ScanFish Optical Plankton Counter ( OPC ) data from R / V Pelican cruises PE 03-NGOMEX , PE 04-NGOMEX , PE 06-NGOMEX , PE 07-NGOMEX , PE 0905 , and PE 1106 in the Northern Gulf of Mexico between 2003 and 2010

An optical plankton counter (OPC) and CTD mounted to a ScanFish platform were towed and undulated behind the R/V Pelican during cruises PE03-NGOMEX, PE04-NGOMEX, PE06NGOMEX, PE07-NGOMEX, PE09-05, and PE11-06 in the Northern Gulf of Mexico between 2003 and 2010. CTD and MIDAS data were synchronized and merged with simultaneously collected OPC data and aggregated into 1 second time bins. Bottom depth was obtained from the NOAA NCEI coastal relief model. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/746081

the NOAA NCEI coastal relief model.For a complete list of measurements, refer to the supplemental document 'Field_names.pdf',and a full dataset description is included in the supplemental file 'Dataset_description.pdf'.The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/746081

Dataset Description
Subsets of these data were published in the papers listed in the "Related Resources" section.

Methodology:
A CTD and optical plankton counter mounted to a ScanFish platform were towed and undulated behind the vessel.
Sampling and analytical procedures: The ScanFish was towed at a mean speed of 2.7 m/s with mean vertical descent and ascent rates of 0.3 m/s.Notes for specific data columns: Dissolved oxygen concentration (column "oxy"): values corrected vs. CTD rosette casts and Winkler titrations when available.
Sample volume (column "vol"): estimated from OPC mouth opening and changes in lat, lon, and depth Data column definitions for particle counts and biovolume density include the term "ESD" which stands for "equivalent spherical diameter." Biovolume densities (data column names beginning with "v_") were calculated using the following formula: 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:
Previously 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 µm 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.
Temperature, Depth (CTD)  unit is an integrated instrument package designed to measure the conductivity, temperature, and pressure (depth) of the water column.The instrument is lowered via cable through the water column and permits scientists observe the physical properties in real time via a conducting cable connecting the CTD to a deck unit and computer on the ship.The CTD is often configured with additional optional sensors including fluorometers, transmissometers and/or radiometers.It is often combined with a Rosette of water sampling bottles (e.g.Niskin, GO-FLO) for collecting discrete water samples during the cast.This instrument designation is used when specific make and model are not known.vehicle is a generic class of instruments.See the data set specific information for a detailed description.These are often prototype instrument packages designed to make very specific measurements.quantitative measurements of abundance and sizes of mesozooplankton ranging between approximately 0.25 and 14 mm in Equivalent Spherical Diameter (ESD), and has the capability to integrate measurements from other sensors such as a CTD, fluorometer and Global Positioning System (GPS BCO-DMO Data Manager Processing Notes: ).It can be deployed on a variety of instruments such as SeaSoar, Aries, Scanfish, MOCNESS, a bongo net or simple towing frame.The data from an OPC are typically transmitted to a data acquisition computer through two conducting wires in a towing cable at real time, but it can also be modified to have an internal memory.Large amounts of data are produced.The procedures employed by OPC users vary from; i) estimating integrated biomass by integrating the OPC size distributions, ii) comparing size distributions between OPC and net samples, and iii) simply isolating a size region in the OPC size distribution which correspond solely to specific taxa, eg.Calanus spp.. from: Description 2006 Sampling cruise to the Northern Gulf of MexicoNote: Deployment Id and Chief Scientist assigned by BCO-DMO staff (not official) Description 2007 Sampling cruise to the Northern Gulf of MexicoNote: Deployment Id and Chief Scientist assigned by BCO-DMO staff (not official) Description 2010 Sampling cruise to the Northern Gulf of MexicoNote: Cruise ID confirmed with R2R catalog Original cruise data are available from the NSF R2R data catalog [ table of contents | back to top ]