These data describe the abundance and size of a select group of about 50 species of benthic invertebrates and understory algae in fixed plots (either 1mx1m or 20mx1m) along permanent transects. These data are part of SBCLTER?s kelp forest monitoring program to track long-term patterns in species abundance and diversity of reef-associated organisms in the Santa Barbara Channel, California, USA. The sampling locations in this dataset are at nine reef sites along the mainland coast of the Santa Barbara Channel and at two sites on the north side of Santa Cruz Island. These sites reflect several oceanographic regimes in the channel and vary in distance from sources of terrestrial runoff. Sampling began in 2000, and these data are updated annually.