Zooplankton

Dataset description

Zooplankton sampling is done during each CARIACO time-series cruise, and BONGO net tow samples are analyzed to determine dry weight (biomass), and ash (inorganic remains).

Acquisition description

Sampling Methods:

(available as a PDF file)

Zooplankton sampling BONGO tows are oblique and done during the morning (usually between 9 and 10 am) using a BONGO type net (Figure 1) with receptacles of 60cm opening diameter and two different mesh sizes, 200 and 500 microns. A flow meter (General Oceanics) is placed before the 500 micron mesh, in the center of the net’s opening in order to calculate the volume of water filtered through the net during the deployment.

The tows cover a depth between 200m deep to the surface. In order to reach that depth, 200m of cable are released and the ship is set into motion so that the cable has an angle of 40-45 degrees (measured with a clinometer) during the entire tow (10-15 minutes). The ship’s speed during the tow is maintained around 1-1.5 knots. As the ship moves, the net is pulled upwards at a speed of 1 m/s.

Once on the surface, the nets are washed with seawater to move any organism caught down to the receptacle. Its contents are then emptied inside glass jars and kept refrigerated until processing.

Processing description

In the lab, samples are are split in two, using a Folsom splitter. One of the halves is used to determine dry weight (biomass), as well as ash (inorganic remains). If further analyses are required, this half is further split to quarters. Samples are washed with DI water to eliminate salt excess and dried for 48 hours at 60°C in pre-weighed crucibles. Samples are then calcined in a muffle furnace at 450°C for 4 hours. From the remaining half, aliquots are extracted and placed in a 10 ml. Bogorov chamber in order to count and identify taxonomic groups present. Identification and count are done using a stereomicroscope Baush & Lomb (7x). Processed samples are fixed with formaline 5% neutralized with borax, labeled and stored in the collection maintained at the Museo Oceanológico Hermano Benigno Román (MOBR - EDIMAR). The manuals used for zooplankton identification are Newell&Newell (1977); Tregouboff & Rose (1978) and Boltosvkoy (1981).

1. Bongo Nets:

   BONGO type net towed with receptacles of 60cm opening diameter and two different mesh sizes, 200 and 500 microns.

This document is created from the content of the BCO-DMO metadata database.    2009-11-22  09:16:15