Methodology:
\nA CTD and optical plankton counter mounted to a ScanFish platform were towed and undulated behind the vessel.
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Sampling and analytical procedures:
\nThe ScanFish was towed at a mean speed of 2.7 m/s with mean vertical descent and ascent rates of 0.3 m/s.
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Notes for specific data columns:
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Dissolved oxygen concentration (column "oxy"): values corrected vs. CTD rosette casts and Winkler titrations when available.
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Sample volume (column "vol"): estimated from OPC mouth opening and changes in lat, lon, and depth
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Data column definitions for particle counts and biovolume density include the term "ESD" which stands for "equivalent spherical diameter."
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Biovolume densities (data column names beginning with "v_") were calculated using the following formula:
\nv = sum(4/3*pi*(0.5*ESD*1e-3)^3)/vol
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The light attenuance (column "light") has relative units and the OPC unit used starting Sep. 5, 2010 22:30:00 UTC was calibrated differently.
Data processing:
\nPreviously processed CTD files (https://www.bco-dmo.org/dataset/3547) and MIDAS files (https://www.bco-dmo.org/dataset/3548) were synchronized and merged with simultaneously collected OPC data. Quality controlled and interpolated MIDAS data were used as the common reference system for longitude, latitude, and time. Since the OPC clock gradually and unpredictably drifted relative to MIDAS time, synchronization was accomplished by measuring and correcting for temporal lag via cross-correlations of moving windows of OPC and CTD pressure sensor time series (with the remaining error generally <0.5 s). Data were then aggregated into 1 s time bins. The standard reference for depth was OPC pressure, adjusted to compensate for non-zero readings on deck of the research vessel over the course of each cruise. The 15 arc second resolution NOAA NCEI coastal relief model for the northern Gulf of Mexico was used as a reference for bathymetry. Data were divided into distinct vertical profiles, and only those profiles were included in the final dataset that either sampled the water column from <3 m below the surface to <3 above the bottom or sampled >30 m of vertical distance, or both. Estimated OPC particle sizes from 256 to 2048 \u00b5m equivalent spherical diameter were aggregated into 12 logarithmically spaced size bins (other particle sizes were excluded). For CTD files with both raw and corrected oxygen data, the corrected version was used. All data processing was performed using the R language and environment for statistical computing.
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BCO-DMO Data Manager Processing Notes:
\n* added a conventional header with dataset name, PI name, version date.
\n* modified parameter names to conform with BCO-DMO naming conventions. Periods in column names changed to underscores.
\n* added ISO Timestamp column
\n* rounded decimal places of columns. Number of decimal places provided by data contributor.
\n* Missing data values are shown as the BCO-DMO missing data identifier "nd" meaning "no data."