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

These data describe the size frequency distribution of red and purple sea urchins at SBC LTER long-term kelp removal experiment sites. The diameter of the test (shell without spines) is recorded in centimeters to the nearest 0.5 cm for 50 red and 50 purple sea urchins located in 40 m x 2 m transects in each sampling plot. These data can be combined with size-mass relationships established in the laboratory to provide a non-destructive estimate of red and urchin dry mass. The kelp removal experiment was initiated in 2008 at selected reef sites along the mainland coast of the Santa Barbara Channel. The following three giant kelp manipulations are maintained in sampling plots at each site: Control: Macrocystis pyrifera is left intact in a 2000 m 2 plot. Annual removal: Macrocystis pyrifera is removed from an adjacent 2000 m 2 plot once each winter and allowed to re-colonize over the course of the year. Continuous removal: Macrocystis pyrifera is removed from a 200 m 2 area within the 2000 m 2 plot on each sampling date.