1. Estimation from periodic changes in the length of rhizome intervals:
For seagrasses with a seasonal pattern of changing rhizome internode lengths, find runners
(or fragments) of rhizome extending into unvegetated patches in the seagrass meadow
investigated and excavate them from the apex to the oldest point possible. Use known data,
if available, on internodal lengths and plastochrone intervals of the species to estimate the
minimum length of rhizome needed to contain a full year's growth. Collect at least 5 replicate
runners. At the laboratory, wash the rhizomes free of detritus and sediment and remove any
remnants of leaf sheaths. Then measure, to the nearest mm, the length of the rhizome
fragments from the apex to the oldest portion retrieved. For di-meristematic species only,
select the 10 oldest shoots present in the samples collected with the core sampler and
measure, wash them free of detritus and sediment, and remove any remnants of leaf sheaths.
Then measure, under a dissecting microscope, preferably coupled to a digitizing tablet