was tested on aquatic macrophytes. Capacity for primary production and an index based on plant height and lateral spread were compiled for 20 species colonizing brackish soft bottom areas of different wave exposure, in the Baltic Sea. Typical curves for annual biomass variation, primary productivity and life-cycles for different strategies are described. Instead of the triangular R-C-S model, a new square model with four basic strategies is proposed. Besides "ruderal" (R) and "competitors" (C), two, instead of one type of stress-tolerant strategies are included, i.e., "stunted" (S) and "biomass storer" (B). Increased seed size, tendency to vegetative spread and resistance to herbivores were identified as characteristic differences in strategies between terrestrial and aquatic phanerogams. It is suggested that the high amount of monocotyledons in aquatic phanerograms, with a high degree of polyploidization are possible reasons for these differences.