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Microplankton abundance and carbon biomass from CTD bottle samples collected during AMT14 and analysed with FlowCAM

Originator's Protocol for Data Acquisition and Analysis

Seawater samples were collected from the CTD Niskin bottles at the pre-dawn "productivity" cast from 5 depths equivalent to 55%, 33%, 14%, 1% and 0.1% surface irradiance. The samples were slowly poured, avoiding bubbles, into 100 ml glass medical caps bottles pre-filled with 1 ml Lugol's iodine to make up a 1% fixative. The fixed samples were then kept cool and stored in the dark until subsequent size structure determination.

The size structure of the nanoplankton in the 10-20 µm size range and microplankton community in the 20-130 µm size range was determined using the FlowCAM (Sieracki et al. , 1998; FlowCAM 2005), which is an instrument that instantaneously counts, takes a digital image and sizes particles greater than 10 µm flowing through the detection flow chamber. Although an x4 objective was used to detect this size range, the resolution of the images was insufficient for adequate identification of individual organisms. Beads of a known size were passed through the FlowCAM to calibrate the instrument. Distilled water was pumped through the instrument between samples and a small amount of diluted bleach passed through after ca. 30 samples, to clean the tubing. Each Lugol's fixed seawater sample was rotated several times, very carefully, avoiding any bubbles, and poured slowly into the sample inlet. The peristaltic pump was turned on at a flow rate of 1-1.5 ml min ^-1 and the sample analysed for 30 minutes or until the number of particles counted exceeded ca. 300. The particles were assumed to be spherical and the biovolume of each cell was calculated from the equivalent spherical diameter (ESD) determined by the FlowCAM. The volume was corrected for cell shrinkage caused by Lugol's preservation (Montagnes et al. , 1994). The corrected volumes were finally converted to carbon (Menden-Deuer and Lessard, 2000). Further details given in San Martin et al. (2006).

References Cited

FlowCAM, 2005 The FlowCAM: An instrument for continuously monitoring and imaging of phytoplankton. http://www.bigelow.org/flowcam/

Montagnes D.J.S., Berges J.A., Harrison P.J. and Taylor F.J.R., 1994 Estimating carbon, nitrogen, protein, and chlorophyll a from volume in marine phytoplankton. Limnology and Oceanography, 39, 1044-1060

San Martin E., Harris R.P. and Irigoien X., 2006 Latitudinal variation in plankton size spectra in the Atlantic Ocean. Deep-Sea Research: Part II, 53, 1560-1572

Sieracki C.K., Sieracki M.E. and Yentsch C.S., 1998 An imaging-in-flow system for automated analysis of marine microplankton. Marine Ecology Progress Series, 168, 285-296

Instrumentation Description

Not applicable for this data set.

BODC Data Processing Procedures

Data were submitted via email in an Excel spreadsheet with the data from AMT12 and 13 and the file was archived under BODC's accession number PML050118. Sample metadata (Cruise, CTD cast, date, latitude, longitude, and depth) were checked against information held in the database. There were no discrepancies.

Parameter codes defined in BODC parameter dictionary were assigned to the variables. The data was provided in units which were consistent with those used for the relevant parameters in the BODC database.

The data were reformatted and loaded in BODC's samples database under Oracle Relational Database Management System. Data were marked up with BODC parameter codes and loaded into the database. Individual samples were matched through rosette sampling bottle and depth.

A parameter mapping table is provided below;

Data Quality Report

BODC were not advised of specific quality checks carried out by the data originator.

Problem Report

Not relevant to this data set.