Wet Weight Displacement Volume: Wet weight displacement volume measurements (minus gelatinous organisms, including salps) were made for all freshly collected samples. Additional wet weight displacement volume estimates were made for large and small sized zooplankton fractions, the separation of which is largely dependent on the ability to identify and adequately enumerate taxa. Maximum lengths of the small fraction generally were ≤ 10 mm (e.g., copepods, shelled pteropods, ostracods, larval euphausiids and other crustaceans). Due to their large length range chaetognaths were represented in both categories but are treated as part of the small fraction. Large taxa (e.g., ~10-20 mm) include postlarval euphausiids, amphipods and polychaetes. Wet weight displacement volumes determined separately for “extra large” (e.g., >20 mm) postlarval myctophids and Antarctic krill (Euphausia superba) are included with the large taxa.

Taxonomic Identification and Enumeration: The taxonomic identification (to species level if possible, abundance estimates (numbers m-2 and numbers 1000 m-3) and length measurements of known sound scattering organisms were made for as many samples as possible while onboard. This was generally possible for samples collected during southbound transits and opportunistically in the Antarctic Coastal Zone. In order to provide data from the Antarctic Zone comparable to those from long-term data bases off the Antarctic Peninsula (e.g., Loeb et al., 2008, 2010; Loeb and Santora, 2013) all postlarval Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) were removed and enumerated from samples <2 L; for larger catches, abundance estimates were based on 1 to 2 L subsamples. All postlarval krill in samples with <100 individuals were measured, sexed and staged according to Makarov & Denys (1981); in larger samples at least 100 krill were analyzed. The 2 salp life stages were enumerated and internal body lengths of each (Foxton, 1966) were measured to the nearest mm.

Because of time limitations during northbound transits, generally only the large size fractions could be processed onboard; as a consequence representative 4% buffered formalin preserved aliquots of the small size fraction were analyzed at Moss Landing Marine Labs (MLML) following each cruise. Finer resolution identifications of abundant large taxa (e.g., similar euphausiid and pteropod species) in formalin-preserved samples were also made at MLML following completion of field efforts. Due to a combination of funding, time and/or expertise constraints, species identifications of various abundant small zooplankton categories (e.g., euphausiid larvae and copepods) were limited.

BCO-DMO Data Processing Notes:

-reformatted column names to comply with BCO-DMO standards
-compiled each deployment into one table

net_tow_data.csv