Clonality in seagrasses, emergent properties and seagrass landscapes

Seagrasses are clonal monocots that dominate shallow subtidal coastal and estuarine environments worldwide. They are important for their relatively high productivity and their role in coastal sediment stabilization, as habitat and food for invertebrates, fishes, turtles, dugongs and manatees, and as a source for detrital food webs. Seagrasses grow through the iteration of a vegetative ramet, consisting of leaves capable of photosynthesizing attached to a shoot, a portion of rhizome and associated roots. Seagrass research has in the past focused on either the study of growth of the ramet or changes of seagrass distributions over 1000s of ha to 1000s of km2. There has been little attempt to link these scales. Interestingly, growth and space occupation of both measured and modelled patches of seagrasses have been found to be faster than predicted from the growth and iteration, through branching, of ramets. Similarly, predicted radial spread of patches does not agree with observed changes in the distribution of seagrasses in shallow subtidal landscapes. This review assesses the links between growth of ramets and patches of seagrasses and the spread, infilling and distribution of seagrasses in shallow subtidal landscapes. We explore the potential that accelerated growth of patches and seagrass landscapes are an emergent property of ramet growth.