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.本数据集记录了圣巴巴拉海岸长期生态研究（SBC LTER）长期海带移除实验样地中红色海胆与紫色海胆的体型频率分布。每个采样样地内的40米×2米样带上共采集50只红色海胆与50只紫色海胆，记录其壳径（去除棘刺的壳体），测量精度精确至0.5厘米，单位为厘米。该数据集可与实验室中建立的体型-质量关系模型结合，实现对红色与紫色海胆干重的无损估算。 本海带移除实验于2008年在圣巴巴拉海峡沿岸选定的礁体样地启动。每个样地的采样样地均设置以下三种巨藻（Macrocystis pyrifera）操控处理： - 对照组：在2000平方米样地内保留完整的巨藻种群。 - 年度移除组：每年冬季对相邻的2000平方米样地进行一次巨藻移除，任由其在全年内自然重新定植。 - 持续移除组：在每次采样时，对2000平方米样地内的200平方米区域进行巨藻移除。