Sampling at the Wilkinson Basin Time Series (WBTS) station followed as a guideline the protocols established by the Atlantic Zone Monitoring Program (AZMP) established by Fisheries and Oceans Canada (Mitchell et al. 2002).

Sampling and analytical procedures:

Environmental data. The R/V Gulf Challenger system comprised a Sea-Bird Electronics (SBE) 25Plus CTD, an SBE-55 Sampling Rosette with six four-liter Niskin bottles, a dedicated Hawboldt Industries SPR 1424/S Science winch, and a SBE-33 real-time monitoring and sampling deck unit. The system provided high-resolution vertical profiling of hydrographic properties (e.g. conductivity, salinity, temperature), physiochemical properties (e.g. Photosynthetically Active Radiation (PAR)), and surrogates for biological and geological processes (e.g. dissolved oxygen, chlorophyll-a fluorescence, and beam transmittance). The raw CTD data and bottle trips were acquired by SBE Seasave on a Windows 7 workstation and were processed from hex files to .cnv files. Post cruise data processing was completed on a Windows 7 machine running SEABIRD SBE DATA Processing version 7.22.5 At most stations, Niskin bottles were used to capture water samples at depths of 2, 10, 20 and 40 meters. To measure chlorophyll a concentration at discrete depths, duplicate, 100 mL or 500-550 mL subsamples were collected from Niskin bottles at the surface, 10, 20 and 40 meters. Water was filtered immediately on the vessel using glass fiber filters (GF/F) and polycarbonate membrane filters with pore sizes of 0.7 µm and 0.1µm. Chlorophyll-a concentrations were calculated were using equations in Strickland and Parsons (1972). Prior to 2014, IOP profilers calibrated annually were used to measure water column stimulated fluorescence. After 2014, the nominal chlorophyll-a readings from stimulated fluorescence measured with a Wetlabs Wetstar Chlorophyll Fluorometer S/N WSS-164 were corrected with chlorophyll concentrations measured from bottle samples.

Copepod data: To measure zooplankton abundance and biomass, two net two casts were made using a 0.75 meter diameter single ring or a SEA-GEAR Model 9600 twin-ring 200µm mesh net, The nets were towed vertically at approx.. 40m/min from within 5 meters of the bottom. The samples were preserved in 4% buffered formaldehyde. For the dual ring casts, a third sample was preserved in 95%, denatured ethanol and on many occasions, the fourth sample was kept live, diluted with sea water and distributed into 3.7 L plastic containers, and placed in a cooler until they could be transported back to the lab for live image analysis.

The zooplankton samples fixed in formalin were further processed for identification and enumeration of species. Samples were diluted in seawater and subsamples were taken until 200 copepods and at least 75 Calanus were identified.