Dynamics of a landscape mosaic: Size and age distributions, growth and demography of seagrass Cymodocea nodosa patches

Abstract

The patch dynamics (recruitment, growth and mortality) of seagrass Cymodocea nodosa were examined at the landscape scale (i.e. the scale at which disturbances occur) by means of 3-dimensional (X, Y dimensions and depth) mapping of shoot internal density and age structure within the basic units (patches) forming the landscape. Highly skewed patch size and age distributions indicated a high exponential patch mortality rate (m = 0.82 ± 0.07 yr-1) and a slightly higher exponential patch recruitment rate (1.04 yr-1) that ensures the maintenance and fast turnover of this population of patches. Patch growth (i.e. increase in number of shoots per patch) proceeded at an exponential growth rate of 2.28 ± 0.14 yr-1, indicating a doubling time of 111 d for the shoot population within each patch. Moreover, average patch growth rate accelerates with increasing patch size and age. This self-acceleration of patch growth means that this seagrass species has a remarkable potential for rapid space occupation due to its intense clonal growth. The results obtained emphasize the power of a landscape approach for describing the intense dynamics of colonising seagrass populations.