Table of Contents

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

This dataset contains trace element concentrations from 2014 and 2015 in the sea surface microlayer and underlying water column for in-situ sampling.

Microlayer was sampled by a hollow quartz tube dipped vertically into the water column, then slowly pulled vertically out of the water and held over a funnel attached to a receiving bottle for the microlayer sample to drip off. This process was repeated until the desired volume of sample was collected. Corresponding water column samples were collected about 30 cm from the surface where a closed bottle was submerged underwater, opened, then closed again underwater to prevent mixing with the microlayer. Microlayer and water column samples were filtered within 1 hour after collection using 47 mm 0.2 um pore sized polycarbonate track-etched membrane filters by vacuum filtration.

Dissolved trace elements were analyzed by a cation exchange column method described in Milne et al. (2010). Reactive particulate trace elements were leached from the filters using a weak acid (acetic acid) and reducing agent (hydroxylamine hydrochloride) solution described in Berger et al. (2008). Refractory particulate trace elements were digested using a microwave digestion technique described in Ebling and Landing (2015). All samples were analyzed on the Thermo Scientific Element 2 HR-ICP-MS.

Data went through internal lab QAQC process. The spreadsheet uses BDL for below detection limit.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- nd (no data) was entered into all blank cells and NA cells.
- re-formatted date from m/d/yyyy HH:MM to yyyy-mm-ddTHHMM
- replaced spaces with underscores

Description from NSF award abstract:
Dust and mineral aerosols are a significant source of micro and macronutrients to oligotrophic ocean surface waters. Evidence is growing that heterotrophic microbes may play key roles in processing deposited minerals and nutrients. Yet it is not known which components of dust stimulate the heterotrophic bacteria, which cellular mechanisms are responsible for the utilization of those components and how the activity of these bacteria affect the availability and utilization of dust-derived minerals and nutrients by marine autotrophs. Knowledge of these factors is key to understanding how dust deposition impacts carbon cycles and for predicting the response of tropical oceans to future changes in the frequency and intensity of dust deposition events. The objective of this project is to examine the specific effects of aeolian dust on heterotrophic microbes in a tropical marine system under controlled conditions. The central hypothesis is that in oligotrophic tropical systems numerically minor opportunistic bacteria are the first responders to influx of dust constituents and respond primarily by rapidly accessing soluble trace metals and limiting nutrients that are deposited with Saharan dust. The project will focus on two specific aims: 1) Quantify changes in community structure, composition and transcriptional activity among marine microbial populations upon exposure to dust, and 2) Identify key components in Saharan dust aerosols that stimulate or repress growth and/or activity in Vibrio, a model opportunistic marine heterotrophic group. The study will use a series of controlled experiments designed to identify and quantify heterotrophic microbial response to dust deposition events using both natural communities and model bacteria (Vibrio) through metagenomics, transcriptomics and atmospheric and marine biogeochemical techniques. This innovative approach will identify the most critical (reactive) components leached from dust aerosols on the microbial community as well as elucidate potential mechanisms of response.

There is great interest in the biological response to dust aerosols given its potentially large influence on biogeochemical cycling, but there has been relatively little work that has addressed the mechanisms of response (especially among the heterotrophic microbial fraction) or identified the relative importance of specific constituents of dust aerosols. A detailed framework for microbial response (focusing on opportunistic heterotrophs) will facilitate efforts to link autotrophic and heterotrophic processing. This contribution is significant because it will provide one of the first end-to-end (chemistry to physiology to ecology) mechanistic pathways for marine biological response to desert dust aerosols.