Ocean Frontal Areas: Phytoplankton Enumberation and Biomass Estimates--Operation Guiding Light (April-May 1985)

Document Type

Article

Publication Date

3-5-1986

School

Biological, Environmental, and Earth Sciences

Abstract

  1. During the pilot field exercise for Operation Guiding Light (April-May, 1985), 39 phytoplankton samples were collected in the shelf-slope frontal region and 72 phytoplankton samples were collected in the Gulf Stream frontal region (both survey areas are located in the western North Atlantic Ocean). Samples were obtained using either a towed underwater pumping system (TUPS) at a depth of two meters or a rosette sampler (various depths) and preserved for subsequent analysis.
  2. Based on preliminary pigment analyses completed several weeks subsequent to the cruise, the Chief Scientific Officer selected a total of 52 samples for analysis (21 TUPS samples and 31 station samples). For those samples, we identified (to species, where possible) enumerated and estimated biomass of the phytoplankton present.
  3. The results detailed herein may be summarized as follows:
    1. Phytoplankton biomass ranged from 5-29,308 mm3 × 10−6/x.
    2. Phytoplankton biomass south of the Gulf Stream front was significantly greater than north of the front or at the frontal boundary (TUPS samples); biomass estimates for station samples far exceeded those for underway samples and were usually substantially greater for samples obtained in cool water (12-16°C) than in warm water (18-21°C).
    3. In the shelf slope-frontal region, estimated biomass for several of the underway samples was considerably greater than for any of the underway samples obtained in the southern survey area; in contrast to TUPS results obtained in the southern survey area, sample biomass south of the frontal boundary was low compared with that of samples obtained both at and north of the frontal boundary.
    4. In most samples, biomass of dinoflagellates exceeded (often by 2-4 fold) biomass of diatoms; only in some of the samples obtained in the shelf-slope frontal area did biomass of groups other than diatoms and dinoflagellates comprise a substantial (>25%) proportion of total biomass.

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