Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Abundance of Calanus finmarchicus stages caught in 200um vertical ring nets(bottom to surface) at two time series stations in the Gulf of Maine (2012 - 2013).

Users are requested to consult with Jeffrey Runge prior to preparation of any manuscripts or reports, either written or online, that make use of zooplankton and hydrographic data originating from this study. The data are freely available without need for consultation with Dr. Runge after October, 2017.

These deployments followed the AZMP protocols (Mitchell et al. 2002). Using a 0.75 meter diameter SEA-GEAR Model 9600 twin-ring, 200µm mesh net, two vertical casts were made to within 5 meters of the bottom at each station.  

Two replicate samples from separate casts were preserved in a 4% seawater-buffered formaldehyde solution. In the laboratory, all formalin preserved zooplankton samples were split in half using a Folsom Plankton Splitter. Half of the sample was archived for identification and enumeration of zooplankton, and the other half was processed for biomass determination. To estimate abundances the archival split was diluted and sub-sampled with a 5 mL Stempel pipette. Depending on abundance in the sample, multiple subsamples were taken until a target number of 75-150 C. finmarchicus copepodids were enumerated and staged and in addition at least 200 specimens in total were counted and identified to the lowest possible taxa.

Mitchell, M. R., G. Harrison, K. Pauley, A. Gagné, G. Maillet, and P. Strain. (2002) Atlantic Zonal Monitoring Program Sampling Protocol. Canadian Technical Report of Hydrography and Ocean Sciences 223.

The counts were normalized to abundance (number m-2), taking into account the subsample dilution, the split, and volume sampled by the net at the station. Because of unreliable flowmeter readings, we calculated volume filtered by the net from net area and net depth. The filtered volume calculated geometrically, as we have done here, is closely related to the flowmeter volume when flowmeters were working properly.

Volume = Net Depth * Net Area

Abundance (number m-2) = ( (count*Dilution Factor / Archival split) / Volume) *Station Depth

"The copepod, Calanus finmarchicus, is a dominant member of the plankton in the Gulf of Maine, (GoM), despite its location at the southern edge of the species' subarctic range. Wilkinson Basin, one of the three deep basins in the GoM, harbors very high concentrations of the early developmental stages of C. finmarchicus in the summer through winter and serves as a source of C. finmarchicus to GoM coastal ledges and banks. A recent study based on C. finmarchicus habitat characteristics across the North Atlantic predicts that climate-driven change will force the distribution of C. finmarchicus northward out of the GoM over the next several decades. However, the oceanographic and life history responses of C. finmarchicus to environmental variability in the Gulf are complex and largely unknown. The research in this RAPID proposal takes advantage of a rare opportunity to test a hypothesis about the control of C. finmarchicus abundance in the GoM from climate change related external forcing. The hypothesis states that a distinctly lower C. finmarchicus abundance follows, with a two-year lag, the occurrence of a very negative North Atlantic Oscillation (NAO). The specific processes that causally connect low C. finmarchicus with the NAO are not known. The research here tests the prediction that C. finmarchicus abundance will be very low in Wilkinson Basin in 2012, two years after one of the most negative NAOs on record, dating back to the 1860?s. Field observations in the form of a time series of measurements of hydrography, food availability and C. finmarchicus stage abundance will be taken at a fixed station in Wilkinson Basin and in the Maine coastal region, supported by measurements taken on the Scotian Shelf. A research survey, coordinated with a scheduled cruise in the Gulf of Maine in September, 2012, will take additional collections in Wilkinson Basin and throughout the GoM. Frozen and ethanol preserved samples of C. finmarchicus will also be collected for population genetic studies. The abundance results will be compared with historical time series and survey data collected over the past two decades, confirming or refuting the expectation of extreme NAO influence on GoM C. finmarchicus populations." (from the Award abstract)