SBC LTER: Reef: Benthic Composition Experiment: hourly photon irradiance at the seafloor

Photosynthetically Active Radiation (PAR) sensors measure photosynthetic light levels in both water and air in micromoles of photons per meter squared per minute (μmol m-2 min-1). PAR light sensors are deployed on the seafloor at the center of each BCE plot across 5 sampling sites (Arroyo Quemado, Naples, Isla Vista, Mohawk, Carpentaria) along the Santa Barbara Coast and 2 sites at Santa Cruz Island (San Pedro Point, and Cavern Point). Sampling began December 2021 and is conducted seasonally every 3 months. An additional sensor is placed in air on the roof at the Marine Science Biotech building near Campus Point which acts as a calibration control when analyzing underwater light measurements. Data collected from these PAR sensors are used to model primary production by both giant kelp and understory algae in terms of light availability and to compare the differences between control and experimental plots cleared of giant kelp. Plot 1 represents the control plot with no giant kelp removal and plot 2 represents the kelp clearing plot where all giant kelp are removed. Additionally, understory algae are removed seasonally from half of the rock slates for both plots (Plot 1 rock plates #1-6 and Plot 2 rock plates #13-18). Continuous light data are contained in one table depicting seasonally collected light measurements across all sites and sampling periods.