Nutrient and chlorophyll vertical profiles and aerial contour plots are
available for the Georges Bank region of the northwest Atlantic Ocean near the
Gulf of Maine.
Data were collected on the following cruises during 1997-1999:
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)
March 15 - 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)
11-23 February (R/V Oceanus)
10-23 March (R/V Oceanus)
16-28 April (R/V Oceanus)
19-27 May (R/V Albatross)
14-24 June (R/V Albatross).
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 example).
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
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 Auto-Analyzer.
In addition to dissolved inorganic nutrients and chlorophyll, in 1999 we also
analyzed samples for particulate organic carbon and nitrogen, dissolved organic
nitrogen, and particulate and dissolved organic phosphorus.
Results from the vertical profiles taken at each station can be viewed as
contour plots (using Surfer Software, Golden Colorado) for 1997, 1998 and 1999.
Plotted variables include Temperature and Salinity for the hydrographic data,
Chlorophyll a for the pigment analyses and Nitrate plus Nitrite, Silicate,
Ammonium and Phosphate for the inorganic nutrient analyses. The hydrographic
data were contoured only for the surface (2m). The pigment and inorganic
nutrient concentrations were contoured for the surface (2m), 20 meter and 60