DOI: 10.5061/dryad.xpnvx0ktd
title: Nutrient addition incubation experiments over an annual cycle in coastal Newport Beach, CA

description: 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.
description: # Nutrient addition incubation experiments over an annual cycle in coastal
 Newport Beach, CA Dataset DOI:
 [10.5061/dryad.xpnvx0ktd](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