Biological modification of coastal pH depends on community composition and time

Biological processes play important roles in determining how global changes manifest at local scales. Primary producers can absorb increased CO2 via daytime photosynthesis, modifying pH in aquatic ecosystems. Yet producers and consumers also increase CO2 via respiration. It is unclear whether biological modification of pH differs across the year, and, if so, what biotic and abiotic drivers underlie temporal differences. We addressed these questions using intensive study of tide pool ecosystems in Alaska, USA, including quarterly surveys of 34 pools over one year and monthly surveys of 5 pools from spring to fall in a second year. Here, we report values for physical conditions and changes in pH and dissolved oxygen during day and night as part of our effort to link physical and biological processes - and particularly the importance of time of year in determining the relationship between community composition and pH conditions - in coastal ecosystems., Our study was conducted in 34 tide pools on a rocky shore at John Brown’s Beach on Japonski Island near Sitka, Alaska, USA (57.06°N, 135.37°W). Substrate type (hard rock; Sitka graywacke) was consistent across pools. During Year 1 of our study, we sampled all 34 pools quarterly: summer (21 – 29 June 2018), fall (03 – 11 September 2018), winter (16 – 22 January 2019), and spring (24 March – 01 April 2019). In Year 2, sampling was conducted monthly in a subset of 5 pools, beginning with the spring (24 March – 01 April 2019) sampling followed by 28 April – 02 May, 11 – 14 June, 08 – 10 July, 06 – 07 August, and 19 – 21 September 2019.
Tide pool characteristics were quantified during our summer 2018 sampling. For each pool, we determined (mean ± 1 SE) shore height (2.50 ± 0.06 m above mean lower-low water), volume (11.1 ± 1.5 L), and bottom surface area (0.23 ± 0.02 m2). The subset of 5 pools studied in Year 2 was determined randomly and did not differ significantly from the full group of 3..., The data are presented in a comma-delimited .csv text file.