Abstract:

In Situ Ichthyoplankton Imaging System (ISIIS) images were collected during two different summers (2011 and 2016) to determine the distribution of large scyphomedusae on the northern Gulf of Mexico shelf and their diel variability. Two different towing methods were used. In 2011 we towed the ISIIS at 3 fixed depths (10, 25, and 35 m) to measure the horizontal patchiness of jellies and associated zooplankton, and we also performed tow-yos in the same area. In 2016, we deployed the ISIIS in tow-yo fashion during the day and night in shallower waters (~25 m deep). We also examined the association of larval/juvenile fishes with these large scyphomedusae, examining the oceanographic variables related to these associations. Sizes and angles of orientation for each medusa were also measured.

Suggested Citation:

Adam T. Greer, Jessica Y. Luo, Robert K. Cowen, William M. Graham. 2018. In Situ Ichthyoplankton Imaging System (ISIIS) Pelagia noctiluca abundance, distribution, and associated zooplankton during the summer in 2011 and 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N76Q1V98

Publications:

OUP accepted manuscript. (2017). ICES Journal of Marine Science. doi:10.1093/icesjms/fsx168

Purpose:

The dataset examines the fine-scale distribution of Pelagia noctiluca jellies, associated environmental data, and abundances of zooplankton during July in both 2011 and 2016. We were examining the drivers of Pelagia noctiluca patches on a diel cycle.

Data Parameters and Units:

Pelagia_DVM and PelVertDist files: Depth bin (m), Site, Day or night, Average depth (m), Concentration (individuals/m^3), m3samp = volume sampled (m^3), pel (number of Pelagia medusae counted within depth bin) Environment files: neearestenv/nearjul= julian time (CDT), Label = image file name, Diameter = bell diameter (cm), Angle = angle of bell orientation (-180 to 180 degrees), Taxa = taxonomic identification, Time = Unix timestamp (local time when individual was found), slice = image number within an image stack of 430 images, xloc = x pixel location within the larger frame, yloc = y pixel location within the larger frame, width = width of bounding box (pixels), height = height of bounding box (pixels), hr = hour of local time image was taken, min = minute of local time image was taken, sec = seconds of local time image was taken, sec1000 = thousandths of a second, julian = julian time of physical data collection, pressure (decibars), depth, temp = temperature (degrees Celsius), salinity (psu), fluor = chlorophyll-a fluorescence (raw voltage), oxygen = oxygen concentration (mL/L or mg/L), o2volts (volts), par (/m^2), parvolts (volts), irradiance (microEinsteins/cm^2), horz.velocity = horizontal velocity (mm/sec), vert.velocity = vertical velocity (mm/sec), vol.image = NA (not valid data), altitude = distance from benthos (m), pitch = pitch of ISIIS vehicle (degrees), roll = roll of the ISIIS vehicle (degrees), heading = heading of the ISIIS vehicle (degrees), lat = latitude (decimal degrees), lon = longitude (decimal degrees), rel normal velocity (mm/sec), trans velocity (mm/sec), long velocity (mm/sec), norm velocity (mm/sec), transect = transect number (1-6), distance = distance along transect (m), depthr = rounded depth (to 10m, 25m, or 35m), fvel = forward velocity (m/s, 0 indicates unreliable reading from ADCP), altok (binary variable indicates if altitude data are valid, 1-valid, 0-error), ID (plankton), Central time (HH:MM:SS), Time (UTC), corroxy = corrected oxygen (mg/L), daynight (day, afternoon, or night), numfish = number of fish present Note: The “Time” column (column E) in July2011PelagiaSizeandEnvironment.csv corresponds to the local time when the individual was found (82648078 means 8:26:48.078 central daylight savings time). The other column (column Q) is called “time” is incorrect – it should be 8:27 am not 12:27 am – I am not sure why this happened. This data frame comes from a merger of two datasets using the “nearestenv” (which stands for nearest environment – the environmental data and images are not collected at the same rate – 6 Hz for environment, 17 Hz for images) variable, and is the Julian time of the observation (0.350299 is ~8:27 am). So the Julian times are the most reliable and the ones that were used. Note: The "time" variable in the PhysicalData072411.csv dataset has a mistake – the hours appear to be off by 8 hrs. The Julian time is correct (first data point of 0.342448 would translate to 08:13:08 am) and was used to merge with the biological data from that year. Oxygen in this dataset is recorded as mL/L. I convert to mg/L by multiplying the oxygen values by 0.75189 (see ICES unit conversion). Note: For corrected oxygen/corroxy: we used the formula supplied by the oxygen sensor (Seabird electronics) to convert the oxygen voltage, temperature, salinity, and depth to dissolved oxygen concentration. The values for “oxygen” are incorrect for the summer 2016 data due to an error in the software that converts the voltage. Zooplankton count files: m3bin = the horizontal distance (m) covered by 1 m^3 of water sampled, Taxa (individuals/m^2), transect = transect number (1-6), mdepth = mean depth (m) across the 1 cubic meter bin, mtemp = mean temperature across the 1 cubic meter bin (deg C), msal = mean salinity across the 1 cubic meter bin (psu), mfluor = mean chlorophyll-a fluorescence (volts) across the 1 cubic meter bin, moxy = mean oxygen across the 1 cubic meter bin (mL/L), mirr = mean irradiance across the 1 cubic meter bin (microEinsteins/cm^2), mlat = mean latitude (decimal degrees), mlon = mean longitude (decimal degrees) The taxa are as follows: chaeto = chaeotgnaths, copepod = copepods, cumaean = cumacean, fish = larval fish, Hydro = hydromedusae, LC = lobate, cteno = ctenophore, pleuro = ctenophore with tentacles, pteropod = pteropod, scyphomedusae = scyphomedusae (mostly Pelagia), shrimp = shrimp, siphon = siphonophore, stomato = stomatopod, Thaliac = thaliacean (salps and doliolids), Unk = unknown ID, zooea

Methods:

BiophysicalData2011/July2011_Inshore_Pelagia_DVM.csv – the data are averaged from 2 locations. The “day” data come from samples at the locations, which are transects, that have a mean lat/lon of 29.781 deg N and -87.36 deg W and 29.4185 deg N and -88.44 deg W. All of the data were collected on 29 July 2011 from 02:11 to 08:39 local time (CDT) and 30 July 2011 from 17:47 to 2:06 CDT BiophysicalData2016/PelVertDist-day.csv – this was a ~10 km transect that produced an average vertical distribution of the jellies. The mean lat/lon for this transect was 29.800 deg N, -88.610 deg W. These data were collected on July 28, 2016 from 10:30 to 14:15 CTD BiophysicalData2016/PelVertDist-night.csv – this ~10km transect was performed in the exact same location as the 2016 day transect (mean lat/lon for this transect was 29.800 deg N, -88.610 deg W). These data were collected on July 27-28, 2016 from 22:00 to 01:30 CTD 13 cm = 2048 pixels

Individual Files: