Sampling consists of visual surveys of the percent cover of conspicuous colonial sessile invertebrates and individually indistinguishable macroalgae by SCUBA divers. Surveys are conducted at sites distributed throughout the study region (Carmel Bay and southern Monterey Bay). Each sample site is divided into three "zones" (by depth - 20m, 12.5m, 5m - or from offshore to inshore at sites with little depth variation) to assure that samples are distributed across the face of a reef from inshore to offshore. Where possible, taxa (or taxonomic categories) are enumerated on six transects stratified across the three depth strata (two per stratum) per site (typically a 100m length of coastline, extending from onshore to the 20m isobath). Each "transect" is a 2m x 30m swath haphazardly located within one of the three depth strata.  Transects within a stratum are separated end-to-end by approximately 5m. Sampling of each transect is conducted by three divers simultaneously. One diver records the number of individual invertebrates and macroalgae within each of three 10m-long segments of the 60m2 swath. A second diver records the organism and substratum type beneath each of 30 points uniformly distributed along the 30m length of the transect (i.e. 1.0m increments) and the vertical relief (highest to lowest height of the reef surface) within a 0.5m long by 1m wide area centered on each uniform point.  A third diver records the number and size of sea urchins and abalone within each of the 10m long segments of the 60m2 swath.  Surveys are designed to measure year-to-year site-wide variability in species density or percent cover, from which community structure and interannual dynamics are derived.