DOI: 10.7280/d10d8g
title: Data from: Biological modification of coastal pH depends on community composition and time

description: 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.
description: 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 m<sup>2</sup>). The
 subset of 5 pools studied in Year 2 was determined randomly and did not
 differ significantly from the full group of 34 pools in shore height (2.69
 ± 0.12 m), volume (9.5 ± 4.7 L), or surface area (0.27 ± 0.01
 m<sup>2</sup>). During each quarter (Year
 1) or month (Year 2), we conducted measurements over one daytime and one
 nighttime low tide event to characterize change in pH and dissolved oxygen
 (DO). To complete our sampling during the relatively short daytime (in
 winter) and nighttime (in summer), we typically sampled half of the pools
 on each of 2 nights and 2 days. Daytime measurements were taken when
 irradiance levels saturated photosynthetic rates of the most widespread
 seaweed species in the pools, <em>Neorhodomela oregona</em>
 (&gt; 47 µmol photons m<sup>-2</sup>
 s<sup>-1</sup>; M. Bracken, unpublished data). Nighttime
 measurements were collected when most pools were isolated by the receding
 tide after dark (0 µmol photons m<sup>-2</sup>
 s<sup>-1</sup>). The order of daytime and nighttime sampling
 differed by month based on natural variation in tide timing.
 Each sampling event took ~3.5 hr (2.4 – 5.3 hr) and started when
 pools were isolated by the receding tide. Pools not flushed by the
 previous high tide were flushed manually with buckets of seawater. We took
 initial readings of pH (HI9829 Meter with 7609829 glass pH electrode,
 Hanna Instruments, Woonsocket, RI, USA), as well as temperature, DO, and
 salinity (ProDSS optical DO meter, YSI, Inc., Yellow Springs, OH, USA), at
 a marked location in the pool center. After intervals of ~1.5 hr,
 subsequent measurements (for a total of 3 measurements) were
 taken.  We calculated rate of change per hour for pH
 and DO between our first and last (third) measurements reducing the data
 to single values per pool. Measured pH data (mV) were corrected by pool
 temperatures and converted to total scale using calibrations with Tris
 standards (Dickson Marine Physical Lab, Scripps Institution of
 Oceanography, La Jolla, California, USA).
description: The data are presented in a comma-delimited .csv text file.