SBC LTER: Reef: Long-term experiment: Kelp removal: Urchin size frequency distribution

These data describe the size frequency distribution of red
( Mesocentrotus franciscanus ) and purple
( Strongylocentrotus purpuratus ) sea urchins
within permanent plots of a long-term experiment designed to
examine trajectories of change in the structure and productivity
of kelp forest communities in response to changes in the frequency
and severity of disturbance to giant kelp. The diameter of the
test (shell without spines) was recorded to the nearest 0.5 cm for
50 red and 50 purple sea urchins located within a 40 m x 2 m area
of each plot. Size frequency data of red and purple sea urchins
are not collected in the continual kelp removal plots. When
combined with size-mass relationships established in the
laboratory these data were used to provide a non-destructive, in
situ estimate of the dry mass per unit area of bottom for each
species. The experiment was initiated in 2008 at five reef sites
along the mainland coast of the Santa Barbara Channel and included
an annual kelp removal treatment designed to simulate increases in
the frequency and severity of winter wave disturbance and a
continual kelp removal treatment that allowed the effects of giant
kelp on the community to be evaluated. The last experimental
removals of giant kelp occurred in winter 2016 or winter 2017,
depending on the site. Data collection continued in all plots
until spring 2023 to document the recovery trajectory of the reef
fish community following the cessation of experimental kelp
removal.