Back in the lab, the zooplankton samples were split in half using Folsom Plankton Splitter. Half of the sample was archived for abundance analysis of meso-zooplankton species. Target N of organisms counted was 200. All copepods were identified to species and staged. All other animals were identified to family or to species where possible. The Calanus finmarchicus target N was 75-100 where few stages were present or 150-200 where many stages were present.
The remaining half of the sample was rinsed of its preservative by sieving through a nitex mesh filter made of the net used in sampling. The mesh filters were pre-weighed for subtraction from the sample material weight.
The sample was then rinsed with 100 ml of freshwater to remove salts and placed in a clean, pre-weighed petri dish. It was then placed in a 65C oven (Precision Econotherm Lab Oven) for 48 hours for drying
Dried samples are then weighed to the nearest 0.001 gram on PG403-S Delta Range Mettler Toledo precision scale
Zooplankton abundance (#/m2) was calculated by first determining the #/m3 and then multiplying by net depth. The abundance (#/m3) = (the count *dilution factor/ split / volume filtered). Dilution factor = the dilution/aliquot; volume filtered = ring net mouth area (m2)* distance (M); distance is measured by the flowmeter.
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