Abstract
Nutritional constraints were examined on establishment from seed and vegetative development of patches of the seagrass
Cymodocea nodosa Ucria (Aschers.) growing in phosphorus-deficient sandy sediments in the shallow Alfacs Bay of the Spanish Mediterranean coast. Seedlings were extremely P-deficient, this P-deficiency increasing with seedling age, which may be a major reason for the failure of most seedlings (90%) to initiate patches, and the arrest of their vegetative proliferation for up to 3 years. Shoots located at the colonising apices of horizontal rhizomes had, in contrast, three-fold higher P and two-fold higher N concentrations, which could facilitate the rapid horizontal expansion of existing patches. Apical shoots may receive nutrients from older shoots connected along the rhizome chains, as suggested by exponentially increasing gradients of N and P concentrations towards the rhizome apex. These results indicate that resource limitation probably plays a more important role in constraining the initiation of patches from seedlings in nutrient-poor areas than the expansion of existing patches.