San Nicolas Island Macrocystis holdfast diameters and stipe counts 1980-2019

These data represent holdfast diameters of giant kelp (Macrocystis pyrifera) that were greater than one meter tall and were on fixed 10-meter by 2-meter benthic transects on permanent subtidal monitoring sites around San Nicolas Island between 1980 and 2019. The number of stipes counted on the plants is also listed if recorded. Holdfast diameters give an indication of the M. pyrifera age structure because the holdfast continues to grow throughout the life of the alga. Stipe counts are more variable with age but give an indication of algal biomass. Stipe counts were made on some transects beginning in 1997 and on all plants beginning in 2014. Between 1980 and 2006, 3694 of the plants were tagged and followed over time. Tagged plants have been assigned unique identifier numbers so they can be tracked over multiple sampling periods. There are a total of nine sites, each of which has five 20 square meter band transects. Six of the sites were first sampled in 1980, one additional was added in 1987, and the other two were added in 2014. The sites have usually been monitored twice per year, most often in October and April.

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  "010:12"
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[
  "geospatial"
]