Nutrient addition incubation experiments over an annual cycle in coastal Newport Beach, CA
Data files
Sep 07, 2025 version files 15.91 KB
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Incubation_chlorophyll.xlsx
13.79 KB
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README.md
2.12 KB
Abstract
Phytoplankton communities in coastal California are influenced by changing physical and chemical conditions throughout the year. To identify the conditions that limit phytoplankton growth in coastal Southern California over an annual cycle, 15 monthly nutrient addition incubation experiments were conducted off of Newport Beach from August 2017 through September 2018. Treatments included control (no addition), nitrate, ammonium, phosphate, silicate, and a simulated upwelling treatment that received all of the listed nutrients in combination. Results showed that the availability of light and N were the two main growth limiting factors of the bulk phytoplankton community. The January, February, March, and April 2018 experiments are examples of relief from light limitation; whereas, the remaining experiments were all limited by N. In several of the N limited experiments, the effect of light limitation was sometimes apparent at low levels. These included experiments in August and September of both years, as well as the May 2018 experiment. Light limitation is likely the effect of winter mixing, which brings nutrients into the surface mixed layer, but limits cells for light as they are mixed away from the surface. N limitation is likely the result of greater stratification in the warmer summer months, where a shallower mixed layer allows enough sunlight for cells to grow and deplete N to growth-limiting levels.
Dataset DOI: 10.5061/dryad.xpnvx0ktd
Description of the data and file structure
Files and variables
File: Incubation_chlorophyll.xlsx
Description: The file “incubation_chlorophyll.xlxs” gives concentrations in the unit microgram chlorophyll per liter. Empty cells indicate missing data.
Variables
- chlorophyll a concentration
- Nutrient addition incubation experiments were conducted over an annual cycle. Seawater was collected from Newport Pier (33.60, 117.93oW °W) in 2017 on August 16, September 6, September 25, October 16, November 13, and December 13, and in 2018 on January 16, February 21, March 14, April 18, May 21, June 15, July 8, August 29, and September 26. All plasticware used in the experiments was acid-cleaned and triple rinsed with sample water before use. On each sampling date, a 20 L plastic carboy was filled with seawater collected by casting a plastic bucket off the end of the pier. Water was dispensed into 21 polycarbonate bottles (500 mL).
- Three of the bottles were immediately sampled for chlorophyll a baseline measurements.
- The remaining bottles were divided into six groups of three replicates, and received the following treatment final concentrations: control (no addition), 5 micromolar Na2HPO4, 10 micromolar Na2SiO3, 10 micromolar NH4Cl, 10 micromolar NaNO3, and a simulated upwelling treatment that received all of the listed nutrients in combination. Bottles were incubated for two days in an outdoor tank with running seawater to maintain ambient temperature, and were shaded with a neutral density shade cloth to attenuate sunlight by about half.
- After the two-day incubation, bottles were sampled to measure the concentration of chlorophyll a.
Code/software
No specialized software is needed to view the dataset. All files are in .xlsx format.
Access information
Other publicly accessible locations of the data:
- Not applicable
Data was derived from the following sources:
- Not applicable