Dataset: Percent coverage along a transect or subsample of each of four substrate types recorded during emergent and rapid emergent surveys conducted in the subtidal zone of northern California, Sonoma and Mendocino counties, from 1999 to 2023

All surveys were done using Scuba along 30-meter x 2-meter (m) transects randomly placed in the subtidal zone in rocky habitats dominated by bull kelp, Nereocystis luetkeana, forests. These randomly placed band transect surveys were stratified by depth (A=0-15, B=16-30, C=31-45, D=46-60 ft) as we know sea urchin and abalone populations differ by depth.

Each diver (2 divers) surveyed a 1-m wide swath along each the transect, collecting the following data: the number of live, dying (in some years during the mass mortality events), and sea urchins (red-Mesocentrotus franciscanus and purple-Strongylocentrotus purpuratus), red abalone (Haliotis rufescens), pinto abalone (H. kamtschatkana), flat abalone (H. walallensis), as well as empty abalone shells (again in some years).

The data specific to this dataset are the percentages of four different substrate types: reef, boulder, cobble, and sand. Data on the substrate types differed depending on the year and the focus of the studies in response to ecosystem conditions. Note that some transects were subsampled: "L" is left side, "R" is right side, "LR" is the entire 30m x 2m transect, both sides. Not all transects were subsampled due to time constraints; not all survey transects were sampled.

In some rare cases, substrate can range from 95-105 for a subsample, and from 190-210 for both sides of the full transect, so they should be rounded off to 100 or 200%.