Table of Contents

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

Sampling and Analytical Methodology:
Nutrient and aerosol addition bioassay experiments were carried out over 3 days in February 2012. Seawater was collected from offshore (water depth >700 m) outside the Bellairs Research Institute at West Barbados (13^o 11.309’N, 59^o 38.267’W). Surface water was pumped into acid cleaned sample rinsed carboys using a peristaltic pump with acid washed Teflon tubing and pre filtered through a 50 um mesh acid washed Nitex^© net to remove grazers. The seawater was stored in the dark until transport to the lab (within <2 hours). Seawater was dispensed into acid washed and sample rinsed polycarbonate bottles (500 mL each), pre-labeled with treatment type (12-20 bottles per treatment). Treatments included single nutrient (N, P, Fe) additions as well as a combination of N and P and a combination of N and Fe at concentrations representative of deep water in this area. Three aerosol treatments were used in this study representing aerosols deposited in three seasons, winter, spring and summer. Aerosols representing each of the seasons were added at concentrations simulating high and low deposition rates. High deposition was calculated to represent the cumulative deposition flux over 10 days of a strong dust storm event over the North Atlantic (300 g m^-2 yr^-1) to the upper 10 m mixed layer. Low deposition treatments were equivalent to the normal average deposition rate for Barbados (10 g m^-2 yr^-1) during spring and summer. A control (no addition, blank filter) treatment and procedural blanks (Milli-Q water) were also included. All bottles were incubated in a pool filled with circulating seawater to maintain local surface ocean temperature. The pool was covered with a neutral density shading screen to reduce light intensity by 50%. Water samples used for the experiment (pre additions) was collected to characterize the baseline conditions (baseline, 5 replicates) and 3 replicate bottles for each treatment were also collected immediately after the additions were administered (time zero, t0). The experiment took place over 3 days, and each day 3 (for nutrients) or 5 (for aerosols) randomly selected bottles for each treatment were collected at 4pm in the afternoon (e.g. time points t1-t3). Immediately upon collection each bottle was sampled for chlorophyll a, flow cytometry, nutrients, and trace metal concentrations.

Water from each of the retrieved incubation bottles was filtered through a 0.2 um filter tower, collected in acid washed 50 mL falcon tubes and frozen until nutrients were analyzed. Phosphate and ammonium were measured by continuous flow autoanalyzer (TechniconAutoAnalyzer II™). Soluble reactive phosphate (SRP) measurements followed a modification of the molybdenum blue procedure (Bernhardt & Wilhelms, 1967) and ammonium (NH₄) analysis was done using a method modified from ALPKEM RFA methodology. Nitrate plus nitrite (N+N) were analyzed by Alpkem RFA 300 following methods from Armstrong et al. (1967) (Armstrong, Stearns, & Strickland, 1967). Detection limits for SRP, N+N and NH₄ are 0.012 uM, 0.30 uM and 0.05 uM, respectively.

Data Processing:
BD: Below detection limit
*: Contaminated samples

BCO-DMO Processing Notes
 - Generated from original file: "Data_nutrient concentrations from Barbados incubation experiment.xlsx" contributed by Chia-Te Chien
 - Parameter names edited to conform to BCO-DMO naming convention found at Choosing Parameter Name
 - Common parameter names standardized between the four contributed Barbados datasets
 - Experiment Site Id and Lat/Lon appended to enable data discovery in MapServer
 - Data fields with "*" (contaminated samples) converted to "CS"

Chemical components delivered to the surface ocean through atmospheric deposition influence ocean productivity and ecosystem structure thus are tightly related to the global carbon cycle and climate. Accordingly, the major aim of this project is to quantitatively estimate the variable impact of aerosols on marine phytoplankton and to determine the specific effects on various taxa. Such data could in the future be used to better understand the global impact of aerosols on the oceanic ecosystem. To accomplish this goal the PI will monitor aerosol dry deposition fluxes, determine aerosol sources, obtain the chemical composition and solubility of aerosols, and evaluate the contribution of aerosols to nutrient and trace metal budgets of seawater at two oceanographically different sites (Bermuda and Monterey Bay) representing open ocean and coastal setting. The effects of the different aerosol "types" (defined by source and chemical characteristics) on specific phytoplankton taxa will also be evaluated using pure culture and natural samples bioassays. This project is particularly important in light of the role atmospheric deposition can resume in oligotrophic and coastal settings and the predicted future global conditions of increased aridity and urbanization and associated changes in dust fluxes and composition.