The project began in the winter of 1997 as part of the U.S.
GLOBEC Georges Bank Program. The purpose of our component of that
multi-institutional study is to investigate the idea that the growth and production of
zooplankton and fish on Georges Bank are limited by the amount of nutrients (especially
nitrogen) that is brought onto the Bank from the nutrient-rich, deeper waters around the
Banks edges (cf. Townsend and Pettigrew, 1997).
The sampling period was chosen to bracket the winter-to-spring transition, which is
coincident with the Georges Bank GLOBEC broad scale cruises conducted in 1997, 1998 and
1999. The cruise dates were:
1997 January 13 - 20 (R/V Albatross)
February 11 - 22 (R/V Oceanus)
March 16 - 29 (R/V Oceanus)
April 20 - May 3 (R/V Oceanus)
May 19 - 30 (R/V Oceanus)
June 18 - 28 (R/V Albatross)
1998 February 7 -17 (R/V Oceanus)
March15 - 26 (R/V Oceanus)
April 16 - 26 (R/V Oceanus)
May 10 - 20 (R/V Albatross)
June 17 - 25 (R/V Albatross)
1999 11-24 January (R/V Albatross)
February (R/V Oceanus)
10-23 March (R/V
16-28 April (R/V
19-27 May (R/V
14-24 June (R/V
here to look for other Globec cruises...
Water samples were collected on all cruises for the analysis of phytoplankton biomass
(chlorophyll a and phaeophytin). In addition, dissolved inorganic nutrient
concentrations (NO3+NO2, SiO4, PO4 and NH4) were determined for four of the six Broadscale
cruises in 1997, five of six in 1998, and all six in 1999. Water collections were made at
various depths at all of the regular hydrographic stations (1-40 or Sta 41 after 1997)
using Niskin bottles mounted on the rosette sampler. Additional surface water samples were
collected at positions between the regular stations (numbered >41; refer to
Station Location Map for
Phytoplankton chlorophyll a and phaeopigments were determined fluorometrically
(Parsons et al., 1984). The extracted chlorophyll measurements involved
collecting 100ml from all bottle samples taken at depths shallower than 60m, filtering
through GF/F filters, and extracting in 90% acetone in a freezer for at least 12 hours.
The samples were analyzed at sea using a Turner Model 10 fluorometer.
Water samples for DIN were filtered through 0.45 Millipore cellulose acetate membrane
filters and then frozen immediately in 20ml acid-washed polyethylene scintillation vials
by first placing the vials in a seawater-ice bath for approximately 10 minutes. Samples
were analyzed in the lab following the cruise using a Technicon II 4-Channel
Contour plots and tabulated data are available
Parsons, T.R., Y. Maita and C.M. Lalli. 1984. A Manual of Chemical and Biological Methods
for Seawater Analysis. Pergamon, Oxford. 173pp.
Townsend, D.W. and N.R. Pettigrew. 1997. Nutrient limitation of secondary production on
Georges Bank. J. Plankton Res. 19: 221-235.