Suggested Citation:
Daly, Kendra. 2015. Zooplankton abundance and distribution data for the northeastern Gulf of Mexico and west Florida shelf: June 2012 – August 2014. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7319SVT
Data Parameters and Units:
1. Date (local and GMT), time (local and GMT), Latitude (N), Longitude (W), station, bottom depth (m), estimated depth of tow (m), volume filtered (m3), zooplankton abundance of species and taxa (number/m3). 2. Information on the specific zooplankton taxa and species are in a separate attached document “Bongo Net Abundance Analyses: Notes for Zooplankton Taxa/Species List”.
Methods:
Bongo nets sample collection. Bongo nets (61 cm diameter, 333 µm mesh nets) were towed obliquely through the water column from 200 meters to the surface, while the ship was underway at 1 - 2 knots keeping an approximate 45 degree wire angle. At stations shallower than 200 m, the maximum sampling depth was targeted to be 5 m above the bottom. The wire was let out at 50 m/min until the maximum depth was reached, held at depth for 30 seconds, and then retrieved at a constant rate (20 m/min). Flow meters in each net were read before and after each net deployment. The sample in the right cod end was preserved in buffered 10% formalin for zooplankton identification by microscopy. The left cod end was frozen for zooplankton biomass (reported separately). Zooplankton laboratory methods. In the laboratory, the entire preserved sample was poured onto a 64 µm mesh sieve, rinsed with filtered seawater, and then poured into a large clear pyrex dish for sorting. Large (easily detectable by eye) non-copepod taxa (e.g. sergestids, myctophids, mysids, heteropods, pteropods, large chaetognaths, hyperids, euphausiids, etc.) were rinsed with filtered seawater and removed for later enumeration and identification. These taxa were identified to group or species and then stored in glass vials with 4% sodium borate buffered fomaldehyde in filtered seawater. Some taxa (e.g. fish larvae) were categorized further to life stage (e.g. preflexion, flexion and postflexion). To obtain abundances of copepods and other small taxa, the preserved sample with large taxa removed was again poured onto a 64 µm mesh sieve and back-rinsed with filtered seawater into a Folsom plankton splitter. The sample was split between 1/8 and 1/1024, depending on the abundance of calanoid copepods. The target was to obtain approximately 100 calanoid copepods in a split. This split was then sorted using a dissecting microscope (15-60 X). Calanoids (e.g. Eucalanidae, Metridiidae, Aetidiidae, etc.) and non-calanoids (e.g. Corycaeus, Lubbockia, etc.) were removed, identified, enumerated and then stored in glass vials with 4% sodium borate buffered fomaldehyde in filtered seawater. Calanoids were identified to the lowest possible taxon (see Gulf Mexico taxa.doc) and staged. In some cases (e.g. Paracalanus spp., Clausocalanus furcatus, Ctenocalanus vanus, etc.), identification was confirmed under a compound microscope. Non-calanoids were identified to genera (e.g. Oncaea, Oithona, Corycaeus, etc.), but not staged. If damage to the copepod prevented identification or staging, the individual was labeled “damaged” and placed in the lowest category possible. Small non-copepod taxa (e.g. ostracods, cladocerans, larvaceans, forams, echinoderm larvae, etc.) were also removed from the split and identified to group or species, enumerated, and stored in glass vials. Zooplankton abundances (#/m3) were calculated as: Large taxa (#/m3) = [(number of individuals) / volume filtered (m3) Copepod and other small taxa (#/m3) = [(number of individuals in the split) x (the inverse of the split fraction)] / volume filtered (m3) Where, 1 split = 1/2 2 splits = ¼ 3 splits = 1/8, etc. Zooplankton abundance data are provided in excel files, with each cruise in a separate excel file. Files are named by cruise/date, where BE: RV Bellows; WB: RV Weatherbird II.
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