Dataset: Percent cover of algal habitat types on a by-transect and/or subsample basis recorded during emergent and rapid emergent surveys conducted in the subtidal zone of northern California, Sonoma and Mendocino counties, from 1999 to 2023

Data were collected during day-trips aboard California Department of Fish and Wildlife or NOAA patrol boats, generally 2-5 days at select survey locations in 1999-2001, 2003-2016.

All surveys were done using SCUBA along 30-meter x 2-meter (m) transects (60 square meters total area) 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, recording the percent coverage of six algal/substrate types: bare rock, encrusting, turf, foliose, subcanopy, and canopy. Data on algae and associated species differed depending on the year and the focus of the studies in response to ecosystem conditions. Note that a transect may have more than 100 percent coverage, e.g., 5% encrusting, 60% turf, and 50% foliose all under a canopy of 75% (total=190).

In some years after the marine heatwave (2014), there are Uniform Point Contact Algae data as well collected at every meter mark along the 30m transect.

The data specific to this dataset are the percent of bottom coverage by algal types for a transect or transect subsample.