Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

Users of these data are requested to contact Matthew Bracken (m.bracken@uci.edu) prior to use.

Methodology:
High-intertidal pools are common in all three regions, allowing us to work at two spatially separated sites in each region. At each site, we identified 18 tide pools, marking each pool and quantifying physical attributes, including surface area, volume, and height on the shore. We also anchored TidbiT temperature datalogger (Onset; Bourne, Massachusetts, USA) in most pools. In the fall of 2017, we identified tide pools and conducted initial surveys and measurements. We repeated surveys every three months until immediately prior to the establishment of grazing experiments at each site in the summer of 2018. These surveys provided insights into the natural temporal variability in community and ecosystem metrics and provided baseline information on relationships between grazer abundances and producer biomass.

Sampling and analytical procedures:
During the quarterly surveys, we quantified consumer abundances, nutrient fluxes, oxygen fluxes, and photosynthetic biomass in each tide pool. Organism abundances were measured by pumping the water from each pool into a bucket, spreading a flexible mesh quadrat over the bottom of the pool, and censusing the algae and invertebrates present in each pool. Nutrient and oxygen fluxes were measured during whole-pool incubations in the dark and in the light.

Pool Characteristics:
Pool characteristics include overall attributes of the tide pools in each of our three study regions. Values were measured at the beginning of our surveys (in October 2017) and refined and remeasured throughout the year (see related dataset "Seasonal Surveys"). Latitude (decimal degrees; values are positive indicating degrees north) and longitude (decimal degrees; values are negative indicating degrees west) were determined for each pool using a Garmin eTrex handheld GPS unit set to WGS84. Tidal elevation (meters above mean lower-low water) was measured using a CST/berger self-leveling rotary laser system. Maximum tidepool depth (cm) was measured using a probe and ruler. Perimeter (m) was measured using a transect tape. Surface area (square count, m2) was measured using a flexible mesh quadrat (Bracken and Nielsen 2004), with 10cm x 10cm squares. Dye volume was determined by adding a known quantity of blue dye to the pool mixing it, measuring it on a spectrophotometer at 640 nm, and relating it to a standard curve relating absorbance to volume (Bracken et al. 2018). Pump volume was determined by pumping the water from each tidepool into a graduated 20L bucket using a hand bilge pump.

This work was conducted at sites located in three regions along the California (USA) coast: (1) Bodega Head, Sonoma County (38.31°N, 123.07°W); (2) Kenneth Norris Rancho Marino Reserve and Hazards Canyon Reef, San Luis Obispo County (35.54°N, 121.09°W and 35.29°N, 128.88°W, respectively); and (3) Corona del Mar State Beach, Orange County (33.59°N, 117.87°W).

Known Problems/Issues:
Some environmentally-related (e.g., tides, darkness) issues caused gaps in the data. These are indicated by "nd".

Data Processing:
Data reported here were recorded in the field, transcribed into a database, then collated using R.

BCO-DMO Processing:
- Added a conventional header with dataset name, PI names, version date
- Rounded Latitude and Longitude columns to 6 decimal places; rounded Dye_Volume column to 3 decimal places

Humans are modifying marine food webs both from the top-down, by reducing consumer abundances, and from the bottom-up, by adding nutrients to coastal habitats. Predicting these impacts is complicated because herbivores affect primary producers both from the top-down, by eating them, and from the bottom-up, by recycling nutrients and facilitating the recruitment of algae into local marine ecosystems. This project uses experimental manipulations along a natural gradient in nutrient availability on the California coast to evaluate the complex interactions between top-down and bottom-up processes in marine communities. This project includes experiments and outreach in a location with substantial exposure to the public, and the investigators will work with community and university outreach personnel to communicate this research to broader audiences. Specifically, the project includes mechanisms for curriculum development and outreach and will train undergraduate and graduate students in marine science.

The investigators are implementing a suite of innovative approaches to understand the multiple roles that herbivores play in marine systems. Traditional experimental methods for herbivore removal result in the loss of both the consumptive and facilitative effects of herbivores. In contrast, the investigators' experimental design allows them to partition the different effects of herbivores on marine primary producers. These methods, including observations, experiments, and modeling approaches, allow researchers to (i) calculate the relative importance of herbivores' consumptive and facilitative effects on algal diversity and abundance; (ii) determine the effects of temperature, nutrients, and herbivores on the microbial community; and (iii) evaluate the relative importance of internal processes and spatial subsidies.