This dataset represents measured marine intertidal habitat temperatures from June to October of 2012 and 2013 on horizontal surfaces in experimentally formed rock clearings and inside two different biogenic habitats dominated by the foundation species Mytilus californianus Conrad 1837, the California mussel, and the turf-forming ‘black pine’ alga, Neorhodomela larix (Turner) Masuda, 1982.

Study sites were embedded within three regions: a high-heat ‘hot spot’ for adult invertebrates living directly on rock surfaces (48° N, Washington, USA), a cooler mid-region (38° N, northern California), and a warm, lower latitude region (34° N, southern California). To account for potentially appreciable variation at the site level, we replicated measurements at two sites within each region that differed in wave exposure, directional orientation, and bedrock type. At each site, we measured habitat temperatures every 30 minutes for roughly 20 weeks in 2012 (June 3–October 15; 135 days) and 2013 (May 27–October 20; 147 days) with small temperature loggers placed in M. californianus beds (4–6 centimeters (cm) deep), N. larix turfs (2–6 cm deep) and in bare rock clearings scraped of biota (N = 4 loggers per habitat per site).

To compare how latitude, shore elevation, and habitat influence the occurrence of stressful high temperatures on rocky shores, we used ecologically relevant assays of physiological stress in intertidal invertebrates that occupy biogenic habitats. We used published studies and experiments to select two temperature thresholds beyond which lethal and sub-lethal stresses were highly likely for multiple rocky shore taxa. We then determined lethal thresholds experimentally for sample populations of a subset of invertebrates commonly found in the relevant habitats: juvenile mussels, Mytilus californianus; the predatory whelks Acanthinucella spirata Blainville, 1832 and Nucella ostrina Gould, 1852; and the herbivorous chink snail, Lacuna vincta Montagu, 1803.

We analyzed patterns in the duration of exposure to habitat temperatures over 35 °C and 26 °C thresholds by latitude, shore elevation, and habitat type. We calculated this response metric as the cumulative hours that habitat temperatures exceeded each threshold over the duration of temperature measurements. For analysis, we used the total hours per 30 days of measurement that habitat temperatures exceeded each threshold.

Data are summarized from files extracted from individual temperature loggers (Maxim thermochron iButtons) deployed in each associated location, as described in Materials and Methods.

Reading counts are different due to differences in hours and days deployed by year (due to shifts in the timing of low tides between years, which affected the dates we affixed and retrieved instruments in the study locations)

For further details see: Jurgens & Gaylord (2018).