Species cover in 15 permanent survey plots in the lower intertidal zone of Tatoosh Island, Makah Tribal Nation, Washington, USA 2012-2022

Diagonal corners of each quadrat site were marked with a pair of different stainless steel screws allowing precise determination and orientation of the quadrat in subsequent annual sampling. Quadrats where subdivided with 10 monofilament lines in both top-down and side-side directions.

In 2012, each quadrat was sampled visually under each point where monofilament lines crossed, both for the species first encountered from above, and for the species occupying the rock surfaces. Beginning in 2014 (through 2026 to date), plots were documented annually through digital photographs of both the undisturbed plot, and the plot with overstory kelp moved to reveal understory organisms as much as possible. Photographs were analyzed for the percentage of area covered by mussels (<i>Mytilus californianus</i>) from 2014-2022, and for the percentage area covered by all identifiable organisms to the lowest taxonomic level possible in 2014 and 2019, using the 121 squares defined by the monofilament lines and the outer frame of the quadrat.