Abstract:

This dataset contains measurements of mesozooplankton gut phaeopigments and associated metadata collected from 12 sampling locations during R/V Point Sur cruise PTS01 from 2015-10-29 to 2015-11-05 in the Mississippi Bight, Gulf of Mexico. Mesozooplankton samples were taken during the fall of 2015 using a mininess (BIONESS) tow system. Samples were taken from three nets, corresponding to three depth intervals (e.g., bottom, midwater, surface). Nets had 202-micrometer mesh size, but in some cases, samples were taken from nets with 0.333-micrometer mesh due to system issues. Samples were transferred into a bucket immediately after retrieval and carbonated water was added to the sample to stop or avoid further 'net feeding' or regurgitation from individual zooplankton. Typically, each net sample was split into two aliquots using a Folsom Splitter aboard the ship. The 1/2 aliquot separated from the original sample was then split further into two subsamples: one was used to measure mesozooplankton gut fluorescence and the other was processed for dry weight (reported separately). When samples were too thick, the initial sample was split into smaller aliquots (clearly indicated in the dataset). The corresponding aliquot was then size fractionated into five size bins using sieves with meshes measuring: 0.212, 0.5, 1, 2, and 4.75 mm. Filtered seawater was used during sample split and size fractionation. After fractionation, each sample was poured onto a GF filter (2.5 mm diameter) using a filtering system aboard the ship, rinsed with DI water, wrapped in aluminum foil and quick-frozen immediately after filtering by depositing the sample into liquid nitrogen. Before filtering, each sample was kept in the dark in an ice bath. Samples were processed following Strickland and Parsons (1968) spectrophotometric determination of phaeopigments protocol. These data will be used in combination with other mesozooplankton net data to study zooplankton processes in the river-dominated northern Gulf of Mexico. Data is reported in units of micrograms of phaeopigments per liter. Related mesozooplankton size-fractionated dry weight data and BIONESS profile data are available under GRIIDC UDIs R4.x260.000:0026 and R4.x260.204:0037 respectively. The gut fluorescence data come from the same net analyzed for dry weight, and both gut fluorescence and dry weight data come from the net tows, BIONESS profile datasets, which contains all the detailed information about the station, net start/end coordinates, and sampling information.

Suggested Citation:

Christian Briseno-Avena; Frank J. Hernandez; Robert K. Cowen; Jeffrey W. Krause. 2018. Mesozooplankton size-fractionated gut fluorescence data collected during R/V Point Sur cruise PTS01 from 2015-10-29 to 2015-11-05. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N72J6984

Purpose:

These data will be used in combination with other mesozooplankton net data to study zooplankton grazing rates in the river-dominated northern Gulf of Mexico.

Data Parameters and Units:

Cruise id, station (Corridor where net was towed. MCORR= middle corridor, ECORR= eastern corridor, WCORR= western corridor, ARRAY= mixing mooring array), Date_UTC (dd/mmm/yy, UTC), Time_UTC (time when net was deployed, HH:MM, UTC), Latitude_Decimal (location of net deployment, decimal degrees North), Longitude_Decimal (location of net deployment, decimal degrees West), Tow_Number (unique number ID of the net tow deployment), Net_Number (number of the BIONESS net where the sample was obtained), Net_Mesh_um (mesh size, micrometers), Depth_Open_m (depth where the net started sampling, m), Depth_Close_m (depth where the net stopped sampling, m), Swept_Volume_m3 (amount of water sampled by the net, m^3), Mean_Temperature_Celsius (mean temperature measured by the environmental sensor system during the interval the net was collecting samples, degrees C), Mean_Salinity_PSU (mean salinity measured by the environmental sensor system during the interval the net was collecting samples, PSU), GF_Number (unique number of the aliquot obtained from the net), Sieve_Size_mm (size of the sieve's mesh in millimeters where the subsample was obtained for this analysis), Net_Split_Factor (fraction of the original sample taken from the net), Filter_Section_Factor (fraction of the GF filter used for pigment extraction and laboratory analysis), Gut_Phaeopigments_ug_per_L (micrograms of mesozooplankton gut phaeopigments per liter), Notes (notes of dominant organisms found in filter; notes of non-grazing organisms removed prior to pigment extraction)

Methods:

GF filters were transferred from liquid nitrogen to -80 freezers and kept there until laboratory analyses. Gut pigments were measured using the Strickland and Parsons (1968) spectrophotometric determination of phaeopigments protocol. GF filters were processed in the following manner: for subsamples coming from sieve sizes 4.75 & 2 mm the whole filter was used for pigment extraction; for subsamples from sieve size 1 mm, 1/4 of the filter was processed; and 1/8 of the filter was used for filters with samples from sieve sizes 0.5 and 0.212 mm. Pigment extraction was done in 90% acetone as per standard pigment analyses protocols and using the acidification method (HCl). All laboratory analyses were conducted in dark conditions as much as possible to avoid pigment photodegradation. Pigment measurements were carried out on an SpectraMax M2 (Molecular Devices) spectrophotometer using a cuvette of 1 cm path length. The nets were fished for about 6 minutes each. Volume swept and depth bin intervals were targeted to three depth bins: deep, mid-water column, and near the surface. For these data, samples from 3 out of the 9 nets used on the BIONESS dataset were used. The start and end coordinates and time for each of these 3 nets are very close to each other that end towing information are not provided in this dataset. However, the full station metadata, net data, and detailed environmental data for each net can be found in the BIONESS dataset under GRIIDC UDI R4.x260.204:0037.

Provenance and Historical References:

Briseño-Avena, Christian, Alison L. Deary, Robert K. Cowen, Frank J. Hernandez, and Jeffrey W. Krause. 2018. Mesozooplankton Size-Fractionated Dry Weight, cruise PTS01, Fall 2015 . Consortium for Oil Spill Exposure Pathways in Coastal River-Dominated Ecosystems (CONCORDE). DOI: 10.7266/N798853D Frank J. Hernandez. 2018. BIONESS profile and plankton sample collection data, cruise PTS01, northern Gulf of Mexico, October – November 2015 . Consortium for Oil Spill Exposure Pathways in Coastal River-Dominated Ecosystems (CONCORDE). DOI: 10.7266/N7S46Q0W

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